The invention relates to a method for reducing SO3 concentration in diluted
phosphoric acid, which is characterized in that a desulfurizer is additionally arranged between a wet process
phosphoric acid extraction tank and a diluted
phosphoric acid storage tank, an ore pulp storage groove is connected into the desulfurizer through a pipeline, the diluted phosphoric acid obtained through filtering and extraction through the phosphoric acid extraction tank is connected to the desulfurizer through a pipeline, the desulfurizer is also connected to the diluted phosphoric acid
storage tank through a pipeline, the diluted phosphoric acid obtained through the filtering and the extraction through the phosphoric acid extraction tank is pumped into the desulfurizer through a pump, simultaneously, ore pulp is also pumped into the desulfurizer, the diluted phosphoric acid and the ore pulp take reaction in the desulfurizer for reducing the free
sulfuric acid content in the diluted phosphoric acid, and the desulfurized diluted phosphoric acid is pumped into the diluted phosphoric acid
storage tank through the pump. The method has solves the problem of
ammonium phosphate production affected by
mass fluctuation of the
phosphate ore and has the advantages that: (1) the quality of the
ammonium phosphate product is stable, 1 percent of SO3 in the phosphoric acid is reduced, the total
nutrient content of the produced monoammonium
phosphate product is improved by about 1.0 percent, and the total
nutrient content of the produced
diammonium phosphate product is improved by about 0.6 percent; and (2) the extraction work procedure cost is saved, and simultaneously, the contraction work procedure cost is reduced.