Integrated method for producing sulphur dioxide quality suitable for a sulphuric acid process from calcium sulphate/phosphogypsum from phosphoric acid production

A process for producing sulfuric acid and cement clinker using calcium sulfate that is formed as a solid by-product and separated off in phosphoric acid production in a reaction of raw phosphate with sulfuric acid to form phosphoric acid, wherein the process comprises:

• (a) treating the calcium sulfate that is separated off from the phosphoric acid with an acid to obtain a suspension comprising purified calcium sulfate;
• (b) separating the purified calcium sulfate in solid form from a liquid phase of the suspension, wherein the purified calcium sulfate that is separated off contains at least 50% by weight of anhydrite based on dry calcium sulfate;
• (c) mixing the purified calcium sulfate that is separated off with admixtures and reducing agents to obtain a raw meal mixture for cement clinker production;
• (d) burning the raw meal mixture to obtain the cement clinker, forming sulfur dioxide as an offgas;
• (e) subjecting the sulfur dioxide to offgas purification, wherein the offgas purification comprises:
• (e1) dry depositioning particles having a size greater than 100 μm,
• (e2) wet depositioning particles having a size of 20 to 100 μm,
• (e3) removing particles having a size less than 20 μm, and
• (e4) removing nitrogen oxides;
• and
• (f) feeding the sulfur dioxide as raw material to a sulfuric acid production to produce the sulfuric acid.