GB357508A - Process for preparing phosphatic fertilizing materials - Google Patents

Abstract

A process of preparing phosphatic fertilizers comprises passing a stream of acid towards a receiving zone, intermixing said stream with a stream of finely divided phosphatic material and allowing the acid and phosphate to react under pressure in the said zone. Acid from a tank 1, heated by steam coil 2, is fed via measuring device 6 to acid charging tank 9, and thence under pressure to a mixing valve 25, where it is mixed with ground phosphate rock. This is conveyed thereto from a hopper 12 via measuring device 15, pump 18 and dust-charging hopper 21, and on its passage is aerated by jets 14, 19, 23. In the mixing valve 25, the stream of dust is enclosed by a stream of acid, and thorough mixing occurs. The mixture passes via control gate valve 26 on to a baffle 28 in a jacketed rotating autoclave 27, attached to which is a condenser 32, and vacuum pump 36. When charged, the autoclave is sealed, and, if desired, heated. The pressure is then intermittently released, the vapours evolved being condensed and removed via pipe 38. The mixture may be crystallized by cooling, and dried by heating under reduced pressure. The material is then conveyed to a hopper 41, and thence it may be passed to grinding apparatus 48, and discharged by a conduit 49; alternatively it may be treated, preferably under reduced pressure, with gaseous, anhydrous or aqueous ammonia in a tank 45, then ground and <PICT:0357508/III/1> discharged; or it may be ground prior to the ammonia treatment. The autoclave product may be mixed with an inert substance such as sawdust prior to ammonification.ALSO:A phosphatic fertilizer, obtained by a process comprising the mixing of a stream of acid with a stream of finely divided phosphatic material and allowing the acid and phosphate to interact under pressure, is treated after drying, preferably under reduced pressure, with gaseous, anhydrous or aqueous ammonia, then ground and discharged. Alternatively, it may be ground prior to the ammonia treatment. The autoclave product may be mixed with an inert substance such as sawdust prior to ammonification.