CONTINUOUS PROCESS FOR THE PRODUCTION OF SOLID CALCIUM PHOSPHATES FROM RAW PHOSPHATE WITHOUT THE ADDITION OF PHOSPHORIC ACID AND LIME

摘要

Solid calcium phosphates are prepd. in a continuous process from raw phosphates without the addn. of ether-phosphoric acid or lime. 50-200 g raw phosphate is dissolved in 1l of processing acid contg. 100-750g P2O5 and 0-80g CaO. The soln is agitated for 20 mins.-6 hrs. at 20-120 deg.C. When mono-calcium phosphate is prepd. the processing acid contains 0-5 wt% CaO and 35-75 wt% P2O5. Any sediment is filtered out. The soln. is cooled and mono-sodium phosphate is sepd. by filtration. For the prepn of di:calcium-phosphate the process acid contains 0-8 wt% CaO and 5-35 wt.% P2O5. The prod. is filtered out. Mixed phosphates are prepd from process acid, which contains 1-5 wt% CaO and 25-40 wt% P2O5. the prod is filtered out. - In all three cases any excess calcium-over and above that, stoichiometrically necessary for the prepn of a cpd. in the next cycle-is removed from the filtrate, and the filtrate is then recirculated as process-acid.