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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)
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THE EUROPEAN COMMISSION,
Having regard to the Treaty on the Functioning of the European Union,
Having regard to Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control)(1), and in particular Article 13(5) thereof,
Whereas:
(1) Best available techniques (BAT) conclusions are the reference for setting permit conditions for installations covered by Chapter II of Directive 2010/75/EU and competent authorities should set emission limit values which ensure that, under normal operating conditions, emissions do not exceed the emission levels associated with the best available techniques as laid down in the BAT conclusions.
(2) The forum composed of representatives of Member States, the industries concerned and non-governmental organisations promoting environmental protection, established by Commission Decision of 16 May 2011(2), provided the Commission on 5 April 2017 with its opinion on the proposed content of the BAT reference document for the production of large volume organic chemicals. That opinion is publicly available.
(3) The BAT conclusions set out in the Annex to this Decision are the key element of that BAT reference document.
(4) The measures provided for in this Decision are in accordance with the opinion of the Committee established by Article 75(1) of Directive 2010/75/EU,
HAS ADOPTED THIS DECISION:
The best available techniques (BAT) conclusions for the production of large volume organic chemicals, as set out in the Annex, are adopted.
This Decision is addressed to the Member States.
Done at Brussels, 21 November 2017.
For the Commission
Karmenu Vella
Member of the Commission
These BAT conclusions concern the production of the following organic chemicals, as specified in Section 4.1 of Annex I to Directive 2010/75/EU:
simple hydrocarbons (linear or cyclic, saturated or unsaturated, aliphatic or aromatic);
oxygen-containing hydrocarbons such as alcohols, aldehydes, ketones, carboxylic acids, esters and mixtures of esters, acetates, ethers, peroxides and epoxy resins;
sulphurous hydrocarbons;
nitrogenous hydrocarbons such as amines, amides, nitrous compounds, nitro compounds or nitrate compounds, nitriles, cyanates, isocyanates;
phosphorus-containing hydrocarbons;
halogenic hydrocarbons;
organometallic compounds;
surface-active agents and surfactants.
These BAT conclusions also cover the production of hydrogen peroxide as specified in Section 4.2(e) of Annex I to Directive 2010/75/EU.
These BAT conclusions cover combustion of fuels in process furnaces/heaters, where this is part of the abovementioned activities.
These BAT conclusions cover production of the aforementioned chemicals in continuous processes where the total production capacity of those chemicals exceeds 20 kt/year.
These BAT conclusions do not address the following:
combustion of fuels other than in a process furnace/heater or a thermal/catalytic oxidiser; this may be covered by the BAT conclusions for Large Combustion Plants (LCP);
incineration of waste; this may be covered by the BAT conclusions for Waste Incineration (WI);
ethanol production taking place on an installation covered by the activity description in Section 6.4(b)(ii) of Annex I to Directive 2010/75/EU or covered as a directly associated activity to such an installation; this may be covered by the BAT conclusions for Food, Drink and Milk Industries (FDM).
Other BAT conclusions which are complementary for the activities covered by these BAT conclusions include:
Common Waste Water/Waste Gas Treatment/Management Systems in the Chemical Sector (CWW);
Common Waste Gas Treatment in the Chemical Sector (WGC).
Other BAT conclusions and reference documents which may be of relevance for the activities covered by these BAT conclusions are the following:
Economics and Cross-media Effects (ECM);
Emissions from Storage (EFS);
Energy Efficiency (ENE);
Industrial Cooling Systems (ICS);
Large Combustion Plants (LCP);
Refining of Mineral Oil and Gas (REF);
Monitoring of Emissions to Air and Water from IED installations (ROM);
Waste Incineration (WI);
Waste Treatment (WT).
The techniques listed and described in these BAT conclusions are neither prescriptive nor exhaustive. Other techniques may be used that ensure at least an equivalent level of environmental protection.
Unless otherwise stated, the BAT conclusions are generally applicable.
Unless stated otherwise, the emission levels associated with the best available techniques (BAT-AELs) for emissions to air given in these BAT conclusions refer to values of concentration, expressed as mass of emitted substance per volume of waste gas under standard conditions (dry gas at a temperature of 273,15 K, and a pressure of 101,3 kPa), and expressed in the unit mg/Nm3.
Unless stated otherwise, the averaging periods associated with the BAT-AELs for emissions to air are defined as follows.
a For any parameter where, due to sampling or analytical limitations, 30-minute sampling is inappropriate, a suitable sampling period is employed. | ||
b For PCDD/F, a sampling period of 6 to 8 hours is used. | ||
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 eacha b |
Where BAT-AELs refer to specific emission loads, expressed as load of emitted substance per unit of production output, the average specific emission loads ls are calculated using Equation 1:
where:
=
number of measurement periods;
=
average concentration of the substance during ith measurement period;
=
average flow rate during ith measurement period;
=
production output during ith measurement period.
For process furnaces/heaters, the reference oxygen level of the waste gases (OR ) is 3 vol-%.
The emission concentration at the reference oxygen level is calculated using Equation 2:
where:
=
emission concentration at the reference oxygen level OR ;
=
reference oxygen level in vol-%;
=
measured emission concentration;
=
measured oxygen level in vol-%.
Unless stated otherwise, the averaging periods associated with the environmental performance levels associated with the best available techniques (BAT-AEPLs) for emissions to water expressed in concentrations are defined as follows.
a Time-proportional composite samples can be used provided that sufficient flow stability can be demonstrated. | |
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 conditionsa |
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 conditionsa |
Flow-weighted average concentrations of the parameter (cw ) are calculated using Equation 3:
where:
=
number of measurement periods;
=
average concentration of the parameter during ith measurement period;
=
average flow rate during ith measurement period.
Where BAT-AEPLs refer to specific emission loads, expressed as load of emitted substance per unit of production output, the average specific emission loads are calculated using Equation 1.
For the purposes of these BAT conclusions, the following acronyms and definitions apply.
a Commission Implementing Decision 2012/119/EU of 10 February 2012 laying down rules concerning guidance on the collection of data and on the drawing up of BAT reference documents and on their quality assurance referred to in Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions (OJ L 63, 2.3.2012, p. 1). | |
Term used | Definition |
---|---|
BAT-AEPL | Environmental performance level associated with BAT, as described in Commission Implementing Decision 2012/119/EUa. BAT-AEPLs include emission levels associated with the best available techniques (BAT-AELs) as defined in Article 3(13) of Directive 2010/75/EU |
BTX | Collective term for benzene, toluene and ortho-/meta-/para-xylene or mixtures thereof |
CO | Carbon monoxide |
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) |
Continuous measurement | Measurement using an ‘automated measuring system’ permanently installed on site |
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 |
Copper | The sum of copper and its compounds, in dissolved or particulate form, expressed as Cu |
DNT | Dinitrotoluene |
EB | Ethylbenzene |
EDC | Ethylene dichloride |
EG | Ethylene glycols |
EO | Ethylene oxide |
Ethanolamines | Collective term for monoethanolamine, diethanolamine and triethanolamine, or mixtures thereof |
Ethylene glycols | Collective term for monoethylene glycol, diethylene glycol and triethylene glycol, or mixtures thereof |
Existing plant | A plant that is not a new plant |
Existing unit | A unit that is not a new unit |
Flue-gas | The exhaust gas exiting a combustion unit |
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 |
Lower olefins | Collective term for ethylene, propylene, butylene and butadiene, or mixtures thereof |
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 |
MDA | Methylene diphenyl diamine |
MDI | Methylene diphenyl diisocyanate |
MDI plant | Plant for the production of MDI from MDA via phosgenation |
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 |
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 |
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 |
PCDD/F | Polychlorinated dibenzo-dioxins and -furans |
Periodic measurement | Measurement at specified time intervals using manual or automated methods |
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. |
Process off-gas | The gas leaving a process which is further treated for recovery and/or abatement |
NOX | The sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2), expressed as NO2 |
Residues | Substances or objects generated by the activities covered by the scope of this document, as waste or by-products |
RTO | Regenerative thermal oxidiser |
SCR | Selective catalytic reduction |
SMPO | Styrene monomer and propylene oxide |
SNCR | Selective non-catalytic reduction |
SRU | Sulphur recovery unit |
TDA | Toluene diamine |
TDI | Toluene diisocyanate |
TDI plant | Plant for the production of TDI from TDA via phosgenation |
TOC | Total organic carbon, expressed as C; includes all organic compounds (in water) |
Total suspended solids (TSS) | Mass concentration of all suspended solids, measured via filtration through glass fibre filters and gravimetry |
TVOC | Total volatile organic carbon; total volatile organic compounds which are measured by a flame ionisation detector (FID) and expressed as total carbon |
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 |
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 |
VCM | Vinyl chloride monomer |
VOCs | Volatile organic compounds as defined in Article 3(45) of Directive 2010/75/EU |
The sector-specific BAT conclusions included in Sections 2 to 11 apply in addition to the general BAT conclusions given in this section.
a Generic EN standards for continuous measurements are EN 15267-1, -2, and -3, and EN 14181. EN standards for periodic measurements are given in the table. | ||||
b Refers to the total rated thermal input of all process furnaces/heaters connected to the stack where emissions occur. | ||||
c In the case of process furnaces/heaters with a total rated thermal input of less than 100 MWth operated less than 500 hours per year, the monitoring frequency may be reduced to at least once every year. | ||||
d The minimum monitoring frequency for periodic measurements may be reduced to once every 6 months, if the emission levels are proven to be sufficiently stable. | ||||
e Monitoring of dust does not apply when combusting exclusively gaseous fuels. | ||||
f Monitoring of NH3 only applies when SCR or SNCR is used. | ||||
g In the case of process furnaces/heaters combusting gaseous fuels and/or oil with a known sulphur content and where no flue-gas desulphurisation is carried out, continuous monitoring can be replaced either by periodic monitoring with a minimum frequency of once every 3 months or by calculation ensuring the provision of data of an equivalent scientific quality. | ||||
Substance/Parameter | Standard(s)a | Total rated thermal input (MWth)b | Minimum monitoring frequencyc | Monitoring associated with |
---|---|---|---|---|
CO | Generic EN standards | ≥ 50 | Continuous | Table 2.1, Table 10.1 |
EN 15058 | 10 to < 50 | Once every 3 monthsd | ||
Duste | Generic EN standards and EN 13284-2 | ≥ 50 | Continuous | BAT 5 |
EN 13284-1 | 10 to < 50 | Once every 3 monthsd | ||
NH3 f | Generic EN standards | ≥ 50 | Continuous | BAT 7, Table 2.1 |
No EN standard available | 10 to < 50 | Once every 3 monthsd | ||
NOX | Generic EN standards | ≥ 50 | Continuous | BAT 4, Table 2.1, Table 10.1 |
EN 14792 | 10 to < 50 | Once every 3 monthsd | ||
SO2 g | Generic EN standards | ≥ 50 | Continuous | BAT 6 |
EN 14791 | 10 to < 50 | Once every 3 monthsd |
a The monitoring applies where the pollutant is present in the waste gas based on the inventory of waste gas streams specified by the CWW BAT conclusions. | ||||
b The minimum monitoring frequency for periodic measurements may be reduced to once every year, if the emission levels are proven to be sufficiently stable. | ||||
c All (other) processes/sources where the pollutant is present in the waste gas based on the inventory of waste gas streams specified by the CWW BAT conclusions. | ||||
d EN 15058 and the sampling period need adaptation so that the measured values are representative of the whole decoking cycle. | ||||
e EN 13284-1 and the sampling period need adaptation so that the measured values are representative of the whole decoking cycle. | ||||
f The monitoring applies where the chlorine and/or chlorinated compounds are present in the waste gas and thermal treatment is applied | ||||
Substance/Parameter | Processes/Sources | Standard(s) | Minimum monitoring frequency | Monitoring associated with |
---|---|---|---|---|
Benzene | Waste gas from the cumene oxidation unit in phenol productiona | No EN standard available | Once every monthb | BAT 57 |
All other processes/sourcesc | BAT 10 | |||
Cl2 | TDI/MDIa | No EN standard available | Once every monthb | BAT 66 |
EDC/VCM | BAT 76 | |||
CO | Thermal oxidiser | EN 15058 | Once every monthb | BAT 13 |
Lower olefins (decoking) | No EN standard availabled | Once every year or once during decoking, if decoking is less frequent | BAT 20 | |
EDC/VCM (decoking) | BAT 78 | |||
Dust | Lower olefins (decoking) | No EN standard availablee | Once every year or once during decoking, if decoking is less frequent | BAT 20 |
EDC/VCM (decoking) | BAT 78 | |||
All other processes/sourcesc | EN 13284-1 | Once every monthb | BAT 11 | |
EDC | EDC/VCM | No EN standard available | Once every monthb | BAT 76 |
Ethylene oxide | Ethylene oxide and ethylene glycols | No EN standard available | Once every monthb | BAT 52 |
Formaldehyde | Formaldehyde | No EN standard available | Once every monthb | BAT 45 |
Gaseous chlorides, expressed as HCl | TDI/MDIa | EN 1911 | Once every monthb | BAT 66 |
EDC/VCM | BAT 76 | |||
All other processes/sourcesc | BAT 12 | |||
NH3 | Use of SCR or SNCR | No EN standard available | Once every monthb | BAT 7 |
NOX | Thermal oxidiser | EN 14792 | Once every monthb | BAT 13 |
PCDD/F | TDI/MDIf | EN 1948-1, -2, and -3 | Once every 6 monthsb | BAT 67 |
PCDD/F | EDC/VCM | BAT 77 | ||
SO2 | All processes/sourcesc | EN 14791 | Once every monthb | BAT 12 |
Tetrachloromethane | TDI/MDIa | No EN standard available | Once every monthb | BAT 66 |
TVOC | TDI/MDI | EN 12619 | Once every monthb | BAT 66 |
EO (desorption of CO2 from scrubbing medium) | Once every 6 monthsb | BAT 51 | ||
Formaldehyde | Once every monthb | BAT 45 | ||
Waste gas from the cumene oxidation unit in phenol production | EN 12619 | Once every monthb | BAT 57 | |
Waste gas from other sources in phenol production when not combined with other waste gas streams | Once every year | |||
Waste gas from the oxidation unit in hydrogen peroxide production | Once every monthb | BAT 86 | ||
EDC/VCM | Once every monthb | BAT 76 | ||
All other processes/sourcesc | Once every monthb | BAT 10 | ||
VCM | EDC/VCM | No EN standard available | Once every monthb | BAT 76 |
Optimised combustion is achieved by good design and operation of the equipment which includes optimisation of the temperature and residence time in the combustion zone, efficient mixing of the fuel and combustion air, and combustion control. Combustion control is based on the continuous monitoring and automated control of appropriate combustion parameters (e.g. O2, CO, fuel to air ratio, and unburnt substances).
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 |
BAT-associated emission levels (BAT-AELs): See Table 2.1 and Table 10.1.
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 |
BAT-associated emission levels (BAT-AELs) for emissions from a lower olefins cracker furnace when SCR or SNCR is used: Table 2.1.
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 |
Applicability:
Sending process off-gas streams to a combustion unit may be restricted due to the presence of contaminants or due to safety considerations.
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 |
Description:
For the description of wet scrubbing, see Section 12.1
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 |
Technique | Description | |
---|---|---|
a. | Catalyst selection | Select the catalyst to achieve the optimal balance between the following factors:
|
b. | Catalyst protection | Techniques used upstream of the catalyst to protect it from poisons (e.g. raw material pretreatment) |
c. | Process optimisation | Control of reactor conditions (e.g. temperature, pressure) to achieve the optimal balance between conversion efficiency and catalyst lifetime |
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) |
Description:
Organic solvents used in processes (e.g. chemical reactions) or operations (e.g. extraction) are recovered using appropriate techniques (e.g. distillation or liquid phase separation), purified if necessary (e.g. using distillation, adsorption, stripping or filtration) and returned to the process or operation. The amount recovered and reused is process-specific.
Technique | Description | Applicability | |
---|---|---|---|
Techniques to prevent or reduce the generation of waste | |||
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 | |||
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 | |||
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 |
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. |
start-up and shutdown operations;
other circumstances (e.g. regular and extraordinary maintenance work and cleaning operations of the units and/or of the waste gas treatment system) including those that could affect the proper functioning of the installation.
The BAT conclusions in this section apply to the production of lower olefins using the steam cracking process, and apply in addition to the general BAT conclusions given in Section 1.
BAT-AELs for emissions to air of NOX and NH3 from a lower olefins cracker furnace
a Where the flue gases of two or more furnaces are discharged through a common stack, the BAT-AEL applies to the combined discharge from the stack. | ||
b The BAT-AELs do not apply during decoking operations. | ||
c No BAT-AEL applies for CO. As an indication, the CO emission level will generally be 10–50 mg/Nm3 expressed as a daily average or an average over the sampling period. | ||
d The BAT-AEL only applies when SCR or SNCR are used. | ||
Parameter | BAT-AELsa b c(daily average or average over the sampling period)(mg/Nm3, at 3 vol-% O2) | |
---|---|---|
New furnace | Existing furnace | |
NOX | 60–100 | 70–200 |
NH3 | < 5–15d |
The associated monitoring is in BAT 1.
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 |
Description:
The technique consists of ensuring an effective separation of organic and aqueous phases. The recovered hydrocarbons are recycled to the cracker or used as raw materials in other chemical processes. Organic recovery can be enhanced, e.g. through the use of steam or gas stripping, or the use of a reboiler. Treated quench water is reused within the dilution steam generation system. A quench water purge stream is discharged to downstream final waste water treatment to prevent the build-up of salts in the system.
Description:
For the description of stripping see Section 12.2. The stripping of scrubber liquors is carried out using a gaseous stream, which is then combusted (e.g. in the cracker furnace).
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 |
The BAT conclusions in this section apply to the production of benzene, toluene, ortho-, meta- and para-xylene (commonly known as BTX aromatics) and cyclohexane from the pygas by-product of steam crackers and from reformate/naphtha produced in catalytic reformers; and apply in addition to the general BAT conclusions given in Section 1.
Description:
The process off-gas is sent to wet or dry dust abatement devices to remove dust and then to a combustion unit or a thermal oxidiser to remove organic compounds in order to avoid direct emissions to air or flaring. The use of decoking drums alone is not sufficient.
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 |
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 |
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 |
The BAT conclusions in this section apply to the production of ethlybenzene using either the zeolite or AlCl3 catalysed alkylation process; and the production of styrene monomer either by ethylbenzene dehydrogenation or co-production with propylene oxide; and apply in addition to the general BAT conclusions given in Section 1.
Description:
For the description of caustic scrubbing, see Section 12.1.
Applicability:
Only applicable to existing plants using the AlCl3 catalysed ethylbenzene production process.
Description:
For the description of wet scrubbing, see Section 12.1.
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 |
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 |
Description:
For the description of hydrolysis see Section 12.2.
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 |
Description:
Steam stripping is first used to remove VOCs, then the spent catalyst solution is concentrated by evaporation to give a usable AlCl3 by-product. The vapour phase is condensed to give a HCl solution that is recycled into the process.
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 |
The BAT conclusions in this section apply in addition to the general BAT conclusions given in Section 1.
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 |
BAT-AELs for emissions of TVOC and formaldehyde to air from formaldehyde production
a The lower end of the range is achieved when using a thermal oxidiser in the silver process. | |
Parameter | BAT-AEL(daily average or average over the sampling period)(mg/Nm3, no correction for oxygen content) |
---|---|
TVOC | < 5–30a |
Formaldehyde | 2–5 |
The associated monitoring is in BAT 2.
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 |
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 |
The BAT conclusions in this section apply in addition to the general BAT conclusions given in Section 1.
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 |
Description:
The addition of small amounts of an organochlorine inhibitor (such as ethylchloride or dichloroethane) to the reactor feed in order to reduce the proportion of ethylene that is fully oxidised to carbon dioxide. Suitable parameters for the monitoring of catalyst performance include the heat of reaction and the CO2 formation per tonne of ethylene feed.
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 |
BAT-AEL for emissions of organic compounds to air from the desorption of CO2 from the scrubbing medium used in the EO plant
a The BAT-AEL is expressed as an average of values obtained during 1 year. | |
b In the case of significant methane content in the emission, methane monitored according to EN ISO 25140 or EN ISO 25139 is subtracted from the result. | |
c EO produced is defined as the sum of EO produced for sale and as an intermediate. | |
Parameter | BAT-AEL |
---|---|
TVOC | 1–10 g/t of EO produceda b c |
The associated monitoring is in BAT 2.
Description:
For the description of wet scrubbing, see Section 12.1. Scrubbing with water to remove EO from waste gas streams before direct release or before further abatement of organic compounds.
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 |
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 |
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 |
The BAT conclusions in this section apply to the production of phenol from cumene, and apply in addition to the general BAT conclusions given in Section 1.
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 |
BAT-AELs for emissions of TVOC and benzene to air from the production of phenol
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 | — |
The associated monitoring is in BAT 2.
Description:
For the description of hydrolysis, see Section 12.2. Waste water (mainly from the condensers and the adsorber regeneration, after phase separation) is treated thermally (at temperatures above 100 °C and a high pH) or catalytically to decompose organic peroxides to non-ecotoxic and more readily biodegradable compounds.
BAT-AEPL for organic peroxides at the outlet of the peroxides decomposition unit
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) |
Description:
Recovery of phenol from phenol-containing waste water streams by adjustment of the pH to < 7, followed by extraction with a suitable solvent and stripping of the waste water to remove residual solvent and other low-boiling compounds (e.g. acetone). For the description of the treatment techniques, see Section 12.2.
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 |
The BAT conclusions in this section apply in addition to the general BAT conclusions given in Section 1.
Description:
For the description of wet scrubbing, see Section 12.1. Unreacted ammonia is recovered from the off-gas of the ammonia stripper and also from the evaporation unit by wet scrubbing in at least two stages followed by ammonia recycling into the process.
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 |
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 |
The BAT conclusions in this section cover the production of:
dinitrotoluene (DNT) from toluene;
toluene diamine (TDA) from DNT;
TDI from TDA;
methylene diphenyl diamine (MDA) from aniline;
MDI from MDA;
and apply in addition to the general BAT conclusions given in Section 1.
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 |
Description:
The individual waste gas streams from DNT, TDA, TDI, MDA and MDI plants are combined to one or several waste gas streams for treatment. (See Section 12.1 for the descriptions of thermal oxidiser and scrubbing.) Instead of a thermal oxidiser, an incinerator may be used for the combined treatment of liquid waste and the waste gas. Caustic scrubbing is wet scrubbing with caustic added to improve the HCl and chlorine removal efficiency.
BAT-AELs for emissions of TVOC, tetrachloromethane, Cl2, HCl and PCDD/F to air from the TDI/MDI process
a The BAT-AEL only applies to combined waste gas streams with flow rates of > 1 000 Nm3/h. | |
b The BAT-AEL is expressed as a daily average or an average over the sampling period. | |
c The BAT-AEL is expressed as an average of values obtained during 1 year. TDI and/or MDI produced refers to the product without residues, in the sense used to define the capacity of the plant. | |
d In the case of NOX values above 100 mg/Nm3 in the sample, the BAT-AEL may be higher and up to 3 mg/Nm3 due to analytical interferences. | |
Parameter | BAT-AEL(mg/Nm3, no correction for oxygen content) |
---|---|
TVOC | 1–5a b |
Tetrachloromethane | ≤ 0,5 g/t MDI producedc ≤ 0,7 g/t TDI producedc |
Cl2 | < 1b d |
HCl | 2–10b |
PCDD/F | 0,025–0,08 ng I-TEQ/Nm3 b |
The associated monitoring is in BAT 2.
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 |
BAT-associated emission levels (BAT-AELs): See Table 9.1.
a In the case of discontinuous waste water discharges, the minimum monitoring frequency is once per discharge. | |||||
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 weeka | 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 |
BAT-associated waste water volume: See Table 9.2.
Technique | Description | Applicability | |
---|---|---|---|
a. | Extraction | See Section 12.2 | Generally applicable |
b. | Chemical oxidation | See Section 12.2 |
BAT-AEPLs for discharge from the DNT plant at the outlet of the pretreatment unit to further waste water treatment
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 |
The associated monitoring for TOC is in BAT 68.
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 |
BAT-AEPL for discharge from the TDA plant to waste water treatment
Parameter | BAT-AEPL(average of values obtained during 1 month) |
---|---|
Specific waste water volume | < 1 m3/t TDA produced |
BAT-AEPL for discharge to waste water treatment from a TDI or MDI plant
a The BAT-AEPL refers to the product without residues, in the sense used to define the capacity of the plant. | |
Parameter | BAT-AEPL(average of values obtained during 1 year) |
---|---|
TOC | < 0,5 kg/t product (TDI or MDI)a |
The associated monitoring is in BAT 68.
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 |
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 |
The BAT conclusions in this section apply in addition to the general BAT conclusions given in Section 1.
BAT-AELs for emissions to air of NOX from an EDC cracker furnace
a Where the flue-gases of two or more furnaces are discharged through a common stack, the BAT-AEL applies to the combined discharge from the stack. | |
b The BAT-AELs do not apply during decoking operations. | |
c No BAT-AEL applies for CO. As an indication, the CO emission level will generally be 5–35 mg/Nm3 expressed as a daily average or an average over the sampling period. | |
Parameter | BAT-AELsa b c(daily average or average over the sampling period)(mg/Nm3, at 3 vol-% O2) |
---|---|
NOx | 50–100 |
The associated monitoring is in BAT 1.
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 |
Description:
For the description of thermal oxidiser, wet and caustic scrubbing, see Section 12.1. Thermal oxidation can be carried out in a liquid waste incineration plant. In this case, the oxidation temperature exceeds 1 100 °C with a minimum residence time of 2 seconds, with subsequent rapid cooling of exhaust gases to prevent the de novo synthesis of PCDD/F.
Scrubbing is carried out in two stages: Wet scrubbing with water and, typically, recovery of hydrochloric acid, followed by wet scrubbing with caustic.
BAT-AELs for emissions of TVOC, the sum of EDC and VCM, Cl2, HCl and PCDD/F to air from the production of EDC/VCM
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 |
The associated monitoring is in BAT 2.
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 |
BAT-associated emission levels (BAT-AELs): See Table 10.2.
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 |
a The minimum monitoring frequency may be reduced to once every month if adequate performance of the solids and copper removal is controlled by frequent monitoring of other parameters (e.g. by continuous measurement of turbidity). | |||||
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 daya | BAT 81 |
PCDD/F | No EN standard available | Once every 3 months | |||
Total suspended solids (TSS) | EN 872 | Once every daya | |||
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 |
Description:
For the description of hydrolysis and stripping, see Section 12.2. Hydrolysis is carried out at alkaline pH to decompose chloral hydrate from the oxychlorination process. This results in the formation of chloroform which is then removed by stripping, together with EDC and VCM.
BAT-associated environmental performance levels (BAT-AEPLs): See Table 10.3.
BAT-associated emission levels (BAT-AELs) for direct emissions to a receiving water body at the outlet of the final treatment: See Table 10.5.
BAT-AEPLs for chlorinated hydrocarbons in waste water at the outlet of a waste water stripper
a The average of values obtained during 1 month is calculated from the averages of values obtained during each day (at least three spot samples taken at intervals of at least half an hour). | |
Parameter | BAT-AEPL(average of values obtained during 1 month)a |
---|---|
EDC | 0,1–0,4 mg/l |
VCM | < 0,05 mg/l |
The associated monitoring is in BAT 79.
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 |
BAT-AEPLs for emissions to water from EDC production via oxychlorination at the outlet of the pretreatment for solids removal at 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 |
The associated monitoring is in BAT 79.
BAT-AELs for direct emissions of copper, EDC and PCDD/F to a receiving water body from EDC production
a The lower end of the range is typically achieved when the fixed-bed design is used. | |
b The average of values obtained during one year is calculated from the averages of values obtained during each day (at least three spot samples taken at intervals of at least half an hour). | |
c Purified EDC is the sum of EDC produced by oxychlorination and/or direct chlorination and of EDC returned from VCM production to purification. | |
Parameter | BAT-AEL(average of values obtained during 1 year) |
---|---|
Copper | 0,04–0,2 g/t EDC produced by oxychlorinationa |
EDC | 0,01–0,05 g/t EDC purifiedb c |
PCDD/F | 0,1– 0,3 μg I-TEQ/t EDC produced by oxychlorination |
The associated monitoring is in BAT 79.
Description:
The reaction in the boiling reactor system for the direct chlorination of ethylene is typically carried out at a temperature between below 85 °C and 200 °C. In contrast to the low-temperature process, it allows for the effective recovery and reuse of the heat of reaction (e.g. for the distillation of EDC).
Applicability:
Only applicable to new direct chlorination plants.
Description:
Promoters, such as chlorine or other radical-generating species, are used to enhance the cracking reaction and reduce the reaction temperature and therefore the required heat input. Promoters may be generated by the process itself or added.
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 |
The BAT conclusions in this section apply in addition to the general BAT conclusions given in Section 1.
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 |
BAT-AELs for emissions of TVOC to air from the oxidation unit
a The BAT-AEL does not apply when the emission is below 150 g/h. | |
b When adsorption is used, the sampling period is representative of a complete adsorption cycle. | |
c In the case of significant methane content in the emission, methane monitored according to EN ISO 25140 or EN ISO 25139 is subtracted from the result. | |
Parameter | BAT-AELa(daily average or average over the sampling period)b(no correction for oxygen content) |
---|---|
TVOC | 5–25 mg/Nm3 c |
The associated monitoring is in BAT 2.
Description:
For the description of condensation and adsorption, see Section 12.1.
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 |
Applicability:
Only applicable to waste water streams carrying the main organic load from the hydrogen peroxide plant and when the reduction of the TOC load from the hydrogen peroxide plant by means of biological treatment is lower than 90 %.
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. |
All of the techniques listed below can also be used to purify water streams in order to enable reuse/recycling of water. Most of them are also used to recover organic compounds from process water streams.
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. |
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. |
Commission Decision of 16 May 2011 establishing a forum for the exchange of information pursuant to Article 13 of the Directive 2010/75/EU on industrial emissions (OJ C 146, 17.5.2011, p. 3).
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