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

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Chapter 2 When graphite anodes were used, the diaphragm became inoperable after 90 – 100 days due to its clogging plugging of the diaphragm by particles of graphite. Nowadays As of 2011, all plants in the European Union use metal anodes and the lifetime of the diaphragm can be several years is over one year. Their service life has also increased because their compositions have changed. The earliest diaphragms were made of sheets of asbestos paper which in the late 1920s were replaced by the deposited asbestos diaphragm. Pure asbestos diaphragms At the beginning the diaphragms were made of asbestos only and were rapidly clogged by calcium and magnesium ions coming from the brine. Asbestos was chosen because of its good chemical and mechanical stability and because it is a relatively inexpensive and abundant material. Beginning in the early 1970s, pure asbestos diaphragms began to be replaced by diaphragms containing a minimum of 75 % asbestos and up to 25 % of fibrous fluorocarbon polymer of high chemical resistance. These Polymer Modified Asbestos (PMA) diaphragms, trade named Modified Diaphragms, are more stable. The polymer stabilises the asbestos, which in itself lowers cell voltage and also allows for the use of the expandable anode [ 1, Ullmann's 2006 ][Le Chlore, 1995], [Ullmann’s, 1996]. Chrysotile asbestos (‘white asbestos’) is the only form of asbestos used in diaphragm cells. Due to the potential exposure of employees to asbestos and emissions in the environment, efforts have been made are being expanded to replace the asbestos with other diaphragm materials. The development of non-asbestos diaphragms started in the middle of the 1980s and two non-asbestos diaphragm systems were commercially available in 2011 [ 31, Euro Chlor 2010 ] some companies have now succeeded in operating with them. The basis of the material used is the same in all asbestos-free diaphragms developed free of asbestos, i.e. a fluorocarbon polymer, mainly PTFE (polytetrafluoroethylene). The differences lie in the fillers used and the way the hydrophobic PTFE fibres are treated and deposited in order to form a permeable and hydrophilic diaphragm (see Section 4.2.2). In 2011, three plants in the EU-27 were using asbestos diaphragms: Dow in Stade (Germany), Solvay in Rheinberg (Germany) and Zachem in Bydgoszcz (Poland). The Solvay plant was in the process of conversion to asbestos-free diaphragms and is scheduled to finalise it in 2012. All three diaphragm plants in France (Arkema in Fos-sur-mer and Lavera, Perstorp in Le Pont de Claix) have been operating with asbestos-free diaphragms since 2003. A commercial plant has multiple cell elements combined into a single unit, called the electrolyser. Both diaphragm and membrane electrolysers are classified as either monopolar or bipolar. This is described in detail in Section 2.4.3. There are many more monopolar diaphragm electrolysers in chlor-alkali production facilities than bipolar electrolysers [ 1, Ullmann's 2006 ]. Both diaphragm and membrane cells for the production of chlorine and sodium hydroxide are classified as either monopolar or bipolar. The designation does not refer to the electrochemical reactions that take place, which of course require two poles or electrodes for all cells, but to the electrolyser construction or assembly. There are many more chlor-alkali production facilities with monopolar cells than with bipolar cells. The monopolar electrolyser is assembled so that the anodes and cathodes are arranged in parallel. As a result of this configuration, all cells have WORKING DRAFT IN PROGRESS the same voltage of about three to four volts; up to 200 cells can be constructed in one circuit. Bipolar electrolysers have unit assemblies of the anode of one cell unit directly connected to the cathode of the next cell unit, thus minimising intercell voltage loss. These units are assembled in series. 30 December 2011 TB/EIPPCB/CAK_Draft_1
2.4 The membrane cell technique process Chapter 2 {The paragraphs under this section have been rearranged to follow the same logic as the mercury and diaphragm cell techniques.} 2.4.1 General description In the 1970s, the development of ion-exchange membranes enabled a new technology to produce chlorine: the membrane electrolysis process. The first ion-exchange membranes were developed at the beginning of the 1970s by Du Pont (Nafion), followed by Asahi Glass (Flemion) which installed the first industrial membrane plant in Japan in 1975 due to the pressure of Japanese environmental regulations. Non-chlor-alkali related mercury pollution in Minamata drove the authorities to prohibit all mercury processes and Japan was the first country to install the membrane process on a massive scale in the mid-1980s. 3 At the beginning of the 1970s, the development of the first ion-exchange membranes introduced a new technique to produce chlorine: the membrane cell technique. The first industrial membrane plant was installed in Japan in 1975. Due to the pressure of Japanese environmental regulations in the aftermath of the Minamata disease caused by methylmercury-containing waste water which had been discharged in the 1950s into the Minamata Bay, Japan was the first country where the technique was installed on a broad scale in the middle of the 1980s. In 2011, the membrane cell technique is the state-of-the-art technique for producing chlorine and caustic soda/potash [ 1, Ullmann's 2006 ]. Today, it is the most promising and fast-developing technique for the production of chlor-alkali and it will undoubtedly replace the other two techniques in time. This can be deduced from the fact that since 1987 practically 100% of the new chlor-alkali plants worldwide apply the membrane process. The replacement of existing mercury and diaphragm cell capacity with membrane cells is taking place at a much slower rate because of the long lifetime of the former and because of the high capital costs of replacement. {This is covered in Chapter 1.} In this technique process, the anode and cathode are separated by an water-impermeable ion-conducting membrane (Figure 2.2). Brine solution flows through the anode compartment where chloride ions are oxidised to chlorine gas. The sodium ions together with approximately 3.5 to 4.5 moles of water per mole of sodium migrate through the membrane to the cathode compartment which contains flowing a caustic soda solution [ 1, Ullmann's 2006 ]. The demineralised water added to the catholyte circuit is hydrolysed The water is electrolysed at the cathode releasing hydrogen gas and hydroxide ions. The sodium and hydroxide ions combine to produce caustic soda which is typically brought to a concentration of 32 – 35 % kept at 32 ± 1 wt-% in the cell by diluting a part of the product stream with demineralised water to a concentration of approximately 30 wt-% and subsequent recycling as catholyte inlet (see Figure 2.1) by recirculating the solution before it is discharged from the cell. Caustic soda is continuously removed from the circuit. Depleted brine is discharged from the anode compartment and resaturated with salt. The membrane largely prevents the migration of chloride ions from the anode compartment to the cathode compartment; therefore, the caustic WORKING DRAFT IN PROGRESS soda solution produced does not contains only approximately 50 mg/l of sodium chloride. Back-migration of hydroxide is also largely prevented by the membrane but nevertheless takes place to a certain extent increasing the formation of oxygen, hypochlorite and chlorate in the anode compartment and resulting in a loss of current efficiency of 3 – 7 % with respect to caustic soda production [ 1, Ullmann's 2006 ], [ 10, Kirk-Othmer 2002 ], [ 22, Uhde 2009 ]. salt as in the diaphragm cell process. Depleted brine is discharged from the anode compartment and 3 There are 2 mercury plants in Japan (Toagosei Co. and Nippon Soda Co.) producing potassium hydroxide (total capacity of both: 45 000 tonnes/year) which are allowed to operate because of the high grade KOH produced which is needed for the optical glass industry. The reason why membrane technology cannot achieve the same performances, however, is not known (source: Asahi Glass Co). TB/EIPPCB/CAK_Draft_1 December 2011 31
Page 1 and 2: EUROPEAN COMMISSION JOINT RESEARCH
Page 3 and 4: 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: Source: [ 2, Le Chlore 2002 ] [USEP
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 and 56: 2.5 Brine supply 2.5.1 Sources, qua
Page 57 and 58: Chapter 2 centrifuges before dispos
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
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28 kg of hydrogen is produced {Thes
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Chapter 3 depleted brine is recircu
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Chapter 3 Table 3.10: Emissions of
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Chapter 3 When measuring chlorine i
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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.,
Page 323 and 324:
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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