COMMISSION IMPLEMENTING DECISION
of 9 December 2013
establishing the best available techniques (BAT) conclusions, under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions, for the production of chlor-alkali
(notified under document C(2013) 8589)
(Text with EEA relevance)
(2013/732/EU)
Article 1
Article 2
ANNEX
BAT CONCLUSIONS FOR THE PRODUCTION OF CHLOR-ALKALI
SCOPE
Reference document |
Subject |
Common Waste Water and Waste Gas Treatment/Management Systems in the Chemical Sector BREF (CWW) |
Common waste water and waste gas treatment/management systems |
Economics and Cross-Media Effects (ECM) |
Economics and cross-media effects of techniques |
Emissions from Storage (EFS) |
Storage and handling of materials |
Energy Efficiency (ENE) |
General aspects of energy efficiency |
Industrial Cooling Systems (ICS) |
Indirect cooling with water |
Large Combustion Plants (LCP) |
Combustion plants with a rated thermal input of 50 MW or more |
General Principles of Monitoring (MON) |
General aspects of emissions and consumption monitoring |
Waste Incineration (WI) |
Waste incineration |
Waste Treatments Industries (WT) |
Waste treatment |
GENERAL CONSIDERATIONS
DEFINITIONS
Term used |
Definition |
New plant |
A plant first operated at the installation following the publication of these BAT conclusions or a complete replacement of a plant on the existing foundations of the installation following the publication of these BAT conclusions. |
Existing plant |
A plant which is not a new plant. |
New chlorine liquefaction unit |
A chlorine liquefaction unit first operated at the plant following the publication of these BAT conclusions or a complete replacement of a chlorine liquefaction unit following the publication of these BAT conclusions. |
Chlorine and chlorine dioxide, expressed as Cl2 |
The sum of chlorine (Cl2) and chlorine dioxide (ClO2), measured together and expressed as chlorine (Cl2). |
Free chlorine, expressed as Cl2 |
The sum of dissolved elementary chlorine, hypochlorite, hypochlorous acid, dissolved elementary bromine, hypobromite, and hypobromic acid, measured together and expressed as Cl2 |
Mercury, expressed as Hg |
The sum of all inorganic and organic mercury species, measured together and expressed as Hg. |
BAT CONCLUSIONS
1.
Cell technique
|
Technique |
Description |
Applicability |
a |
Bipolar membrane cell technique |
Membrane cells consist of an anode and a cathode separated by a membrane. In a bipolar configuration, individual membrane cells are electrically connected in series. |
Generally applicable. |
b |
Monopolar membrane cell technique |
Membrane cells consist of an anode and a cathode separated by a membrane. In a monopolar configuration, individual membrane cells are electrically connected in parallel. |
Not applicable to new plants with a chlorine capacity of > 20 kt/yr. |
c |
Asbestos-free diaphragm cell technique |
Asbestos-free diaphragm cells consist of an anode and a cathode separated by an asbestos-free diaphragm. Individual diaphragm cells are electrically connected in series (bipolar) or in parallel (monopolar). |
Generally applicable. |
2.
Decommissioning or conversion of mercury cell plants
|
Technique |
Description |
a |
Oxidation and ion exchange |
Oxidising agents such as hypochlorite, chlorine or hydrogen peroxide are used to fully convert mercury into its oxidised form, which is subsequently removed by ion-exchange resins. |
b |
Oxidation and precipitation |
Oxidising agents such as hypochlorite, chlorine or hydrogen peroxide are used to fully convert mercury into its oxidised form, which is subsequently removed by precipitation as mercury sulphide, followed by filtration. |
c |
Reduction and adsorption on activated carbon |
Reducing agents such as hydroxylamine are used to fully convert mercury into its elemental form, which is subsequently removed by coalescence and recovery of metallic mercury, followed by adsorption on activated carbon. |
3.
Generation of waste water
|
Technique |
Description |
Applicability |
a |
Brine recirculation |
The depleted brine from the electrolysis cells is resaturated with solid salt or by evaporation and fed back to the cells. |
Not applicable to diaphragm cell plants. Not applicable to membrane cell plants using solution-mined brine when abundant salt and water resources and a saline receiving water body, which tolerates high chloride emission levels, are available. Not applicable to membrane cell plants using the brine purge in other production units. |
b |
Recycling of other process streams |
Process streams from the chlor-alkali plant such as condensates from chlorine, sodium/potassium hydroxide and hydrogen processing are fed back to various steps of the process. The degree of recycling is limited by the purity requirements of the liquid stream to which the process stream is recycled and the water balance of the plant. |
Generally applicable. |
c |
Recycling of salt-containing waste water from other production processes |
Salt-containing waste water from other production processes is treated and fed back into the brine system. The degree of recycling is limited by the purity requirements of the brine system and the water balance of the plant. |
Not applicable to plants where an additional treatment of this waste water offsets the environmental benefits. |
d |
Use of waste water for solution mining |
Waste water from the chlor-alkali plant is treated and pumped back to the salt mine. |
Not applicable to membrane cell plants using the brine purge in other production units. Not applicable if the mine is located at a significantly higher altitude than the plant. |
e |
Concentration of brine filtration sludges |
Brine filtration sludges are concentrated in filter presses, rotary drum vacuum filters or centrifuges. The residual water is fed back into the brine system. |
Not applicable if the brine filtration sludges can be removed as dry cake. Not applicable to plants that reuse waste water for solution mining. |
f |
Nanofiltration |
A specific type of membrane filtration with membrane pore sizes of approximately 1 nm, used to concentrate sulphate in the brine purge, thereby reducing the waste water volume. |
Applicable to membrane cell plants with brine recirculation, if the brine purge rate is determined by the sulphate concentration. |
g |
Techniques to reduce chlorate emissions |
Techniques to reduce chlorate emissions are described in BAT 14. These techniques reduce the brine purge volume. |
Applicable to membrane cell plants with brine recirculation, if the brine purge rate is determined by the chlorate concentration. |
4.
Energy efficiency
|
Technique |
Description |
Applicability |
a |
High-performance membranes |
High-performance membranes show low voltage drops and high current efficiencies while ensuring mechanical and chemical stability under the given operating conditions. |
Applicable to membrane cell plants when renewing membranes at the end of their lifetime. |
b |
Asbestos-free diaphragms |
Asbestos-free diaphragms consist of a fluorocarbon polymer and fillers such as zirconium dioxide. These diaphragms show lower resistance overpotentials than asbestos diaphragms. |
Generally applicable |
c |
High-performance electrodes and coatings |
Electrodes and coatings with improved gas release (low gas bubble overpotential) and low electrode overpotentials. |
Applicable when renewing coatings at the end of their lifetime. |
d |
High-purity brine |
The brine is sufficiently purified to minimise contamination of the electrodes and diaphragms/membranes, which could otherwise increase energy consumption. |
Generally applicable. |
Description
5.
Monitoring of emissions
Environmental medium |
Substance(s) |
Sampling point |
Method |
Standard(s) |
Minimum monitoring frequency |
Monitoring associated with |
Air |
Chlorine and chlorine dioxide, expressed as Cl2 (2) |
Outlet of chlorine absorption unit |
Electrochemical cells |
No EN or ISO standard available |
Continuous |
— |
Absorption in a solution, with subsequent analysis |
No EN or ISO standard available |
Yearly (at least three consecutive hourly measurements) |
BAT 8 |
|||
Water |
Chlorate |
Where the emission leaves the installation |
Ion chromatography |
EN ISO 10304–4 |
Monthly |
BAT 14 |
Chloride |
Brine purge |
Ion chromatography or flow analysis |
EN ISO 10304–1 or EN ISO 15682 |
Monthly |
BAT 12 |
|
Free chlorine(2) |
Close to the source |
Reduction potential |
No EN or ISO standard available |
Continuous |
— |
|
Where the emission leaves the installation |
Free chlorine |
EN ISO 7393–1 or –2 |
Monthly |
BAT 13 |
||
Halogenated organic compound |
Brine purge |
Adsorbable organically-bound halogens (AOX) |
Annex A to EN ISO 9562 |
Yearly |
BAT 15 |
|
Mercury |
Outlet of the mercury treatment unit |
Atomic absorption spectrometry or atomic fluorescence spectrometry |
EN ISO 12846 or EN ISO 17852 |
Daily |
BAT 3 |
|
Sulphate |
Brine purge |
Ion chromatography |
EN ISO 10304–1 |
Yearly |
— |
|
Relevant heavy metals (e.g. nickel, copper) |
Brine purge |
Inductively-coupled plasma optical emission spectrometry or inductively-coupled plasma mass spectrometry |
EN ISO 11885 or EN ISO 17294-2 |
Yearly |
— |
6.
Emissions to air
Description
Applicability
7.
Emissions to water
|
Technique |
Description |
a |
Process-integrated techniques(3) |
Techniques that prevent or reduce the generation of pollutants |
b |
Waste water treatment at source(3) |
Techniques to abate or recover pollutants prior to their discharge to the waste water collection system |
c |
Waste water pre-treatment(4) |
Techniques to abate pollutants before the final waste water treatment |
d |
Final waste water treatment(4) |
Final waste water treatment by mechanical, physico-chemical and/or biological techniques before discharge to a receiving water body |
|
Technique |
Description |
a |
Chemical reduction |
The free chlorine is destroyed by reaction with reducing agents, such as sulphite and hydrogen peroxide, in stirred tanks. |
b |
Catalytic decomposition |
The free chlorine is decomposed to chloride and oxygen in catalytic fixed-bed reactors. The catalyst can be a nickel oxide promoted with iron on an alumina support. |
c |
Thermal decomposition |
The free chlorine is converted to chloride and chlorate by thermal decomposition at approximately 70 °C. The resulting effluent requires further treatment to reduce emissions of chlorate and bromate (BAT 14). |
d |
Acidic decomposition |
The free chlorine is decomposed by acidification, with a subsequent release and recovery of chlorine. Acidic decomposition can be carried out in a separate reactor or by recycling of the waste water to the brine system. The degree of recycling of waste water to the brine circuit is restricted by the water balance of the plant. |
e |
Waste water recycling |
Waste water streams from the chlor-alkali plant that contain free chlorine are recycled to other production units. |
|
Technique |
Description |
Applicability |
a |
High-performance membranes |
Membranes showing high current efficiencies, that reduce chlorate formation while ensuring mechanical and chemical stability under the given operating conditions. |
Applicable to membrane cell plants when renewing membranes at the end of their lifetime. |
b |
High-performance coatings |
Coatings with low electrode overpotentials leading to reduced chlorate formation and increased oxygen formation at the anode. |
Applicable when renewing coatings at the end of their lifetime. The applicability may be restricted by the quality requirements of the produced chlorine (oxygen concentration). |
c |
High-purity brine |
The brine is sufficiently purified to minimise contamination of electrodes and diaphragms/membranes, which could otherwise increase the formation of chlorate. |
Generally applicable. |
d |
Brine acidification |
The brine is acidified prior to electrolysis, in order to reduce the formation of chlorate. The degree of acidification is limited by the resistivity of the equipment used (e.g. membranes and anodes). |
Generally applicable. |
e |
Acidic reduction |
Chlorate is reduced with hydrochloric acid at pH values of 0 and at temperatures higher than 85 °C. |
Not applicable to once-through brine plants. |
f |
Catalytic reduction |
In a pressurised trickle-bed reactor, chlorate is reduced to chloride by using hydrogen and a rhodium catalyst in a three-phase reaction. |
Not applicable to once-through brine plants. |
g |
Use of waste water streams containing chlorate in other production units |
The waste water streams from the chlor-alkali plant are recycled to other production units, most typically to the brine system of a sodium chlorate production unit. |
Restricted to sites that can make use of waste water streams of this quality in other production units. |
|
Technique |
Description |
a |
Selection and control of salt and ancillary materials |
Salt and ancillary materials are selected and controlled to reduce the level of organic contaminants in the brine. |
b |
Water purification |
Techniques such as membrane filtration, ion exchange, UV irradiation and adsorption on activated carbon can be used to purify process water, thereby reducing the level of organic contaminants in the brine. |
c |
Selection and control of equipment |
Equipment, such as cells, tubes, valves and pumps, is carefully selected to reduce the potential leaching of organic contaminants into the brine. |
8.
Generation of waste
|
Technique |
Description |
Applicability |
a |
Use on site or off site |
The spent acid is used for other purposes, such as to control the pH in process and waste water, or to destroy surplus hypochlorite. |
Applicable to sites with an on-site or off-site demand for spent acid of this quality. |
b |
Reconcentration |
The spent acid is reconcentrated on site or off site in closed-loop evaporators under vacuum by indirect heating or by strengthening using sulphur trioxide. |
Off-site reconcentration is restricted to sites where a service provider is located nearby. |