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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 Sodium sulphate is recovered from <strong>the</strong> solution called “mo<strong>the</strong>r liquor” by concentration and water evaporation in a multi-effects evaporator. With temperature increase and concentration, sodium sulphate solubility decreases and leads to <strong>the</strong> precipitation of <strong>the</strong> sodium salt while methionine remains in solution. The solid phase is separated from <strong>the</strong> solution by decantation <strong>the</strong>n filtration on a centrifuge in which <strong>the</strong> cake is washed by water. At <strong>the</strong> outlet of <strong>the</strong> centrifuge, sodium sulphate is dried in a hot air stream heated by steam. Then <strong>the</strong> solid is separated from <strong>the</strong> gaseous phase by cyclone and sent by pneumatic transport to <strong>the</strong> bulk storage silos from which it is loaded in bulk onto trucks to deliver to customers. Downstream <strong>the</strong> dryer, airflow is cleaned in a scrubber supplied with process water to remove <strong>the</strong>fine particles. During <strong>the</strong> drying, <strong>the</strong> humidity of sodium sulphate and <strong>the</strong> organic sulphur compounds dissolved in <strong>the</strong> water, are transferred to <strong>the</strong> air. Before being released to <strong>the</strong> atmosphere, <strong>the</strong> airflow is deodorised by contact with bleach in air-mix equipment in which a chemical oxidation of <strong>the</strong> organic compounds is carried out. Part of <strong>the</strong> production is purified in order to obtain a white coloured solid without odours. The process treatment is performed in three steps: 26 humidification and spraying with sodium chlorate (NaClO3) oxidation by calcination in a rotary kiln cooling by air in a rotary mixer. The off-gases from <strong>the</strong> calcination have to be purified before <strong>the</strong>y can be released to <strong>the</strong> atmosphere. In <strong>the</strong> first step, <strong>the</strong> solid particles are kept by a cyclone and recycled into <strong>the</strong> process. The gaseous effluent is sent to a scrubber fed with water in order to eliminate residual dust. The liquid waste only contains sulphate and chloride in such a low concentration that it can be released to <strong>the</strong> environment. A flow scheme of <strong>the</strong> production of sodium sulphate from <strong>the</strong> methionine process is given in Figure 1.14.
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 Sodium Calcination on rotary kiln Purified sodium sulphate Liquid waste Figure 1.14: Flow scheme of <strong>the</strong> production of sodium sulphate from <strong>the</strong> methionine process [64, CEFIC-SSPA, 2004] 1.6.2.6 Formic acid process In <strong>the</strong> formic acid process, sodium formate is chemically reacted with sulphuric acid in <strong>the</strong> presence of formic acid. The solution from <strong>the</strong> reactor, containing formic acid and sodium sulphate, is fed to a centrifuge where sodium sulphate crystals are separated from <strong>the</strong> solution. The mo<strong>the</strong>r liquor is pumped into an evaporator where an additional amount of sodium sulphate is crystallised. This step is followed by ano<strong>the</strong>r centrifuging step. The sodium sulphate crystals are sent to a multi-coil dryer heated by steam, followed by cooling and sieving before <strong>the</strong> material is packed into bags or stored in bulk silos. 27
Page 1 and 2: EUROPEAN COMMISSION DIRECTORATE-GEN
Page 3 and 4: 2 PURIFICATION OF NON-FERTILISER GR
Page 5: List of tables Table 1.1: Typical c
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Page 48 and 49: References 41 Solvay S.A. (2003). "
Page 50 and 51: References 95 CEFIC-Brunner Mond (2
Page 52 and 53: Glossary SS Suspended Solids (conte
Page 54 and 55: Glossary Ca 2+ Calcium ion CaC2 Cal
Page 56: Glossary (NH4)2SO4 Ammonium sulphat

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