COMMISSION IMPLEMENTING DECISION (EU) 2017/2117
of 21 November 2017
establishing best available techniques (BAT) conclusions, under Directive 2010/75/EU of the European Parliament and of the Council, for the production of large volume organic chemicals
(notified under document C(2017) 7469)
(Text with EEA relevance)
Article 1
Article 2
ANNEX
BEST AVAILABLE TECHNIQUES (BAT) CONCLUSIONS FOR THE PRODUCTION OF LARGE VOLUME ORGANIC CHEMICALS
SCOPE
GENERAL CONSIDERATIONS
Best Available Techniques
Averaging periods and reference conditions for emissions to air
Type of measurement |
Averaging period |
Definition |
Continuous |
Daily average |
Average over a period of 1 day based on valid hourly or half-hourly averages |
Periodic |
Average over the sampling period |
Average of three consecutive measurements of at least 30 minutes each(1) (2) |
Equation 1: |
[Bild bitte in Originalquelle ansehen] |
Reference oxygen level
Conversion to reference oxygen level
Equation 2: |
[Bild bitte in Originalquelle ansehen] |
Averaging periods for emissions to water
Averaging period |
Definition |
Average of values obtained during one month |
Flow-weighted average value from 24-hour flow-proportional composite samples obtained during 1 month under normal operating conditions(3) |
Average of values obtained during one year |
Flow-weighted average value from 24-hour flow-proportional composite samples obtained during 1 year under normal operating conditions(3) |
Equation 3: |
[Bild bitte in Originalquelle ansehen] |
Acronyms and definitions
Term used |
Definition |
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BAT-AEPL |
Environmental performance level associated with BAT, as described in Commission Implementing Decision 2012/119/EU(4). BAT-AEPLs include emission levels associated with the best available techniques (BAT-AELs) as defined in Article 3(13) of Directive 2010/75/EU |
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BTX |
Collective term for benzene, toluene and ortho-/meta-/para-xylene or mixtures thereof |
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CO |
Carbon monoxide |
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Combustion unit |
Any technical apparatus in which fuels are oxidised in order to use the heat thus generated. Combustion units include boilers, engines, turbines and process furnaces/heaters, but do not include waste gas treatment units (e.g. a thermal/catalytic oxidiser used for the abatement of organic compounds) |
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Continuous measurement |
Measurement using an ‘automated measuring system’ permanently installed on site |
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Continuous process |
A process in which the raw materials are fed continuously into the reactor with the reaction products then fed into connected downstream separation and/or recovery units |
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Copper |
The sum of copper and its compounds, in dissolved or particulate form, expressed as Cu |
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DNT |
Dinitrotoluene |
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EB |
Ethylbenzene |
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EDC |
Ethylene dichloride |
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EG |
Ethylene glycols |
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EO |
Ethylene oxide |
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Ethanolamines |
Collective term for monoethanolamine, diethanolamine and triethanolamine, or mixtures thereof |
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Ethylene glycols |
Collective term for monoethylene glycol, diethylene glycol and triethylene glycol, or mixtures thereof |
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Existing plant |
A plant that is not a new plant |
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Existing unit |
A unit that is not a new unit |
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Flue-gas |
The exhaust gas exiting a combustion unit |
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I-TEQ |
International toxic equivalent – derived by using the international toxic equivalence factors, as defined in Annex VI, part 2 to Directive 2010/75/EU |
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Lower olefins |
Collective term for ethylene, propylene, butylene and butadiene, or mixtures thereof |
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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 units and associated equipment |
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MDA |
Methylene diphenyl diamine |
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MDI |
Methylene diphenyl diisocyanate |
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MDI plant |
Plant for the production of MDI from MDA via phosgenation |
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New plant |
A plant first permitted on 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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New unit |
A unit first permitted following the publication of these BAT conclusions or a complete replacement of a unit following the publication of these BAT conclusions |
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NOX precursors |
Nitrogen-containing compounds (e.g. ammonia, nitrous gases and nitrogen-containing organic compounds) in the input to a thermal treatment that lead to NOX emissions. Elementary nitrogen is not included |
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PCDD/F |
Polychlorinated dibenzo-dioxins and -furans |
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Periodic measurement |
Measurement at specified time intervals using manual or automated methods |
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Process furnace/heater |
Process furnaces or heaters are:
It should be noted that, as a consequence of the application of good energy recovery practices, some of the process furnaces/heaters may have an associated steam/electricity generation system. This is considered to be an integral design feature of the process furnace/heater that cannot be considered in isolation. |
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Process off-gas |
The gas leaving a process which is further treated for recovery and/or abatement |
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NOX |
The sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2), expressed as NO2 |
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Residues |
Substances or objects generated by the activities covered by the scope of this document, as waste or by-products |
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RTO |
Regenerative thermal oxidiser |
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SCR |
Selective catalytic reduction |
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SMPO |
Styrene monomer and propylene oxide |
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SNCR |
Selective non-catalytic reduction |
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SRU |
Sulphur recovery unit |
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TDA |
Toluene diamine |
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TDI |
Toluene diisocyanate |
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TDI plant |
Plant for the production of TDI from TDA via phosgenation |
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TOC |
Total organic carbon, expressed as C; includes all organic compounds (in water) |
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Total suspended solids (TSS) |
Mass concentration of all suspended solids, measured via filtration through glass fibre filters and gravimetry |
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TVOC |
Total volatile organic carbon; total volatile organic compounds which are measured by a flame ionisation detector (FID) and expressed as total carbon |
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Unit |
A segment/subpart of a plant in which a specific process or operation is carried out (e.g. reactor, scrubber, distillation column). Units can be new units or existing units |
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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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VCM |
Vinyl chloride monomer |
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VOCs |
Volatile organic compounds as defined in Article 3(45) of Directive 2010/75/EU |
1. GENERAL BAT CONCLUSIONS
1.1.
Monitoring of emissions to air
Substance/Parameter |
Standard(s)(5) |
Total rated thermal input (MWth)(6) |
Minimum monitoring frequency(7) |
Monitoring associated with |
CO |
Generic EN standards |
≥ 50 |
Continuous |
Table 2.1, Table 10.1 |
EN 15058 |
10 to < 50 |
Once every 3 months(8) |
||
Dust(9) |
Generic EN standards and EN 13284-2 |
≥ 50 |
Continuous |
BAT 5 |
EN 13284-1 |
10 to < 50 |
Once every 3 months(8) |
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NH3 (10) |
Generic EN standards |
≥ 50 |
Continuous |
BAT 7, Table 2.1 |
No EN standard available |
10 to < 50 |
Once every 3 months(8) |
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NOX |
Generic EN standards |
≥ 50 |
Continuous |
BAT 4, Table 2.1, Table 10.1 |
EN 14792 |
10 to < 50 |
Once every 3 months(8) |
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SO2 (11) |
Generic EN standards |
≥ 50 |
Continuous |
BAT 6 |
EN 14791 |
10 to < 50 |
Once every 3 months(8) |
Substance/Parameter |
Processes/Sources |
Standard(s) |
Minimum monitoring frequency |
Monitoring associated with |
Benzene |
Waste gas from the cumene oxidation unit in phenol production(12) |
No EN standard available |
Once every month(13) |
BAT 57 |
All other processes/sources(14) |
BAT 10 |
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Cl2 |
TDI/MDI(12) |
No EN standard available |
Once every month(13) |
BAT 66 |
EDC/VCM |
BAT 76 |
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CO |
Thermal oxidiser |
EN 15058 |
Once every month(13) |
BAT 13 |
Lower olefins (decoking) |
No EN standard available(15) |
Once every year or once during decoking, if decoking is less frequent |
BAT 20 |
|
EDC/VCM (decoking) |
BAT 78 |
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Dust |
Lower olefins (decoking) |
No EN standard available(16) |
Once every year or once during decoking, if decoking is less frequent |
BAT 20 |
EDC/VCM (decoking) |
BAT 78 |
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All other processes/sources(14) |
EN 13284-1 |
Once every month(13) |
BAT 11 |
|
EDC |
EDC/VCM |
No EN standard available |
Once every month(13) |
BAT 76 |
Ethylene oxide |
Ethylene oxide and ethylene glycols |
No EN standard available |
Once every month(13) |
BAT 52 |
Formaldehyde |
Formaldehyde |
No EN standard available |
Once every month(13) |
BAT 45 |
Gaseous chlorides, expressed as HCl |
TDI/MDI(12) |
EN 1911 |
Once every month(13) |
BAT 66 |
EDC/VCM |
BAT 76 |
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All other processes/sources(14) |
BAT 12 |
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NH3 |
Use of SCR or SNCR |
No EN standard available |
Once every month(13) |
BAT 7 |
NOX |
Thermal oxidiser |
EN 14792 |
Once every month(13) |
BAT 13 |
PCDD/F |
TDI/MDI(17) |
EN 1948-1, -2, and -3 |
Once every 6 months(13) |
BAT 67 |
PCDD/F |
EDC/VCM |
BAT 77 |
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SO2 |
All processes/sources(14) |
EN 14791 |
Once every month(13) |
BAT 12 |
Tetrachloromethane |
TDI/MDI(12) |
No EN standard available |
Once every month(13) |
BAT 66 |
TVOC |
TDI/MDI |
EN 12619 |
Once every month(13) |
BAT 66 |
EO (desorption of CO2 from scrubbing medium) |
Once every 6 months(13) |
BAT 51 |
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Formaldehyde |
Once every month(13) |
BAT 45 |
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Waste gas from the cumene oxidation unit in phenol production |
EN 12619 |
Once every month(13) |
BAT 57 |
|
Waste gas from other sources in phenol production when not combined with other waste gas streams |
Once every year |
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Waste gas from the oxidation unit in hydrogen peroxide production |
Once every month(13) |
BAT 86 |
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EDC/VCM |
Once every month(13) |
BAT 76 |
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All other processes/sources(14) |
Once every month(13) |
BAT 10 |
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VCM |
EDC/VCM |
No EN standard available |
Once every month(13) |
BAT 76 |
1.2.
Emissions to air
1.2.1.
Emissions to air from process furnaces/heaters
Technique |
Description |
Applicability |
|
a. |
Choice of fuel |
See Section 12.3. This includes switching from liquid to gaseous fuels, taking into account the overall hydrocarbon balance |
The switch from liquid to gaseous fuels may be restricted by the design of the burners in the case of existing plants |
b. |
Staged combustion |
Staged combustion burners achieve lower NOX emissions by staging the injection of either air or fuel in the near burner region. The division of fuel or air reduces the oxygen concentration in the primary burner combustion zone, thereby lowering the peak flame temperature and reducing thermal NOX formation |
Applicability may be restricted by space availability when upgrading small process furnaces, thus limiting the retrofit of fuel/air staging without reducing capacity For existing EDC crackers, the applicability may be restricted by the design of the process furnace |
c. |
Flue-gas recirculation (external) |
Recirculation of part of the flue-gas to the combustion chamber to replace part of the fresh combustion air, with the effect of reducing the oxygen content and therefore cooling the temperature of the flame |
For existing process furnaces/heaters, the applicability may be restricted by their design. Not applicable to existing EDC crackers |
d. |
Flue-gas recirculation (internal) |
Recirculation of part of the flue-gas within the combustion chamber to replace part of the fresh combustion air, with the effect of reducing the oxygen content and therefore reducing the temperature of the flame |
For existing process furnaces/heaters, the applicability may be restricted by their design |
e. |
Low-NOX burner (LNB) or ultra-low-NOX burner (ULNB) |
See Section 12.3 |
For existing process furnaces/heaters, the applicability may be restricted by their design |
f. |
Use of inert diluents |
‘Inert’ diluents, e.g. steam, water, nitrogen, are used (either by being premixed with the fuel prior to its combustion or directly injected into the combustion chamber) to reduce the temperature of the flame. Steam injection may increase CO emissions |
Generally applicable |
g. |
Selective catalytic reduction (SCR) |
See Section 12.1 |
Applicability to existing process furnaces/heaters may be restricted by space availability |
h. |
Selective non-catalytic reduction (SNCR) |
See Section 12.1 |
Applicability to existing process furnaces/heaters may be restricted by the temperature window (900–1 050 °C) and the residence time needed for the reaction. Not applicable to EDC crackers |
Technique |
Description |
Applicability |
|
a. |
Choice of fuel |
See Section 12.3. This includes switching from liquid to gaseous fuels, taking into account the overall hydrocarbon balance |
The switch from liquid to gaseous fuels may be restricted by the design of the burners in the case of existing plants |
b. |
Atomisation of liquid fuels |
Use of high pressure to reduce the droplet size of liquid fuel. Current optimal burner design generally includes steam atomisation |
Generally applicable |
c. |
Fabric, ceramic or metal filter |
See Section 12.1 |
Not applicable when only combusting gaseous fuels |
Technique |
Description |
Applicability |
|
a. |
Choice of fuel |
See Section 12.3. This includes switching from liquid to gaseous fuels, taking into account the overall hydrocarbon balance |
The switch from liquid to gaseous fuels may be restricted by the design of the burners in the case of existing plants |
b. |
Caustic scrubbing |
See Section 12.1 |
Applicability may be restricted by space availability |
1.2.2.
Emissions to air from the use of SCR or SNCR
1.2.3.
Emissions to air from other processes/sources
1.2.3.1.
Techniques to reduce emissions from other processes/sources
Technique |
Description |
Applicability |
|
a. |
Recovery and use of excess or generated hydrogen |
Recovery and use of excess hydrogen or hydrogen generated from chemical reactions (e.g. for hydrogenation reactions). Recovery techniques such as pressure swing adsorption or membrane separation may be used to increase the hydrogen content |
Applicability may be restricted where the energy demand for recovery is excessive due to the low hydrogen content or when there is no demand for hydrogen |
b. |
Recovery and use of organic solvents and unreacted organic raw materials |
Recovery techniques such as compression, condensation, cryogenic condensation, membrane separation and adsorption may be used. The choice of technique may be influenced by safety considerations, e.g. presence of other substances or contaminants |
Applicability may be restricted where the energy demand for recovery is excessive due to the low organic content |
c. |
Use of spent air |
The large volume of spent air from oxidation reactions is treated and used as low-purity nitrogen |
Only applicable where there are available uses for low-purity nitrogen which do not compromise process safety |
d. |
Recovery of HCl by wet scrubbing for subsequent use |
Gaseous HCl is absorbed in water using a wet scrubber, which may be followed by purification (e.g. using adsorption) and/or concentration (e.g. using distillation) (see Section 12.1 for the technique descriptions). The recovered HCl is then used (e.g. as acid or to produce chlorine) |
Applicability may be restricted in the case of low HCl loads |
e. |
Recovery of H2S by regenerative amine scrubbing for subsequent use |
Regenerative amine scrubbing is used for recovering H2S from process off-gas streams and from the acidic off-gases of sour water stripping units. H2S is then typically converted to elemental sulphur in a sulphur recovery unit in a refinery (Claus process). |
Only applicable if a refinery is located nearby |
f. |
Techniques to reduce solids and/or liquids entrainment |
See Section 12.1 |
Generally applicable |
Technique |
Description |
Applicability |
|
a. |
Condensation |
See Section 12.1. The technique is generally used in combination with further abatement techniques |
Generally applicable |
b. |
Adsorption |
See Section 12.1 |
Generally applicable |
c. |
Wet scrubbing |
See Section 12.1 |
Only applicable to VOCs that can be absorbed in aqueous solutions |
d. |
Catalytic oxidiser |
See Section 12.1 |
Applicability may be restricted by the presence of catalyst poisons |
e. |
Thermal oxidiser |
See Section 12.1. Instead of a thermal oxidiser, an incinerator for the combined treatment of liquid waste and waste gas may be used |
Generally applicable |
Technique |
Description |
Applicability |
|
a. |
Cyclone |
See Section 12.1. The technique is used in combination with further abatement techniques |
Generally applicable |
b. |
Electrostatic precipitator |
See Section 12.1 |
For existing units, the applicability may be restricted by space availability or safety considerations |
c. |
Fabric filter |
See Section 12.1 |
Generally applicable |
d. |
Two-stage dust filter |
See Section 12.1 |
|
e. |
Ceramic/metal filter |
See Section 12.1 |
|
f. |
Wet dust scrubbing |
See Section 12.1 |
1.2.3.2.
Techniques to reduce emissions from a thermal oxidiser
Technique |
Description |
Main pollutant targeted |
Applicability |
|
a. |
Removal of high levels of NOX precursors from the process off-gas streams |
Remove (if possible, for reuse) high levels of NOX precursors prior to thermal treatment, e.g. by scrubbing, condensation or adsorption |
NOX |
Generally applicable |
b. |
Choice of support fuel |
See Section 12.3 |
NOX, SO2 |
Generally applicable |
c. |
Low-NOX burner (LNB) |
See Section 12.1 |
NOX |
Applicability to existing units may be restricted by design and/or operational constraints |
d. |
Regenerative thermal oxidiser (RTO) |
See Section 12.1 |
NOX |
Applicability to existing units may be restricted by design and/or operational constraints |
e. |
Combustion optimisation |
Design and operational techniques used to maximise the removal of organic compounds, while minimising emissions to air of CO and NOX (e.g. by controlling combustion parameters such as temperature and residence time) |
CO, NOX |
Generally applicable |
f. |
Selective catalytic reduction (SCR) |
See Section 12.1 |
NOX |
Applicability to existing units may be restricted by space availability |
g. |
Selective non-catalytic reduction (SNCR) |
See Section 12.1 |
NOX |
Applicability to existing units may be restricted by the residence time needed for the reaction |
1.3.
Emissions to water
1.4.
Resource efficiency
Technique |
Description |
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a. |
Catalyst selection |
Select the catalyst to achieve the optimal balance between the following factors:
|
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b. |
Catalyst protection |
Techniques used upstream of the catalyst to protect it from poisons (e.g. raw material pretreatment) |
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c. |
Process optimisation |
Control of reactor conditions (e.g. temperature, pressure) to achieve the optimal balance between conversion efficiency and catalyst lifetime |
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d. |
Monitoring of catalyst performance |
Monitoring of the conversion efficiency to detect the onset of catalyst decay using suitable parameters (e.g. the heat of reaction and the CO2 formation in the case of partial oxidation reactions) |
1.5.
Residues
Technique |
Description |
Applicability |
|
Techniques to prevent or reduce the generation of waste |
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a. |
Addition of inhibitors to distillation systems |
Selection (and optimisation of dosage) of polymerisation inhibitors that prevent or reduce the generation of residues (e.g. gums or tars). The optimisation of dosage may need to take into account that it can lead to higher nitrogen and/or sulphur content in the residues which could interfere with their use as a fuel |
Generally applicable |
b. |
Minimisation of high-boiling residue formation in distillation systems |
Techniques that reduce temperatures and residence times (e.g. packing instead of trays to reduce the pressure drop and thus the temperature; vacuum instead of atmospheric pressure to reduce the temperature) |
Only applicable to new distillation units or major plant upgrades |
Techniques to recover materials for reuse or recycling |
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c. |
Material recovery (e.g. by distillation, cracking) |
Materials (i.e. raw materials, products, and by-products) are recovered from residues by isolation (e.g. distillation) or conversion (e.g. thermal/catalytic cracking, gasification, hydrogenation) |
Only applicable where there are available uses for these recovered materials |
d. |
Catalyst and adsorbent regeneration |
Regeneration of catalysts and adsorbents, e.g. using thermal or chemical treatment |
Applicability may be restricted where regeneration results in significant cross-media effects. |
Techniques to recover energy |
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e. |
Use of residues as a fuel |
Some organic residues, e.g. tar, can be used as fuels in a combustion unit |
Applicability may be restricted by the presence of certain substances in the residues, making them unsuitable to use in a combustion unit and requiring disposal |
1.6.
Other than normal operating conditions
Technique |
Description |
Applicability |
|
a. |
Identification of critical equipment |
Equipment critical to the protection of the environment (‘critical equipment’) is identified on the basis of a risk assessment (e.g. using a Failure Mode and Effects Analysis) |
Generally applicable |
b. |
Asset reliability programme for critical equipment |
A structured programme to maximise equipment availability and performance which includes standard operating procedures, preventive maintenance (e.g. against corrosion), monitoring, recording of incidents, and continuous improvements |
Generally applicable |
c. |
Back-up systems for critical equipment |
Build and maintain back-up systems, e.g. vent gas systems, abatement units |
Not applicable if appropriate equipment availability can be demonstrated using technique b. |
2. BAT CONCLUSIONS FOR LOWER OLEFINS PRODUCTION
2.1.
Emissions to air
2.1.1.
BAT-AELs for emissions to air from a lower olefins cracker furnace
Parameter |
BAT-AELs(18) (19) (20) (daily average or average over the sampling period) (mg/Nm3, at 3 vol-% O2) |
|
New furnace |
Existing furnace |
|
NOX |
60–100 |
70–200 |
NH3 |
< 5–15(21) |
2.1.2.
Techniques to reduce emissions from decoking
Technique |
Description |
Applicability |
|
Techniques to reduce the frequency of decoking |
|||
a. |
Tube materials that retard coke formation |
Nickel present at the surface of the tubes catalyses coke formation. Employing materials that have lower nickel levels, or coating the interior tube surface with an inert material, can therefore retard the rate of coke build-up |
Only applicable to new units or major plant upgrades |
b. |
Doping of the raw material feed with sulphur compounds |
As nickel sulphides do not catalyse coke formation, doping the feed with sulphur compounds when they are not already present at the desired level can also help retard the build-up of coke, as this will promote the passivation of the tube surface |
Generally applicable |
c. |
Optimisation of thermal decoking |
Optimisation of operating conditions, i.e. airflow, temperature and steam content across the decoking cycle, to maximise coke removal |
Generally applicable |
Abatement techniques |
|||
d. |
Wet dust scrubbing |
See Section 12.1 |
Generally applicable |
e. |
Dry cyclone |
See Section 12.1 |
Generally applicable |
f. |
Combustion of decoking waste gas in process furnace/heater |
The decoking waste gas stream is passed through the process furnace/heater during decoking where the coke particles (and CO) are further combusted |
Applicability for existing plants may be restricted by the design of the pipework systems or fire-duty restrictions |
2.2.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Use of low-sulphur raw materials in the cracker feed |
Use of raw materials that have a low sulphur content or have been desulphurised |
Applicability may be restricted by a need for sulphur doping to reduce coke build-up |
b. |
Maximisation of the use of amine scrubbing for the removal of acid gases |
The scrubbing of the cracked gases with a regenerative (amine) solvent to remove acid gases, mainly H2S, to reduce the load on the downstream caustic scrubber |
Not applicable if the lower olefin cracker is located far away from an SRU. Applicability for existing plants may be restricted by the capacity of the SRU |
c. |
Oxidation |
Oxidation of sulphides present in the spent scrubbing liquor to sulphates, e.g. using air at elevated pressure and temperature (i.e. wet air oxidation) or an oxidising agent such as hydrogen peroxide |
Generally applicable |
3. BAT CONCLUSIONS FOR AROMATICS PRODUCTION
3.1.
Emissions to air
3.2.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Water-free vacuum generation |
Use mechanical pumping systems in a closed circuit procedure, discharging only a small amount of water as blowdown, or use dry-running pumps. In some cases, waste-water-free vacuum generation can be achieved by use of the product as a barrier liquid in a mechanical vacuum pump, or by use of a gas stream from the production process |
Generally applicable |
b. |
Source segregation of aqueous effluents |
Aqueous effluents from aromatics plants are segregated from waste water from other sources in order to facilitate the recovery of raw materials or products |
For existing plants, the applicability may be restricted by site-specific drainage systems |
c. |
Liquid phase separation with recovery of hydrocarbons |
Separation of organic and aqueous phases with appropriate design and operation (e.g. sufficient residence time, phase boundary detection and control) to prevent any entrainment of undissolved organic material |
Generally applicable |
d |
Stripping with recovery of hydrocarbons |
See Section 12.2. Stripping can be used on individual or combined streams |
Applicability may be restricted when the concentration of hydrocarbons is low |
e. |
Reuse of water |
With further treatment of some waste water streams, water from stripping can be used as process water or as boiler feed water, replacing other sources of water |
Generally applicable |
3.3.
Resource efficiency
3.4.
Energy efficiency
Technique |
Description |
Applicability |
|
a. |
Distillation optimisation |
For each distillation column, the number of trays, reflux ratio, feed location and, for extractive distillations, the solvents to feed ratio are optimised |
Applicability to existing units may be restricted by design, space availability and/or operational constraints |
b. |
Recovery of heat from column overhead gaseous stream |
Reuse condensation heat from the toluene and the xylene distillation column to supply heat elsewhere in the installation |
|
c. |
Single extractive distillation column |
In a conventional extractive distillation system, the separation would require a sequence of two separation steps (i.e. main distillation column with side column or stripper). In a single extractive distillation column, the separation of the solvent is carried out in a smaller distillation column that is incorporated into the column shell of the first column |
Only applicable to new plants or major plant upgrades. Applicability may be restricted for smaller capacity units as operability may be constrained by combining a number of operations into one piece of equipment |
d. |
Distillation column with a dividing wall |
In a conventional distillation system, the separation of a three-component mixture into its pure fractions requires a direct sequence of at least two distillation columns (or main columns with side columns). With a dividing wall column, separation can be carried out in just one piece of apparatus |
|
e. |
Thermally coupled distillation |
If distillation is carried out in two columns, energy flows in both columns can be coupled. The steam from the top of the first column is fed to a heat exchanger at the base of the second column |
Only applicable to new plants or major plant upgrades. Applicability depends on the set-up of the distillation columns and process conditions, e.g. working pressure |
3.5.
Residues
Technique |
Description |
Applicability |
|
a. |
Selective hydrogenation of reformate or pygas |
Reduce the olefin content of reformate or pygas by hydrogenation. With fully hydrogenated raw materials, clay treaters have longer operating cycles |
Only applicable to plants using raw materials with a high olefin content |
b. |
Clay material selection |
Use a clay that lasts as long as possible for its given conditions (i.e. having surface/structural properties that increase the operating cycle length), or use a synthetic material that has the same function as the clay but that can be regenerated |
Generally applicable |
4. BAT CONCLUSIONS FOR ETHYLBENZENE AND STYRENE MONOMER PRODUCTION
4.1.
Process selection
4.2.
Emissions to air
Technique |
Description |
Applicability |
|
a. |
Techniques to reduce liquids entrainment |
See Section 12.1 |
Generally applicable |
b. |
Condensation |
See Section 12.1 |
Generally applicable |
c. |
Adsorption |
See Section 12.1 |
Generally applicable |
d. |
Scrubbing |
See Section 12.1. Scrubbing is carried out with a suitable solvent (e.g. the cool, recirculated ethylbenzene) to absorb ethylbenzene, which is recycled to the reactor |
For existing plants, the use of the recirculated ethylbenzene stream may be restricted by the plant design |
4.3.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Optimised liquid phase separation |
Separation of organic and aqueous phases with appropriate design and operation (e.g. sufficient residence time, phase boundary detection and control) to prevent any entrainment of undissolved organic material |
Generally applicable |
b. |
Steam stripping |
See Section 12.2 |
Generally applicable |
c. |
Adsorption |
See Section 12.2 |
Generally applicable |
d. |
Reuse of water |
Condensates from the reaction can be used as process water or as boiler feed after steam stripping (see technique b.) and adsorption (see technique c.) |
Generally applicable |
4.4.
Resource efficiency
Technique |
Description |
Applicability |
|
a. |
Condensation |
See Section 12.1 |
Generally applicable |
b. |
Scrubbing |
See Section 12.1. The absorbent consists of commercial organic solvents (or tar from ethylbenzene plants) (see BAT 42b). VOCs are recovered by stripping of the scrubber liquor |
4.5.
Residues
Technique |
Description |
Applicability |
|
a. |
Material recovery (e.g. by distillation, cracking) |
See BAT 17c |
Only applicable where there are available uses for these recovered materials |
b. |
Use of tar as an absorbent for scrubbing |
See section 12.1. Use the tar as an absorbent in the scrubbers used in styrene monomer production by ethylbenzene dehydrogenation, instead of commercial organic solvents (see BAT 38b). The extent to which tar can be used depends on the scrubber capacity |
Generally applicable |
c. |
Use of tar as a fuel |
See BAT 17e |
Generally applicable |
Technique |
Description |
Applicability |
|
a. |
Addition of inhibitors to distillation systems |
See BAT 17a |
Generally applicable |
b. |
Minimisation of high-boiling residue formation in distillation systems |
See BAT 17b |
Only applicable to new distillation units or major plant upgrades |
c. |
Use of residues as a fuel |
See BAT 17e |
Generally applicable |
5. BAT CONCLUSIONS FOR FORMALDEHYDE PRODUCTION
5.1.
Emissions to air
Technique |
Description |
Applicability |
|
a. |
Send the waste gas stream to a combustion unit |
See BAT 9 |
Only applicable to the silver process |
b. |
Catalytic oxidiser with energy recovery |
See Section 12.1. Energy is recovered as steam |
Only applicable to the metal oxide process. The ability to recover energy may be restricted in small stand-alone plants |
c. |
Thermal oxidiser with energy recovery |
See Section 12.1. Energy is recovered as steam |
Only applicable to the silver process |
Parameter |
BAT-AEL (daily average or average over the sampling period) (mg/Nm3, no correction for oxygen content) |
TVOC |
< 5–30(22) |
Formaldehyde |
2–5 |
5.2.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Reuse of water |
Aqueous streams (e.g. from cleaning, spills and condensates) are recirculated into the process mainly to adjust the formaldehyde product concentration. The extent to which water can be reused depends on the desired formaldehyde concentration |
Generally applicable |
b. |
Chemical pretreatment |
Conversion of formaldehyde into other substances which are less toxic, e.g. by addition of sodium sulphite or by oxidation |
Only applicable to effluents which, due to their formaldehyde content, could have a negative effect on the downstream biological waste water treatment |
5.3.
Residues
Technique |
Description |
Applicability |
|
a. |
Minimisation of paraformaldehyde generation |
The formation of paraformaldehyde is minimised by improved heating, insulation and flow circulation |
Generally applicable |
b. |
Material recovery |
Paraformaldehyde is recovered by dissolution in hot water where it undergoes hydrolysis and depolymerisation to give a formaldehyde solution, or is reused directly in other processes |
Not applicable when the recovered paraformaldehyde cannot be used due to its contamination |
c. |
Use of residues as a fuel |
Paraformaldehyde is recovered and used as a fuel |
Only applicable when technique b. cannot be applied |
6. BAT CONCLUSIONS FOR ETHYLENE OXIDE AND ETHYLENE GLYCOLS PRODUCTION
6.1.
Process selection
6.2.
Emissions to air
Technique |
Description |
Applicability |
|
Techniques to recover organic material for reuse or recycling |
|||
a. |
Use of pressure swing adsorption or membrane separation to recover ethylene from the inerts purge |
With the pressure swing adsorption technique, the target gas (in this case ethylene) molecules are adsorbed on a solid (e.g. molecular sieve) at high pressure, and subsequently desorbed in more concentrated form at lower pressure for reuse or recycling. For membrane separation, see Section 12.1 |
Applicability may be restricted when the energy demand is excessive due to a low ethylene mass flow |
Energy recovery techniques |
|||
b. |
Send the inerts purge stream to a combustion unit |
See BAT 9 |
Generally applicable |
Technique |
Description |
Applicability |
|
Process-integrated techniques |
|||
a. |
Staged CO2 desorption |
The technique consists of conducting the depressurisation necessary to liberate the carbon dioxide from the absorption medium in two steps rather than one. This allows an initial hydrocarbon-rich stream to be isolated for potential recirculation, leaving a relatively clean carbon dioxide stream for further treatment. |
Only applicable to new plants or major plant upgrades |
Abatement techniques |
|||
b. |
Catalytic oxidiser |
See Section 12.1 |
Generally applicable |
c. |
Thermal oxidiser |
See Section 12.1 |
Generally applicable |
Parameter |
BAT-AEL |
TVOC |
1–10 g/t of EO produced(23) (24) (25) |
Technique |
Description |
Applicability |
|
a. |
Indirect cooling |
Use indirect cooling systems (with heat exchangers) instead of open cooling systems |
Only applicable to new plants or major plant upgrades |
b. |
Complete EO removal by stripping |
Maintain appropriate operating conditions and use online monitoring of the EO stripper operation to ensure that all EO is stripped out; and provide adequate protection systems to avoid EO emissions during other than normal operating conditions |
Only applicable when technique a. cannot be applied |
6.3.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Use of the purge from the EO plant in the EG plant |
The purge streams from the EO plant are sent to the EG process and not discharged as waste water. The extent to which the purge can be reused in the EG process depends on EG product quality considerations. |
Generally applicable |
b. |
Distillation |
Distillation is a technique used to separate compounds with different boiling points by partial evaporation and recondensation. The technique is used in EO and EG plants to concentrate aqueous streams to recover glycols or enable their disposal (e.g. by incineration, instead of their discharge as waste water) and to enable the partial reuse/recycling of water. |
Only applicable to new plants or major plant upgrades |
6.4.
Residues
Technique |
Description |
Applicability |
|
a. |
Hydrolysis reaction optimisation |
Optimisation of the water to EO ratio to both achieve lower co-production of heavier glycols and avoid excessive energy demand for the dewatering of glycols. The optimum ratio depends on the target output of di- and triethylene glycols |
Generally applicable |
b. |
Isolation of by-products at EO plants for use |
For EO plants, the concentrated organic fraction obtained after the dewatering of the liquid effluent from EO recovery is distilled to give valuable short-chain glycols and a heavier residue |
Only applicable to new plants or major plant upgrades |
c. |
Isolation of by-products at EG plants for use |
For EG plants, the longer chain glycols fraction can either be used as such or further fractionated to yield valuable glycols |
Generally applicable |
7. BAT CONCLUSIONS FOR PHENOL PRODUCTION
7.1.
Emissions to air
Technique |
Description |
Applicability |
|
Process-integrated techniques |
|||
a. |
Techniques to reduce liquids entrainment |
See Section 12.1 |
Generally applicable |
Techniques to recover organic material for reuse |
|||
b. |
Condensation |
See Section 12.1 |
Generally applicable |
c. |
Adsorption (regenerative) |
See Section 12.1 |
Generally applicable |
Technique |
Description |
Applicability |
|
a. |
Send the waste gas stream to a combustion unit |
See BAT 9 |
Only applicable where there are available uses for the waste gas as gaseous fuel |
b. |
Adsorption |
See Section 12.1 |
Generally applicable |
c. |
Thermal oxidiser |
See Section 12.1 |
Generally applicable |
d. |
Regenerative thermal oxidiser (RTO) |
See Section 12.1 |
Generally applicable |
Parameter |
Source |
BAT-AEL (daily average or average over the sampling period) (mg/Nm3, no correction for oxygen content) |
Conditions |
Benzene |
Cumene oxidation unit |
< 1 |
The BAT-AEL applies if the emission exceeds 1 g/h |
TVOC |
5–30 |
— |
7.2.
Emissions to water
Parameter |
BAT-AEPL (average value from at least three spot samples taken at intervals of at least half an hour) |
Associated monitoring |
Total organic peroxides, expressed as cumene hydroperoxide |
< 100 mg/l |
No EN standard available. The minimum monitoring frequency is once every day and may be reduced to four times per year if adequate performance of the hydrolysis is demonstrated by controlling the process parameters (e.g. pH, temperature and residence time) |
7.3.
Residues
Technique |
Description |
Applicability |
|
a. |
Material recovery (e.g. by distillation, cracking) |
See BAT 17c. Use distillation to recover cumene, α-methylstyrene phenol, etc. |
Generally applicable |
b. |
Use of tar as a fuel |
See BAT 17e. |
Generally applicable |
8. BAT CONCLUSIONS FOR ETHANOLAMINES PRODUCTION
8.1.
Emissions to air
8.2.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Water-free vacuum generation |
Use of dry-running pumps, e.g. positive displacement pumps |
Applicability to existing plants may be restricted by design and/or operational constraints |
b. |
Use of water ring vacuum pumps with recirculation of the ring water |
The water used as the sealant liquid of the pump is recirculated to the pump casing via a closed loop with only small purges, so that waste water generation is minimised |
Only applicable when technique a. cannot be applied. Not applicable for triethanolamine distillation |
c. |
Reuse of aqueous streams from vacuum systems in the process |
Return aqueous streams from water ring pumps or steam ejectors to the process for recovery of organic material and reuse of the water. The extent to which water can be reused in the process is restricted by the water demand of the process |
Only applicable when technique a. cannot be applied |
d. |
Condensation of organic compounds (amines) upstream of vacuum systems |
See Section 12.1 |
Generally applicable |
8.3.
Raw material consumption
Technique |
Description |
Applicability |
|
a. |
Use of excess ammonia |
Maintaining a high level of ammonia in the reaction mixture is an effective way of ensuring that all the ethylene oxide is converted into products |
Generally applicable |
b. |
Optimisation of the water content in the reaction |
Water is used to accelerate the main reactions without changing the product distribution and without significant side reactions with ethylene oxide to glycols |
Only applicable for the aqueous process |
c. |
Optimise the process operating conditions |
Determine and maintain the optimum operating conditions (e.g. temperature, pressure, residence time) to maximise the conversion of ethylene oxide to the desired mix of mono-, di-, triethanolamines |
Generally applicable |
9. BAT CONCLUSIONS FOR TOLUENE DIISOCYANATE (TDI) AND METHYLENE DIPHENYL DIISOCYANATE (MDI) PRODUCTION
9.1.
Emissions to air
Technique |
Description |
Applicability |
|
a. |
Condensation |
See Section 12.1 |
Generally applicable |
b. |
Wet scrubbing |
See Section 12.1. In many cases, scrubbing efficiency is enhanced by the chemical reaction of the absorbed pollutant (partial oxidation of NOX with recovery of nitric acid, removal of acids with caustic solution, removal of amines with acidic solutions, reaction of aniline with formaldehyde in caustic solution) |
|
c. |
Thermal reduction |
See Section 12.1 |
Applicability to existing units may be restricted by space availability |
d. |
Catalytic reduction |
See Section 12.1 |
Technique |
Description |
Applicability |
|
a. |
Absorption of HCl by wet scrubbing |
See BAT 8d. |
Generally applicable |
b. |
Absorption of phosgene by scrubbing |
See Section 12.1. The excess phosgene is absorbed using an organic solvent and returned to the process |
Generally applicable |
c. |
HCl/phosgene condensation |
See Section 12.1 |
Generally applicable |
Parameter |
BAT-AEL (mg/Nm3, no correction for oxygen content) |
TVOC |
1–5(26) (27) |
Tetrachloromethane |
≤ 0,5 g/t MDI produced(28) ≤ 0,7 g/t TDI produced(28) |
Cl2 |
< 1(27) (29) |
HCl |
2–10(27) |
PCDD/F |
0,025–0,08 ng I-TEQ/Nm3 (27) |
Technique |
Description |
Applicability |
|
a. |
Rapid quenching |
Rapid cooling of exhaust gases to prevent the de novo synthesis of PCDD/F |
Generally applicable |
b. |
Activated carbon injection |
Removal of PCDD/F by adsorption onto activated carbon that is injected into the exhaust gas, followed by dust abatement |
9.2.
Emissions to water
Substance/Parameter |
Plant |
Sampling point |
Standard(s) |
Minimum monitoring frequency |
Monitoring associated with |
TOC |
DNT plant |
Outlet of the pretreatment unit |
EN 1484 |
Once every week(30) |
BAT 70 |
MDI and/or TDI plant |
Outlet of the plant |
Once every month |
BAT 72 |
||
Aniline |
MDA plant |
Outlet of the final waste water treatment |
No EN standard available |
Once every month |
BAT 14 |
Chlorinated solvents |
MDI and/or TDI plant |
Various EN standards available (e.g. EN ISO 15680) |
BAT 14 |
Technique |
Description |
Applicability |
|
a. |
Use of highly concentrated nitric acid |
Use highly concentrated HNO3 (e.g. about 99 %) to increase the process efficiency and to reduce the waste water volume and the load of pollutants |
Applicability to existing units may be restricted by design and/or operational constraints |
b. |
Optimised regeneration and recovery of spent acid |
Perform the regeneration of the spent acid from the nitration reaction in such a way that water and the organic content are also recovered for reuse, by using an appropriate combination of evaporation/distillation, stripping and condensation |
Applicability to existing units may be restricted by design and/or operational constraints |
c. |
Reuse of process water to wash DNT |
Reuse process water from the spent acid recovery unit and the nitration unit to wash DNT |
Applicability to existing units may be restricted by design and/or operational constraints |
d. |
Reuse of water from the first washing step in the process |
Nitric and sulphuric acid are extracted from the organic phase using water. The acidified water is returned to the process, for direct reuse or further processing to recover materials |
Generally applicable |
e. |
Multiple use and recirculation of water |
Reuse water from washing, rinsing and equipment cleaning e.g. in the counter-current multistep washing of the organic phase |
Generally applicable |
Technique |
Description |
Applicability |
|
a. |
Extraction |
See Section 12.2 |
Generally applicable |
b. |
Chemical oxidation |
See Section 12.2 |
Parameter |
BAT-AEPL (average of values obtained during 1 month) |
TOC |
< 1 kg/t DNT produced |
Specific waste water volume |
< 1 m3/t DNT produced |
Technique |
Description |
Applicability |
|
a. |
Evaporation |
See Section 12.2 |
Generally applicable |
b. |
Stripping |
See Section 12.2 |
|
c. |
Extraction |
See Section 12.2 |
|
d. |
Reuse of water |
Reuse of water (e.g. from condensates or from scrubbing) in the process or in other processes (e.g. in a DNT plant). The extent to which water can be reused at existing plants may be restricted by technical constraints |
Generally applicable |
Parameter |
BAT-AEPL (average of values obtained during 1 month) |
Specific waste water volume |
< 1 m3/t TDA produced |
Parameter |
BAT-AEPL (average of values obtained during 1 year) |
TOC |
< 0,5 kg/t product (TDI or MDI)(31) |
Technique |
Description |
Applicability |
|
a. |
Evaporation |
See Section 12.2. Used to facilitate extraction (see technique b) |
Generally applicable |
b. |
Extraction |
See Section 12.2. Used to recover/remove MDA |
Generally applicable |
c. |
Steam stripping |
See Section 12.2. Used to recover/remove aniline and methanol |
For methanol, the applicability depends on the assessment of alternative options as part of the waste water management and treatment strategy |
d. |
Distillation |
See Section 12.2. Used to recover/remove aniline and methanol |
9.3.
Residues
Technique |
Description |
Applicability |
|
Techniques to prevent or reduce the generation of waste |
|||
a. |
Minimisation of high-boiling residue formation in distillation systems |
See BAT 17b. |
Only applicable to new distillation units or major plant upgrades |
Techniques to recover organic material for reuse or recycling |
|||
b. |
Increased recovery of TDI by evaporation or further distillation |
Residues from distillation are additionally processed to recover the maximum amount of TDI contained therein, e.g. using a thin film evaporator or other short-path distillation units followed by a dryer. |
Only applicable to new distillation units or major plant upgrades |
c. |
Recovery of TDA by chemical reaction |
Tars are processed to recover TDA by chemical reaction (e.g. hydrolysis). |
Only applicable to new plants or major plant upgrades |
10. BAT CONCLUSIONS FOR ETHYLENE DICHLORIDE AND VINYL CHLORIDE MONOMER PRODUCTION
10.1.
Emissions to air
10.1.1.
BAT-AEL for emissions to air from an EDC cracker furnace
Parameter |
BAT-AELs(32) (33) (34) (daily average or average over the sampling period) (mg/Nm3, at 3 vol-% O2) |
NOx |
50–100 |
10.1.2.
Techniques and BAT-AEL for emissions to air from other sources
Technique |
Description |
Applicability |
|
Process-integrated techniques |
|||
a. |
Control of feed quality |
Control the quality of the feed to minimise the formation of residues (e.g. propane and acetylene content of ethylene; bromine content of chlorine; acetylene content of hydrogen chloride) |
Generally applicable |
b. |
Use of oxygen instead of air for oxychlorination |
Only applicable to new oxychlorination plants or major oxychlorination plant upgrades |
|
Techniques to recover organic material |
|||
c. |
Condensation using chilled water or refrigerants |
Use condensation (see Section 12.1) with chilled water or refrigerants such as ammonia or propylene to recover organic compounds from individual vent gas streams before sending them to final treatment |
Generally applicable |
Parameter |
BAT-AEL (daily average or average over the sampling period) (mg/Nm3, at 11 vol-% O2) |
TVOC |
0,5–5 |
Sum of EDC and VCM |
< 1 |
Cl2 |
< 1–4 |
HCl |
2–10 |
PCDD/F |
0,025–0,08 ng I-TEQ/Nm3 |
Technique |
Description |
Applicability |
|
a. |
Rapid quenching |
Rapid cooling of exhaust gases to prevent the de novo synthesis of PCDD/F |
Generally applicable |
b. |
Activated carbon injection |
Removal of PCDD/F by adsorption onto activated carbon that is injected into the exhaust gas, followed by dust abatement |
Technique |
Description |
Applicability |
|
Techniques to reduce the frequency of decoking |
|||
a. |
Optimisation of thermal decoking |
Optimisation of operating conditions, i.e. airflow, temperature and steam content across the decoking cycle, to maximise coke removal |
Generally applicable |
b. |
Optimisation of mechanical decoking |
Optimise mechanical decoking (e.g. sand jetting) to maximise coke removal as dust |
Generally applicable |
Abatement techniques |
|||
c. |
Wet dust scrubbing |
See Section 12.1 |
Only applicable to thermal decoking |
d. |
Cyclone |
See Section 12.1 |
Generally applicable |
e. |
Fabric filter |
See Section 12.1 |
Generally applicable |
10.2.
Emissions to water
Substance/Parameter |
Plant |
Sampling point |
Standard(s) |
Minimum monitoring frequency |
Monitoring associated with |
EDC |
All plants |
Outlet of the waste water stripper |
EN ISO 10301 |
Once every day |
BAT 80 |
VCM |
|||||
Copper |
Oxy-chlorination plant using the fluidised-bed design |
Outlet of the pretreatment for solids removal |
Various EN standards available, e.g. EN ISO 11885, EN ISO 15586, EN ISO 17294-2 |
Once every day(35) |
BAT 81 |
PCDD/F |
No EN standard available |
Once every 3 months |
|||
Total suspended solids (TSS) |
EN 872 |
Once every day(35) |
|||
Copper |
Oxy-chlorination plant using the fluidised-bed design |
Outlet of the final waste water treatment |
Various EN standards available, e.g. EN ISO 11885, EN ISO 15586, EN ISO 17294-2 |
Once every month |
BAT 14 and BAT 81 |
EDC |
All plants |
EN ISO 10301 |
Once every month |
BAT 14 and BAT 80 |
|
PCDD/F |
No EN standard available |
Once every 3 months |
BAT 14 and BAT 81 |
Parameter |
BAT-AEPL (average of values obtained during 1 month)(36) |
EDC |
0,1–0,4 mg/l |
VCM |
< 0,05 mg/l |
Technique |
Description |
Applicability |
|
Process-integrated techniques |
|||
a. |
Fixed-bed design for oxychlorination |
Oxychlorination reaction design: in the fixed-bed reactor, catalyst particulates entrained in the overhead gaseous stream are reduced |
Not applicable to existing plants using the fluidised-bed design |
b. |
Cyclone or dry catalyst filtration system |
A cyclone or a dry catalyst filtration system reduces catalyst losses from the reactor and therefore also their transfer to waste water |
Only applicable to plants using the fluidised-bed design |
Waste water pretreatment |
|||
c. |
Chemical precipitation |
See Section 12.2. Chemical precipitation is used to remove dissolved copper |
Only applicable to plants using the fluidised-bed design |
d. |
Coagulation and flocculation |
See Section 12.2 |
Only applicable to plants using the fluidised-bed design |
e. |
Membrane filtration (micro- or ultrafiltration) |
See Section 12.2 |
Only applicable to plants using the fluidised-bed design |
Parameter |
BAT-AEPL (average of values obtained during 1 year) |
Copper |
0,4–0,6 mg/l |
PCDD/F |
< 0,8 ng I-TEQ/l |
Total suspended solids (TSS) |
10–30 mg/l |
Parameter |
BAT-AEL (average of values obtained during 1 year) |
Copper |
0,04–0,2 g/t EDC produced by oxychlorination(37) |
EDC |
0,01–0,05 g/t EDC purified(38) (39) |
PCDD/F |
0,1– 0,3 μg I-TEQ/t EDC produced by oxychlorination |
10.3.
Energy efficiency
10.4.
Residues
Technique |
Description |
Applicability |
|
a. |
Use of promoters in cracking |
See BAT 83 |
Generally applicable |
b. |
Rapid quenching of the gaseous stream from EDC cracking |
The gaseous stream from EDC cracking is quenched by direct contact with cold EDC in a tower to reduce coke formation. In some cases, the stream is cooled by heat exchange with cold liquid EDC feed prior to quenching |
Generally applicable |
c. |
Pre-evaporation of EDC feed |
Coke formation is reduced by evaporating EDC upstream of the reactor to remove high-boiling coke precursors |
Only applicable to new plants or major plant upgrades |
d. |
Flat flame burners |
A type of burner in the furnace that reduces hot spots on the walls of the cracker tubes |
Only applicable to new furnaces or major plant upgrades |
Technique |
Description |
Applicability |
|
a. |
Hydrogenation of acetylene |
HCl is generated in the EDC cracking reaction and recovered by distillation. Hydrogenation of the acetylene present in this HCl stream is carried out to reduce the generation of unwanted compounds during oxychlorination. Acetylene values below 50 ppmv at the outlet of the hydrogenation unit are advisable |
Only applicable to new plants or major plant upgrades |
b. |
Recovery and reuse of HCl from incineration of liquid waste |
HCl is recovered from incinerator off-gas by wet scrubbing with water or diluted HCl (see Section 12.1) and reused (e.g. in the oxychlorination plant) |
Generally applicable |
c. |
Isolation of chlorinated compounds for use |
Isolation and, if needed, purification of by-products for use (e.g. monochloroethane and/or 1,1,2-trichloroethane, the latter for the production of 1,1-dichloroethylene) |
Only applicable to new distillation units or major plant upgrades. Applicability may be restricted by a lack of available uses for these compounds |
11. BAT CONCLUSIONS FOR HYDROGEN PEROXIDE PRODUCTION
11.1.
Emissions to air
Technique |
Description |
Applicability |
|
Process-integrated techniques |
|||
a. |
Optimisation of the oxidation process |
Process optimisation includes elevated oxidation pressure and reduced oxidation temperature in order to reduce the solvent vapour concentration in the process off-gas |
Only applicable to new oxidation units or major plant upgrades |
b. |
Techniques to reduce solids and/or liquids entrainment |
See Section 12.1 |
Generally applicable |
Techniques to recover solvent for reuse |
|||
c. |
Condensation |
See Section 12.1 |
Generally applicable |
d. |
Adsorption (regenerative) |
See Section 12.1 |
Not applicable to process off-gas from oxidation with pure oxygen |
Parameter |
BAT-AEL(40) (daily average or average over the sampling period)(41) (no correction for oxygen content) |
TVOC |
5–25 mg/Nm3 (42) |
11.2.
Emissions to water
Technique |
Description |
Applicability |
|
a. |
Optimised liquid phase separation |
Separation of organic and aqueous phases with appropriate design and operation (e.g. sufficient residence time, phase boundary detection and control) to prevent any entrainment of undissolved organic material |
Generally applicable |
b. |
Reuse of water |
Reuse of water, e.g. from cleaning or liquid phase separation. The extent to which water can be reused in the process depends on product quality considerations |
Generally applicable |
Technique |
Description |
|
a. |
Adsorption |
See Section 12.2. Adsorption is carried out prior to sending waste water streams to the final biological treatment |
b. |
Waste water incineration |
See Section 12.2 |
12. DESCRIPTIONS OF TECHNIQUES
12.1.
Process off-gas and waste gas treatment techniques
Technique |
Description |
Adsorption |
A technique for removing compounds from a process off-gas or waste gas stream by retention on a solid surface (typically activated carbon). Adsorption may be regenerative or non-regenerative (see below). |
Adsorption (non-regenerative) |
In non-regenerative adsorption, the spent adsorbent is not regenerated but disposed of. |
Adsorption (regenerative) |
Adsorption where the adsorbate is subsequently desorbed, e.g. with steam (often on site) for reuse or disposal and the adsorbent is reused. For continuous operation, typically more than two adsorbers are operated in parallel, one of them in desorption mode. |
Catalytic oxidiser |
Abatement equipment which oxidises combustible compounds in a process off-gas or waste gas stream with air or oxygen in a catalyst bed. The catalyst enables oxidation at lower temperatures and in smaller equipment compared to a thermal oxidiser. |
Catalytic reduction |
NOx is reduced in the presence of a catalyst and a reducing gas. In contrast to SCR, no ammonia and/or urea are added. |
Caustic scrubbing |
The removal of acidic pollutants from a gas stream by scrubbing using an alkaline solution. |
Ceramic/metal filter |
Ceramic filter material. In circumstances where acidic compounds such as HCl, NOX, SOX and dioxins are to be removed, the filter material is fitted with catalysts and the injection of reagents may be necessary. In metal filters, surface filtration is carried out by sintered porous metal filter elements. |
Condensation |
A technique for removing the vapours of organic and inorganic compounds from a process off-gas or waste gas stream by reducing its temperature below its dew point so that the vapours liquefy. Depending on the operating temperature range required, there are different methods of condensation, e.g. cooling water, chilled water (temperature typically around 5 °C) or refrigerants such as ammonia or propene. |
Cyclone (dry or wet) |
Equipment for removal of dust from a process off-gas or waste gas stream based on imparting centrifugal forces, usually within a conical chamber. |
Electrostatic precipitator (dry or wet) |
A particulate control device that uses electrical forces to move particles entrained within a process off-gas or waste gas stream onto collector plates. The entrained particles are given an electrical charge when they pass through a corona where gaseous ions flow. Electrodes in the centre of the flow lane are maintained at a high voltage and generate the electrical field that forces the particles to the collector walls. |
Fabric filter |
Porous woven or felted fabric through which gases flow to remove particles by use of a sieve or other mechanisms. Fabric filters can be in the form of sheets, cartridges or bags with a number of the individual fabric filter units housed together in a group. |
Membrane separation |
Waste gas is compressed and passed through a membrane which relies on the selective permeability of organic vapours. The enriched permeate can be recovered by methods such as condensation or adsorption, or can be abated, e.g. by catalytic oxidation. The process is most appropriate for higher vapour concentrations. Additional treatment is, in most cases, needed to achieve concentration levels low enough to discharge. |
Mist filter |
Commonly mesh pad filters (e.g. mist eliminators, demisters) which usually consist of woven or knitted metallic or synthetic monofilament material in either a random or specific configuration. A mist filter is operated as deep-bed filtration, which takes place over the entire depth of the filter. Solid dust particles remain in the filter until it is saturated and requires cleaning by flushing. When the mist filter is used to collect droplets and/or aerosols, they clean the filter as they drain out as a liquid. It works by mechanical impingement and is velocity-dependent. Baffle angle separators are also commonly used as mist filters. |
Regenerative thermal oxidiser (RTO) |
Specific type of thermal oxidiser (see below) where the incoming waste gas stream is heated by a ceramic-packed bed by passing through it before entering the combustion chamber. The purified hot gases exit this chamber by passing through one (or more) ceramic-packed bed(s) (cooled by an incoming waste gas stream in an earlier combustion cycle). This reheated packed bed then begins a new combustion cycle by preheating a new incoming waste gas stream. The typical combustion temperature is 800–1 000 °C. |
Scrubbing |
Scrubbing or absorption is the removal of pollutants from a gas stream by contact with a liquid solvent, often water (see ‘Wet scrubbing’). It may involve a chemical reaction (see ‘Caustic scrubbing’). In some cases, the compounds may be recovered from the solvent. |
Selective catalytic reduction (SCR) |
The reduction of NOX to nitrogen in a catalytic bed by reaction with ammonia (usually supplied as an aqueous solution) at an optimum operating temperature of around 300–450 °C. One or more layers of catalyst may be applied. |
Selective non-catalytic reduction (SNCR) |
The reduction of NOX to nitrogen by reaction with ammonia or urea at a high temperature. The operating temperature window must be maintained between 900 °C and 1 050 °C. |
Techniques to reduce solids and/or liquids entrainment |
Techniques that reduce the carry-over of droplets or particles in gaseous streams (e.g. from chemical processes, condensers, distillation columns) by mechanical devices such as settling chambers, mist filters, cyclones and knock-out drums. |
Thermal oxidiser |
Abatement equipment which oxidises the combustible compounds in a process off-gas or waste gas stream by heating it with air or oxygen to above its auto-ignition point in a combustion chamber and maintaining it at a high temperature long enough to complete its combustion to carbon dioxide and water. |
Thermal reduction |
NOX is reduced at elevated temperatures in the presence of a reducing gas in an additional combustion chamber, where an oxidation process takes place but under low oxygen conditions/deficit of oxygen. In contrast to SNCR, no ammonia and/or urea are added. |
Two-stage dust filter |
A device for filtering on a metal gauze. A filter cake builds up in the first filtration stage and the actual filtration takes place in the second stage. Depending on the pressure drop across the filter, the system switches between the two stages. A mechanism to remove the filtered dust is integrated into the system. |
Wet scrubbing |
See ‘Scrubbing’ above. Scrubbing where the solvent used is water or an aqueous solution, e.g. caustic scrubbing for abating HCl. See also ‘Wet dust scrubbing’. |
Wet dust scrubbing |
See ‘Wet scrubbing’ above. Wet dust scrubbing entails separating the dust by intensively mixing the incoming gas with water, mostly combined with the removal of the coarse particles by the use of centrifugal force. In order to achieve this, the gas is released inside tangentially. The removed solid dust is collected at the bottom of the dust scrubber. |
12.2.
Waste water treatment techniques
Technique |
Description |
Adsorption |
Separation method in which compounds (i.e. pollutants) in a fluid (i.e. waste water) are retained on a solid surface (typically activated carbon). |
Chemical oxidation |
Organic compounds are oxidised with ozone or hydrogen peroxide, optionally supported by catalysts or UV radiation, to convert them into less harmful and more easily biodegradable 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. |
Distillation |
Distillation is a technique to separate compounds with different boiling points by partial evaporation and recondensation. Waste water distillation is the removal of low-boiling contaminants from waste water by transferring them into the vapour phase. Distillation is carried out in columns, equipped with plates or packing material, and a downstream condenser. |
Extraction |
Dissolved pollutants are transferred from the waste water phase to an organic solvent, e.g. in counter-current columns or mixer-settler systems. After phase separation, the solvent is purified, e.g. by distillation, and returned to the extraction. The extract containing the pollutants is disposed of or returned to the process. Losses of solvent to the waste water are controlled downstream by appropriate further treatment (e.g. stripping). |
Evaporation |
The use of distillation (see above) to concentrate aqueous solutions of high-boiling substances for further use, processing or disposal (e.g. waste water incineration) by transferring water to the vapour phase. Typically carried out in multistage units with increasing vacuum, to reduce the energy demand. The water vapours are condensed, to be reused or discharged as waste water. |
Filtration |
The separation of solids from a waste water carrier by passing it through a porous medium. It includes different types of techniques, e.g. sand filtration, microfiltration and ultrafiltration. |
Flotation |
A process in which solid or liquid particles are separated from the waste water phase by attaching to fine gas bubbles, usually air. The buoyant particles accumulate at the water surface and are collected with skimmers. |
Hydrolysis |
A chemical reaction in which organic or inorganic compounds react with water, typically in order to convert non-biodegradable to biodegradable or toxic to non-toxic compounds. To enable or enhance the reaction, hydrolysis is carried out at an elevated temperature and possibly pressure (thermolysis) or with the addition of strong alkalis or acids or using a catalyst. |
Precipitation |
The conversion of dissolved pollutants (e.g. metal ions) into insoluble compounds by reaction with added precipitants. The solid precipitates formed are subsequently separated by sedimentation, flotation or filtration. |
Sedimentation |
Separation of suspended particles and suspended material by gravitational settling. |
Stripping |
Volatile compounds are removed from the aqueous phase by a gaseous phase (e.g. steam, nitrogen or air) that is passed through the liquid, and are subsequently recovered (e.g. by condensation) for further use or disposal. The removal efficiency may be enhanced by increasing the temperature or reducing the pressure. |
Waste water incineration |
The oxidation of organic and inorganic pollutants with air and simultaneous evaporation of water at normal pressure and temperatures between 730 °C and 1 200 °C. Waste water incineration is typically self-sustaining at COD levels of more than 50 g/l. In the case of low organic loads, a support/auxiliary fuel is needed. |
12.3.
Techniques to reduce emissions to air from combustion
Technique |
Description |
Choice of (support) fuel |
The use of fuel (including support/auxiliary fuel) with a low content of potential pollution-generating compounds (e.g. lower sulphur, ash, nitrogen, mercury, fluorine or chlorine content in the fuel). |
Low-NOX burner (LNB) and ultra-low-NOX burner (ULNB) |
The technique is based on the principles of reducing peak flame temperatures, delaying but completing the combustion and increasing the heat transfer (increased emissivity of the flame). It may be associated with a modified design of the furnace combustion chamber. The design of ultra-low-NOX burners (ULNB) includes (air/)fuel staging and exhaust/flue-gas recirculation. |