(BAT) Reference Document for the Production of Chlor-alkali ...

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Chapter 2 almost always added to prevent caking in the case of vacuum salt, but rarely in the case of rock salt. Solution-mined brine is sometimes transported by pipelines over distances which can exceed 100 km. The brine is kept in storage tanks [ 1, Ullmann's 2006 ]. 2.4.2 Brine purification and resaturation 2.5.2 Brine preparation When solid salt is the raw material, a dissolving operation becomes necessary which is carried out in open or closed vessels. The water and/or depleted brine can be sprayed onto the salt or introduced at the base of the saturator for progressive saturation when running through it. In the latter case, the saturated brine overflows the equipment at the top. Modern saturators are closed vessels to reduce emissions of salt spray or mist as well as of mercury in the case of the mercury cell technique. NaCl concentrations in the saturated brine reach values of 310 – 315 g/l [ 1, Ullmann's 2006 ]. 2.5.3 Brine purification 2.5.3.1 General description As can be seen in Figure 2.1 on page10, the brine purification process consists of a primary system for all chlor-alkali techniques consisting of precipitation and filtration mercury and diaphragm technologies and an additional secondary system for the membrane cell technique technology. This operation is needed to reduce the concentration of avoid any undesirable components (sulphate anions, cations of Ca, Mg, Ba and metals) that can affect the electrolytic process. The quality of the raw material and the brine quality requirements for each of the three techniques technologies determine the complexity of the brine treatment unit. 2.5.3.2 Primary purification Precipitation The initial stage of purification uses sodium carbonate and sodium hydroxide to precipitate calcium and magnesium ions as calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2). Metals (iron, titanium, molybdenum, nickel, chromium, vanadium, tungsten) may also precipitate as hydroxide during this operation. The usual way to reduce the concentrations of avoid metals is to specify maximum concentration values their exclusion in the purchase and transport specifications for the salt. Sodium sulphate can be is controlled by adding calcium chloride (CaCl2) or barium salts (BaCO3 or BaCl2) to remove sulphate anions by precipitation of calcium sulphate (CaSO4) or barium sulphate (BaSO4). The precipitation of barium sulphate can take place simultaneously with the precipitation of calcium carbonate and magnesium hydroxide, whereas the precipitation of calcium sulphate requires a separate vessel. WORKING DRAFT IN PROGRESS When vacuum salt is used as raw material, only a part of the brine stream is treated in the primary purification unit, while the total stream is usually treated when using other salt types [ 3, Euro Chlor 2011 ]. Filtration The precipitated impurities are removed by sedimentation, filtration or a combination of both. The separated filter cake is generally concentrated to 50 – 60 % (although a figure of 60-80% is reported in the literature) solids content in filter presses, rotary drum vacuum filters or 40 December 2011 TB/EIPPCB/CAK_Draft_1
Chapter 2 centrifuges before disposal. [Ullmann’s, 1996] {Please TWG provide information if the value of 50 – 60 % is correct because [ 1, Ullmann's 2006 ] reports 60 – 80 %.} The sulphate content can also be reduced without the use of expensive barium salts by purging a part of the brine, by cooling the brine stream and crystallising Na2SO4 · 10 H2O, by precipitating the double salt Na2SO4 · CaSO4, by ion exchange, or by nanofiltration combined with purging of the brine. In the diaphragm cell technique, the removal of sulphate is not always necessary because sulphate can be removed from the cell liquor as pure Na2SO4 during the concentration process [ 1, Ullmann's 2006 ]. In the case of the membrane cell technique, the use of barium salts is generally avoided to protect the membrane against potential precipitations (see Table 2.4) [ 3, Euro Chlor 2011 ]. The purified brine should ideally contain ideally [Ullmann’s, 1996] [ 1, Ullmann's 2006 ]: Ca 2+ : < 2 mg/l; Mg 2+ : < 1 mg/l; SO4 2- : < 5 g/l. Before the brine enters the mercury or diaphragm electrolysis cells, it is usually acidified with hydrochloric acid to pH < 6 which increases the lifetime of the anode coating and reduces the formation of oxygen, hypochlorite and chlorate [ 1, Ullmann's 2006 ]. 2.5.3.3 Secondary purification: membrane cell technique circuit To maintain the high performance of the ion-exchange membrane, the feed brine must be purified to a greater degree than in the conventional mercury or diaphragm cell techniques processes. The precipitation step alone is not enough to reduce the levels of calcium and magnesium, and additional softening is required. Figure 2.15 shows the flow diagram of a possible layout for the brine purification system used in the membrane cell technique process. Raw salt Water V-1 V-2 V-3 SP - 1 SP-2 SP-3 V-1 Brine saturator SP-1 Sand filter E-1 Electrolyser V-2 Brine reactor SP-2 Brine filter T-1 Dechlorinationtower V-3 Clarifier Porous carbon filter V-4 Chlorate decomposer Pre- coating (if necessary) SP-3 Chelating resin towers Source: [ 29, Asahi Glass 1998 ] (Source: Asahi Glass CO) WORKING DRAFT IN PROGRESS TB/EIPPCB/CAK_Draft_1 December 2011 41 E-1 V-4 Cl 2 T-1 Depleted brine Figure 2.15: Flow diagram of a possible layout for the brine purification system used in the membrane cell technique process The Secondary brine purification generally consists of a polishing filtration step (Figure 2.16) and brine softening in an ion-exchange unit (Figure 2.17).
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EUROPEAN COMMISSION JOINT RESEARCH
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PREFACE 1. Status of this document
Page 5 and 6: Reference Document on Best Availabl
Page 7 and 8: 3.4.7 Emissions of noise ..........
Page 9 and 10: 4.3.6.3.3 Chemical reduction ......
Page 11 and 12: List of Tables Table 2.1: Main char
Page 13 and 14: List of Figures Figure 1.1: Share p
Page 15 and 16: SCOPE WORKING DRAFT IN PROGRESS Sco
Page 17 and 18: 1 GENERAL INFORMATION 1.1 Industria
Page 19 and 20: Chlorine production in Mt/yr 12 11
Page 21 and 22: Chapter 1 Figure 1.4 shows the annu
Page 23 and 24: Share of total capacity in % 70 70%
Page 25 and 26: 1.4 Chlor-alkali products and their
Page 27 and 28: Total consumption: 9 801 kt Miscell
Page 29 and 30: 1.4.5 Consumption of hydrogen Chapt
Page 31 and 32: Chapter 1 and hazardous waste incin
Page 33 and 34: 2 APPLIED PROCESSES AND TECHNIQUES
Page 35 and 36: Chapter 2 WORKING DRAFT IN PROGRESS
Page 37 and 38: Chapter 2 The main characteristics
Page 39 and 40: 2.2 The mercury cell technique proc
Page 41 and 42: Chapter 2 Characteristics of the ca
Page 43 and 44: 2.3 The diaphragm cell technique pr
Page 45 and 46: Source: [ 2, Le Chlore 2002 ] [USEP
Page 47 and 48: 2.4 The membrane cell technique pro
Page 49 and 50: Chapter 2 (carcinogenic) [ 76, Regu
Page 51 and 52: Chapter 2 The membranes used in the
Page 53 and 54: Table 2.2: Typical configurations o
Page 55: 2.5 Brine supply 2.5.1 Sources, qua
Page 59 and 60: Source: [ 29, Asahi Glass 1998 ] (p
Page 61 and 62: Impurity Source Upper limit of brin
Page 63 and 64: Chapter 2 No such dechlorination tr
Page 65 and 66: Chapter 2 The cooling water is gene
Page 67 and 68: Chapter 2 composition of the chlori
Page 69 and 70: 2.6.11 Dealing with impurities 2.6.
Page 71 and 72: Chapter 2 amount of chlorine, and t
Page 73 and 74: 2.6.12.2 Chemical reactions Chapter
Page 75 and 76: 2.7 Caustic processing production,
Page 77 and 78: Chapter 2 2.8 Hydrogen processing p
Page 79 and 80: 3 CURRENT PRESENT EMISSION AND CONS
Page 81 and 82: Chapter 3 Table 3.1: Overview of em
Page 83 and 84: 3.3 Consumption levels of all cell
Page 85 and 86: 3.3.3 Ancillary materials Ancillary
Page 87 and 88: Further materials and/or further us
Page 89 and 90: Chapter 3 current) and the efficien
Page 91 and 92: Chapter 3 distance means a higher f
Page 93 and 94: 3.3.4.3.6 Production of caustic pot
Page 95 and 96: Chapter 3 hydrogen at low pressure
Page 97 and 98: 28 kg of hydrogen is produced {Thes
Page 99 and 100: Chapter 3 depleted brine is recircu
Page 101 and 102: Chapter 3 Table 3.10: Emissions of
Page 103 and 104: Chapter 3 When measuring chlorine i
Page 105 and 106: Chapter 3 Table 3.13: Emissions of
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Chapter 3 Table 3.15: Emissions of
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Chapter 3 concentrations of organic
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Chapter 3 3.4.3 Emissions and waste
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Chapter 3 {Please TWG provide infor
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Chapter 3 in process and waste wate
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Chapter 3 produced per year has bee
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Chapter 3 of chlorine capacity. The
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Table 3.23: Mercury emissions from
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Mercury emissions in g Hg/t Cl capa
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Chapter 3 Table 3.24: Mercury emiss
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Chapter 3 KCl are higher than from
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Chapter 3 When concentrated solid c
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Chapter 3 Generally, storage of con
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Chapter 3 recycled brine systems si
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Process Maintenance To solid treatm
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3.5.9.5 Graphite and activated Acti
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Chapter 3 Table 3.31: Yearly waste
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Chapter 3 The fact that the differe
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Chapter 3 3.6 Emissions Emission an
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Reported asbestos concentrations ar
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Chapter 3 3.7 Emissions Emission an
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{A list of techniques used on full
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3.8.3 PCDDs/PCDFs, PCBs, PCNs and P
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Chapter 3 The ‘dioxin’ pattern
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Chapter 4 4 TECHNIQUES TO CONSIDER
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Heading within the sections Cross-m
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4.1 Mercury cell plants 4.1.1 Overv
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Chapter 4 plants at comparable capa
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Chapter 4 Table 4.2: Data from the
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Chapter 4 environment can be expect
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4. Plant size Chapter 4 An increase
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Table 4.6: Comparison of reported c
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Chapter 4 Generally, conversion cos
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4.1.3 Decommissioning 4.1.3.1 Decom
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3. Emptying of the cells and handli
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Chapter 4 Table 4.7: Overview of co
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Table 4.8: Techniques for monitorin
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Chapter 4 Table 4.10: Decommissioni
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4.2 Diaphragm cell plants 4.2.1 Aba
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Source: [ 146, Arkema 2009 ] Figure
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Chapter 4 diaphragms [ 31, Euro Chl
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Driving force for implementation Th
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Chapter 4 4.2.3 Conversion of asbes
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Chapter 4 directly from the cells.
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4.3 All Diaphragm and membrane cell
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Chapter 4 non-standardised) will be
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Chapter 4 removal of conductive com
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Chapter 4 Cross-media effects Plant
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Environmental performance and opera
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Example plants Dow, Stade (Germany)
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Chapter 4 current density resulting
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Chapter 4 modifications to auxiliar
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Table 4.14: Cost calculation for th
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Chapter 4 membrane lifetimes range
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Chapter 4 Cross-media effects Some
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Chapter 4 The drawback of using fer
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Chapter 4 evaporation unit integrat
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Chapter 4 Environmental performance
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Chapter 4 Technical description The
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Chapter 4 Table 4.17: Monitoring te
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Chapter 4 Environmental performance
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Environmental performance and opera
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Chapter 4 Prevention of chlorine re
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Chapter 4 Good pipework design to m
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Chapter 4 was the solution at that
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differential pressure at inlet and
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Chapter 4 chlorine scrubber, immedi
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Chapter 4 Achieved environmental be
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{Please TWG provide more informatio
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environmental legislation; generati
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Chapter 4 Table 4.21: Examples of o
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Chapter 4 Driving force for impleme
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4.3.6.3.4 Catalytic decomposition r
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Chapter 4 In both cases, the spent
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Chapter 4 Example plants Thermal de
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Chapter 4 migration of hydroxide io
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eduction of chlorate emissions; red
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Example plants Solvin in Antwerp-Li
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eduction of costs related to equipm
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Chapter 4 Off-site reconcentration
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Chapter 4 b) closing of doors and w
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4.4 Membrane cell plants 4.4.1 High
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4.5.3 Containment Chapter 4 Descrip
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Chapter 4 Sections 4.5.4.2 and 4.5.
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Chapter 4 At this site, mercury con
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Chapter 4 However, the soil washing
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5 BEST AVAILABLE TECHNIQUES Scope
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General considerations In these BAT
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5.2 Decommissioning of mercury cell
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5.3 Environmental management system
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Chapter 5 The BAT-associated enviro
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Chapter 5 6. In order to reduce ene
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5.6 Monitoring of emissions Chapter
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[This BAT conclusion is based on in
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5.9 Generation of waste Chapter 5 1
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5.11 Site remediation Chapter 5 20.
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Chapter 5 inorganic chloramines, di
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6 EMERGING TECHNIQUES 6.1 Introduct
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Chapter 6 cooperation with the Japa
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Chapter 6 In December 1998 a test w
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6.3 Use of fuel cells in chlor-alka
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Chapter 6 hydrogen that is burnt to
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Chapter 7 7 CONCLUDING REMARKS AND
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REFERENCES References [1] Ullmann's
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References [63] Euro Chlor, Euro Ch
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References [112] Santorelli et al.,
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References [161] Germany, 'Verordnu
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[212] Florkiewicz, Long life diaphr
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References [259] Rappe et al., 'Lev
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GLOSSARY OF TERMS AND ABBREVIATIONS
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V. Units · VI. Chemical elements T
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VIII. Acronyms and definitions AC A
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EOX Extractable Organically-bound H
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Glossary Technique Ensemble of both
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ANNEX Annex {The CAK plant capaciti
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Euro Chlor No. Country code Company
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