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Spray drying method: add 10%~15% water into the dissolution tank to add sodium phosphate dodecahydrate crystal, heat it to 85~95 ℃, stir and dissolve it, purify the solution, pump the refined solution to the metering tank, atomize it with a spray, select a two flow air flow nozzle, spray the product to anhydrous sodium phosphate under the atomization steam conduction angle of 30 ° to the horizontal, atomization steam pressure of 0.15~0.3 Mpa, inlet temperature of 650~750 ℃, and outlet temperature of 140~170 ℃.

Hot phosphoric acid method: The neutralization reaction between hot phosphoric acid and caustic soda is carried out, and the neutralized liquid is cooled, crystallized, centrifuged, and dried to obtain the product.

H3PO4+3NaOH→Na3PO4+3H2O

Extraction phosphoric acid method

At 90-100 ℃, neutralize and extract phosphoric acid with industrial soda ash until 50% -70% of the acid is converted to monosodium phosphate, and precipitate sodium fluorosilicate. Filter and continue neutralizing the filtrate with soda ash until slightly alkaline (pH 8.4-8.6); Then neutralize with sodium hydroxide solution to generate trisodium phosphate, filter while hot, concentrate the clear solution to a relative density of 1.24-1.26 (28-30 ° B é), and cool to 25-70 ° C for crystallization; The product is obtained by centrifugal separation and drying, and the mother liquor can be reused.

Na2CO3+H3PO4→Na2HPO4+H2O+CO2↑

Na2HPO4+NaOH→Na3PO4+H2O [2]