1. Neutralization method
Mix solid caustic potassium into a 30% aqueous solution, clarify and filter to remove impurities, measure, and add to a corrosion resistant reaction tank. Slowly add an appropriate amount of 50% phosphoric acid solution while stirring, and perform neutralization reaction at 90~100 ℃. The reaction endpoint is controlled at pH 8.5~9.0 (using phenolphthalein as an indicator until it turns red). Heat to 120~124 ℃ for concentration, filter and remove insoluble substances until the solution concentration reaches the required range. The clarified filtrate is cooled to below 20 ℃ to precipitate crystals, then centrifuged and slightly air dried to obtain the finished product of potassium hydrogen phosphate.
2. Potassium carbonate method
Under continuous stirring, add potassium carbonate solution to 30% phosphoric acid solution for reaction, and the neutralization endpoint is pH 8.5-9.0 (phenolphthalein indicator just turns red); Concentrate the neutralization solution to 120~124 ℃, filter to remove insoluble substances, and then cool to below 20~C for crystallization; The product is separated and dried by centrifugation, and the mother liquor is sent to the neutralization process for reuse.