Method and apparatus used for preparing ammonium phosphate fertilizer from phosphoric acid sediment

The invention discloses a method and an apparatus used for preparing ammonium phosphate fertilizer from phosphoric acid sediment. The method comprises following steps: the phosphoric acid sediment with a P2O5 content of 30 to 35% is mixed with diluted phosphoric acid with a concentration of 18 to 20% so as to obtain intermediate mixture I with a phosphoric acid content of 20 to 25%; the intermediate mixture I and gaseous ammonia with a concentration of 99% are subjected to neutralization reaction at a N mole/P mole ratio of 1.3-1.35, and a certain amount of sulfuric acid is added so as to neutralize unreacted gaseous ammonia; the N mole/P mole ratio is increased to 1.4-1.45 so as to obtain intermediate mixture II; and the intermediate mixture II is subjected to condensation, granulation and screening treatment. Gaseous ammonia is used for neutralizing the intermediate mixture I with a phosphoric acid content of 21 to 25%, ammonium bicarbonate or liquid ammonia are not used, and reaction contact area and react