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Exergy analysis of the process of production of dicalcium phosphate dihydrate by decomposition of rock phosphate with hydrochloric acid

Lubka Georgieva Atanasova

Dicalcium phosphate dihydrate (precipitate) is used in agriculture as an additive to livestock food and as phosphorous containing mineral fertilizer. There are several methods for its production depending on the mineral acid used for the decomposition of natural phosphate. The present paper discusses a process where natural phosphate is decomposed using hydrochloric acid. This is a chemical technological process consuming large amount of energy. To assess its exergy efficiency, the exergy method is used. The aim of the work is to make exergy analysis of the process of production of precipitate by decomposition of rock phosphate with hydrochloric acid. The material, energy and exergy balances are made for the individual stages of precipitate preparation and for the whole process. The internal and external exergy losses are calculated. The exergy efficiency is low - 2.33 %. Suggestions are made which could increase the exergy efficiency up to 21 %.