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This document has not been fully peer reviewed and <strong>the</strong> <strong>information</strong> within is not validated nor endorsed by <strong>the</strong> TWG on LVIC-S or by <strong>the</strong> European Commission, it is meant for <strong>information</strong>, only 1.5 Potassium carbonate Potassium carbonate (K2CO3) finds its major application in <strong>the</strong> speciality glass industry e.g. in television screens where it performs better than glass made with soda ash [6, CEFIC, 2002]. Potassium carbonate is produced by reacting potassium hydroxide with carbon dioxide, as follows: 18 2KOH + CO2 F K2CO3 + H2O It is shipped both as an aqueous solution, or it is crystallised and shipped as crystals. Air emissions are due to <strong>the</strong> handling of solid materials. Water emissions are due to <strong>the</strong> water evaporated <strong>during</strong> <strong>the</strong> crystallisation step. Waste generation is negligible [6, CEFIC, 2002]. Potassium carbonate (potash) was formerly produced by <strong>the</strong> ashing of wood and o<strong>the</strong>r raw materials from plants. Since <strong>the</strong> middle of <strong>the</strong> XIX century, <strong>the</strong> saline residues from <strong>the</strong> rock salt industry and salt deposits have been <strong>the</strong> raw materials used for <strong>the</strong> production of potassium carbonate. Currently, <strong>the</strong> most important process is <strong>the</strong> carbonation of electrolytically produced potassium hydroxide as described by <strong>the</strong> reaction above [48, W. Buchner et al, 1989]. Potassium hydroxide solutions (50 % KOH) are saturated with CO2, <strong>the</strong> solution is partially eveporated and <strong>the</strong> potassium carbonate hydrate K2CO3 . 1.5 H2O which precipitates is separated off. After drying, <strong>the</strong> product is ei<strong>the</strong>r marketed as potash hydrate or is calcined in a rotary kiln at temperatures of 250 to 350 ºC. Anhydrous potassium carbonate is also produced using a fluid bed process, in which KOH is reacted with CO2 gas countercurrently in a fluidised bed reactor. In Russia, potassium carbonate is also produced from deposits of alkali aluminosilicates (e.g. nepheline) toge<strong>the</strong>r with aluminium oxide, cement and sodium carbonate. The main applications of potassium carbonate include [48, W. Buchner et al, 1989]: glass manufacture (special glasses, crystal glass, CRT-tubes for TV) soaps, detergents enamels food industry pigment manufacture o<strong>the</strong>r downstream K compounds (potassium hydrogen carbonate, potassium silicate) syn<strong>the</strong>sis of many organic chemicals and pharmaceutical products. Since no <strong>information</strong> was <strong>submitted</strong> on potassium carbonate, <strong>the</strong>refore, <strong>the</strong> ‘Techniques to consider in <strong>the</strong> determination of BAT’ relevant to <strong>the</strong> production of potassium carbonate could not have been analysed in this document. No fur<strong>the</strong>r <strong>information</strong> provided.
This document has not been fully peer reviewed and <strong>the</strong> <strong>information</strong> within is not validated nor endorsed by <strong>the</strong> TWG on LVIC-S or by <strong>the</strong> European Commission, it is meant for <strong>information</strong>, only 1.6 Sodium sulphate 1.6.1 General <strong>information</strong> The production of natural sodium sulphate (like <strong>the</strong> production of natural NaCl or CaSO4) is based on <strong>the</strong> extraction of a mineral with high content of sodium sulphate and its recovery in a high purity grade through successive crystallisation/separation stages. This type of extractive industry is not classified by <strong>the</strong> IPPC Directive and, <strong>the</strong>refore, it is not included in this document. There are four producers of natural sodium sulphate in <strong>the</strong> EU-15, all of <strong>the</strong>m located in Spain and <strong>the</strong>ir emission values have not been included in this section. 1.6.1.1 Introduction The world production of sodium sulphate (anhydrous or as Glauber’s salt – sodium sulphate decahydrate Na2SO4 . 10H2O) was reported to be at <strong>the</strong> level of 4.2 million tonnes per year in 1985, out of which almost 50 % was produced from natural deposits [48, W. Buchner et al, 1989]. The production of pure sodium sulphate or Glauber’s salt from natural minerals such as <strong>the</strong>nardite Na2SO4 or glauberite Na2SO4 . CaSO4 is still important in Spain, Canada, <strong>the</strong> US, Russia and China. O<strong>the</strong>r production processes of sodium sulphate from salt lakes, salt brines and potassium salt deposits (in this latter case via reaction of kieserite MgSO4 . H2O with sodium chloride NaCl), and in particular, sodium sulphate by-produced in large quantities in various chemical and metallurgical processes are increasing [48, W. Buchner et al, 1989]. Sodium sulphate is a solid salt having wide range of applications in miscellaneous industrial sectors like detergents, glass production or cellulose fibres [6, CEFIC, 2002]. Half of <strong>the</strong> production is extracted from natural deposits while <strong>the</strong> remaining part is a by-product of o<strong>the</strong>r industrial chemical processes, usually resulting from <strong>the</strong> neutralisation of excess sulphuric acid. Therefore, <strong>the</strong> production of sodium sulphate may, in some places, exceed <strong>the</strong> commercial demand, and processes have been developed to address this issue, using e.g. an electrochemical decomposition route. The direct production processes based on <strong>the</strong> reaction of solid sodium chloride with sulphuric acid or sulphur dioxide/oxygen have become less important [EIPPCB, 2004-2005 #85]. Chemical processes like viscose-fibre spinning, ascorbic acid syn<strong>the</strong>sis or sodium dichromate production, deliver aqueous solutions of sodium sulphate which are, if necessary, concentrated, and <strong>the</strong>n directed to a crystallisation system which produces ei<strong>the</strong>r directly anhydrous sodium sulphate crystals or Glauber salt crystals (sodium sulphate decahydrate Na2SO4 . 10H2O) that are fur<strong>the</strong>r dehydrated. Electrolysis and electrodialysis processes intended to decompose sodium sulphate into sulphuric acid and sodium hydroxide solutions, have been largely developed, but <strong>the</strong>ir operational cost (e.g. <strong>the</strong> consumption of electricity) is an obstacle to <strong>the</strong>ir implementation. Dust emissions to <strong>the</strong> atmosphere are <strong>the</strong> result of handling <strong>the</strong> solids. Water emissions include dissolved salts.The generation of wastes is not an issue. Organic contamination of air, water and wastes is to be considered, depending on <strong>the</strong> organic process generating <strong>the</strong> sodium sulphate solution [6, CEFIC, 2002]. 1.6.1.2 Basic data on sodium sulphate production Sodium sulphate is a non toxic, hygroscopic white powder. It derives from natural deposits or is recovered as a by-product from various industrial processes. Natural sodium sulphate is extracted from sodium sulphate-rich brines or lakes, while <strong>the</strong> most common industrial sources are <strong>the</strong> production of man-made fibres, hydrochloric acid, chromium chemicals, formic acid, desulphurisation of flue-gases or lead battery recycling [64, CEFIC-SSPA, 2004]. 19
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Page 56: Glossary (NH4)2SO4 Ammonium sulphat

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