INTEGRATED METHOD FOR THE COMMERCIAL AND INDUSTRIAL UTILISATION OF CALCIUM SULPHATE WHILST OBTAINING RARE EARTH ELEMENTS FROM THE PRODUCTION OF PHOSPHORIC ACID

摘要

The invention relates to a method for producing sulphuric acid and cement clinker and for obtaining rare earth elements using calcium sulphate, which is formed and separated as a solid by-product during the production of phosphoric acid when raw phosphate is reacted with sulphuric acid to form phosphoric acid, wherein the method comprises the following steps: a) the calcium sulphate separated from the phosphoric acid is treated with an acid in order to obtain a suspension containing purified calcium sulphate; b) the purified calcium sulphate is separated from the liquid phase of the resulting suspension as a solid material, wherein the resulting liquid phase can be introduced into the reaction unit of the phosphoric acid production as a feedstock; b1) the purified calcium sulphate obtained in step b) is treated with water or with an aqueous solution containing salt and/or chelating ligand, in order to release the rare earth elements from the calcium sulphate; b2) from the suspension obtained in step b1), the further purified calcium sulphate is separated as a solid material from the liquid phase, the liquid phase containing one or more rare earth elements; c) the separated purified calcium sulphate is mixed with additives and reducing agents in order to obtain a raw meal mixture for cement clinker production; d) the raw meal mixture is burnt in order to obtain the cement clinker, whilst sulphur dioxide is formed as a waste gas; and e) the formed sulphur dioxide is supplied as a raw material for sulphuric acid production, in order to produce the sulphuric acid, wherein the produced sulphuric acid is used as a feedstock in phosphoric acid production. The method is, in particular, an integrated method. The integrative approach as an overall concept ranging from phosphogypsum to cement clinker and sulphur dioxide takes into consideration the requirements in an existing phosphoric acid and sulphuric acid complex.