Abstract:

The construction of a new plant for producing phosphoric acid by wet-process of phosphate rock usually needs to be designed independently according to the different properties of phosphate rock（chemical composition,material equivalence）. By simulating the industrial process of wet-process phosphoric acid （reaction, crystallization and filtration） in laboratory,the process parameters of acid production under specific phosphate rock could be obtained,which would reduce the test cost of industrial unit.According to the customer′s entrustment,the acid production simulation experiment in laboratory of a medium grade phosphate rock from Nigeria was carried out by using the traditional dihydrate process method process,and single factor method was used to study the effects of the main control parameters of WPA process,including free SO₃ concentration, phosphoric acid concentration,residence time,temperature and mass ratio of liquid to solid in slurry.The optimum conditions were as follows：the concentration of free SO₃ was 25~30 g/L,the concentration of phosphoric acid（based on the mass fraction of P₂O₅） was 22%~23%,the residence time was 4 h,the reaction temperature was 75~78 ℃,and the mass ratio of liquid to solid in slurry was 2.5∶1.Under the above conditions,the conversion rate of P₂O₅ in phosphate ore was ≥93%,the yield of P ₂O₅ was about 90%,and the filtration strength of slurry（based on P₂O₅）was 8.1 t/（d·m²）.It was found that in late tracking the experimental results obtained in the laboratory were basically consistent with the test results of late industrialization.

Key words: middle-grade phosphate ore, wet-process phosphoric acid, phosphogypsum crystal