Thermal phosphoric acid method
It is composed of heat phosphate and caustic soda, and the neutralizing liquid is cooled, separated by centrifuge, and dry.
H3PO4 + 3 and naoh Na3PO4 + 3 h2o
Extraction method of phosphate
Under 90 ~ 100 ℃, with industrial soda ash and extraction of phosphoric acid and 50% ~ 70% of acid precipitation into a sodium phosphate sodium fluorosilicate, filtration, the filtrate to continue with soda ash neutral to slightly alkaline (pH 8.4 ~ 8.6);
Is generated by sodium hydroxide solution and then trisodium phosphate, hot filtration, clear liquid enrichment to relative density 1.24 ~ 1.26 (28 ~ 30 ° Be), then the cooling crystallization to 25 ~ 70 ℃;
Centrifugal separation, dry product, mother liquid can be reused.
Write Na2CO3 + H3PO4 - Na2HPO4 + H2O + CO2
Na2HPO4 + NaOH - Na3PO4 + H2O