SODIUM TRIPOLYPHOSPHATE PRODUCTION PROCESS Russian patent published in 2003 - IPC

FIELD: industrial inorganic synthesis. SUBSTANCE: process of production of sodium tripolyphosphate appropriate for use in chemical, textile, household, and food areas comprises desulfatization of acid with calcium and barium compounds, defluorination with soda, removal of calcium sulfate and sodium silicofluoride precipitates, and neutralizing barium sulfate suspension with soda followed by separation of phosphorus-containing impurity precipitate. Process further envisages neutralization of extraction phosphoric acid with soda conducted until Na/P ratio in liquid phase is reached 1.62-1.63; 0.1-0.3% of activated carbon is added at 70-75 C followed by 25-40-min aging and product after drying containing 70-85% of fraction -4 to +1 mm is subjected to calcination conducted in drum-type calcinator provided with inverse screw and supporting rings at temperature of incoming gases 615-635 C and released gases 450-470 C, residence time product in calcinator being 3-5 h. Degree of conversion of orthophosphates into sodium tripolyphosphate achieves 97.5-98.5%. Product includes 0.003-0.01% iron, 0.03-0.1% calcium oxide, and 0.03-0.1% fluorine. Content of l-form of tripolyphosphate ranges between 35 and 65%. ROH test data: 81-89 C after 1 min and 88-94 C after 5 min. EFFECT: increased yield and purity of product. 2 tbl, 3 ex