Method for producing sodium tetrapolyphosphate with high pH value

The invention provides a method for producing high-pH-value sodium tetrapolyphosphate, which comprises the following steps: heating water to be more than or equal to 90 DEG C, adding a certain amount of liquid caustic soda, simultaneously adding sodium carbonate, liquid caustic soda and phosphoric acid into a neutralization reaction kettle, carrying out chemical reaction under stirring, adding a catalyst ammonium phosphate, adjusting the neutralization degree K value of the neutralized solution to be 2.65 +/-0.1, adjusting the specific gravity of the neutralized solution to be 1.6-1.7 g/cm < 3 >, and reacting for 2-3 hours; continuously reacting until the solution is viscous; carrying out spray drying dehydration on the neutralized viscous solution, and polymerizing to obtain a sodium tetrapolyphosphate semi-finished product; the sodium tetrapolyphosphate semi-finished product is subjected to shock cooling to generate glassy sodium tetrapolyphosphate, and then the glassy sodium tetrapolyphosphate is crushed a