METHOD FOR PRODUCING SODIUM PHOSPHATE

摘要

1. A method for producing sodium phosphate, e.g. sodium tripoliphosphate, from extraction phosphoric acid and soda, comprising decomposition of phosphate raw material with sulphuric acid, treating the suspension with a part of phosphate raw material, filtration, treating the filtrate with barium compounds, neutralization of the suspension with soda solution, filtration, additional neutralization of the suspension of the filtrate, evaporation, drying and calcination, characterized in that the suspension produced from low-quality phosphate raw material is treated with a part of the same material to CaO concentration 0.8-1.7% in a liquid phase and SO4 ( 0.7-0.4%, the suspension is neutralized in two steps: in a first step - with neutralized solution from second step to the mole ratio Na2O:P2O5 ( 0.9-1.3, in a second step - with soda solution to mole ratio 1.55 - 1.63 with subsequent separation into two parts, one of which is directed to the suspension neutralization, and the remaining to filtration, the calcination is carried out at 350-400 degree C during 3-4 hours. 2. The method of claim 1, characterized in that filtrate is treated with sodium-containing solution to the mole ratio Na2O:P2O5 ( 0.6-0.75. 3. The method of claim 1, characterized in that soda solution prepared using cleansing solutions or filtrate after suspension neutralization with soda solution are used as sodium-containing solution when treating the filtrate. 4. The method of claim 1, characterized in that ammonia to pH ( 7.0-8.5 is introduced into the remaining part of solution directed to filtration.