Method for preparing trisodium phosphate
1. Spray drying method Add the crystal of trisodium phosphate trihydrate to the dissolution tank, add 10%~15% water, heat to 85~95 °C, stir and dissolve, then purify the solution, pump the refined solution to the metering The tank is atomized by a sprayer. The atomizer uses a two-flow air jet nozzle. The atomization steam is 30° at the angle and level, the atomizing steam pressure is 0.15~0.3 Mpa, the inlet temperature is 650~750°C, and the outlet temperature is 140~170. Spray drying was carried out at ° C to obtain an anhydrous sodium trisodium phosphate product.
Hot phosphoric acid method: neutralization reaction is carried out by hot phosphoric acid and caustic soda, and the neutralized liquid is cooled and crystallized, centrifuged and dried to obtain a product.
Chemical reaction equation: H3PO4+3NaOH→Na3PO4+3H2O
Extraction of phosphoric acid: at 90~100 °C, neutralizing the extraction of phosphoric acid with industrial soda ash to 50%~70% of the acid is converted to monosodium phosphate, sodium fluorosilicate is precipitated, filtered, and the filtrate is further neutralized with soda ash to slightly alkali (pH 8.4~8.6); then neutralize with sodium hydroxide solution to form trisodium phosphate, filter it hot, concentrate to a relative density of 1.24~1.26 (28~30°Bé), then cool to 25~70° C crystal; centrifuged, dried to obtain the product, the mother liquor can be reused.
2. Neutralization method The food grade phosphoric acid is diluted with a non-ionized water to a certain concentration and then added to the stirred reactor. The food grade caustic soda solution is slowly added under stirring to carry out the neutralization reaction, and the Na/P ratio is adjusted to 3.24~3.26. Then, the decoloring agent, the heavy metal removing agent and the arsenic removing agent are added for solution purification, and then the impurities are removed by filtration. The filtrate is cooled and crystallized, centrifuged and dried to obtain a finished product of trisodium phosphate trihydrate.
The phosphoric acid method is used to react the phosphate rock with sulfuric acid to obtain an extracted phosphoric acid, and an appropriate amount of washing water is added, and the phosphorus pentoxide content in the solution is diluted to 18% to 20%, heated to 85 ° C, and slowly added to 30 to 35 with stirring. The B6 sodium carbonate solution was subjected to a neutralization reaction to bring the pH to 8 to 8.4. The trisodium phosphate mother liquor is further added to make the phosphorus pentoxide content in the solution less than 12%. Incubate for 15~20min, filter and evaporate to 24~25°Bé. Add liquid caustic soda to achieve a sodium storage ratio of 3.24 to 3.26. After cooling crystallization, centrifugation, and air drying, the finished product of trisodium phosphate dodecahydrate is obtained.
The hot process phosphoric acid method is used to add the hot process phosphoric acid to the reactor, and the liquid caustic soda is slowly added under stirring to carry out the neutralization reaction to form trisodium phosphate, which is cooled and crystallized, centrifuged and dried to obtain a finished product of trisodium phosphate dodecahydrate.
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