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COMMISSION IMPLEMENTING DECISION (EU) 2022/2110
of 11 October 2022
establishing the best available techniques (BAT) conclusions, under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions, for the ferrous metals processing industry
(notified under document C(2022) 7054)
(Text with EEA relevance)
Article 1
Article 2
ANNEX
1.
BEST AVAILABLE TECHNIQUES (BAT) CONCLUSIONS FOR THE FERROUS METALS PROCESSING INDUSTRY
SCOPE
DEFINITIONS
General terms |
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Term used |
Definition |
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Batch galvanising |
Discontinuous immersion of steel workpieces in a bath containing molten zinc to coat their surface with zinc. This also includes any directly associated pre- and post-treatment processes (e.g. degreasing and passivation). |
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Bottom dross |
A reaction product of molten zinc with iron or with iron salts carried over from pickling or fluxing. This reaction product sinks to the bottom of the zinc bath. |
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Carbon steel |
Steel in which the content of each alloy element is less than 5 wt-%. |
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Channelled emissions |
Emissions of pollutants into the environment through any kind of duct, pipe, stack, etc. |
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Cold rolling |
Compression of steel by rollers at ambient temperatures to change its characteristics (e.g. size, shape and/or metallurgical properties). This also includes any directly associated pre- and post-treatment processes (e.g. pickling, annealing and oiling). |
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Continuous measurement |
Measurement using an automated measuring system permanently installed on site. |
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Direct discharge |
Discharge to a receiving water body without further downstream waste water treatment. |
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Existing plant |
A plant that is not a new plant. |
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Feedstock |
Any steel input (unprocessed or partly processed) or workpieces entering a production process step. |
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Feedstock heating |
Any process step where feedstock is heated. This does not include feedstock drying or the heating of the galvanising kettle. |
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Ferrochromium |
An alloy of chromium and iron typically containing between 50 wt-% and 70 wt-% chromium. |
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Flue-gas |
The exhaust gas exiting a combustion unit. |
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High-alloy steel |
Steel in which the content of one or more alloy elements is 5 wt-% or more. |
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Hot dip coating |
Continuous immersion of steel sheets or wires through a bath containing molten metal(s), e.g. zinc and/or aluminium, to coat the surface with metal(s). This also includes any directly associated pre- and post-treatment processes (e.g. pickling and phosphating). |
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Hot rolling |
Compression of heated steel by rollers at temperatures typically ranging from 1 050 °C to 1 300 °C to change its characteristics (e.g. size, shape and/or metallurgical properties). This includes hot ring rolling and hot rolling of seamless tubes as well as any directly associated pre- and post-treatment processes (e.g. scarfing, finishing, pickling and oiling). |
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Indirect discharge |
A discharge that is not a direct discharge. |
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Intermediate heating |
Heating of the feedstock between the hot rolling stages. |
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Iron and steel process gases |
Blast furnace gas, basic oxygen furnace gas, coke oven gas or mixtures thereof originating from iron and steel production. |
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Leaded steel |
Steel grades in which the content of lead added is typically between 0,15 wt-% and 0,35 wt-%. |
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Major plant upgrade |
A major change in the design or technology of a plant with major adjustments or replacements of the process and/or abatement technique(s) and associated equipment. |
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Mass flow |
The mass of a given substance or parameter which is emitted over a defined period of time. |
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Mill scale |
Iron oxides formed on the surface of steel when oxygen reacts with hot metal. This occurs immediately after casting, during reheating and hot rolling. |
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Mixed acid |
A mixture of hydrofluoric acid and nitric acid. |
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New plant |
A plant first permitted at the site of the installation following the publication of these BAT conclusions or a complete replacement of a plant following the publication of these BAT conclusions. |
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Periodic measurement |
Measurement at specified time intervals using manual or automated methods. |
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Plant |
All parts of an installation covered by the scope of these BAT conclusions and any other directly associated activities which have an effect on consumption and/or emissions. Plants may be new plants or existing plants. |
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Post-heating |
Heating of the feedstock after hot rolling. |
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Process chemicals |
Substances and/or mixtures as defined in Article 3 of Regulation (EC) No 1907/2006 of the European Parliament and of the Council(1) and used in the process(es). |
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Recovery |
Recovery as defined in Article 3(15) of Directive 2008/98/EC of the European Parliament and of the Council(2). The recovery of spent acids includes their regeneration, reclamation and recycling. |
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Regalvanising |
The processing of used galvanised articles (e.g. highway guard rails) that are returned to be galvanised after long service periods. Processing of these articles requires additional process steps due to the presence of partly corroded surfaces or the need to remove any residual zinc coating. |
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Reheating |
Heating of the feedstock before hot rolling. |
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Residue |
Substance or object generated by the activities covered by the scope of these BAT conclusions as waste or by-product. |
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Sensitive receptor |
Areas which need special protection, such as:
|
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Stainless steel |
High-alloy steel which contains chromium typically within the range 10–23 wt-%. It includes austenitic steel, which also contains nickel typically within the range 8–10 wt-%. |
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Top dross |
In hot dipping, the oxides formed on the surface of the molten zinc bath by reaction of iron and aluminium. |
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Valid hourly (or half-hourly) average |
An hourly (or half-hourly) average is considered valid when there is no maintenance or malfunction of the automated measuring system. |
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Volatile substance |
A substance capable of readily changing from a solid or liquid form to a vapour, having a high vapour pressure and a low boiling point (e.g. HCl). This includes volatile organic compounds as defined in Article 3(45) of Directive 2010/75/EU. |
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Wire drawing |
Drawing of steel rods or wires through dies to reduce their diameter. This also includes any directly associated pre- and post-treatment processes (e.g. wire rod pickling and feedstock heating after drawing). |
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Zinc ash |
A mixture comprising zinc metal, zinc oxide and zinc chloride that is formed on the surface of the molten zinc bath. |
Pollutants and parameters |
|
Term used |
Definition |
B |
The sum of boron and its compounds, dissolved or bound to particles, expressed as B. |
Cd |
The sum of cadmium and its compounds, dissolved or bound to particles, expressed as Cd. |
CO |
Carbon monoxide. |
COD |
Chemical oxygen demand. Amount of oxygen needed for the total chemical oxidation of the organic matter to carbon dioxide using dichromate. COD is an indicator for the mass concentration of organic compounds. |
Cr |
The sum of chromium and its compounds, dissolved or bound to particles, expressed as Cr. |
Cr(VI) |
Hexavalent chromium, expressed as Cr(VI), includes all chromium compounds where the chromium is in the oxidation state +6. |
Dust |
Total particulate matter (in air). |
Fe |
The sum of iron and its compounds, dissolved or bound to particles, expressed as Fe. |
F- |
Dissolved fluoride, expressed as F-. |
HCl |
Hydrogen chloride. |
HF |
Hydrogen fluoride. |
Hg |
The sum of mercury and its compounds, dissolved or bound to particles, expressed as Hg. |
HOI |
Hydrocarbon oil index. The sum of compounds extractable with a hydrocarbon solvent (including long-chain or branched aliphatic, alicyclic, aromatic or alkyl-substituted aromatic hydrocarbons). |
H2SO4 |
Sulphuric acid. |
NH3 |
Ammonia. |
Ni |
The sum of nickel and its compounds, dissolved or bound to particles, expressed as Ni. |
NOX |
The sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2), expressed as NO2. |
Pb |
The sum of lead and its compounds, dissolved or bound to particles, expressed as Pb. |
Sn |
The sum of tin and its compounds, dissolved or bound to particles, expressed as Sn. |
SO2 |
Sulphur dioxide. |
SOX |
The sum of sulphur dioxide (SO2), sulphur trioxide (SO3) and sulphuric acid aerosols, expressed as SO2. |
TOC |
Total organic carbon, expressed as C (in water); includes all organic compounds. |
Total P |
Total phosphorus, expressed as P, includes all inorganic and organic phosphorus compounds. |
TSS |
Total suspended solids. Mass concentration of all suspended solids (in water), measured via filtration through glass fibre filters and gravimetry. |
TVOC |
Total volatile organic carbon, expressed as C (in air). |
Zn |
The sum of zinc and its compounds, dissolved or bound to particles, expressed as Zn. |
ACRONYMS
Acronym |
Definition |
BG |
Batch galvanising |
CMS |
Chemicals management system |
CR |
Cold rolling |
EMS |
Environmental management system |
FMP |
Ferrous metals processing |
HDC |
Hot dip coating |
HR |
Hot rolling |
OTNOC |
Other than normal operating conditions |
SCR |
Selective catalytic reduction |
SNCR |
Selective non-catalytic reduction |
WD |
Wire drawing |
GENERAL CONSIDERATIONS
Best Available Techniques
BAT-AELs and indicative emission levels for emissions to air
Source of emissions |
Reference oxygen level (OR) |
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Combustion processes associated with:
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3 dry vol-% |
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All other sources |
No correction for the oxygen level |
Type of measurement |
Averaging period |
Definition |
Continuous |
Daily average |
Average over a period of one day based on valid hourly or half-hourly averages. |
Periodic |
Average over the sampling period |
Average value of three consecutive measurements of at least 30 minutes each(3). |
BAT-AELs for emissions to water
Other environmental performance levels associated with the best available techniques (BAT-AEPLs)
BAT-AEPLs for specific energy consumption (energy efficiency)
BAT-AEPLs for specific water consumption
BAT-AEPLs for specific material consumption
1.1.
General BAT conclusions for the ferrous metals processing industry
1.1.1.
General environmental performance
Applicability
Applicability
Applicability
Technique |
Description |
Applicability |
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a. |
Set-up and implementation of a plan for the prevention and control of leaks and spillages |
A plan for the prevention and control of leaks and spillages is part of the EMS (see BAT 1) and includes, but is not limited to:
|
The level of detail of the plan will generally be related to the nature, scale and complexity of the plant, as well as to the type and quantity of liquids used. |
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b. |
Use of oil-tight trays or cellars |
Hydraulic stations and oil- or grease-lubricated equipment are situated in oil-tight trays or cellars. |
Generally applicable. |
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c. |
Prevention and handling of acid spillages and leaks |
Storage tanks for both fresh and spent acid are equipped with sealed secondary containment protected with an acid-resistant coating which is regularly inspected for potential damage and cracks. Loading and unloading areas for the acids are designed in such a way that any potential spillages and leaks are contained and sent to on-site treatment (see BAT 31) or off-site treatment. |
Generally applicable. |
1.1.2.
Monitoring
Description
Substance/Parameter |
Specific process(es) |
Sector |
Standard(s) |
Minimum monitoring frequency(4) |
Monitoring associated with |
|
CO |
Feedstock heating(5) |
HR, CR, WD, HDC |
EN 15058(6) |
Once every year |
BAT 22 |
|
Heating of the galvanising kettle(5) |
HDC of wires, BG |
Once every year |
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Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
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Dust |
Feedstock heating |
HR, CR, WD, HDC |
EN 13284-1(6) (7) |
Continuous for any stack with dust mass flows > 2 kg/h Once every 6 months for any stack with dust mass flows between 0,1 kg/h and 2 kg/h Once every year for any stack with dust mass flows < 0,1 kg/h |
BAT 20 |
|
Hot dipping after fluxing |
HDC, BG |
Once every year(8) |
BAT 26 |
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Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting or by evaporation |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
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Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
Once every year |
BAT 42 |
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Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year |
BAT 46 |
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Lead baths |
WD |
Once every year |
BAT 51 |
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Dry drawing |
Once every year |
BAT 52 |
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HCl |
Pickling with hydrochloric acid |
HR, CR, HDC, WD |
EN 1911(6) |
Once every year |
BAT 24 |
|
Pickling and stripping with hydrochloric acid |
BG |
Once every year |
BAT 62 |
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Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
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Pickling and stripping with hydrochloric acid in open pickling baths |
BG |
No EN standard available |
Once every year(9) |
BAT 62 |
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HF |
Pickling with acid mixtures containing hydrofluoric acid |
HR, CR, HDC |
EN standard under development(6) |
Once every year |
BAT 24 |
|
Recovery of mixed acid by spray roasting or by evaporation |
HR, CR |
Once every year |
BAT 29 |
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Metals |
Ni |
Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
EN 14385 |
Once every year(10) |
BAT 42 |
Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year(10) |
BAT 46 |
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Pb |
Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
Once every year(10) |
BAT 42 |
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Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year(10) |
BAT 46 |
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Lead baths |
WD |
Once every year |
BAT 51 |
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Zn |
Hot dipping after fluxing |
HDC, BG |
Once every year(8) |
BAT 26 |
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NH3 |
When SNCR and/or SCR is used |
HR, CR, WD, HDC |
EN ISO 21877(6) |
Once every year |
BAT 22, BAT 25, BAT 29 |
|
NOX |
Feedstock heating(5) |
HR, CR, WD, HDC |
EN 14792(6) |
Continuous for any stack with NOX mass flows > 15 kg/h Once every 6 months for any stack with NOX mass flows between 1 kg/h and 15 kg/h Once every year for any stack with NOX mass flows < 1 kg/h |
BAT 22 |
|
Heating of the galvanising kettle(5) |
HDC of wires, BG |
Once every year |
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Pickling with nitric acid alone or in combination with other acids |
HR, CR |
Once every year |
BAT 25 |
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Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting or by evaporation |
HR, CR, WD, HDC |
Once every year |
BAT 29 |
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SO2 |
Feedstock heating(11) |
HR, CR, WD, coating of sheets in HDC |
EN 14791(6) |
Continuous for any stack with SO2 mass flows > 10 kg/h Once every 6 months for any stack with SO2 mass flows between 1 kg/h and 10 kg/h Once a year for any stack with SO2 mass flows < 1 kg/h |
BAT 21 |
|
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors |
HR, CR, HDC, WD |
Once every year(8) |
BAT 29 |
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SOX |
Pickling with sulphuric acid |
HR, CR, HDC, WD |
Once every year |
BAT 24 |
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BG |
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TVOC |
Degreasing |
CR, HDC |
EN 12619(6) |
Once every year(8) |
BAT 23 |
|
Rolling, wet tempering and finishing |
CR |
Once every year(8) |
BAT 48 |
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Lead baths |
WD |
Once every year(8) |
— |
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Oil quench baths |
WD |
Once every year(8) |
BAT 53 |
Substance/Parameter |
Specific process(es) |
Standard(s) |
Minimum monitoring frequency(12) |
Monitoring associated with |
|
Total suspended solids (TSS)(13) |
All processes |
EN 872 |
Once every week(14) |
BAT 31 |
|
Total organic carbon (TOC)(13) (15) |
All processes |
EN 1484 |
Once every month |
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Chemical oxygen demand (COD)(13) (15) |
All processes |
No EN standard available |
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Hydrocarbon oil index (HOI)(16) |
All processes |
EN ISO 9377-2 |
Once every month |
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Metals/metalloids(16) |
Boron |
Processes where borax is used |
Various EN standards available (e.g. EN ISO 11885, EN ISO 17294-2) |
Once every month |
|
Cadmium |
All processes(17) |
Various EN standards available (e.g. EN ISO 11885, EN ISO 15586, EN ISO 17294-2) |
Once every month |
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Chromium |
All processes(17) |
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Iron |
All processes |
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Nickel |
All processes(17) |
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Lead |
All processes(17) |
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Tin |
Hot dip coating using tin |
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Zinc |
All processes(17) |
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Mercury |
All processes(17) |
Various EN standards available (e.g. EN ISO 12846, EN ISO 17852) |
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Hexavalent chromium |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
Various EN standards available (e.g. EN ISO 10304-3, EN ISO 23913) |
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Total phosphorus (Total P)(13) |
Phosphating |
Various EN standards available (e.g. EN ISO 6878, EN ISO 11885, EN ISO 15681-1 and -2) |
Once every month |
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Fluoride (F-)(16) |
Pickling with acid mixtures containing hydrofluoric acid |
EN ISO 10304-1 |
Once every month |
1.1.3.
Hazardous substances
Applicability
1.1.4.
Energy efficiency
Technique |
Description |
Applicability |
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a. |
Energy efficiency plan and energy audits |
An energy efficiency plan is part of the EMS (see BAT 1) and entails defining and monitoring the specific energy consumption of the activity/processes (see BAT 6), setting key performance indicators on an annual basis (e.g. MJ/t of product) and planning the periodic improvement targets and related actions. Energy audits are carried out at least once a year to ensure that the objectives of the energy management plan are met. The energy efficiency plan and the energy audits may be integrated in the overall energy efficiency plan of a larger installation (e.g. for iron and steel production). |
The level of detail of the energy efficiency plan, of the energy audits and of the energy balance record will generally be related to the nature, scale and complexity of the plant and the types of energy sources used. |
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b. |
Energy balance record |
Drawing up on an annual basis of an energy balance record which provides a breakdown of the energy consumption and generation (including energy export) by the type of energy source (e.g. electricity, natural gas, iron and steel process gases, renewable energy, imported heat and/or cooling). This includes:
|
Technique |
Description |
Applicability |
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Design and operation |
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a. |
Optimum furnace design for feedstock heating |
This includes techniques such as:
|
Only applicable to new plants and major plant upgrades. |
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b. |
Optimum galvanising kettle design |
This includes techniques such as:
|
Only applicable to new plants and major plant upgrades. |
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c. |
Optimum galvanising kettle operation |
This includes techniques such as: minimisation of heat losses from the galvanising kettle in hot dip coating of wires or in batch galvanising, e.g. by using insulated covers during idle periods. |
Generally applicable. |
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d. |
Combustion optimisation |
See Section 1.7.1. |
Generally applicable. |
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e. |
Furnace automation and control |
See Section 1.7.1. |
Generally applicable. |
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f. |
Process gas management system |
See Section 1.7.1. The calorific value of iron and steel process gases and/or CO-rich gas from ferrochromium production is used. |
Only applicable when iron and steel process gases and/or CO-rich gas from ferrochromium production are available. |
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g. |
Batch annealing with 100 % hydrogen |
Batch annealing is carried out in furnaces using 100 % hydrogen as a protective gas with increased thermal conductivity. |
Only applicable to new plants and major plant upgrades. |
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h. |
Oxy-fuel combustion |
See Section 1.7.1. |
Applicability may be restricted for furnaces processing high-alloy steel. Applicability to existing plants may be restricted by furnace design and the need for a minimum waste gas flow. Not applicable to furnaces equipped with radiant tube burners. |
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i. |
Flameless combustion |
See Section 1.7.1. |
Applicability to existing plants may be limited by furnace design (i.e. furnace volume, space for burners, distance between burners) and the need for a change of the refractory lining. Applicability may be limited for processes where close control of temperature or temperature profile is required (e.g. recrystallisation). Not applicable to furnaces operating at a temperature lower than the auto-ignition temperature required for flameless combustion or to furnaces equipped with radiant tube burners. |
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j. |
Pulse-fired burner |
The heat input to the furnace is controlled by the firing duration of the burners or by the sequential start of the individual burners instead of adjusting combustion air and fuel flows. |
Only applicable to new plants and major plant upgrades. |
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Heat recovery from flue-gases |
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k. |
Feedstock preheating |
Feedstock is preheated by blowing hot flue-gases directly onto it. |
Only applicable to continuous reheating furnaces. Not applicable to furnaces equipped with radiant tube burners. |
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l. |
Drying of workpieces |
In batch galvanising, the heat from flue-gases is used to dry the workpieces. |
Generally applicable. |
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m. |
Preheating of combustion air |
See Section 1.7.1. This may be achieved for example by using regenerative or recuperative burners. A balance has to be achieved between maximising heat recovery from the flue-gas and minimising NOX emissions. |
Applicability to existing plants may be restricted by a lack of space for the installation of regenerative burners. |
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n. |
Waste heat recovery boiler |
The heat from hot flue-gases is used to generate steam or hot water that is used in other processes (e.g. for heating pickling and fluxing baths), for district heating or for generating electricity. |
Applicability to existing plants may be restricted by a lack of space and/or a suitable steam or hot water demand. |
Specific process(es) Steel products at the end of the rolling process |
Unit |
BAT-AEPL (Yearly average) |
Feedstock reheating |
||
Hot rolled coils (strips) |
MJ/t |
1 200 –1 500 (18) |
Heavy plates |
MJ/t |
1 400 –2 000 (19) |
Bars, rods |
MJ/t |
600 –1 900 (19) |
Beams, billets, rails, tubes |
MJ/t |
1 400 –2 200 |
Feedstock intermediate heating |
|
|
Bars, rods, tubes |
MJ/t |
100 –900 |
Feedstock post-heating |
||
Heavy plates |
MJ/t |
1 000 –2 000 |
Bars, rods |
MJ/t |
1 400 –3 000 (20) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Annealing after cold rolling (batch and continuous) |
MJ/t |
600 –1 200 (21) (22) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Feedstock heating before hot dip coating |
MJ/t |
700 –1 100 (23) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Batch galvanising |
kWh/t |
300 –800 (24) (25) (26) |
1.1.5.
Material efficiency
Technique |
Description |
Applicability |
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Avoiding or reducing the need for degreasing |
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a. |
Use of feedstock with low oil and grease contamination |
The use of feedstock with low oil and grease contamination prolongs the lifetime of the degreasing solution. |
Applicability may be limited if the feedstock quality cannot be influenced. |
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b. |
Use of a direct-flame furnace in the case of hot dip coating of sheets |
The oil on the surface of the sheet is burnt in a direct-flame furnace. Degreasing before the furnace may be needed for some high-quality products or in the case of sheets with high residual oil levels. |
Applicability may be limited if a very high level of surface cleanliness and zinc adhesion is required. |
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Degreasing optimisation |
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c. |
General techniques for increased degreasing efficiency |
These include techniques such as:
|
Generally applicable. |
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d. |
Minimisation of drag-out of degreasing solution |
This includes techniques such as:
|
Generally applicable. |
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e. |
Reverse cascade degreasing |
Degreasing is carried out in two or more baths in series where the feedstock is moved from the most contaminated degreasing bath to the cleanest. |
Generally applicable. |
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Extending the lifetime of the degreasing baths |
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f. |
Cleaning and reuse of the degreasing solution |
Magnetic separation, oil separation (e.g. skimmers, discharge launders, weirs), micro- or ultrafiltration or biological treatment is used to clean the degreasing solution for reuse. |
Generally applicable. |
Technique |
Description |
|
a. |
Acid heating with heat exchangers |
Corrosion-resistant heat exchangers are immersed in the pickling acid for indirect heating, e.g. with steam. |
b. |
Acid heating by submerged combustion |
Combustion gases pass through the pickling acid, releasing the energy via direct heat transfer. |
Technique |
Description |
Applicability |
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Avoiding or reducing the need for pickling |
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a. |
Minimisation of steel corrosion |
This includes techniques such as:
|
Generally applicable. |
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b. |
Mechanical (pre)descaling |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. Applicability may be restricted due to product specifications. |
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c. |
Electrolytic prepickling of high-alloy steel |
Use of an aqueous solution of sodium sulphate (Na2SO4) to pretreat high-alloy steel before pickling with mixed acid, in order to speed up and improve the removal of the surface oxide scale. The waste water containing hexavalent chromium is treated using technique BAT 31 (f). |
Only applicable to cold rolling. Applicability to existing plants may be restricted by a lack of space. |
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Pickling optimisation |
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d. |
Rinsing after alkaline degreasing |
Carry-over of alkaline degreasing solution to the pickling bath is reduced by rinsing feedstock after degreasing. |
Applicability to existing plants may be restricted by a lack of space. |
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e. |
General techniques for increased pickling efficiency |
These include techniques such as:
|
Generally applicable. |
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f. |
Cleaning of the pickling bath and reuse of free acid |
A cleaning circuit, e.g. with filtration, is used to remove particles from the pickling acid followed by reclamation of the free acid via ion exchange, e.g. using resins. |
Not applicable if cascade pickling (or similar) is used, as this results in very low levels of free acid. |
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g. |
Reverse cascade pickling |
Pickling is carried out in two or more baths in series where the feedstock is moved from the bath with the lowest acid concentration to the one with the highest. |
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
h. |
Minimisation of drag-out of pickling acid |
This includes techniques such as:
|
Generally applicable. |
||||||||||
i. |
Turbulence pickling |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
j. |
Use of pickling inhibitors |
Pickling inhibitors are added to the pickling acid to protect metallically clean parts of the feedstock from over-pickling. |
Not applicable to high- alloy steel. Applicability may be restricted due to product specifications. |
||||||||||
k. |
Activated pickling in hydrochloric acid pickling |
Pickling is carried out with a low hydrochloric acid concentration (i.e. around 4–6 wt-%) and a high iron concentration (i.e. around 120–180 g/l) at temperatures of 20–25 °C. |
Generally applicable. |
Pickling acid |
Unit |
BAT-AEPL (3-year average) |
Hydrochloric acid, 28 wt-% |
kg/t |
13 –30 (27) |
Technique |
Description |
Applicability |
|||||||
a. |
Rinsing of workpieces after pickling |
In batch galvanising, carry-over of iron to the fluxing solution is reduced by rinsing workpieces after pickling. |
Applicability to existing plants may be restricted by a lack of space. |
||||||
b. |
Optimised fluxing operation |
The chemical composition of the fluxing solution is monitored and adjusted frequently. The amount of fluxing agent used is reduced to the minimum level required to achieve the product specifications. |
Generally applicable. |
||||||
c. |
Minimisation of drag-out of fluxing solution |
The drag-out of the fluxing solution is minimised by allowing enough time for it to drip off. |
Generally applicable. |
||||||
d. |
Iron removal and reuse of the fluxing solution |
Iron is removed from the fluxing solution by one of the following techniques:
After iron removal, the fluxing solution is reused. |
Applicability to existing batch galvanising plants may be restricted by a lack of space. |
||||||
e. |
Recovery of salts from the spent fluxing solution for production of fluxing agents |
Spent fluxing solution is used to recover the salts contained therein to produce fluxing agents. This may take place on site or off site. |
Applicability may be restricted depending on the availability of a market. |
Technique |
Description |
|||||||
a. |
Reduction of the generation of bottom dross |
The generation of bottom dross is reduced, e.g. by sufficient rinsing after pickling, removing the iron from the fluxing solution (see BAT 15 (d)), using fluxing agents with a mild pickling effect and avoiding local overheating in the galvanising kettle. |
||||||
b. |
Prevention, collection and reuse of zinc splashes in batch galvanising |
The generation of zinc splashes from the galvanising kettle is reduced by minimising carry-over of the fluxing solution (see BAT 26 (b)). Zinc splashes out of the kettle are collected and reused. The area surrounding the kettle is kept clean to reduce contamination of the splashes. |
||||||
c. |
Reduction of the generation of zinc ash |
The formation of zinc ash, i.e. zinc oxidation on the bath surface, is reduced for example by:
|
Technique |
Description |
|
Extending the lifetime of the treatment baths |
||
a. |
Cleaning and reuse of the phosphating or passivation solution |
A cleaning circuit, for example with filtration, is used to clean the phosphating or passivation solution for reuse. |
Treatment optimisation |
||
b. |
Use of roll coaters for strips |
Roll coaters are used to apply a passivation or a phosphate-containing layer on the surface of strips. This allows better control of the layer thickness and thus the reduction of the consumption of chemicals. |
c. |
Minimisation of drag-out of chemical solution |
The drag-out of chemical solution is minimised, e.g. by passing the strips through squeeze rolls or by allowing for sufficient dripping time for workpieces. |
Description
Applicability
1.1.6.
Water use and waste water generation
Technique |
Description |
Applicability |
|||||||
a. |
Water management plan and water audits |
A water management plan and water audits are part of the EMS (see BAT 1) and include:
Water audits are carried out at least once every year to ensure that the objectives of the water management plan are met. The water management plan and the water audits may be integrated in the overall water management plan of a larger installation (e.g. for iron and steel production). |
The level of detail of the water management plan and water audits will generally be related to the nature, scale and complexity of the plant. |
||||||
b. |
Segregation of water streams |
Each water stream (e.g. surface run-off water, process water, alkaline or acidic waste water, spent degreasing solution) is collected separately, based on the pollutant content and on the required treatment techniques. Waste water streams that can be recycled without treatment are segregated from waste water streams that require treatment. |
Applicability to existing plants may be limited by the layout of the water collection system. |
||||||
c. |
Minimisation of hydrocarbon contamination of process water |
The contamination of process water by oil and lubricant losses is minimised by using techniques such as:
|
Generally applicable. |
||||||
d. |
Reuse and/or recycling of water |
Water streams (e.g. process water, effluents from wet scrubbing or quench baths) are reused and/or recycled in closed or semi-closed circuits, if necessary after treatment (see BAT 30 and BAT 31). |
The degree of water reuse and/or recycling is limited by the water balance of the plant, the content of impurities and/or the characteristics of the water streams. |
||||||
e. |
Reverse cascade rinsing |
Rinsing is carried out in two or more baths in series where the feedstock is moved from the most contaminated rinsing bath to the cleanest. |
Applicability to existing plants may be restricted by a lack of space. |
||||||
f. |
Recycling or reuse of rinsing water |
Water from rinsing after pickling or degreasing is recycled/reused, if necessary after treatment, to the preceding process baths as make-up water, rinsing water or, if the acid concentration is sufficiently high, for acid recovery. |
Generally applicable. |
||||||
g. |
Treatment and reuse of oil- and scale-bearing process water in hot rolling |
Oil- and scale-bearing waste water from hot rolling mills is treated separately using different cleaning steps including scale pits, settling tanks, cyclones and filtration to separate oil and scale. A large proportion of the treated water is reused in the process. |
Generally applicable. |
||||||
h. |
Water spray descaling triggered by sensors in hot rolling |
Sensors and automation are used to track the position of the feedstock and adjust the volume of the descaling water passing through the water sprays. |
Generally applicable. |
Sector |
Unit |
BAT-AEPL (Yearly average) |
Hot rolling |
m3/t |
0,5 –5 |
Cold rolling |
m3/t |
0,5 –10 |
Wire drawing |
m3/t |
0,5 –5 |
Hot dip coating |
m3/t |
0,5 –5 |
1.1.7.
Emissions to air
1.1.7.1.
Emissions to air from heating
Technique |
Description |
Applicability |
|||||||
a. |
Use of fuels with low dust and ash content |
Fuels with low dust and ash content include for example natural gas, liquefied petroleum gas, dedusted blast furnace gas and dedusted basic oxygen furnace gas. |
Generally applicable. |
||||||
b. |
Limiting the entrainment of dust |
Entrainment of dust is limited by for example:
|
Avoiding direct contact of the flames with the feedstock is not applicable in the case of direct flame furnaces. |
Parameter |
Sector |
Unit |
BAT-AEL(28) (Daily average or average over the sampling period) |
Dust |
Hot rolling |
mg/Nm3 |
< 2 –10 |
Cold rolling |
< 2 –10 |
||
Wire drawing |
< 2 –10 |
||
Hot dip coating |
< 2 –10 |
Description
Parameter |
Sector |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
SO2 |
Hot rolling |
mg/Nm3 |
50 –200 (29) (30) |
Cold rolling, wire drawing, hot dip coating of sheets |
20 –100 (29) |
Technique |
Description |
Applicability |
|
Reduction of generation of emissions |
|||
a. |
Use of a fuel or a combination of fuels with low NOX formation potential |
Fuels with a low NOX formation potential, e.g. natural gas, liquefied petroleum gas, blast furnace gas and basic oxygen furnace gas. |
Generally applicable. |
b. |
Furnace automation and control |
See Section 1.7.2. |
Generally applicable. |
c. |
Combustion optimisation |
See Section 1.7.2. Generally used in combination with other techniques. |
Generally applicable. |
d. |
Low-NOX burners |
See Section 1.7.2. |
Applicability may be restricted at existing plants by design and/or operational constraints. |
e. |
Flue-gas recirculation |
Recirculation (external) of part of the flue-gas to the combustion chamber to replace part of the fresh combustion air, with the dual effect of lowering the temperature and limiting the O2 content for nitrogen oxidation, thus limiting the NOX generation. It implies the supply of flue-gas from the furnace into the flame to reduce the oxygen content and therefore the temperature of the flame. |
Applicability to existing plants may be restricted by a lack of space. |
f. |
Limiting the temperature of air preheating |
Limiting the air preheating temperature leads to a decrease of the concentration of NOX emissions. A balance has to be achieved between maximising heat recovery from the flue-gas and minimising NOX emissions. |
May not be applicable in the case of furnaces equipped with radiant tube burners. |
g. |
Flameless combustion |
See Section 1.7.2. |
Applicability to existing plants may be limited by furnace design (i.e. furnace volume, space for burners, distance between burners) and the need for a change of the refractory lining. Applicability may be limited for processes where close control of the temperature or temperature profile is required (e.g. recrystallisation). Not applicable to furnaces operating at a temperature lower than the auto-ignition temperature required for flameless combustion, or to furnaces equipped with radiant tube burners. |
h. |
Oxy-fuel combustion |
See Section 1.7.2. |
Applicability may be restricted for furnaces processing high-alloy steel. Applicability to existing plants may be restricted by furnace design and the need for a minimum waste gas flow. Not applicable to furnaces equipped with radiant tube burners. |
Waste gas treatment |
|||
i. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. Applicability may be restricted in batch annealing due to the varying temperatures during the annealing cycle. |
j. |
Selective non-catalytic reduction (SNCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by the optimum temperature window and the residence time needed for the reaction. Applicability may be restricted in batch annealing due to the varying temperatures during the annealing cycle. |
k. |
Optimisation of the SNCR/SCR design and operation |
See Section 1.7.2. |
Only applicable where SNCR/SCR is used for the reduction of NOX emissions. |
Parameter |
Type of fuel |
Specific process |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level Daily average or average over the sampling period) |
NOX |
100 % natural gas |
Reheating |
mg/Nm3 |
New plants: 80 –200 Existing plants: 100 –350 |
No indicative level |
Intermediate heating |
mg/Nm3 |
100 –250 |
|||
Post-heating |
mg/Nm3 |
100 –200 |
|||
Other fuels |
Reheating, intermediate heating, post-heating |
mg/Nm3 |
100 –350 (31) |
||
CO |
100 % natural gas |
Reheating |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Intermediate heating |
mg/Nm3 |
10 –100 |
|||
Post-heating |
mg/Nm3 |
10 –100 |
|||
Other fuels |
Reheating, intermediate heating, post-heating |
mg/Nm3 |
10 –50 |
Parameter |
Type of fuel |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level Daily average or average over the sampling period) |
NOX |
100 % natural gas |
mg/Nm3 |
100 –250 (32) |
No indicative level |
Other fuels |
mg/Nm3 |
100 –300 (33) |
||
CO |
100 % natural gas |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Other fuels |
mg/Nm3 |
No BAT-AEL |
10 –100 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Average over the sampling period) |
NOX |
mg/Nm3 |
100 –250 |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
100 –300 (34) |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –100 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
70 –300 |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –100 |
1.1.7.2.
emissions to air from degreasing
Technique |
Description |
|
Collection of emissions |
||
a. |
Closed degreasing tanks combined with air extraction in the case of continuous degreasing |
Degreasing is carried out in closed tanks and air is extracted. |
Waste gas treatment |
||
b. |
Wet scrubbing |
See Section 1.7.2. |
c. |
Demister |
See Section 1.7.2. |
1.1.7.3.
Emissions to air from pickling
Technique |
Description |
|
Collection of emissions |
||
a. |
Continuous pickling in closed tanks combined with fume extraction |
Continuous pickling is carried out in closed tanks with limited entry and exit openings for the steel strip or wire. The fumes from the pickling tanks are extracted. |
b. |
Batch pickling in tanks equipped with lids or enclosing hoods combined with fume extraction |
Batch pickling is carried out in tanks equipped with lids or enclosing hoods that can be opened to allow charging of the wire rod coils. The fumes from the pickling tanks are extracted. |
Waste gas treatment |
||
c. |
Wet scrubbing followed by a demister |
See Section 1.7.2. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –10 (35) |
HF |
mg/Nm3 |
< 1 (36) |
SOX |
mg/Nm3 |
< 1 –6 (37) |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –10 (38) |
SOX |
mg/Nm3 |
< 1 –6 (39) |
Technique |
Description |
Applicability |
|
Reduction of generation of emissions |
|||
a. |
Nitric-acid-free pickling of high-alloy steel |
Pickling of high-alloy steel is carried out by fully substituting nitric acid with a strong oxidising agent (e.g. hydrogen peroxide). |
Only applicable to new plants and major plant upgrades. |
b. |
Addition of hydrogen peroxide or urea to the pickling acid |
Hydrogen peroxide or urea is added directly to the pickling acid to reduce NOX emissions. |
Generally applicable. |
Collection of emissions |
|||
c. |
Continuous pickling in closed tanks combined with fume extraction |
Continuous pickling is carried out in closed tanks with limited entry and exit openings for the steel strip or wire. The fumes from the pickling bath are extracted. |
Generally applicable. |
d. |
Batch pickling in tanks equipped with lids or enclosing hoods combined with fume extraction |
Batch pickling is carried out in tanks equipped with lids or enclosing hoods that can be opened to allow charging of the wire rod coils. The fumes from the pickling tanks are extracted. |
Generally applicable. |
Waste gas treatment |
|||
e. |
Wet scrubbing with addition of an oxidising agent (e.g. hydrogen peroxide) |
See Section 1.7.2. An oxidising agent (e.g. hydrogen peroxide) is added to the scrubbing solution to reduce NOX emissions. When using hydrogen peroxide, the nitric acid formed can be recycled to the pickling tanks. |
Generally applicable. |
f. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. |
g. |
Optimisation of the SCR design and operation |
See Section 1.7.2. |
Only applicable where SCR is used for the reduction of NOX emissions. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
10 –200 |
1.1.7.4.
Emissions to air from hot dipping
Technique |
Description |
Applicability |
|||||
Reduction of generation of emissions |
|
||||||
a. |
Low-fume flux |
Ammonium chloride in fluxing agents is partly substituted with other alkali chlorides (e.g. potassium chloride) to reduce dust formation. |
Applicability may be restricted due to product specifications. |
||||
b. |
Minimisation of carry-over of the fluxing solution |
This includes techniques such as:
|
Generally applicable. |
||||
Collection of emissions |
|
||||||
c. |
Air extraction as close as possible to the source |
Air from the kettle is extracted, for example using lateral hood or lip extraction. |
Generally applicable. |
||||
d. |
Enclosed kettle combined with air extraction |
Hot dipping is carried out in an enclosed kettle and air is extracted. |
Applicability to existing plants may be limited where enclosure interferes with an existing transport system for workpieces in batch galvanising. |
||||
Waste gas treatment |
|
||||||
e. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
1.1.7.4.1.
Emissions to air from oiling
Technique |
Description |
|
a. |
Electrostatic oiling |
Oil is sprayed on the metal surface through an electrostatic field, which ensures homogeneous oil application and optimises the quantity of oil applied. The oiling machine is enclosed and oil that does not deposit on the metal surface is recovered and reused within the machine. |
b. |
Contact lubrication |
Roller lubricators, e.g. felt rolls or squeeze rolls, are used in direct contact with the metal surface. |
c. |
Oiling without compressed air |
Oil is applied with nozzles close to the metal surface using high-frequency valves. |
1.1.7.5.
Emissions to air from post-treatment
Technique |
Description |
Applicability |
|||||||||
Collection of emissions |
|||||||||||
a. |
Air extraction as close as possible to the source |
Emissions from the chemical storage tanks and chemical baths are captured, e.g. by using one or a combination of the following techniques:
The captured emissions are then extracted. |
Only applicable when the treatment is carried out by spraying or when volatile substances are used. |
||||||||
b. |
Closed tanks combined with air extraction in the case of continuous post-treatment |
Phosphating and passivation are carried out in closed tanks and the air is extracted from the tanks. |
Only applicable when the treatment is carried out by spraying or when volatile substances are used. |
||||||||
Waste gas treatment |
|||||||||||
c. |
Wet scrubbing |
See Section 1.7.2. |
Generally applicable. |
||||||||
d. |
Demister |
See Section 1.7.2. |
Generally applicable. |
1.1.7.6.
Emissions to air from acid recovery
Technique |
Description |
Applicability |
|
a. |
Use of a fuel or a combination of fuels with low sulphur content and/or low NOX formation potential |
See BAT 21 and BAT 22 (a). |
Generally applicable. |
b. |
Combustion optimisation |
See Section 1.7.2. Generally used in combination with other techniques. |
Generally applicable. |
c. |
Low-NOX burners |
See Section 1.7.2. |
Applicability may be restricted at existing plants by design and/or operational constraints. |
d. |
Wet scrubbing followed by a demister |
See Section 1.7.2. In the case of mixed acid recovery, an alkali is added to the scrubbing solution to remove traces of HF and/or an oxidising agent (e.g. hydrogen peroxide) is added to the scrubbing solution to reduce NOX emissions. When using hydrogen peroxide, the nitric acid formed can be recycled to the pickling tanks. |
Generally applicable. |
e. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. |
f. |
Optimisation of the SCR design and operation |
See Section 1.7.2. |
Only applicable where SCR is used for the reduction of NOX emissions. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –15 |
HCl |
mg/Nm3 |
< 2 –15 |
SO2 |
mg/Nm3 |
< 10 |
NOX |
mg/Nm3 |
50 -180 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HF |
mg/Nm3 |
< 1 |
NOX |
mg/Nm3 |
50 –100 (40) |
Dust |
mg/Nm3 |
< 2 –10 |
1.1.8.
Emissions to water
Description
Technique(41) |
Typical pollutants targeted |
|
Preliminary, primary and general treatment, e.g. |
||
a. |
Equalisation |
All pollutants |
b. |
Neutralisation |
Acids, alkalis |
c. |
Physical separation, e.g. screens, sieves, grit separators, grease separators, hydrocyclones, oil-water separation or primary settlement tanks |
Gross solids, suspended solids, oil/grease |
Physico-chemical treatment, e.g. |
||
d. |
Adsorption |
Adsorbable dissolved non-biodegradable or inhibitory pollutants, e.g. hydrocarbons, mercury |
e. |
Chemical precipitation |
Precipitable dissolved non-biodegradable or inhibitory pollutants, e.g. metals, phosphorus, fluoride |
f. |
Chemical reduction |
Reducible dissolved non-biodegradable or inhibitory pollutants, e.g. hexavalent chromium |
g. |
Nanofiltration/reverse osmosis |
Soluble non-biodegradable or inhibitory pollutants, e.g. salts, metals |
Biological treatment, e.g. |
||
h. |
Aerobic treatment |
Biodegradable organic compounds |
Solids removal, e.g. |
||
i. |
Coagulation and flocculation |
Suspended solids and particulate-bound metals |
j. |
Sedimentation |
|
k. |
Filtration (e.g. sand filtration, microfiltration, ultrafiltration) |
|
l. |
Flotation |
Substance/Parameter |
Unit |
BAT-AEL (42) |
Process(es) to which the BAT-AEL applies |
|
Total suspended solids (TSS) |
mg/l |
5–30 |
All processes |
|
Total organic carbon (TOC)(43) |
mg/l |
10–30 |
All processes |
|
Chemical oxygen demand (COD)(43) |
mg/l |
30–90 |
All processes |
|
Hydrocarbon oil index (HOI) |
mg/l |
0,5–4 |
All processes |
|
Metals |
Cd |
μg/l |
1-5 |
All processes(44) |
Cr |
mg/l |
0,01–0,1(45) |
All processes(44) |
|
Cr(VI) |
μg/l |
10–50 |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
|
Fe |
mg/l |
1–5 |
All processes |
|
Hg |
μg/l |
0,1–0,5 |
All processes(44) |
|
Ni |
mg/l |
0,01–0,2(46) |
All processes(44) |
|
Pb |
μg/l |
5–20(47) (48) |
All processes(44) |
|
Sn |
mg/l |
0,01–0,2 |
Hot dip coating using tin |
|
Zn |
mg/l |
0,05–1 |
All processes(44) |
|
Total phosphorus (Total P) |
mg/l |
0,2–1 |
Phosphating |
|
Fluoride (F-) |
mg/l |
1–15 |
Pickling with acid mixtures containing hydrofluoric acid |
Substance/Parameter |
Unit |
BAT-AEL (49) (50) |
Process(es) to which the BAT-AEL applies |
|
Hydrocarbon oil index (HOI) |
mg/l |
0,5 –4 |
All processes |
|
Metals |
Cd |
μg/l |
1 –5 |
All processes(51) |
Cr |
mg/l |
0,01 –0,1 (52) |
All processes(51) |
|
Cr(VI) |
μg/l |
10 –50 |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
|
Fe |
mg/l |
1 –5 |
All processes |
|
Hg |
μg/l |
0,1 –0,5 |
All processes(51) |
|
Ni |
mg/l |
0,01 –0,2 (53) |
All processes(51) |
|
Pb |
μg/l |
5 –20 (54) (55) |
All processes(51) |
|
Sn |
mg/l |
0,01 –0,2 |
Hot dip coating using tin |
|
Zn |
mg/l |
0,05 –1 |
All processes(51) |
|
Fluoride (F-) |
mg/l |
1 –15 |
Pickling with acid mixtures containing hydrofluoric acid |
1.1.9.
Noise and vibrations
Applicability
Technique |
Description |
Applicability |
|||||||||||
a. |
Appropriate location of equipment and buildings |
Noise levels can be reduced by increasing the distance between the emitter and the receiver, by using buildings as noise screens and by relocating the exits or entrances of the buildings. |
For existing plants, the relocation of equipment and the exits or entrances of the buildings may not be applicable due to a lack of space and/or excessive costs. |
||||||||||
b. |
Operational measures |
These include techniques such as:
|
Generally applicable. |
||||||||||
c. |
Low-noise equipment |
This includes techniques such as direct drive motors, low-noise compressors, pumps and fans. |
|
||||||||||
d. |
Noise and vibration control equipment |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
e. |
Noise abatement |
Inserting obstacles between emitters and receivers (e.g. protection walls, embankments and buildings). |
Only applicable to existing plants, as the design of new plants should make this technique unnecessary. For existing plants, the insertion of obstacles may not be applicable due to a lack of space. |
1.1.10.
Residues
Technique |
Description |
Applicability |
|||||
a. |
Residues management plan |
A residues management plan is part of the EMS (see BAT 1) and is a set of measures aiming to (1) minimise the generation of residues; (2) optimise the reuse, recycling and/or recovery of residues; and (3) ensure the proper disposal of waste. The residues management plan may be integrated in the overall residues management plan of a larger installation (e.g. for iron and steel production). |
The level of detail and the degree of formalisation of the residues management plan will generally be related to the nature, scale and complexity of the installation. |
||||
b. |
Pretreatment of oily mill scale for further use |
This includes techniques such as:
|
Generally applicable. |
||||
c. |
Use of mill scale |
Mill scale is collected and used on site or off site, e.g. in iron and steel production or in cement production. |
Generally applicable. |
||||
d. |
Use of metallic scrap |
Metallic scrap from mechanical processes (e.g. from trimming and finishing) is used in iron and steel production. This may take place on site or off site. |
Generally applicable. |
||||
e. |
Recycling of metal and metal oxides from dry waste gas cleaning |
The coarse fraction of metal and metal oxides originating from dry cleaning (e.g. fabric filters) of waste gases from mechanical processes (e.g. scarfing or grinding) is selectively isolated using mechanical techniques (e.g. sieves) or magnetic techniques and recycled, e.g. to iron and steel production. This may take place on site or off site. |
Generally applicable. |
||||
f. |
Use of oily sludge |
Residual oily sludge, e.g. from degreasing, is dewatered to recover the oil contained therein for material or energy recovery. If the water content is low, the sludge can be directly used. This may take place on site or off site. |
Generally applicable. |
||||
g. |
Thermal treatment of hydroxide sludge from the recovery of mixed acid |
Sludge generated from the recovery of mixed acid is thermally treated in order to produce a material rich in calcium fluoride that can be used in argon oxygen decarburisation converters. |
Applicability may be restricted by a lack of space. |
||||
h. |
Recovery and reuse of shot blast media |
Where mechanical descaling is carried out by shot blasting, the shot blast media are separated from the scale and reused. |
Generally applicable. |
Technique |
Description |
Applicability |
|
a. |
Recycling of fabric filter dust |
Dust from fabric filters containing ammonium chloride and zinc chloride is collected and reused, e.g. to produce fluxing agents. This may take place on site or off site. |
Only applicable in hot dipping after fluxing. Applicability may be restricted depending on the availability of a market. |
b. |
Recycling of zinc ash and top dross |
Metallic zinc is recovered from zinc ash and top dross by melting in recovery furnaces. The remaining zinc-containing residue is used, e.g. for zinc oxide production. This may take place on site or off site. |
Generally applicable. |
c. |
Recycling of bottom dross |
Bottom dross is used, e.g. in the non-ferrous metals industries to produce zinc. This may take place on site or off site. |
Generally applicable. |
Technique |
Description |
|
a. |
Cleaning and reuse of grinding emulsion |
Grinding emulsions are treated using lamellar or magnetic separators or using a sedimentation/clarification process in order to remove the grinding sludge and reuse the grinding emulsion. |
b. |
Treatment of grinding sludge |
Treatment of grinding sludge by magnetic separation for recovery of metal particles and recycling of metals, e.g. to iron and steel production. |
c. |
Recycling of worn working rolls |
Worn working rolls which are unsuitable for texturing are recycled to iron and steel production or returned to the manufacturer for refabrication. |
1.2.
BAT conclusions for hot rolling
1.2.1.
Energy efficiency
Technique |
Description |
Applicability |
|
a. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
See Section 1.7.1. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
b. |
Hot/direct charging |
Continuous-cast steel products are directly charged hot into the reheating furnaces. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
c. |
Heat recovery from skids cooling |
Steam produced when cooling the skids supporting the feedstock in the reheating furnaces is extracted and used in other processes of the plant. |
Applicability to existing plants may be restricted by a lack of space and/or of a suitable steam demand. |
d. |
Heat conservation during transfer of feedstock |
Insulated covers are used between the continuous caster and the reheating furnace, and between the roughing mill and the finishing mill. |
Generally applicable within the limitations of the plant layout. |
e. |
Coil boxes |
See Section 1.7.1. |
Generally applicable. |
f. |
Coil recovery furnaces |
Coil recovery furnaces are used as an addition to coil boxes to restore the rolling temperature of coils and return them to a normal rolling sequence in the event of rolling mill interruptions. |
Generally applicable. |
g. |
Sizing press |
See BAT 39 (a). A sizing press is used to increase the energy efficiency in feedstock heating because it enables the hot charging rate to be increased. |
Only applicable to new plants and major plant upgrades for hot strip mills. |
Technique |
Description |
Applicability |
|
a. |
Sizing press |
The use of a sizing press before the roughing mill enables the hot charging rate to be significantly increased and results in a more uniform width reduction both at the edges and centre of the product. The shape of the final slab is nearly rectangular, reducing significantly the number of rolling passes necessary to reach product specifications. |
Only applicable to hot strip mills. Only applicable to new plants and major plant upgrades. |
b. |
Computer-aided rolling optimisation |
The thickness reduction is controlled using a computer to minimise the number of rolling passes. |
Generally applicable. |
c. |
Reduction of the rolling friction |
See Section 1.7.1. |
Only applicable to hot strip mills. |
d. |
Coil boxes |
See Section 1.7.1. |
Generally applicable. |
e. |
Three-roll stand |
A three-roll stand increases the section reduction per pass, resulting in an overall reduction of the number of rolling passes required for producing wire rods and bars. |
Generally applicable. |
f. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
See Section 1.7.1. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
Steel products at the end of the rolling process |
Unit |
BAT-AEPL (yearly average) |
Hot rolled coils (strips), heavy plates |
MJ/t |
100–400 |
Bars, rods |
MJ/t |
100–500(56) |
Beams, billets, rails, tubes |
MJ/t |
100–300 |
1.2.2.
Material efficiency
Technique |
Description |
Applicability |
|
a. |
Computer-aided quality control |
The quality of slabs is controlled by a computer which allows the adjustment of the casting conditions to minimise surface defects and enables manual scarfing of the damaged area(s) only rather than scarfing of the entire slab. |
Only applicable to plants with continuous casting. |
b. |
Slab slitting |
The slabs (often cast in multiple widths) are slit before hot rolling by means of slitting devices, slit rolling or torches either manually operated or mounted on a machine. |
May not be applicable for slabs produced from ingots. |
c. |
Edging or trimming of wedge-type slabs |
Wedge-type slabs are rolled under special settings where the wedge is eliminated by edging (e.g. using automatic width control or a sizing press) or by trimming. |
May not be applicable for slabs produced from ingots. Only applicable to new plants and major plant upgrades. |
Technique |
Description |
|
a. |
Crop optimisation |
The cropping of the feedstock after roughing is controlled by a shape measurement system (e.g. camera) in order to minimise the amount of metal cut off. |
b. |
Control of the feedstock shape during rolling |
Any deformations of the feedstock during rolling are monitored and controlled in order to ensure that the rolled steel has as rectangular a shape as possible and to minimise the need for trimming. |
1.2.3.
Emissions to air
Technique |
Description |
Applicability |
|
Collection of emissions |
|
||
a. |
Enclosed scarfing and grinding combined with air extraction |
Scarfing (other than manual scarfing) and grinding operations are carried out completely enclosed (e.g. under closed hoods) and air is extracted. |
Generally applicable. |
b. |
Air extraction as close as possible to the emission source |
Emissions from slitting, descaling, roughing, rolling, finishing, levelling and welding are collected, for example using hood or lip extraction. For roughing and rolling, in the case of low levels of dust generation, e.g. below 100 g/h, water sprays can be used instead (see BAT 43). |
May not be applicable for welding in the case of low levels of dust generation, e.g. below 50 g/h. |
Waste gas treatment |
|
||
c. |
Electrostatic precipitator |
See Section 1.7.2. |
Generally applicable. |
d. |
Fabric filter |
See Section 1.7.2. |
May not be applicable in the case of waste gases with a high moisture content. |
e. |
Wet scrubbing |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 (57) |
Ni |
0,01 –0,1 (58) |
|
Pb |
0,01 –0,035 (58) |
Description
1.3.
BAT conclusions for cold rolling
1.3.1.
Energy efficiency
Technique |
Description |
Applicability |
|
a. |
Continuous rolling for low-alloy and alloy steel |
Continuous rolling (e.g. using tandem mills) is employed instead of conventional discontinuous rolling (e.g. using reversing mills), allowing for stable feed and less frequent start-ups and shutdowns. |
Only applicable to new plants and major plant upgrades. Applicability may be restricted due to product specifications. |
b. |
Reduction of the rolling friction |
See Section 1.7.1. |
Generally applicable. |
c. |
Computer-aided rolling optimisation |
The thickness reduction is controlled using a computer to minimise the number of rolling passes. |
Generally applicable. |
Steel products at the end of the rolling process |
Unit |
BAT-AEPL (Yearly average) |
Cold rolled coils |
MJ/t |
100 –300 (59) |
Packaging steel |
MJ/t |
250 –400 |
1.3.2.
Material efficiency
Technique |
Description |
Applicability |
|||||||||
a. |
Monitoring and adjustment of the rolling emulsion quality |
Important characteristics of the rolling emulsion (e.g. oil concentration, pH, emulsion droplet size, saponification index, acid concentration, concentration of iron fines, concentration of bacteria) are monitored regularly or continuously to detect anomalies in the emulsion quality and take corrective action, if needed. |
Generally applicable. |
||||||||
b. |
Prevention of contamination of the rolling emulsion |
Contamination of the rolling emulsion is prevented by techniques such as:
|
Generally applicable. |
||||||||
c. |
Cleaning and reuse of the rolling emulsion |
Particulate matter (e.g. dust, steel slivers and scale) contaminating the rolling emulsion is removed in a cleaning circuit (usually based on sedimentation combined with filtration and/or magnetic separation) in order to maintain the emulsion quality and the treated rolling emulsion is reused. The degree of reuse is limited by the content of impurities in the emulsion. |
Applicability may be restricted due to product specifications. |
||||||||
d. |
Optimal choice of rolling oil and emulsion system |
Rolling oil and emulsion systems are carefully selected to provide the optimum performance for the given process and product. Relevant characteristics to be considered are, for example:
|
Generally applicable. |
||||||||
e. |
Minimisation of oil/rolling emulsion consumption |
The consumption of oil/rolling emulsion is minimised by using techniques such as:
|
Generally applicable. |
1.3.3.
Emissions to air
Technique |
Description |
Applicability |
|
Collection of emissions |
|||
a. |
Air extraction as close as possible to the emission source |
Emissions from decoiling, mechanical predescaling, levelling and welding are collected, for example using hood or lip extraction. |
May not be applicable for welding in the case of low levels of dust generation, e.g. below 50 g/h. |
Waste gas treatment |
|||
b. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
Ni |
0,01 –0,1 (60) |
|
Pb |
≤ 0,003 (60) |
Technique |
Description |
Applicability |
|
a. |
Dry tempering |
No water or lubricants are used for tempering. |
Not applicable to tinplate packaging products and other products with high elongation requirements. |
b. |
Low-volume lubrication in wet tempering |
Low-volume lubrication systems are employed to supply precisely the amount of lubricants needed for reducing the friction between the working rolls and the feedstock. |
Applicability may be restricted due to product specifications in the case of stainless steel. |
Technique |
Description |
|
Collection of emissions |
||
a. |
Air extraction as close as possible to the emission source |
Emissions from rolling, wet tempering and finishing are collected, for example using hood or lip extraction. |
Waste gas treatment |
||
b. |
Demister |
See Section 1.7.2. |
c. |
Oil mist separator |
Separators containing baffle packing, impingement plates or mesh pads are used to separate the oil from the extracted air. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
TVOC |
mg/Nm3 |
< 3–8 |
1.4.
BAT conclusions for wire drawing
1.4.1.
Energy efficiency
Description
1.4.2.
Material efficiency
Description
1.4.3.
Emissions to air
Technique |
Description |
|
Reduction of generation of emissions |
||
a. |
Minimisation of carry-over of lead |
Techniques include the use of anthracite gravel to scrape off lead and the coupling of the lead bath with in-line pickling. |
b. |
Floating protective layer or tank cover |
See BAT 49. Floating protective layers and tank covers also reduce emissions to air. |
Collection of emissions |
||
c. |
Air extraction as close as possible to the emission source |
Emissions from the lead bath are collected, for example using hood or lip extraction. |
Waste gas treatment |
||
d. |
Fabric filter |
See Section 1.7.2. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2–5 |
Pb |
mg/Nm3 |
≤ 0,5 |
Technique |
Description |
Applicability |
|
Collection of emissions |
|||
a. |
Enclosed drawing machine combined with air extraction |
The entire drawing machine is enclosed in order to avoid dispersion of dust and air is extracted. |
Applicability to existing plants may be restricted by the plant layout. |
b. |
Air extraction as close as possible to the emission source |
Emissions from the drawing machine are collected, for example using hood or lip extraction. |
Generally applicable. |
Waste gas treatment |
|||
c. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
Technique |
Description |
|
Collection of emissions |
||
a. |
Air extraction as close as possible to the emission source |
Emissions from oil quench baths are collected, for example using lateral hood or lip extraction. |
Waste gas treatment |
||
b. |
Demister |
See Section 1.7.2. |
1.4.4.
Residues
1.5.
BAT conclusions for hot dip coating of sheets and wires
1.5.1.
Material efficiency
Technique |
Description |
|
a. |
Air knives for coating thickness control |
After leaving the molten zinc bath, air jets stretching over the width of the strip blow the surplus coating metal off the strip surface back into the galvanising kettle. |
b. |
Stabilisation of the strip |
The efficiency of the excess coating removal by air knives is improved by limiting the oscillations of the strip, e.g. by increasing strip tension, using low-vibration pot bearings, using electromagnetic stabilisers. |
Technique |
Description |
|
a. |
Air or nitrogen wiping |
After leaving the molten zinc bath, circular air or gas jets around the wire blow the surplus coating metal off the wire surface back into the galvanising kettle. |
b. |
Mechanical wiping |
After leaving the molten zinc bath, the wire is passed through wiping equipment/material (e.g. pads, nozzles, rings, charcoal granulate) which takes the surplus coating metal off the wire surface back into the galvanising kettle. |
1.6.
BAT conclusions for batch galvanising
1.6.1.
Residues
Description
Applicability
Description
1.6.2.
Material efficiency
Technique |
Description |
|
a. |
Optimised dipping time |
The dipping time is limited to the duration required to achieve the coating thickness specifications. |
b. |
Slow withdrawal of workpieces from the bath |
By withdrawing the galvanised workpieces slowly from the galvanising kettle, the drain-off is improved and zinc splashes are reduced. |
1.6.3.
Emissions to air
Technique |
Description |
Applicability |
|||||
Collection of emissions |
|||||||
a. |
Enclosed pretreatment section with extraction |
The entire pretreatment section (e.g. degreasing, pickling, fluxing) is encapsulated and the fumes are extracted from the enclosure. |
Only applicable to new plants and major plant upgrades |
||||
b. |
Extraction by lateral hood or lip extraction |
Acid fumes from the pickling tanks are extracted using lateral hoods or lip extraction at the edge of the pickling tanks. This may also include emissions from degreasing tanks. |
Applicability in existing plants may be restricted by a lack of space. |
||||
Waste gas treatment |
|||||||
c. |
Wet scrubbing followed by a demister |
See Section 1.7.2. |
Generally applicable |
||||
Reduction of generation of emissions |
|||||||
d. |
Restricted operating range for hydrochloric acid open pickling baths |
Hydrochloric acid baths are strictly operated within the temperature and HCl concentration range determined by the following conditions:
where T is the pickling acid temperature expressed in °C and w the HCl concentration expressed in wt-%. The bath temperature is measured at least once every day. The HCl concentration in the bath is measured every time fresh acid is replenished and in any case at least once every week. To limit evaporation, movement of air across the bath surfaces (e.g. due to ventilation) is minimised. |
Generally applicable |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –6 |
1.6.4.
Waste water discharge
Description
1.7.
Descriptions of techniques
1.7.1.
Techniques to increase energy efficiency
Technique |
Description |
Coil boxes |
Insulated boxes are installed between the roughing mill and the finishing mill to minimise temperature losses from feedstock during coiling/uncoiling processes and allow for lower rolling forces in hot strip mills. |
Combustion optimisation |
Measures taken to maximise the efficiency of energy conversion in the furnace while minimising emissions (in particular of CO). This is achieved by a combination of techniques including good design of the furnace, optimisation of the temperature (e.g. efficient mixing of the fuel and combustion air) and residence time in the combustion zone, and use of furnace automation and control. |
Flameless combustion |
Flameless combustion is achieved by injecting fuel and combustion air separately into the combustion chamber of the furnace at high velocity to suppress flame formation and reduce the formation of thermal NOX while creating a more uniform heat distribution throughout the chamber. Flameless combustion can be used in combination with oxy-fuel combustion. |
Furnace automation and control |
The heating process is optimised by using a computer system controlling in real time key parameters such as furnace and feedstock temperature, the air to fuel ratio and the furnace pressure. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
Thin slabs and beam blanks are produced by combining casting and rolling in one process step. The need to reheat the feedstock before rolling and the number of rolling passes are reduced. |
Optimisation of the SNCR/SCR design and operation |
Optimisation of the reagent to NOX ratio over the cross-section of the furnace or duct, of the size of the reagent drops and of the temperature window in which the reagent is injected. |
Oxy-fuel combustion |
Combustion air is replaced fully or partially with pure oxygen. Oxy-fuel combustion can be used in combination with flameless combustion. |
Preheating of combustion air |
Reuse of part of the heat recovered from the combustion flue-gas to preheat the air used in combustion. |
Process gas management system |
A system that enables iron and steel process gases to be directed to the feedstock heating furnaces, depending on their availability. |
Recuperative burner |
Recuperative burners employ different types of recuperators (e.g. heat exchangers with radiation, convection, compact or radiant tube designs) to directly recover heat from the flue-gases, which are then used to preheat the combustion air. |
Reduction of the rolling friction |
Rolling oils are carefully selected. Pure oil and/or emulsion systems are used to reduce the friction between the working rolls and the feedstock and to ensure minimal oil consumption. In HR, this is usually carried out in the first stands of the finishing mill. |
Regenerative burner |
Regenerative burners consist of two burners which are operated alternately and which contain beds of refractory or ceramic materials. While one burner is in operation, the heat of the flue-gas is absorbed by the refractory or ceramic materials of the other burner and then used to preheat the combustion air. |
Waste heat recovery boiler |
Heat from hot flue-gases is used to generate steam using a waste heat recovery boiler. The generated steam is used in other processes of the plant, for supplying a steam network or for generating electricity in a power plant. |
1.7.2.
Techniques to reduce emissions to air
Technique |
Description |
Combustion optimisation |
See Section 1.7.1. |
Demister |
Demisters are filter devices that remove entrained liquid droplets from a gas stream. They consist of a woven structure of metal or plastic wires, with a high specific surface area. Through their momentum, small droplets present in the gas stream impinge against the wires and coalesce into bigger drops. |
Electrostatic precipitator |
Electrostatic precipitators (ESPs) operate such that particles are charged and separated under the influence of an electrical field. Electrostatic precipitators are capable of operating under a wide range of conditions. Abatement efficiency may depend on the number of fields, residence time (size), and upstream particle removal devices. They generally include between two and five fields. Electrostatic precipitators can be of the dry or of the wet type depending on the technique used to collect the dust from the electrodes. Wet ESPs are typically used at the polishing stage to remove residual dust and droplets after wet scrubbing. |
Fabric filter |
Fabric filters, often referred to as bag filters, are constructed from porous woven or felted fabric through which gases are passed to remove particles. The use of a fabric filter requires the selection of a fabric suitable for the characteristics of the waste gas and the maximum operating temperature. |
Flameless combustion |
See Section 1.7.1. |
Furnace automation and control |
See Section 1.7.1. |
Low-NOX burner |
The technique (including ultra-low-NOX burners) is based on the principles of reducing peak flame temperatures. The air/fuel mixing reduces the availability of oxygen and reduces the peak flame temperature, thus retarding the conversion of fuel-bound nitrogen to NOX and the formation of thermal NOX, while maintaining high combustion efficiency. |
Optimisation of the SNCR/SCR design and operation |
See Section 1.7.1. |
Oxy-fuel combustion |
See Section 1.7.1. |
Selective catalytic reduction (SCR) |
The SCR technique is based on the reduction of NOX to nitrogen in a catalytic bed by reaction with urea or ammonia at an optimum operating temperature of around 300–450 °C. Several layers of catalyst may be applied. A higher NOX reduction is achieved with the use of several catalyst layers. |
Selective non-catalytic reduction (SNCR) |
SNCR is based on the reduction of NOX to nitrogen by reaction with ammonia or urea at a high temperature. The operating temperature window is maintained between 800 °C and 1 000 °C for optimal reaction. |
Wet scrubbing |
The removal of gaseous or particulate pollutants from a gas stream via mass transfer to a liquid solvent, often water or an aqueous solution. It may involve a chemical reaction (e.g. in an acid or alkaline scrubber). In some cases, the compounds may be recovered from the solvent. |
1.7.3.
Techniques to reduce emissions to water
Technique |
Description |
Adsorption |
The removal of soluble substances (solutes) from the waste water by transferring them to the surface of solid, highly porous particles (typically activated carbon). |
Aerobic treatment |
The biological oxidation of dissolved organic pollutants with oxygen using the metabolism of microorganisms. In the presence of dissolved oxygen, injected as air or pure oxygen, the organic components are mineralised into carbon dioxide and water or are transformed into other metabolites and biomass. |
Chemical precipitation |
The conversion of dissolved pollutants into an insoluble compound by adding chemical precipitants. The solid precipitates formed are subsequently separated by sedimentation, air flotation or filtration. If necessary, this may be followed by microfiltration or ultrafiltration. Multivalent metal ions (e.g. calcium, aluminium, iron) are used for phosphorus precipitation. |
Chemical reduction |
The conversion of pollutants by chemical reducing agents into similar but less harmful or hazardous compounds. |
Coagulation and flocculation |
Coagulation and flocculation are used to separate suspended solids from waste water and are often carried out in successive steps. Coagulation is carried out by adding coagulants with charges opposite to those of the suspended solids. Flocculation is carried out by adding polymers, so that collisions of microfloc particles cause them to bond to produce larger flocs. |
Equalisation |
Balancing of flows and pollutant loads at the inlet of the final waste water treatment by using central tanks. Equalisation may be decentralised or carried out using other management techniques. |
Filtration |
The separation of solids from waste water by passing them through a porous medium, e.g. sand filtration, microfiltration and ultrafiltration. |
Flotation |
The separation of solid or liquid particles from waste water by attaching them to fine gas bubbles, usually air. The buoyant particles accumulate at the water surface and are collected with skimmers. |
Nanofiltration |
A filtration process in which membranes with pore sizes of approximately 1 nm are used. |
Neutralisation |
The adjustment of the pH of waste water to a neutral level (approximately 7) by the addition of chemicals. Sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) is generally used to increase the pH, whereas sulphuric acid (H2SO4), hydrochloric acid (HCl) or carbon dioxide (CO2) is generally used to decrease the pH. The precipitation of some substances may occur during neutralisation. |
Physical separation |
The separation of gross solids, suspended solids and/or metal particles from the waste water using for example screens, sieves, grit separators, grease separators, hydrocyclones, oil-water separation or primary settlement tanks. |
Reverse osmosis |
A membrane process in which a pressure difference applied between the compartments separated by the membrane causes water to flow from the more concentrated solution to the less concentrated one. |
Sedimentation |
The separation of suspended particles and suspended material by gravitational settling. |
COMMISSION IMPLEMENTING DECISION (EU) 2022/2110
of 11 October 2022
establishing the best available techniques (BAT) conclusions, under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions, for the ferrous metals processing industry
(notified under document C(2022) 7054)
(Text with EEA relevance)
Article 1
Article 2
ANNEX
1.
BEST AVAILABLE TECHNIQUES (BAT) CONCLUSIONS FOR THE FERROUS METALS PROCESSING INDUSTRY
SCOPE
DEFINITIONS
General terms |
|||||
Term used |
Definition |
||||
Batch galvanising |
Discontinuous immersion of steel workpieces in a bath containing molten zinc to coat their surface with zinc. This also includes any directly associated pre- and post-treatment processes (e.g. degreasing and passivation). |
||||
Bottom dross |
A reaction product of molten zinc with iron or with iron salts carried over from pickling or fluxing. This reaction product sinks to the bottom of the zinc bath. |
||||
Carbon steel |
Steel in which the content of each alloy element is less than 5 wt-%. |
||||
Channelled emissions |
Emissions of pollutants into the environment through any kind of duct, pipe, stack, etc. |
||||
Cold rolling |
Compression of steel by rollers at ambient temperatures to change its characteristics (e.g. size, shape and/or metallurgical properties). This also includes any directly associated pre- and post-treatment processes (e.g. pickling, annealing and oiling). |
||||
Continuous measurement |
Measurement using an automated measuring system permanently installed on site. |
||||
Direct discharge |
Discharge to a receiving water body without further downstream waste water treatment. |
||||
Existing plant |
A plant that is not a new plant. |
||||
Feedstock |
Any steel input (unprocessed or partly processed) or workpieces entering a production process step. |
||||
Feedstock heating |
Any process step where feedstock is heated. This does not include feedstock drying or the heating of the galvanising kettle. |
||||
Ferrochromium |
An alloy of chromium and iron typically containing between 50 wt-% and 70 wt-% chromium. |
||||
Flue-gas |
The exhaust gas exiting a combustion unit. |
||||
High-alloy steel |
Steel in which the content of one or more alloy elements is 5 wt-% or more. |
||||
Hot dip coating |
Continuous immersion of steel sheets or wires through a bath containing molten metal(s), e.g. zinc and/or aluminium, to coat the surface with metal(s). This also includes any directly associated pre- and post-treatment processes (e.g. pickling and phosphating). |
||||
Hot rolling |
Compression of heated steel by rollers at temperatures typically ranging from 1 050 °C to 1 300 °C to change its characteristics (e.g. size, shape and/or metallurgical properties). This includes hot ring rolling and hot rolling of seamless tubes as well as any directly associated pre- and post-treatment processes (e.g. scarfing, finishing, pickling and oiling). |
||||
Indirect discharge |
A discharge that is not a direct discharge. |
||||
Intermediate heating |
Heating of the feedstock between the hot rolling stages. |
||||
Iron and steel process gases |
Blast furnace gas, basic oxygen furnace gas, coke oven gas or mixtures thereof originating from iron and steel production. |
||||
Leaded steel |
Steel grades in which the content of lead added is typically between 0,15 wt-% and 0,35 wt-%. |
||||
Major plant upgrade |
A major change in the design or technology of a plant with major adjustments or replacements of the process and/or abatement technique(s) and associated equipment. |
||||
Mass flow |
The mass of a given substance or parameter which is emitted over a defined period of time. |
||||
Mill scale |
Iron oxides formed on the surface of steel when oxygen reacts with hot metal. This occurs immediately after casting, during reheating and hot rolling. |
||||
Mixed acid |
A mixture of hydrofluoric acid and nitric acid. |
||||
New plant |
A plant first permitted at the site of the installation following the publication of these BAT conclusions or a complete replacement of a plant following the publication of these BAT conclusions. |
||||
Periodic measurement |
Measurement at specified time intervals using manual or automated methods. |
||||
Plant |
All parts of an installation covered by the scope of these BAT conclusions and any other directly associated activities which have an effect on consumption and/or emissions. Plants may be new plants or existing plants. |
||||
Post-heating |
Heating of the feedstock after hot rolling. |
||||
Process chemicals |
Substances and/or mixtures as defined in Article 3 of Regulation (EC) No 1907/2006 of the European Parliament and of the Council(1) and used in the process(es). |
||||
Recovery |
Recovery as defined in Article 3(15) of Directive 2008/98/EC of the European Parliament and of the Council(2). The recovery of spent acids includes their regeneration, reclamation and recycling. |
||||
Regalvanising |
The processing of used galvanised articles (e.g. highway guard rails) that are returned to be galvanised after long service periods. Processing of these articles requires additional process steps due to the presence of partly corroded surfaces or the need to remove any residual zinc coating. |
||||
Reheating |
Heating of the feedstock before hot rolling. |
||||
Residue |
Substance or object generated by the activities covered by the scope of these BAT conclusions as waste or by-product. |
||||
Sensitive receptor |
Areas which need special protection, such as:
|
||||
Stainless steel |
High-alloy steel which contains chromium typically within the range 10–23 wt-%. It includes austenitic steel, which also contains nickel typically within the range 8–10 wt-%. |
||||
Top dross |
In hot dipping, the oxides formed on the surface of the molten zinc bath by reaction of iron and aluminium. |
||||
Valid hourly (or half-hourly) average |
An hourly (or half-hourly) average is considered valid when there is no maintenance or malfunction of the automated measuring system. |
||||
Volatile substance |
A substance capable of readily changing from a solid or liquid form to a vapour, having a high vapour pressure and a low boiling point (e.g. HCl). This includes volatile organic compounds as defined in Article 3(45) of Directive 2010/75/EU. |
||||
Wire drawing |
Drawing of steel rods or wires through dies to reduce their diameter. This also includes any directly associated pre- and post-treatment processes (e.g. wire rod pickling and feedstock heating after drawing). |
||||
Zinc ash |
A mixture comprising zinc metal, zinc oxide and zinc chloride that is formed on the surface of the molten zinc bath. |
Pollutants and parameters |
|
Term used |
Definition |
B |
The sum of boron and its compounds, dissolved or bound to particles, expressed as B. |
Cd |
The sum of cadmium and its compounds, dissolved or bound to particles, expressed as Cd. |
CO |
Carbon monoxide. |
COD |
Chemical oxygen demand. Amount of oxygen needed for the total chemical oxidation of the organic matter to carbon dioxide using dichromate. COD is an indicator for the mass concentration of organic compounds. |
Cr |
The sum of chromium and its compounds, dissolved or bound to particles, expressed as Cr. |
Cr(VI) |
Hexavalent chromium, expressed as Cr(VI), includes all chromium compounds where the chromium is in the oxidation state +6. |
Dust |
Total particulate matter (in air). |
Fe |
The sum of iron and its compounds, dissolved or bound to particles, expressed as Fe. |
F- |
Dissolved fluoride, expressed as F-. |
HCl |
Hydrogen chloride. |
HF |
Hydrogen fluoride. |
Hg |
The sum of mercury and its compounds, dissolved or bound to particles, expressed as Hg. |
HOI |
Hydrocarbon oil index. The sum of compounds extractable with a hydrocarbon solvent (including long-chain or branched aliphatic, alicyclic, aromatic or alkyl-substituted aromatic hydrocarbons). |
H2SO4 |
Sulphuric acid. |
NH3 |
Ammonia. |
Ni |
The sum of nickel and its compounds, dissolved or bound to particles, expressed as Ni. |
NOX |
The sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2), expressed as NO2. |
Pb |
The sum of lead and its compounds, dissolved or bound to particles, expressed as Pb. |
Sn |
The sum of tin and its compounds, dissolved or bound to particles, expressed as Sn. |
SO2 |
Sulphur dioxide. |
SOX |
The sum of sulphur dioxide (SO2), sulphur trioxide (SO3) and sulphuric acid aerosols, expressed as SO2. |
TOC |
Total organic carbon, expressed as C (in water); includes all organic compounds. |
Total P |
Total phosphorus, expressed as P, includes all inorganic and organic phosphorus compounds. |
TSS |
Total suspended solids. Mass concentration of all suspended solids (in water), measured via filtration through glass fibre filters and gravimetry. |
TVOC |
Total volatile organic carbon, expressed as C (in air). |
Zn |
The sum of zinc and its compounds, dissolved or bound to particles, expressed as Zn. |
ACRONYMS
Acronym |
Definition |
BG |
Batch galvanising |
CMS |
Chemicals management system |
CR |
Cold rolling |
EMS |
Environmental management system |
FMP |
Ferrous metals processing |
HDC |
Hot dip coating |
HR |
Hot rolling |
OTNOC |
Other than normal operating conditions |
SCR |
Selective catalytic reduction |
SNCR |
Selective non-catalytic reduction |
WD |
Wire drawing |
GENERAL CONSIDERATIONS
Best Available Techniques
BAT-AELs and indicative emission levels for emissions to air
Source of emissions |
Reference oxygen level (OR) |
||||
Combustion processes associated with:
|
3 dry vol-% |
||||
All other sources |
No correction for the oxygen level |
Type of measurement |
Averaging period |
Definition |
Continuous |
Daily average |
Average over a period of one day based on valid hourly or half-hourly averages. |
Periodic |
Average over the sampling period |
Average value of three consecutive measurements of at least 30 minutes each(3). |
BAT-AELs for emissions to water
Other environmental performance levels associated with the best available techniques (BAT-AEPLs)
BAT-AEPLs for specific energy consumption (energy efficiency)
BAT-AEPLs for specific water consumption
BAT-AEPLs for specific material consumption
1.1.
General BAT conclusions for the ferrous metals processing industry
1.1.1.
General environmental performance
Applicability
Applicability
Applicability
Technique |
Description |
Applicability |
|||||||||||||||
a. |
Set-up and implementation of a plan for the prevention and control of leaks and spillages |
A plan for the prevention and control of leaks and spillages is part of the EMS (see BAT 1) and includes, but is not limited to:
|
The level of detail of the plan will generally be related to the nature, scale and complexity of the plant, as well as to the type and quantity of liquids used. |
||||||||||||||
b. |
Use of oil-tight trays or cellars |
Hydraulic stations and oil- or grease-lubricated equipment are situated in oil-tight trays or cellars. |
Generally applicable. |
||||||||||||||
c. |
Prevention and handling of acid spillages and leaks |
Storage tanks for both fresh and spent acid are equipped with sealed secondary containment protected with an acid-resistant coating which is regularly inspected for potential damage and cracks. Loading and unloading areas for the acids are designed in such a way that any potential spillages and leaks are contained and sent to on-site treatment (see BAT 31) or off-site treatment. |
Generally applicable. |
1.1.2.
Monitoring
Description
Substance/Parameter |
Specific process(es) |
Sector |
Standard(s) |
Minimum monitoring frequency(4) |
Monitoring associated with |
|
CO |
Feedstock heating(5) |
HR, CR, WD, HDC |
EN 15058(6) |
Once every year |
BAT 22 |
|
Heating of the galvanising kettle(5) |
HDC of wires, BG |
Once every year |
||||
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
|||
Dust |
Feedstock heating |
HR, CR, WD, HDC |
EN 13284-1(6) (7) |
Continuous for any stack with dust mass flows > 2 kg/h Once every 6 months for any stack with dust mass flows between 0,1 kg/h and 2 kg/h Once every year for any stack with dust mass flows < 0,1 kg/h |
BAT 20 |
|
Hot dipping after fluxing |
HDC, BG |
Once every year(8) |
BAT 26 |
|||
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting or by evaporation |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
|||
Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
Once every year |
BAT 42 |
|||
Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year |
BAT 46 |
|||
Lead baths |
WD |
Once every year |
BAT 51 |
|||
Dry drawing |
Once every year |
BAT 52 |
||||
HCl |
Pickling with hydrochloric acid |
HR, CR, HDC, WD |
EN 1911(6) |
Once every year |
BAT 24 |
|
Pickling and stripping with hydrochloric acid |
BG |
Once every year |
BAT 62 |
|||
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors |
HR, CR, HDC, WD |
Once every year |
BAT 29 |
|||
Pickling and stripping with hydrochloric acid in open pickling baths |
BG |
No EN standard available |
Once every year(9) |
BAT 62 |
||
HF |
Pickling with acid mixtures containing hydrofluoric acid |
HR, CR, HDC |
EN standard under development(6) |
Once every year |
BAT 24 |
|
Recovery of mixed acid by spray roasting or by evaporation |
HR, CR |
Once every year |
BAT 29 |
|||
Metals |
Ni |
Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
EN 14385 |
Once every year(10) |
BAT 42 |
Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year(10) |
BAT 46 |
|||
Pb |
Mechanical processing (including slitting, descaling, grinding, roughing, rolling, finishing, levelling), scarfing (other than manual scarfing) and welding |
HR |
Once every year(10) |
BAT 42 |
||
Decoiling, mechanical predescaling, levelling and welding |
CR |
Once every year(10) |
BAT 46 |
|||
Lead baths |
WD |
Once every year |
BAT 51 |
|||
Zn |
Hot dipping after fluxing |
HDC, BG |
Once every year(8) |
BAT 26 |
||
NH3 |
When SNCR and/or SCR is used |
HR, CR, WD, HDC |
EN ISO 21877(6) |
Once every year |
BAT 22, BAT 25, BAT 29 |
|
NOX |
Feedstock heating(5) |
HR, CR, WD, HDC |
EN 14792(6) |
Continuous for any stack with NOX mass flows > 15 kg/h Once every 6 months for any stack with NOX mass flows between 1 kg/h and 15 kg/h Once every year for any stack with NOX mass flows < 1 kg/h |
BAT 22 |
|
Heating of the galvanising kettle(5) |
HDC of wires, BG |
Once every year |
||||
Pickling with nitric acid alone or in combination with other acids |
HR, CR |
Once every year |
BAT 25 |
|||
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors Mixed acid recovery by spray roasting or by evaporation |
HR, CR, WD, HDC |
Once every year |
BAT 29 |
|||
SO2 |
Feedstock heating(11) |
HR, CR, WD, coating of sheets in HDC |
EN 14791(6) |
Continuous for any stack with SO2 mass flows > 10 kg/h Once every 6 months for any stack with SO2 mass flows between 1 kg/h and 10 kg/h Once a year for any stack with SO2 mass flows < 1 kg/h |
BAT 21 |
|
Hydrochloric acid recovery by spray roasting or by using fluidised bed reactors |
HR, CR, HDC, WD |
Once every year(8) |
BAT 29 |
|||
SOX |
Pickling with sulphuric acid |
HR, CR, HDC, WD |
Once every year |
BAT 24 |
||
BG |
||||||
TVOC |
Degreasing |
CR, HDC |
EN 12619(6) |
Once every year(8) |
BAT 23 |
|
Rolling, wet tempering and finishing |
CR |
Once every year(8) |
BAT 48 |
|||
Lead baths |
WD |
Once every year(8) |
— |
|||
Oil quench baths |
WD |
Once every year(8) |
BAT 53 |
Substance/Parameter |
Specific process(es) |
Standard(s) |
Minimum monitoring frequency(12) |
Monitoring associated with |
|
Total suspended solids (TSS)(13) |
All processes |
EN 872 |
Once every week(14) |
BAT 31 |
|
Total organic carbon (TOC)(13) (15) |
All processes |
EN 1484 |
Once every month |
||
Chemical oxygen demand (COD)(13) (15) |
All processes |
No EN standard available |
|||
Hydrocarbon oil index (HOI)(16) |
All processes |
EN ISO 9377-2 |
Once every month |
||
Metals/metalloids(16) |
Boron |
Processes where borax is used |
Various EN standards available (e.g. EN ISO 11885, EN ISO 17294-2) |
Once every month |
|
Cadmium |
All processes(17) |
Various EN standards available (e.g. EN ISO 11885, EN ISO 15586, EN ISO 17294-2) |
Once every month |
||
Chromium |
All processes(17) |
||||
Iron |
All processes |
||||
Nickel |
All processes(17) |
||||
Lead |
All processes(17) |
||||
Tin |
Hot dip coating using tin |
||||
Zinc |
All processes(17) |
||||
Mercury |
All processes(17) |
Various EN standards available (e.g. EN ISO 12846, EN ISO 17852) |
|||
Hexavalent chromium |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
Various EN standards available (e.g. EN ISO 10304-3, EN ISO 23913) |
|||
Total phosphorus (Total P)(13) |
Phosphating |
Various EN standards available (e.g. EN ISO 6878, EN ISO 11885, EN ISO 15681-1 and -2) |
Once every month |
||
Fluoride (F-)(16) |
Pickling with acid mixtures containing hydrofluoric acid |
EN ISO 10304-1 |
Once every month |
1.1.3.
Hazardous substances
Applicability
1.1.4.
Energy efficiency
Technique |
Description |
Applicability |
||||||||
a. |
Energy efficiency plan and energy audits |
An energy efficiency plan is part of the EMS (see BAT 1) and entails defining and monitoring the specific energy consumption of the activity/processes (see BAT 6), setting key performance indicators on an annual basis (e.g. MJ/t of product) and planning the periodic improvement targets and related actions. Energy audits are carried out at least once a year to ensure that the objectives of the energy management plan are met. The energy efficiency plan and the energy audits may be integrated in the overall energy efficiency plan of a larger installation (e.g. for iron and steel production). |
The level of detail of the energy efficiency plan, of the energy audits and of the energy balance record will generally be related to the nature, scale and complexity of the plant and the types of energy sources used. |
|||||||
b. |
Energy balance record |
Drawing up on an annual basis of an energy balance record which provides a breakdown of the energy consumption and generation (including energy export) by the type of energy source (e.g. electricity, natural gas, iron and steel process gases, renewable energy, imported heat and/or cooling). This includes:
|
Technique |
Description |
Applicability |
|||||||
Design and operation |
|||||||||
a. |
Optimum furnace design for feedstock heating |
This includes techniques such as:
|
Only applicable to new plants and major plant upgrades. |
||||||
b. |
Optimum galvanising kettle design |
This includes techniques such as:
|
Only applicable to new plants and major plant upgrades. |
||||||
c. |
Optimum galvanising kettle operation |
This includes techniques such as: minimisation of heat losses from the galvanising kettle in hot dip coating of wires or in batch galvanising, e.g. by using insulated covers during idle periods. |
Generally applicable. |
||||||
d. |
Combustion optimisation |
See Section 1.7.1. |
Generally applicable. |
||||||
e. |
Furnace automation and control |
See Section 1.7.1. |
Generally applicable. |
||||||
f. |
Process gas management system |
See Section 1.7.1. The calorific value of iron and steel process gases and/or CO-rich gas from ferrochromium production is used. |
Only applicable when iron and steel process gases and/or CO-rich gas from ferrochromium production are available. |
||||||
g. |
Batch annealing with 100 % hydrogen |
Batch annealing is carried out in furnaces using 100 % hydrogen as a protective gas with increased thermal conductivity. |
Only applicable to new plants and major plant upgrades. |
||||||
h. |
Oxy-fuel combustion |
See Section 1.7.1. |
Applicability may be restricted for furnaces processing high-alloy steel. Applicability to existing plants may be restricted by furnace design and the need for a minimum waste gas flow. Not applicable to furnaces equipped with radiant tube burners. |
||||||
i. |
Flameless combustion |
See Section 1.7.1. |
Applicability to existing plants may be limited by furnace design (i.e. furnace volume, space for burners, distance between burners) and the need for a change of the refractory lining. Applicability may be limited for processes where close control of temperature or temperature profile is required (e.g. recrystallisation). Not applicable to furnaces operating at a temperature lower than the auto-ignition temperature required for flameless combustion or to furnaces equipped with radiant tube burners. |
||||||
j. |
Pulse-fired burner |
The heat input to the furnace is controlled by the firing duration of the burners or by the sequential start of the individual burners instead of adjusting combustion air and fuel flows. |
Only applicable to new plants and major plant upgrades. |
||||||
Heat recovery from flue-gases |
|||||||||
k. |
Feedstock preheating |
Feedstock is preheated by blowing hot flue-gases directly onto it. |
Only applicable to continuous reheating furnaces. Not applicable to furnaces equipped with radiant tube burners. |
||||||
l. |
Drying of workpieces |
In batch galvanising, the heat from flue-gases is used to dry the workpieces. |
Generally applicable. |
||||||
m. |
Preheating of combustion air |
See Section 1.7.1. This may be achieved for example by using regenerative or recuperative burners. A balance has to be achieved between maximising heat recovery from the flue-gas and minimising NOX emissions. |
Applicability to existing plants may be restricted by a lack of space for the installation of regenerative burners. |
||||||
n. |
Waste heat recovery boiler |
The heat from hot flue-gases is used to generate steam or hot water that is used in other processes (e.g. for heating pickling and fluxing baths), for district heating or for generating electricity. |
Applicability to existing plants may be restricted by a lack of space and/or a suitable steam or hot water demand. |
Specific process(es) Steel products at the end of the rolling process |
Unit |
BAT-AEPL (Yearly average) |
Feedstock reheating |
||
Hot rolled coils (strips) |
MJ/t |
1 200 –1 500 (18) |
Heavy plates |
MJ/t |
1 400 –2 000 (19) |
Bars, rods |
MJ/t |
600 –1 900 (19) |
Beams, billets, rails, tubes |
MJ/t |
1 400 –2 200 |
Feedstock intermediate heating |
|
|
Bars, rods, tubes |
MJ/t |
100 –900 |
Feedstock post-heating |
||
Heavy plates |
MJ/t |
1 000 –2 000 |
Bars, rods |
MJ/t |
1 400 –3 000 (20) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Annealing after cold rolling (batch and continuous) |
MJ/t |
600 –1 200 (21) (22) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Feedstock heating before hot dip coating |
MJ/t |
700 –1 100 (23) |
Specific process(es) |
Unit |
BAT-AEPL (Yearly average) |
Batch galvanising |
kWh/t |
300 –800 (24) (25) (26) |
1.1.5.
Material efficiency
Technique |
Description |
Applicability |
|||||
Avoiding or reducing the need for degreasing |
|||||||
a. |
Use of feedstock with low oil and grease contamination |
The use of feedstock with low oil and grease contamination prolongs the lifetime of the degreasing solution. |
Applicability may be limited if the feedstock quality cannot be influenced. |
||||
b. |
Use of a direct-flame furnace in the case of hot dip coating of sheets |
The oil on the surface of the sheet is burnt in a direct-flame furnace. Degreasing before the furnace may be needed for some high-quality products or in the case of sheets with high residual oil levels. |
Applicability may be limited if a very high level of surface cleanliness and zinc adhesion is required. |
||||
Degreasing optimisation |
|||||||
c. |
General techniques for increased degreasing efficiency |
These include techniques such as:
|
Generally applicable. |
||||
d. |
Minimisation of drag-out of degreasing solution |
This includes techniques such as:
|
Generally applicable. |
||||
e. |
Reverse cascade degreasing |
Degreasing is carried out in two or more baths in series where the feedstock is moved from the most contaminated degreasing bath to the cleanest. |
Generally applicable. |
||||
Extending the lifetime of the degreasing baths |
|||||||
f. |
Cleaning and reuse of the degreasing solution |
Magnetic separation, oil separation (e.g. skimmers, discharge launders, weirs), micro- or ultrafiltration or biological treatment is used to clean the degreasing solution for reuse. |
Generally applicable. |
Technique |
Description |
|
a. |
Acid heating with heat exchangers |
Corrosion-resistant heat exchangers are immersed in the pickling acid for indirect heating, e.g. with steam. |
b. |
Acid heating by submerged combustion |
Combustion gases pass through the pickling acid, releasing the energy via direct heat transfer. |
Technique |
Description |
Applicability |
|||||||||||
Avoiding or reducing the need for pickling |
|||||||||||||
a. |
Minimisation of steel corrosion |
This includes techniques such as:
|
Generally applicable. |
||||||||||
b. |
Mechanical (pre)descaling |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. Applicability may be restricted due to product specifications. |
||||||||||
c. |
Electrolytic prepickling of high-alloy steel |
Use of an aqueous solution of sodium sulphate (Na2SO4) to pretreat high-alloy steel before pickling with mixed acid, in order to speed up and improve the removal of the surface oxide scale. The waste water containing hexavalent chromium is treated using technique BAT 31 (f). |
Only applicable to cold rolling. Applicability to existing plants may be restricted by a lack of space. |
||||||||||
Pickling optimisation |
|||||||||||||
d. |
Rinsing after alkaline degreasing |
Carry-over of alkaline degreasing solution to the pickling bath is reduced by rinsing feedstock after degreasing. |
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
e. |
General techniques for increased pickling efficiency |
These include techniques such as:
|
Generally applicable. |
||||||||||
f. |
Cleaning of the pickling bath and reuse of free acid |
A cleaning circuit, e.g. with filtration, is used to remove particles from the pickling acid followed by reclamation of the free acid via ion exchange, e.g. using resins. |
Not applicable if cascade pickling (or similar) is used, as this results in very low levels of free acid. |
||||||||||
g. |
Reverse cascade pickling |
Pickling is carried out in two or more baths in series where the feedstock is moved from the bath with the lowest acid concentration to the one with the highest. |
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
h. |
Minimisation of drag-out of pickling acid |
This includes techniques such as:
|
Generally applicable. |
||||||||||
i. |
Turbulence pickling |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
j. |
Use of pickling inhibitors |
Pickling inhibitors are added to the pickling acid to protect metallically clean parts of the feedstock from over-pickling. |
Not applicable to high- alloy steel. Applicability may be restricted due to product specifications. |
||||||||||
k. |
Activated pickling in hydrochloric acid pickling |
Pickling is carried out with a low hydrochloric acid concentration (i.e. around 4–6 wt-%) and a high iron concentration (i.e. around 120–180 g/l) at temperatures of 20–25 °C. |
Generally applicable. |
Pickling acid |
Unit |
BAT-AEPL (3-year average) |
Hydrochloric acid, 28 wt-% |
kg/t |
13 –30 (27) |
Technique |
Description |
Applicability |
|||||||
a. |
Rinsing of workpieces after pickling |
In batch galvanising, carry-over of iron to the fluxing solution is reduced by rinsing workpieces after pickling. |
Applicability to existing plants may be restricted by a lack of space. |
||||||
b. |
Optimised fluxing operation |
The chemical composition of the fluxing solution is monitored and adjusted frequently. The amount of fluxing agent used is reduced to the minimum level required to achieve the product specifications. |
Generally applicable. |
||||||
c. |
Minimisation of drag-out of fluxing solution |
The drag-out of the fluxing solution is minimised by allowing enough time for it to drip off. |
Generally applicable. |
||||||
d. |
Iron removal and reuse of the fluxing solution |
Iron is removed from the fluxing solution by one of the following techniques:
After iron removal, the fluxing solution is reused. |
Applicability to existing batch galvanising plants may be restricted by a lack of space. |
||||||
e. |
Recovery of salts from the spent fluxing solution for production of fluxing agents |
Spent fluxing solution is used to recover the salts contained therein to produce fluxing agents. This may take place on site or off site. |
Applicability may be restricted depending on the availability of a market. |
Technique |
Description |
|||||||
a. |
Reduction of the generation of bottom dross |
The generation of bottom dross is reduced, e.g. by sufficient rinsing after pickling, removing the iron from the fluxing solution (see BAT 15 (d)), using fluxing agents with a mild pickling effect and avoiding local overheating in the galvanising kettle. |
||||||
b. |
Prevention, collection and reuse of zinc splashes in batch galvanising |
The generation of zinc splashes from the galvanising kettle is reduced by minimising carry-over of the fluxing solution (see BAT 26 (b)). Zinc splashes out of the kettle are collected and reused. The area surrounding the kettle is kept clean to reduce contamination of the splashes. |
||||||
c. |
Reduction of the generation of zinc ash |
The formation of zinc ash, i.e. zinc oxidation on the bath surface, is reduced for example by:
|
Technique |
Description |
|
Extending the lifetime of the treatment baths |
||
a. |
Cleaning and reuse of the phosphating or passivation solution |
A cleaning circuit, for example with filtration, is used to clean the phosphating or passivation solution for reuse. |
Treatment optimisation |
||
b. |
Use of roll coaters for strips |
Roll coaters are used to apply a passivation or a phosphate-containing layer on the surface of strips. This allows better control of the layer thickness and thus the reduction of the consumption of chemicals. |
c. |
Minimisation of drag-out of chemical solution |
The drag-out of chemical solution is minimised, e.g. by passing the strips through squeeze rolls or by allowing for sufficient dripping time for workpieces. |
Description
Applicability
1.1.6.
Water use and waste water generation
Technique |
Description |
Applicability |
|||||||
a. |
Water management plan and water audits |
A water management plan and water audits are part of the EMS (see BAT 1) and include:
Water audits are carried out at least once every year to ensure that the objectives of the water management plan are met. The water management plan and the water audits may be integrated in the overall water management plan of a larger installation (e.g. for iron and steel production). |
The level of detail of the water management plan and water audits will generally be related to the nature, scale and complexity of the plant. |
||||||
b. |
Segregation of water streams |
Each water stream (e.g. surface run-off water, process water, alkaline or acidic waste water, spent degreasing solution) is collected separately, based on the pollutant content and on the required treatment techniques. Waste water streams that can be recycled without treatment are segregated from waste water streams that require treatment. |
Applicability to existing plants may be limited by the layout of the water collection system. |
||||||
c. |
Minimisation of hydrocarbon contamination of process water |
The contamination of process water by oil and lubricant losses is minimised by using techniques such as:
|
Generally applicable. |
||||||
d. |
Reuse and/or recycling of water |
Water streams (e.g. process water, effluents from wet scrubbing or quench baths) are reused and/or recycled in closed or semi-closed circuits, if necessary after treatment (see BAT 30 and BAT 31). |
The degree of water reuse and/or recycling is limited by the water balance of the plant, the content of impurities and/or the characteristics of the water streams. |
||||||
e. |
Reverse cascade rinsing |
Rinsing is carried out in two or more baths in series where the feedstock is moved from the most contaminated rinsing bath to the cleanest. |
Applicability to existing plants may be restricted by a lack of space. |
||||||
f. |
Recycling or reuse of rinsing water |
Water from rinsing after pickling or degreasing is recycled/reused, if necessary after treatment, to the preceding process baths as make-up water, rinsing water or, if the acid concentration is sufficiently high, for acid recovery. |
Generally applicable. |
||||||
g. |
Treatment and reuse of oil- and scale-bearing process water in hot rolling |
Oil- and scale-bearing waste water from hot rolling mills is treated separately using different cleaning steps including scale pits, settling tanks, cyclones and filtration to separate oil and scale. A large proportion of the treated water is reused in the process. |
Generally applicable. |
||||||
h. |
Water spray descaling triggered by sensors in hot rolling |
Sensors and automation are used to track the position of the feedstock and adjust the volume of the descaling water passing through the water sprays. |
Generally applicable. |
Sector |
Unit |
BAT-AEPL (Yearly average) |
Hot rolling |
m3/t |
0,5 –5 |
Cold rolling |
m3/t |
0,5 –10 |
Wire drawing |
m3/t |
0,5 –5 |
Hot dip coating |
m3/t |
0,5 –5 |
1.1.7.
Emissions to air
1.1.7.1.
Emissions to air from heating
Technique |
Description |
Applicability |
|||||||
a. |
Use of fuels with low dust and ash content |
Fuels with low dust and ash content include for example natural gas, liquefied petroleum gas, dedusted blast furnace gas and dedusted basic oxygen furnace gas. |
Generally applicable. |
||||||
b. |
Limiting the entrainment of dust |
Entrainment of dust is limited by for example:
|
Avoiding direct contact of the flames with the feedstock is not applicable in the case of direct flame furnaces. |
Parameter |
Sector |
Unit |
BAT-AEL(28) (Daily average or average over the sampling period) |
Dust |
Hot rolling |
mg/Nm3 |
< 2 –10 |
Cold rolling |
< 2 –10 |
||
Wire drawing |
< 2 –10 |
||
Hot dip coating |
< 2 –10 |
Description
Parameter |
Sector |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
SO2 |
Hot rolling |
mg/Nm3 |
50 –200 (29) (30) |
Cold rolling, wire drawing, hot dip coating of sheets |
20 –100 (29) |
Technique |
Description |
Applicability |
|
Reduction of generation of emissions |
|||
a. |
Use of a fuel or a combination of fuels with low NOX formation potential |
Fuels with a low NOX formation potential, e.g. natural gas, liquefied petroleum gas, blast furnace gas and basic oxygen furnace gas. |
Generally applicable. |
b. |
Furnace automation and control |
See Section 1.7.2. |
Generally applicable. |
c. |
Combustion optimisation |
See Section 1.7.2. Generally used in combination with other techniques. |
Generally applicable. |
d. |
Low-NOX burners |
See Section 1.7.2. |
Applicability may be restricted at existing plants by design and/or operational constraints. |
e. |
Flue-gas recirculation |
Recirculation (external) of part of the flue-gas to the combustion chamber to replace part of the fresh combustion air, with the dual effect of lowering the temperature and limiting the O2 content for nitrogen oxidation, thus limiting the NOX generation. It implies the supply of flue-gas from the furnace into the flame to reduce the oxygen content and therefore the temperature of the flame. |
Applicability to existing plants may be restricted by a lack of space. |
f. |
Limiting the temperature of air preheating |
Limiting the air preheating temperature leads to a decrease of the concentration of NOX emissions. A balance has to be achieved between maximising heat recovery from the flue-gas and minimising NOX emissions. |
May not be applicable in the case of furnaces equipped with radiant tube burners. |
g. |
Flameless combustion |
See Section 1.7.2. |
Applicability to existing plants may be limited by furnace design (i.e. furnace volume, space for burners, distance between burners) and the need for a change of the refractory lining. Applicability may be limited for processes where close control of the temperature or temperature profile is required (e.g. recrystallisation). Not applicable to furnaces operating at a temperature lower than the auto-ignition temperature required for flameless combustion, or to furnaces equipped with radiant tube burners. |
h. |
Oxy-fuel combustion |
See Section 1.7.2. |
Applicability may be restricted for furnaces processing high-alloy steel. Applicability to existing plants may be restricted by furnace design and the need for a minimum waste gas flow. Not applicable to furnaces equipped with radiant tube burners. |
Waste gas treatment |
|||
i. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. Applicability may be restricted in batch annealing due to the varying temperatures during the annealing cycle. |
j. |
Selective non-catalytic reduction (SNCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by the optimum temperature window and the residence time needed for the reaction. Applicability may be restricted in batch annealing due to the varying temperatures during the annealing cycle. |
k. |
Optimisation of the SNCR/SCR design and operation |
See Section 1.7.2. |
Only applicable where SNCR/SCR is used for the reduction of NOX emissions. |
Parameter |
Type of fuel |
Specific process |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level Daily average or average over the sampling period) |
NOX |
100 % natural gas |
Reheating |
mg/Nm3 |
New plants: 80 –200 Existing plants: 100 –350 |
No indicative level |
Intermediate heating |
mg/Nm3 |
100 –250 |
|||
Post-heating |
mg/Nm3 |
100 –200 |
|||
Other fuels |
Reheating, intermediate heating, post-heating |
mg/Nm3 |
100 –350 (31) |
||
CO |
100 % natural gas |
Reheating |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Intermediate heating |
mg/Nm3 |
10 –100 |
|||
Post-heating |
mg/Nm3 |
10 –100 |
|||
Other fuels |
Reheating, intermediate heating, post-heating |
mg/Nm3 |
10 –50 |
Parameter |
Type of fuel |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level Daily average or average over the sampling period) |
NOX |
100 % natural gas |
mg/Nm3 |
100 –250 (32) |
No indicative level |
Other fuels |
mg/Nm3 |
100 –300 (33) |
||
CO |
100 % natural gas |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Other fuels |
mg/Nm3 |
No BAT-AEL |
10 –100 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Average over the sampling period) |
NOX |
mg/Nm3 |
100 –250 |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –50 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
100 –300 (34) |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –100 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Indicative emission level (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
70 –300 |
No indicative level |
CO |
mg/Nm3 |
No BAT-AEL |
10 –100 |
1.1.7.2.
emissions to air from degreasing
Technique |
Description |
|
Collection of emissions |
||
a. |
Closed degreasing tanks combined with air extraction in the case of continuous degreasing |
Degreasing is carried out in closed tanks and air is extracted. |
Waste gas treatment |
||
b. |
Wet scrubbing |
See Section 1.7.2. |
c. |
Demister |
See Section 1.7.2. |
1.1.7.3.
Emissions to air from pickling
Technique |
Description |
|
Collection of emissions |
||
a. |
Continuous pickling in closed tanks combined with fume extraction |
Continuous pickling is carried out in closed tanks with limited entry and exit openings for the steel strip or wire. The fumes from the pickling tanks are extracted. |
b. |
Batch pickling in tanks equipped with lids or enclosing hoods combined with fume extraction |
Batch pickling is carried out in tanks equipped with lids or enclosing hoods that can be opened to allow charging of the wire rod coils. The fumes from the pickling tanks are extracted. |
Waste gas treatment |
||
c. |
Wet scrubbing followed by a demister |
See Section 1.7.2. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –10 (35) |
HF |
mg/Nm3 |
< 1 (36) |
SOX |
mg/Nm3 |
< 1 –6 (37) |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –10 (38) |
SOX |
mg/Nm3 |
< 1 –6 (39) |
Technique |
Description |
Applicability |
|
Reduction of generation of emissions |
|||
a. |
Nitric-acid-free pickling of high-alloy steel |
Pickling of high-alloy steel is carried out by fully substituting nitric acid with a strong oxidising agent (e.g. hydrogen peroxide). |
Only applicable to new plants and major plant upgrades. |
b. |
Addition of hydrogen peroxide or urea to the pickling acid |
Hydrogen peroxide or urea is added directly to the pickling acid to reduce NOX emissions. |
Generally applicable. |
Collection of emissions |
|||
c. |
Continuous pickling in closed tanks combined with fume extraction |
Continuous pickling is carried out in closed tanks with limited entry and exit openings for the steel strip or wire. The fumes from the pickling bath are extracted. |
Generally applicable. |
d. |
Batch pickling in tanks equipped with lids or enclosing hoods combined with fume extraction |
Batch pickling is carried out in tanks equipped with lids or enclosing hoods that can be opened to allow charging of the wire rod coils. The fumes from the pickling tanks are extracted. |
Generally applicable. |
Waste gas treatment |
|||
e. |
Wet scrubbing with addition of an oxidising agent (e.g. hydrogen peroxide) |
See Section 1.7.2. An oxidising agent (e.g. hydrogen peroxide) is added to the scrubbing solution to reduce NOX emissions. When using hydrogen peroxide, the nitric acid formed can be recycled to the pickling tanks. |
Generally applicable. |
f. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. |
g. |
Optimisation of the SCR design and operation |
See Section 1.7.2. |
Only applicable where SCR is used for the reduction of NOX emissions. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
NOX |
mg/Nm3 |
10 –200 |
1.1.7.4.
Emissions to air from hot dipping
Technique |
Description |
Applicability |
|||||
Reduction of generation of emissions |
|
||||||
a. |
Low-fume flux |
Ammonium chloride in fluxing agents is partly substituted with other alkali chlorides (e.g. potassium chloride) to reduce dust formation. |
Applicability may be restricted due to product specifications. |
||||
b. |
Minimisation of carry-over of the fluxing solution |
This includes techniques such as:
|
Generally applicable. |
||||
Collection of emissions |
|
||||||
c. |
Air extraction as close as possible to the source |
Air from the kettle is extracted, for example using lateral hood or lip extraction. |
Generally applicable. |
||||
d. |
Enclosed kettle combined with air extraction |
Hot dipping is carried out in an enclosed kettle and air is extracted. |
Applicability to existing plants may be limited where enclosure interferes with an existing transport system for workpieces in batch galvanising. |
||||
Waste gas treatment |
|
||||||
e. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
1.1.7.4.1.
Emissions to air from oiling
Technique |
Description |
|
a. |
Electrostatic oiling |
Oil is sprayed on the metal surface through an electrostatic field, which ensures homogeneous oil application and optimises the quantity of oil applied. The oiling machine is enclosed and oil that does not deposit on the metal surface is recovered and reused within the machine. |
b. |
Contact lubrication |
Roller lubricators, e.g. felt rolls or squeeze rolls, are used in direct contact with the metal surface. |
c. |
Oiling without compressed air |
Oil is applied with nozzles close to the metal surface using high-frequency valves. |
1.1.7.5.
Emissions to air from post-treatment
Technique |
Description |
Applicability |
|||||||||
Collection of emissions |
|||||||||||
a. |
Air extraction as close as possible to the source |
Emissions from the chemical storage tanks and chemical baths are captured, e.g. by using one or a combination of the following techniques:
The captured emissions are then extracted. |
Only applicable when the treatment is carried out by spraying or when volatile substances are used. |
||||||||
b. |
Closed tanks combined with air extraction in the case of continuous post-treatment |
Phosphating and passivation are carried out in closed tanks and the air is extracted from the tanks. |
Only applicable when the treatment is carried out by spraying or when volatile substances are used. |
||||||||
Waste gas treatment |
|||||||||||
c. |
Wet scrubbing |
See Section 1.7.2. |
Generally applicable. |
||||||||
d. |
Demister |
See Section 1.7.2. |
Generally applicable. |
1.1.7.6.
Emissions to air from acid recovery
Technique |
Description |
Applicability |
|
a. |
Use of a fuel or a combination of fuels with low sulphur content and/or low NOX formation potential |
See BAT 21 and BAT 22 (a). |
Generally applicable. |
b. |
Combustion optimisation |
See Section 1.7.2. Generally used in combination with other techniques. |
Generally applicable. |
c. |
Low-NOX burners |
See Section 1.7.2. |
Applicability may be restricted at existing plants by design and/or operational constraints. |
d. |
Wet scrubbing followed by a demister |
See Section 1.7.2. In the case of mixed acid recovery, an alkali is added to the scrubbing solution to remove traces of HF and/or an oxidising agent (e.g. hydrogen peroxide) is added to the scrubbing solution to reduce NOX emissions. When using hydrogen peroxide, the nitric acid formed can be recycled to the pickling tanks. |
Generally applicable. |
e. |
Selective catalytic reduction (SCR) |
See Section 1.7.2. |
Applicability to existing plants may be restricted by a lack of space. |
f. |
Optimisation of the SCR design and operation |
See Section 1.7.2. |
Only applicable where SCR is used for the reduction of NOX emissions. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –15 |
HCl |
mg/Nm3 |
< 2 –15 |
SO2 |
mg/Nm3 |
< 10 |
NOX |
mg/Nm3 |
50 -180 |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HF |
mg/Nm3 |
< 1 |
NOX |
mg/Nm3 |
50 –100 (40) |
Dust |
mg/Nm3 |
< 2 –10 |
1.1.8.
Emissions to water
Description
Technique(41) |
Typical pollutants targeted |
|
Preliminary, primary and general treatment, e.g. |
||
a. |
Equalisation |
All pollutants |
b. |
Neutralisation |
Acids, alkalis |
c. |
Physical separation, e.g. screens, sieves, grit separators, grease separators, hydrocyclones, oil-water separation or primary settlement tanks |
Gross solids, suspended solids, oil/grease |
Physico-chemical treatment, e.g. |
||
d. |
Adsorption |
Adsorbable dissolved non-biodegradable or inhibitory pollutants, e.g. hydrocarbons, mercury |
e. |
Chemical precipitation |
Precipitable dissolved non-biodegradable or inhibitory pollutants, e.g. metals, phosphorus, fluoride |
f. |
Chemical reduction |
Reducible dissolved non-biodegradable or inhibitory pollutants, e.g. hexavalent chromium |
g. |
Nanofiltration/reverse osmosis |
Soluble non-biodegradable or inhibitory pollutants, e.g. salts, metals |
Biological treatment, e.g. |
||
h. |
Aerobic treatment |
Biodegradable organic compounds |
Solids removal, e.g. |
||
i. |
Coagulation and flocculation |
Suspended solids and particulate-bound metals |
j. |
Sedimentation |
|
k. |
Filtration (e.g. sand filtration, microfiltration, ultrafiltration) |
|
l. |
Flotation |
Substance/Parameter |
Unit |
BAT-AEL (42) |
Process(es) to which the BAT-AEL applies |
|
Total suspended solids (TSS) |
mg/l |
5–30 |
All processes |
|
Total organic carbon (TOC)(43) |
mg/l |
10–30 |
All processes |
|
Chemical oxygen demand (COD)(43) |
mg/l |
30–90 |
All processes |
|
Hydrocarbon oil index (HOI) |
mg/l |
0,5–4 |
All processes |
|
Metals |
Cd |
μg/l |
1-5 |
All processes(44) |
Cr |
mg/l |
0,01–0,1(45) |
All processes(44) |
|
Cr(VI) |
μg/l |
10–50 |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
|
Fe |
mg/l |
1–5 |
All processes |
|
Hg |
μg/l |
0,1–0,5 |
All processes(44) |
|
Ni |
mg/l |
0,01–0,2(46) |
All processes(44) |
|
Pb |
μg/l |
5–20(47) (48) |
All processes(44) |
|
Sn |
mg/l |
0,01–0,2 |
Hot dip coating using tin |
|
Zn |
mg/l |
0,05–1 |
All processes(44) |
|
Total phosphorus (Total P) |
mg/l |
0,2–1 |
Phosphating |
|
Fluoride (F-) |
mg/l |
1–15 |
Pickling with acid mixtures containing hydrofluoric acid |
Substance/Parameter |
Unit |
BAT-AEL (49) (50) |
Process(es) to which the BAT-AEL applies |
|
Hydrocarbon oil index (HOI) |
mg/l |
0,5 –4 |
All processes |
|
Metals |
Cd |
μg/l |
1 –5 |
All processes(51) |
Cr |
mg/l |
0,01 –0,1 (52) |
All processes(51) |
|
Cr(VI) |
μg/l |
10 –50 |
Pickling of high-alloy steel or passivation with hexavalent chromium compounds |
|
Fe |
mg/l |
1 –5 |
All processes |
|
Hg |
μg/l |
0,1 –0,5 |
All processes(51) |
|
Ni |
mg/l |
0,01 –0,2 (53) |
All processes(51) |
|
Pb |
μg/l |
5 –20 (54) (55) |
All processes(51) |
|
Sn |
mg/l |
0,01 –0,2 |
Hot dip coating using tin |
|
Zn |
mg/l |
0,05 –1 |
All processes(51) |
|
Fluoride (F-) |
mg/l |
1 –15 |
Pickling with acid mixtures containing hydrofluoric acid |
1.1.9.
Noise and vibrations
Applicability
Technique |
Description |
Applicability |
|||||||||||
a. |
Appropriate location of equipment and buildings |
Noise levels can be reduced by increasing the distance between the emitter and the receiver, by using buildings as noise screens and by relocating the exits or entrances of the buildings. |
For existing plants, the relocation of equipment and the exits or entrances of the buildings may not be applicable due to a lack of space and/or excessive costs. |
||||||||||
b. |
Operational measures |
These include techniques such as:
|
Generally applicable. |
||||||||||
c. |
Low-noise equipment |
This includes techniques such as direct drive motors, low-noise compressors, pumps and fans. |
|
||||||||||
d. |
Noise and vibration control equipment |
This includes techniques such as:
|
Applicability to existing plants may be restricted by a lack of space. |
||||||||||
e. |
Noise abatement |
Inserting obstacles between emitters and receivers (e.g. protection walls, embankments and buildings). |
Only applicable to existing plants, as the design of new plants should make this technique unnecessary. For existing plants, the insertion of obstacles may not be applicable due to a lack of space. |
1.1.10.
Residues
Technique |
Description |
Applicability |
|||||
a. |
Residues management plan |
A residues management plan is part of the EMS (see BAT 1) and is a set of measures aiming to (1) minimise the generation of residues; (2) optimise the reuse, recycling and/or recovery of residues; and (3) ensure the proper disposal of waste. The residues management plan may be integrated in the overall residues management plan of a larger installation (e.g. for iron and steel production). |
The level of detail and the degree of formalisation of the residues management plan will generally be related to the nature, scale and complexity of the installation. |
||||
b. |
Pretreatment of oily mill scale for further use |
This includes techniques such as:
|
Generally applicable. |
||||
c. |
Use of mill scale |
Mill scale is collected and used on site or off site, e.g. in iron and steel production or in cement production. |
Generally applicable. |
||||
d. |
Use of metallic scrap |
Metallic scrap from mechanical processes (e.g. from trimming and finishing) is used in iron and steel production. This may take place on site or off site. |
Generally applicable. |
||||
e. |
Recycling of metal and metal oxides from dry waste gas cleaning |
The coarse fraction of metal and metal oxides originating from dry cleaning (e.g. fabric filters) of waste gases from mechanical processes (e.g. scarfing or grinding) is selectively isolated using mechanical techniques (e.g. sieves) or magnetic techniques and recycled, e.g. to iron and steel production. This may take place on site or off site. |
Generally applicable. |
||||
f. |
Use of oily sludge |
Residual oily sludge, e.g. from degreasing, is dewatered to recover the oil contained therein for material or energy recovery. If the water content is low, the sludge can be directly used. This may take place on site or off site. |
Generally applicable. |
||||
g. |
Thermal treatment of hydroxide sludge from the recovery of mixed acid |
Sludge generated from the recovery of mixed acid is thermally treated in order to produce a material rich in calcium fluoride that can be used in argon oxygen decarburisation converters. |
Applicability may be restricted by a lack of space. |
||||
h. |
Recovery and reuse of shot blast media |
Where mechanical descaling is carried out by shot blasting, the shot blast media are separated from the scale and reused. |
Generally applicable. |
Technique |
Description |
Applicability |
|
a. |
Recycling of fabric filter dust |
Dust from fabric filters containing ammonium chloride and zinc chloride is collected and reused, e.g. to produce fluxing agents. This may take place on site or off site. |
Only applicable in hot dipping after fluxing. Applicability may be restricted depending on the availability of a market. |
b. |
Recycling of zinc ash and top dross |
Metallic zinc is recovered from zinc ash and top dross by melting in recovery furnaces. The remaining zinc-containing residue is used, e.g. for zinc oxide production. This may take place on site or off site. |
Generally applicable. |
c. |
Recycling of bottom dross |
Bottom dross is used, e.g. in the non-ferrous metals industries to produce zinc. This may take place on site or off site. |
Generally applicable. |
Technique |
Description |
|
a. |
Cleaning and reuse of grinding emulsion |
Grinding emulsions are treated using lamellar or magnetic separators or using a sedimentation/clarification process in order to remove the grinding sludge and reuse the grinding emulsion. |
b. |
Treatment of grinding sludge |
Treatment of grinding sludge by magnetic separation for recovery of metal particles and recycling of metals, e.g. to iron and steel production. |
c. |
Recycling of worn working rolls |
Worn working rolls which are unsuitable for texturing are recycled to iron and steel production or returned to the manufacturer for refabrication. |
1.2.
BAT conclusions for hot rolling
1.2.1.
Energy efficiency
Technique |
Description |
Applicability |
|
a. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
See Section 1.7.1. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
b. |
Hot/direct charging |
Continuous-cast steel products are directly charged hot into the reheating furnaces. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
c. |
Heat recovery from skids cooling |
Steam produced when cooling the skids supporting the feedstock in the reheating furnaces is extracted and used in other processes of the plant. |
Applicability to existing plants may be restricted by a lack of space and/or of a suitable steam demand. |
d. |
Heat conservation during transfer of feedstock |
Insulated covers are used between the continuous caster and the reheating furnace, and between the roughing mill and the finishing mill. |
Generally applicable within the limitations of the plant layout. |
e. |
Coil boxes |
See Section 1.7.1. |
Generally applicable. |
f. |
Coil recovery furnaces |
Coil recovery furnaces are used as an addition to coil boxes to restore the rolling temperature of coils and return them to a normal rolling sequence in the event of rolling mill interruptions. |
Generally applicable. |
g. |
Sizing press |
See BAT 39 (a). A sizing press is used to increase the energy efficiency in feedstock heating because it enables the hot charging rate to be increased. |
Only applicable to new plants and major plant upgrades for hot strip mills. |
Technique |
Description |
Applicability |
|
a. |
Sizing press |
The use of a sizing press before the roughing mill enables the hot charging rate to be significantly increased and results in a more uniform width reduction both at the edges and centre of the product. The shape of the final slab is nearly rectangular, reducing significantly the number of rolling passes necessary to reach product specifications. |
Only applicable to hot strip mills. Only applicable to new plants and major plant upgrades. |
b. |
Computer-aided rolling optimisation |
The thickness reduction is controlled using a computer to minimise the number of rolling passes. |
Generally applicable. |
c. |
Reduction of the rolling friction |
See Section 1.7.1. |
Only applicable to hot strip mills. |
d. |
Coil boxes |
See Section 1.7.1. |
Generally applicable. |
e. |
Three-roll stand |
A three-roll stand increases the section reduction per pass, resulting in an overall reduction of the number of rolling passes required for producing wire rods and bars. |
Generally applicable. |
f. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
See Section 1.7.1. |
Only applicable to plants adjacent to continuous casting and within the limitations of the plant layout and product specifications. |
Steel products at the end of the rolling process |
Unit |
BAT-AEPL (yearly average) |
Hot rolled coils (strips), heavy plates |
MJ/t |
100–400 |
Bars, rods |
MJ/t |
100–500(56) |
Beams, billets, rails, tubes |
MJ/t |
100–300 |
1.2.2.
Material efficiency
Technique |
Description |
Applicability |
|
a. |
Computer-aided quality control |
The quality of slabs is controlled by a computer which allows the adjustment of the casting conditions to minimise surface defects and enables manual scarfing of the damaged area(s) only rather than scarfing of the entire slab. |
Only applicable to plants with continuous casting. |
b. |
Slab slitting |
The slabs (often cast in multiple widths) are slit before hot rolling by means of slitting devices, slit rolling or torches either manually operated or mounted on a machine. |
May not be applicable for slabs produced from ingots. |
c. |
Edging or trimming of wedge-type slabs |
Wedge-type slabs are rolled under special settings where the wedge is eliminated by edging (e.g. using automatic width control or a sizing press) or by trimming. |
May not be applicable for slabs produced from ingots. Only applicable to new plants and major plant upgrades. |
Technique |
Description |
|
a. |
Crop optimisation |
The cropping of the feedstock after roughing is controlled by a shape measurement system (e.g. camera) in order to minimise the amount of metal cut off. |
b. |
Control of the feedstock shape during rolling |
Any deformations of the feedstock during rolling are monitored and controlled in order to ensure that the rolled steel has as rectangular a shape as possible and to minimise the need for trimming. |
1.2.3.
Emissions to air
Technique |
Description |
Applicability |
|
Collection of emissions |
|
||
a. |
Enclosed scarfing and grinding combined with air extraction |
Scarfing (other than manual scarfing) and grinding operations are carried out completely enclosed (e.g. under closed hoods) and air is extracted. |
Generally applicable. |
b. |
Air extraction as close as possible to the emission source |
Emissions from slitting, descaling, roughing, rolling, finishing, levelling and welding are collected, for example using hood or lip extraction. For roughing and rolling, in the case of low levels of dust generation, e.g. below 100 g/h, water sprays can be used instead (see BAT 43). |
May not be applicable for welding in the case of low levels of dust generation, e.g. below 50 g/h. |
Waste gas treatment |
|
||
c. |
Electrostatic precipitator |
See Section 1.7.2. |
Generally applicable. |
d. |
Fabric filter |
See Section 1.7.2. |
May not be applicable in the case of waste gases with a high moisture content. |
e. |
Wet scrubbing |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 (57) |
Ni |
0,01 –0,1 (58) |
|
Pb |
0,01 –0,035 (58) |
Description
1.3.
BAT conclusions for cold rolling
1.3.1.
Energy efficiency
Technique |
Description |
Applicability |
|
a. |
Continuous rolling for low-alloy and alloy steel |
Continuous rolling (e.g. using tandem mills) is employed instead of conventional discontinuous rolling (e.g. using reversing mills), allowing for stable feed and less frequent start-ups and shutdowns. |
Only applicable to new plants and major plant upgrades. Applicability may be restricted due to product specifications. |
b. |
Reduction of the rolling friction |
See Section 1.7.1. |
Generally applicable. |
c. |
Computer-aided rolling optimisation |
The thickness reduction is controlled using a computer to minimise the number of rolling passes. |
Generally applicable. |
Steel products at the end of the rolling process |
Unit |
BAT-AEPL (Yearly average) |
Cold rolled coils |
MJ/t |
100 –300 (59) |
Packaging steel |
MJ/t |
250 –400 |
1.3.2.
Material efficiency
Technique |
Description |
Applicability |
|||||||||
a. |
Monitoring and adjustment of the rolling emulsion quality |
Important characteristics of the rolling emulsion (e.g. oil concentration, pH, emulsion droplet size, saponification index, acid concentration, concentration of iron fines, concentration of bacteria) are monitored regularly or continuously to detect anomalies in the emulsion quality and take corrective action, if needed. |
Generally applicable. |
||||||||
b. |
Prevention of contamination of the rolling emulsion |
Contamination of the rolling emulsion is prevented by techniques such as:
|
Generally applicable. |
||||||||
c. |
Cleaning and reuse of the rolling emulsion |
Particulate matter (e.g. dust, steel slivers and scale) contaminating the rolling emulsion is removed in a cleaning circuit (usually based on sedimentation combined with filtration and/or magnetic separation) in order to maintain the emulsion quality and the treated rolling emulsion is reused. The degree of reuse is limited by the content of impurities in the emulsion. |
Applicability may be restricted due to product specifications. |
||||||||
d. |
Optimal choice of rolling oil and emulsion system |
Rolling oil and emulsion systems are carefully selected to provide the optimum performance for the given process and product. Relevant characteristics to be considered are, for example:
|
Generally applicable. |
||||||||
e. |
Minimisation of oil/rolling emulsion consumption |
The consumption of oil/rolling emulsion is minimised by using techniques such as:
|
Generally applicable. |
1.3.3.
Emissions to air
Technique |
Description |
Applicability |
|
Collection of emissions |
|||
a. |
Air extraction as close as possible to the emission source |
Emissions from decoiling, mechanical predescaling, levelling and welding are collected, for example using hood or lip extraction. |
May not be applicable for welding in the case of low levels of dust generation, e.g. below 50 g/h. |
Waste gas treatment |
|||
b. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
Ni |
0,01 –0,1 (60) |
|
Pb |
≤ 0,003 (60) |
Technique |
Description |
Applicability |
|
a. |
Dry tempering |
No water or lubricants are used for tempering. |
Not applicable to tinplate packaging products and other products with high elongation requirements. |
b. |
Low-volume lubrication in wet tempering |
Low-volume lubrication systems are employed to supply precisely the amount of lubricants needed for reducing the friction between the working rolls and the feedstock. |
Applicability may be restricted due to product specifications in the case of stainless steel. |
Technique |
Description |
|
Collection of emissions |
||
a. |
Air extraction as close as possible to the emission source |
Emissions from rolling, wet tempering and finishing are collected, for example using hood or lip extraction. |
Waste gas treatment |
||
b. |
Demister |
See Section 1.7.2. |
c. |
Oil mist separator |
Separators containing baffle packing, impingement plates or mesh pads are used to separate the oil from the extracted air. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
TVOC |
mg/Nm3 |
< 3–8 |
1.4.
BAT conclusions for wire drawing
1.4.1.
Energy efficiency
Description
1.4.2.
Material efficiency
Description
1.4.3.
Emissions to air
Technique |
Description |
|
Reduction of generation of emissions |
||
a. |
Minimisation of carry-over of lead |
Techniques include the use of anthracite gravel to scrape off lead and the coupling of the lead bath with in-line pickling. |
b. |
Floating protective layer or tank cover |
See BAT 49. Floating protective layers and tank covers also reduce emissions to air. |
Collection of emissions |
||
c. |
Air extraction as close as possible to the emission source |
Emissions from the lead bath are collected, for example using hood or lip extraction. |
Waste gas treatment |
||
d. |
Fabric filter |
See Section 1.7.2. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2–5 |
Pb |
mg/Nm3 |
≤ 0,5 |
Technique |
Description |
Applicability |
|
Collection of emissions |
|||
a. |
Enclosed drawing machine combined with air extraction |
The entire drawing machine is enclosed in order to avoid dispersion of dust and air is extracted. |
Applicability to existing plants may be restricted by the plant layout. |
b. |
Air extraction as close as possible to the emission source |
Emissions from the drawing machine are collected, for example using hood or lip extraction. |
Generally applicable. |
Waste gas treatment |
|||
c. |
Fabric filter |
See Section 1.7.2. |
Generally applicable. |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
Dust |
mg/Nm3 |
< 2 –5 |
Technique |
Description |
|
Collection of emissions |
||
a. |
Air extraction as close as possible to the emission source |
Emissions from oil quench baths are collected, for example using lateral hood or lip extraction. |
Waste gas treatment |
||
b. |
Demister |
See Section 1.7.2. |
1.4.4.
Residues
1.5.
BAT conclusions for hot dip coating of sheets and wires
1.5.1.
Material efficiency
Technique |
Description |
|
a. |
Air knives for coating thickness control |
After leaving the molten zinc bath, air jets stretching over the width of the strip blow the surplus coating metal off the strip surface back into the galvanising kettle. |
b. |
Stabilisation of the strip |
The efficiency of the excess coating removal by air knives is improved by limiting the oscillations of the strip, e.g. by increasing strip tension, using low-vibration pot bearings, using electromagnetic stabilisers. |
Technique |
Description |
|
a. |
Air or nitrogen wiping |
After leaving the molten zinc bath, circular air or gas jets around the wire blow the surplus coating metal off the wire surface back into the galvanising kettle. |
b. |
Mechanical wiping |
After leaving the molten zinc bath, the wire is passed through wiping equipment/material (e.g. pads, nozzles, rings, charcoal granulate) which takes the surplus coating metal off the wire surface back into the galvanising kettle. |
1.6.
BAT conclusions for batch galvanising
1.6.1.
Residues
Description
Applicability
Description
1.6.2.
Material efficiency
Technique |
Description |
|
a. |
Optimised dipping time |
The dipping time is limited to the duration required to achieve the coating thickness specifications. |
b. |
Slow withdrawal of workpieces from the bath |
By withdrawing the galvanised workpieces slowly from the galvanising kettle, the drain-off is improved and zinc splashes are reduced. |
1.6.3.
Emissions to air
Technique |
Description |
Applicability |
|||||
Collection of emissions |
|||||||
a. |
Enclosed pretreatment section with extraction |
The entire pretreatment section (e.g. degreasing, pickling, fluxing) is encapsulated and the fumes are extracted from the enclosure. |
Only applicable to new plants and major plant upgrades |
||||
b. |
Extraction by lateral hood or lip extraction |
Acid fumes from the pickling tanks are extracted using lateral hoods or lip extraction at the edge of the pickling tanks. This may also include emissions from degreasing tanks. |
Applicability in existing plants may be restricted by a lack of space. |
||||
Waste gas treatment |
|||||||
c. |
Wet scrubbing followed by a demister |
See Section 1.7.2. |
Generally applicable |
||||
Reduction of generation of emissions |
|||||||
d. |
Restricted operating range for hydrochloric acid open pickling baths |
Hydrochloric acid baths are strictly operated within the temperature and HCl concentration range determined by the following conditions:
where T is the pickling acid temperature expressed in °C and w the HCl concentration expressed in wt-%. The bath temperature is measured at least once every day. The HCl concentration in the bath is measured every time fresh acid is replenished and in any case at least once every week. To limit evaporation, movement of air across the bath surfaces (e.g. due to ventilation) is minimised. |
Generally applicable |
Parameter |
Unit |
BAT-AEL (Daily average or average over the sampling period) |
HCl |
mg/Nm3 |
< 2 –6 |
1.6.4.
Waste water discharge
Description
1.7.
Descriptions of techniques
1.7.1.
Techniques to increase energy efficiency
Technique |
Description |
Coil boxes |
Insulated boxes are installed between the roughing mill and the finishing mill to minimise temperature losses from feedstock during coiling/uncoiling processes and allow for lower rolling forces in hot strip mills. |
Combustion optimisation |
Measures taken to maximise the efficiency of energy conversion in the furnace while minimising emissions (in particular of CO). This is achieved by a combination of techniques including good design of the furnace, optimisation of the temperature (e.g. efficient mixing of the fuel and combustion air) and residence time in the combustion zone, and use of furnace automation and control. |
Flameless combustion |
Flameless combustion is achieved by injecting fuel and combustion air separately into the combustion chamber of the furnace at high velocity to suppress flame formation and reduce the formation of thermal NOX while creating a more uniform heat distribution throughout the chamber. Flameless combustion can be used in combination with oxy-fuel combustion. |
Furnace automation and control |
The heating process is optimised by using a computer system controlling in real time key parameters such as furnace and feedstock temperature, the air to fuel ratio and the furnace pressure. |
Near-net-shape casting for thin slabs and beam blanks followed by rolling |
Thin slabs and beam blanks are produced by combining casting and rolling in one process step. The need to reheat the feedstock before rolling and the number of rolling passes are reduced. |
Optimisation of the SNCR/SCR design and operation |
Optimisation of the reagent to NOX ratio over the cross-section of the furnace or duct, of the size of the reagent drops and of the temperature window in which the reagent is injected. |
Oxy-fuel combustion |
Combustion air is replaced fully or partially with pure oxygen. Oxy-fuel combustion can be used in combination with flameless combustion. |
Preheating of combustion air |
Reuse of part of the heat recovered from the combustion flue-gas to preheat the air used in combustion. |
Process gas management system |
A system that enables iron and steel process gases to be directed to the feedstock heating furnaces, depending on their availability. |
Recuperative burner |
Recuperative burners employ different types of recuperators (e.g. heat exchangers with radiation, convection, compact or radiant tube designs) to directly recover heat from the flue-gases, which are then used to preheat the combustion air. |
Reduction of the rolling friction |
Rolling oils are carefully selected. Pure oil and/or emulsion systems are used to reduce the friction between the working rolls and the feedstock and to ensure minimal oil consumption. In HR, this is usually carried out in the first stands of the finishing mill. |
Regenerative burner |
Regenerative burners consist of two burners which are operated alternately and which contain beds of refractory or ceramic materials. While one burner is in operation, the heat of the flue-gas is absorbed by the refractory or ceramic materials of the other burner and then used to preheat the combustion air. |
Waste heat recovery boiler |
Heat from hot flue-gases is used to generate steam using a waste heat recovery boiler. The generated steam is used in other processes of the plant, for supplying a steam network or for generating electricity in a power plant. |
1.7.2.
Techniques to reduce emissions to air
Technique |
Description |
Combustion optimisation |
See Section 1.7.1. |
Demister |
Demisters are filter devices that remove entrained liquid droplets from a gas stream. They consist of a woven structure of metal or plastic wires, with a high specific surface area. Through their momentum, small droplets present in the gas stream impinge against the wires and coalesce into bigger drops. |
Electrostatic precipitator |
Electrostatic precipitators (ESPs) operate such that particles are charged and separated under the influence of an electrical field. Electrostatic precipitators are capable of operating under a wide range of conditions. Abatement efficiency may depend on the number of fields, residence time (size), and upstream particle removal devices. They generally include between two and five fields. Electrostatic precipitators can be of the dry or of the wet type depending on the technique used to collect the dust from the electrodes. Wet ESPs are typically used at the polishing stage to remove residual dust and droplets after wet scrubbing. |
Fabric filter |
Fabric filters, often referred to as bag filters, are constructed from porous woven or felted fabric through which gases are passed to remove particles. The use of a fabric filter requires the selection of a fabric suitable for the characteristics of the waste gas and the maximum operating temperature. |
Flameless combustion |
See Section 1.7.1. |
Furnace automation and control |
See Section 1.7.1. |
Low-NOX burner |
The technique (including ultra-low-NOX burners) is based on the principles of reducing peak flame temperatures. The air/fuel mixing reduces the availability of oxygen and reduces the peak flame temperature, thus retarding the conversion of fuel-bound nitrogen to NOX and the formation of thermal NOX, while maintaining high combustion efficiency. |
Optimisation of the SNCR/SCR design and operation |
See Section 1.7.1. |
Oxy-fuel combustion |
See Section 1.7.1. |
Selective catalytic reduction (SCR) |
The SCR technique is based on the reduction of NOX to nitrogen in a catalytic bed by reaction with urea or ammonia at an optimum operating temperature of around 300–450 °C. Several layers of catalyst may be applied. A higher NOX reduction is achieved with the use of several catalyst layers. |
Selective non-catalytic reduction (SNCR) |
SNCR is based on the reduction of NOX to nitrogen by reaction with ammonia or urea at a high temperature. The operating temperature window is maintained between 800 °C and 1 000 °C for optimal reaction. |
Wet scrubbing |
The removal of gaseous or particulate pollutants from a gas stream via mass transfer to a liquid solvent, often water or an aqueous solution. It may involve a chemical reaction (e.g. in an acid or alkaline scrubber). In some cases, the compounds may be recovered from the solvent. |
1.7.3.
Techniques to reduce emissions to water
Technique |
Description |
Adsorption |
The removal of soluble substances (solutes) from the waste water by transferring them to the surface of solid, highly porous particles (typically activated carbon). |
Aerobic treatment |
The biological oxidation of dissolved organic pollutants with oxygen using the metabolism of microorganisms. In the presence of dissolved oxygen, injected as air or pure oxygen, the organic components are mineralised into carbon dioxide and water or are transformed into other metabolites and biomass. |
Chemical precipitation |
The conversion of dissolved pollutants into an insoluble compound by adding chemical precipitants. The solid precipitates formed are subsequently separated by sedimentation, air flotation or filtration. If necessary, this may be followed by microfiltration or ultrafiltration. Multivalent metal ions (e.g. calcium, aluminium, iron) are used for phosphorus precipitation. |
Chemical reduction |
The conversion of pollutants by chemical reducing agents into similar but less harmful or hazardous compounds. |
Coagulation and flocculation |
Coagulation and flocculation are used to separate suspended solids from waste water and are often carried out in successive steps. Coagulation is carried out by adding coagulants with charges opposite to those of the suspended solids. Flocculation is carried out by adding polymers, so that collisions of microfloc particles cause them to bond to produce larger flocs. |
Equalisation |
Balancing of flows and pollutant loads at the inlet of the final waste water treatment by using central tanks. Equalisation may be decentralised or carried out using other management techniques. |
Filtration |
The separation of solids from waste water by passing them through a porous medium, e.g. sand filtration, microfiltration and ultrafiltration. |
Flotation |
The separation of solid or liquid particles from waste water by attaching them to fine gas bubbles, usually air. The buoyant particles accumulate at the water surface and are collected with skimmers. |
Nanofiltration |
A filtration process in which membranes with pore sizes of approximately 1 nm are used. |
Neutralisation |
The adjustment of the pH of waste water to a neutral level (approximately 7) by the addition of chemicals. Sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) is generally used to increase the pH, whereas sulphuric acid (H2SO4), hydrochloric acid (HCl) or carbon dioxide (CO2) is generally used to decrease the pH. The precipitation of some substances may occur during neutralisation. |
Physical separation |
The separation of gross solids, suspended solids and/or metal particles from the waste water using for example screens, sieves, grit separators, grease separators, hydrocyclones, oil-water separation or primary settlement tanks. |
Reverse osmosis |
A membrane process in which a pressure difference applied between the compartments separated by the membrane causes water to flow from the more concentrated solution to the less concentrated one. |
Sedimentation |
The separation of suspended particles and suspended material by gravitational settling. |