The invention discloses a method for manufacturing food-grade
dipotassium hydrogen phosphate by using wet-process dilute
phosphoric acid. The steps are as follows: (1) performing membrane
filtration:taking the wet-process dilute
phosphoric acid into an acid-resistant container, and performing precision-filtering with membrane
filtration equipment to obtain purified wet-process dilute
phosphoric acid; (2) carrying out a
neutralization reaction and performing simultaneous defluorination and desulfurization: adding a defluorination and desulfurization agent and a
potassium hydroxide solution, performing stirring and filtering to obtain a filtered
neutralization solution; (3) performing
arsenic removal by oxidation, heavy
metal removal under slightly alkaline conditions, and membrane
filtration: adding an oxidant into the filtered
neutralization solution, adjusting the pH value to slightly alkaline, performing heating, cooling and membrane filtration to obtain a solution after
arsenic removal by oxidation, and heavy
metal removal under slightly alkaline conditions; (4) performing pH adjustment and concentration: adjusting the pH value of the solution after
arsenic removal by oxidation, and heavy
metal removal under slightly alkaline conditions, and performing concentration to obtain a concentrated solution of
dipotassium hydrogen phosphate; (5) performing cooling
crystallization:crystallizing
dipotassium hydrogen phosphate in the temperature range of a dipotassium
hydrogen phosphate crystallization metastable zone, and then performing continue
crystallization until no crystallization occurs; and (6)
drying crystals. According to the method, the cost is low, the purity is high,
hygiene and safety are high, the method is easy to implement, the operation is simple and convenient, the
raw material utilization rate is high, the dissolving performance is good, and
mechanization can be realized.