Method for preparing battery-grade anhydrous iron phosphate from liquid crude monoammonium phosphate

A method for preparing battery-grade anhydrous iron phosphate from liquid crude monoammonium phosphate, comprising the following steps:

• S1. preheating ferrous sulfate solution to obtain the preheated ferrous sulfate solution;
• S2. mixing the preheated ferrous sulfate solution, liquid crude monoammonium phosphate and hydrogen peroxide solution for oxidation reaction to obtain iron phosphate intermediate slurry;
• the molar ratio of iron in the preheated ferrous sulfate solution to phosphorus in the liquid crude monoammonium phosphate is 1:(0.9-1.2), the mass fraction of monoammonium phosphate in the liquid crude monoammonium phosphate is 18%-30%, and the liquid crude monoammonium phosphate is an intermediate product in the production process of ammonium phosphate;
• and the temperature of the oxidation reaction is 40-60° C., and the time is 40-100 min;
• wherein the mixing method in step (2) comprises:
• adding liquid crude monoammonium phosphate and hydrogen peroxide solution to the preheated ferrous sulfate solution, the time for adding the liquid crude monoammonium phosphate is 50-70 min, the time for adding the hydrogen peroxide solution is 50-70 min, and the time for adding the hydrogen peroxide solution is 1-5 min later than the time for adding the liquid crude monoammonium phosphate;
• S3. conducting solid-liquid separation of the iron phosphate intermediate slurry, and washing the obtained solid material to obtain crude iron phosphate;
• S4. mixing the crude iron phosphate, water and phosphoric acid, and then aging to obtain aged slurry, wherein the temperature of the aging is 75-95° C., and the time is 1-2.5 h;
• S5. conducting solid-liquid separation of the aged slurry, and washing, drying, dehydrating and breaking up the obtained solid material in sequence to obtain battery-grade anhydrous iron phosphate.