Exergy analysis of the process of wet-process phosphoric acid production with full utilisation of sulphur contained in the waste phosphogypsum

The wet-process phosphoric acid is produced by decomposition of phosphate raw materials with sulphuric acid. This gives a large amount of waste product-phosphogypsum. The thermochemical decomposition of phosphogypsum gives a gas rich in SO2. This gas is processed to obtain sulphuric acid, which is fed back into phosphoric acid production. The aim of this paper is to perform exergy analysis of the wet-process phosphoric acid production including full recycling of the sulphur from the waste phosphogypsum. The results obtained from the analyses show that the utilisation of phosphogypsum increases the exergy efficiency of the phosphoric acid production and decreases to 20.86% when the phosphoric acid production is connected with the process of thermochemical decomposition of phosphogypsum.