Pilot-Plant Production of Ammonium Polyphosphate Sulfate Suspension Fertilizers

摘要

TVA is developing a process for production of ammonium polyphosphate sulfate (APPS) suspension fertilizer from merchant-grade wet-process phosphoric acid, 93% sulfuric acid, and anhydrous ammonia. The two acids are simultaneously ammoniated in an ''enlarged'' pipecross reactor; the molten APPS is dissolved in water; and the fluid then is cooled to room temperature in an evaporative cooler. Attapulgite clay is mixed into the APPS fluid to prevent solids from settling during shipment, storage, and use. The process is energy efficient in that the hot APPS fluid provides all the heat required to preheat the phosphoric acid and vaporize the ammonia. Satisfactory suspension grades up to 11-30-0-3S can be made with 50% of the P sub 2 O sub 5 present as polyphosphate. The sulfur present in the product should be useful either to reduce sulfur deficiencies in the soil or to provide maintenance dosages of sulfur. The APPS fluid fertilizer can be either applied directly to the soil or used in preparation of mixed suspension products of various ratios. 9 figs., 1 tab. (ERA citation 11:025928)