Anhydrous reaction method for preparing polymeric ferric sulfate

An anhydrous reaction method for preparing polymeric ferric sulfate is disclosed. According to the method, 2-20 tons of industrial ferrous sulfate and 0.2-1.8 tons of sulfuric acid are added into a specialized stainless steel reaction unit with its volume being 2-20 cubic meters, and the ratio of ferrous sulfate to sulfuric acid is 10:1; in a nearly vacuum state, 2.5-3.5 kg of a catalyst is poured according to each ton of ferrous sulfate, the catalyst is sodium nitrite or dilute nitric acid, and dissolution and reaction are carried out in the same unit; after an oxygen valve reaches 0.02 MPa, pump type stirring is started, pressure is maintained at 0.02-0.04 MPa, reaction temperature is within 100 DEG C, and the reaction lasts for 3-10 h; after qualified through sampling analysis, an emptying valve is turned on, and a few tail gas is sent into an alkali absorption tower to be treated; after saturated, lye returns to be recycled as a catalyst; polymeric ferric sulfate is directly put into a spray drying tower to be dried, so as to obtain a polymeric ferric sulfate spray-dried product. Moisture content of the produced polymeric ferric sulfate is reduced to 25%, standard coal is saved by 65 kg, energy consumption is reduced by 50%, exhaust gas is minimized by 2/3, and production cost is greatly decreased.