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

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Chapter 4 Since the chemicals are added on a stoichiometric basis, the chemical costs can be considerable when decomposing concentrated solutions of hypochlorite. In addition, to facilitate the reaction, sufficient residence time is required and excess chemical is used to ensure full reaction. Disposal of waste water streams with excess reducing agent can be a problem because of the high load of COD (chemical oxygen demand) [Kelly, 1998]. Environmental performance and operational data The efficiency of the reaction depends on the amount and type of chemical used. In general, chemical reduction can reduce the concentration of free oxidants to levels < 0.5 mg/l [ 3, Euro Chlor 2011 ]. The bleed from the brine circuit at a membrane cell plant contains 10 – 30 mg/l free oxidants and 1000 – 3500 mg/l chlorate after treatment with sodium sulphite in the brine treatment. A reduction efficiency of more than 95 % can be achieved, but depends mainly on the amount of chemicals added. AkzoNobel in Bohus (Sweden) reports the use of hydrogen peroxide and a treatment efficiency of 95 %, the consumption of H2O2 being approximately 30 m 3 per year (100000 tonnes of Cl2 capacity/year). Cross-media effects Many of the reducing agents require careful handling. Sulphur dioxide is classified as toxic. When using sodium sulphide, the pH of the solution requires careful monitoring to avoid the formation of very toxic hydrogen sulphide. Hydrogen peroxide can be oxidising and irritant/corrosive depending on the concentration [ 76, Regulation EC/1272/2008 2008 ]. Chemical reduction leads to the formation of chloride and, depending on the reducing agent, to the formation of oxy sulphur compounds (for example SO4 2- ). The use of sodium sulphide leads to the formation of elemental sulphur in the form of very fine particles. The amount of products formed depends on the amount of free oxidants to be reduced. Any residual reducing agent in the effluent due to an overstoichiometric dosage increases the chemical oxygen demand (COD) of the waste water [ 17, Dutch Ministry 1998 ]. Because of the large number of chemical agents that may be used, this technique may increase the COD of the waste water. Economics The cost of traditional chemical destruction of free oxidants is mainly the cost of chemicals. When the amount of free oxidants to be destroyed is low, chemical destruction might be the cheapest is usually the least expensive option. Whenever large amounts of free oxidants have to be destroyed (for example, in bleach destruction), catalytic or thermal destruction may be more economical [ 17, Dutch Ministry 1998 ]. Some economic data for chemical reduction with hydrogen peroxide are shown in Section 4.3.6.3.4. WORKING DRAFT IN PROGRESS Example plants Many plants use classic chemical reduction to remove free oxidants from the waste water streams. However, chemical costs and the production of oxy sulphur compounds may become a problem, especially in cases where large amounts of off-spec hypochlorite (bleach) have to be destroyed. Reference literature [ 1, Ullmann's 2006 ], [ 2, Le Chlore 2002 ], [ 3, Euro Chlor 2011 ], [ 17, Dutch Ministry 1998 ], [ 76, Regulation EC/1272/2008 2008 ], [ 124, COM 2011 ], [ 207, Stitt et al. 2001 ] [Dutch report, 1998], [Le Chlore, 1996] 238 December 2011 TB/EIPPCB/CAK_Draft_1
4.3.6.3.4 Catalytic decomposition reduction Chapter 4 Description This technique consists in converting free oxidants to chloride and oxygen by using nickel-, iron- or cobalt-based catalysts. Catalytic decomposition can be carried out in fixed-bed reactors or with a catalyst slurry. Technical description The catalytic decomposition occurs The decomposition of free oxidants to chloride and oxygen can be catalysed by a nickel, iron or cobalt based catalyst, according to the following overall reaction: [M] n+ 2 NaOCl V 2 NaCl + O2w This decomposition reaction generally occurs in hypochlorite solutions, albeit too slow to remove free oxidants in technical systems. The reaction is accelerated by metal catalysts, lower pH values and higher temperatures (see Section 2.6.12.2). Depending on the conditions, hypochlorite may instead decompose to chloride and chlorate (see Section 4.3.6.3.5). Some systems operate with a catalyst slurry which uses solutions of nickel, iron or cobalt compounds added to the waste water in stirred or agitated tanks [ 208, Johnson Matthey 2009 ]. Metal concentrations are typically 20 mg/l [ 2, Le Chlore 2002 ]. The high pH value of the solution causes the metal ions to precipitate as their hydroxides, which are then removed and regenerated. Alternatively, a fine dispersion of an insoluble metal compound can be used which removes the need for the catalyst regeneration stage. is blended with the waste water stream to promote the reaction, in a batch process. To avoid emissions of metals In both cases, the catalyst must be allowed to settle before the supernatant water can be discharged, to avoid emissions of heavy metals. The reaction time combined with the settling of the catalyst takes several days [ 208, Johnson Matthey 2009 ]. The catalyst activity decreases from batch to batch, although it is unclear whether this is due to deactivation of the catalyst or loss of metal [ 75, COM 2001 ]. Other systems operate with the catalyst on a fixed-bed reactor (Figure 4.7). The catalyst used is a nickel oxide promoted with iron on an alumina support. The design of the reactor is modular. The gravity-fed hypochlorite solution flows countercurrently with respect to the evolving oxygen [ 206, Denye et al. 1995 ], [ 207, Stitt et al. 2001 ], [ 208, Johnson Matthey 2009 ]. , see Figure 4.7, reducing the loss of metals and increasing the capacity (no settling required) compared to slurry type catalytic systems. Also, the necessary concentration of catalyst is low (20 ppm), [Le Chlore, 1996]. WORKING DRAFT IN PROGRESS TB/EIPPCB/CAK_Draft_1 December 2011 239
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EUROPEAN COMMISSION JOINT RESEARCH
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PREFACE 1. Status of this document
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Reference Document on Best Availabl
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3.4.7 Emissions of noise ..........
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4.3.6.3.3 Chemical reduction ......
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List of Tables Table 2.1: Main char
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List of Figures Figure 1.1: Share p
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SCOPE WORKING DRAFT IN PROGRESS Sco
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1 GENERAL INFORMATION 1.1 Industria
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Chlorine production in Mt/yr 12 11
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Chapter 1 Figure 1.4 shows the annu
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Share of total capacity in % 70 70%
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1.4 Chlor-alkali products and their
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Total consumption: 9 801 kt Miscell
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1.4.5 Consumption of hydrogen Chapt
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Chapter 1 and hazardous waste incin
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2 APPLIED PROCESSES AND TECHNIQUES
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Chapter 2 WORKING DRAFT IN PROGRESS
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Chapter 2 The main characteristics
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2.2 The mercury cell technique proc
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Chapter 2 Characteristics of the ca
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2.3 The diaphragm cell technique pr
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Source: [ 2, Le Chlore 2002 ] [USEP
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2.4 The membrane cell technique pro
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Chapter 2 (carcinogenic) [ 76, Regu
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Chapter 2 The membranes used in the
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Table 2.2: Typical configurations o
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2.5 Brine supply 2.5.1 Sources, qua
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Chapter 2 centrifuges before dispos
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Source: [ 29, Asahi Glass 1998 ] (p
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Impurity Source Upper limit of brin
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Chapter 2 No such dechlorination tr
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Chapter 2 The cooling water is gene
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Chapter 2 composition of the chlori
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2.6.11 Dealing with impurities 2.6.
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Chapter 2 amount of chlorine, and t
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2.6.12.2 Chemical reactions Chapter
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2.7 Caustic processing production,
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Chapter 2 2.8 Hydrogen processing p
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3 CURRENT PRESENT EMISSION AND CONS
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Chapter 3 Table 3.1: Overview of em
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3.3 Consumption levels of all cell
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3.3.3 Ancillary materials Ancillary
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Further materials and/or further us
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Chapter 3 current) and the efficien
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Chapter 3 distance means a higher f
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3.3.4.3.6 Production of caustic pot
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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
Page 203 and 204: Chapter 4 removal of conductive com
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Page 211 and 212: Chapter 4 current density resulting
Page 213 and 214: Chapter 4 modifications to auxiliar
Page 215 and 216: Table 4.14: Cost calculation for th
Page 217 and 218: Chapter 4 membrane lifetimes range
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Page 221 and 222: Chapter 4 The drawback of using fer
Page 223 and 224: Chapter 4 evaporation unit integrat
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Page 227 and 228: Chapter 4 Technical description The
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Page 231 and 232: Chapter 4 Environmental performance
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Page 243 and 244: Chapter 4 chlorine scrubber, immedi
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Page 251 and 252: Chapter 4 Table 4.21: Examples of o
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Page 261 and 262: Chapter 4 migration of hydroxide io
Page 263 and 264: eduction of chlorate emissions; red
Page 265 and 266: Example plants Solvin in Antwerp-Li
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Page 273 and 274: 4.4 Membrane cell plants 4.4.1 High
Page 275 and 276: 4.5.3 Containment Chapter 4 Descrip
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Page 285 and 286: General considerations In these BAT
Page 287 and 288: 5.2 Decommissioning of mercury cell
Page 289 and 290: 5.3 Environmental management system
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Page 295 and 296: 5.6 Monitoring of emissions Chapter
Page 297 and 298: [This BAT conclusion is based on in
Page 299 and 300: 5.9 Generation of waste Chapter 5 1
Page 301 and 302: 5.11 Site remediation Chapter 5 20.
Page 303 and 304: 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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