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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 24 Crude Sodium sulphate from evaporation plant Dissolver Fine maternal returned to process C austic soda Sulphur dioxide Sulphuric acid Classifier Treatment tanks Pure sodium Sulphate to silos Cyclone Filter Precipitated solids Exhaust gases Air Crystalliser Dryer Air Fuel C entrifuge Liquor recycled to crystalliser Figure 1.12: Flow scheme of <strong>the</strong> production of sodium sulphate from <strong>the</strong> chromium process [64, CEFIC-SSPA, 2004] 1.6.2.4 Mannheim furnace process (hydrochloric acid) As mentioned in Section 1.6.1, direct production processes based on <strong>the</strong> reaction of solid sodium chloride with sulphuric acid or sulphur dioxide/oxygen, have become less important, as – apart from <strong>the</strong> natural product – a by-product sodium sulphate from o<strong>the</strong>r processes is readily available. However, in some locations syn<strong>the</strong>tic sodium sulphate may be by-produced by <strong>the</strong> Mannheim furnace process jointly with hydrochloric acid [64, CEFIC-SSPA, 2004]. Approximately two tonnes of 100 % Na2SO4 are produced per one tonne of 100 % HCl, equivalent to approximately three tonnes of HCl solution which is in fact obtained in <strong>the</strong> process. Hydrochloric acid is widely applicable in various industries, including <strong>the</strong> chemical, tannery, textile, ceramic and pharmaceutical industries. In <strong>the</strong> Mannheim furnace process, sulphuric acid reacts with sodium chloride producing sodium sulphate and a 32 % hydrochloric acid solution obtained through absorption. Combustion gases, obtained as intermediate products, are used to heat up <strong>the</strong> combustion air. Producing sodium sulphate, that is free of sulphuric acid and hydrochloric acid, requires equivalent amounts of acid (approx. 0.73 t of 100 % H2SO4 per tonne of Na2SO4) and salt (approx. 0.83 t of 100 % NaCl per tonne of Na2SO4). The salt is measured out by means of a screw, <strong>the</strong> quantity of acid is measured by flow. Based on raw material analyses, <strong>the</strong> quantity ratio of <strong>the</strong> materials is <strong>the</strong>n controlled by an operator. The reaction between sulphuric acid and sodium chloride requires a long reaction time and a high temperature. This is achieved in a muffle furnace with a hearth which is heated with burners to approx. 600 °C. The air volume/oil ratio is kept constant. To prevent any problem of exhaust gas after <strong>the</strong> HCl absorption, <strong>the</strong> air is not blown into <strong>the</strong> process.
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 The hot air produced in <strong>the</strong> upper part of <strong>the</strong> Mannheim furnace (combustion chamber) is not in contact with <strong>the</strong> lower part of <strong>the</strong> Mannheim furnace (reaction chamber). Indirect heating takes place through a special wall. The HCl gases coming from <strong>the</strong> reaction in <strong>the</strong> lower part of <strong>the</strong> furnace do not come into contact with <strong>the</strong> combustion gases in <strong>the</strong> upper part of <strong>the</strong> furnace. The first stage of <strong>the</strong> reaction produces acidic sodium sulphate, or sodium hydrogen sulphate, which <strong>the</strong>n reacts with sodium chloride <strong>during</strong> <strong>the</strong> second stage to generate <strong>the</strong> end-product, sodium sulphate. Mechanical rakes rotate in <strong>the</strong> muffle furnace, pushing <strong>the</strong> sulphuric acid and sodium chloride to <strong>the</strong> centre of <strong>the</strong> furnace and <strong>the</strong> produced sulphate to <strong>the</strong> outer edge. The hot, acidic, and partly caked sodium sulphate is transferred through a conveyor belt to <strong>the</strong> subsequent treatment operations of: grinding, cooling, stabilisation, and sieving. The final product is of homogeneous quality, stored in a closed warehouse and sold in bulk form or packed into 25 kg bags or 1000 kg big bags. The basic chemical reaction governing <strong>the</strong> process is: 2NaCl + H2SO4 - Na2SO4 + 2HCl A flow scheme of <strong>the</strong> production of Na2SO4 by <strong>the</strong> Mannheim furnace process is given in Figure 1.13. Sulphuric acid Sodium chloride FURNACES NEUTRALISATION & CONDITIONING Sodium sulphate HCl WATER ABSORPTION Hydrochloric acid Figure 1.13: Flow scheme of <strong>the</strong> production of Na2SO4 by <strong>the</strong> Mannheim furnace process [64, CEFIC-SSPA, 2004] 1.6.2.5 Methionine process Methionine syn<strong>the</strong>sis leading to sodium sulphate production involves: saponification with caustic soda neutralisation with sulphuric acid. 25
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Page 48 and 49: References 41 Solvay S.A. (2003). "
Page 50 and 51: References 95 CEFIC-Brunner Mond (2
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Page 54 and 55: Glossary Ca 2+ Calcium ion CaC2 Cal
Page 56: Glossary (NH4)2SO4 Ammonium sulphat

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