GB673755A - Improvements in or relating to the production of ammonium phosphate - Google Patents

Abstract

Ammonium metaphosphate is produced by supplying elemental phosphorus, air in substantial excess of that theoretically required to convert phosphorus to phosphorus pentoxide, say 300 per cent, moisture and ammonia gas to a combustion chamber wherein the phosphorus is burned in the presence of the ammonia to form the metaphosphate in the vapour state, cooling the reaction product at such a rate that the resultant particles of metaphosphate do not decompose to a sticky or glass-like condition, and thereafter recovering the particulate metaphosphate. Alternatively elemental phosphorus is burned with excess air <PICT:0673755/III/1> <PICT:0673755/III/2> in a combustion chamber to produce phosphorus pentoxide vapour which with gaseous ammonia in the presence of moisture forms ammonium metaphosphate, which is treated in the same way as described above. In Fig. 1, air, containing ammonia gas from cylinder 10, is pumped by fan 9 into reactor 1. Molten phosphorus, liquified by heating water in tank 6 by burner 7, is forced by constant head siphon 8 from water filled jar 5 through pipe 4. The phosphorus burns spontaneously at 600-900 DEG F. to form the ammonium metaphosphate. The vaporous product is cooled to below 400 DEG F. in a few seconds by the injection of a large initial excess of air and/or by the addition of excess water vapour as a spray to the air supply and/or by water cooling coil 19. The metaphosphate is removed from the gases by filter bags 23 (one shown), which are alternately filled and emptied. The ammonia feed should be at least 30 per cent in excess of that theoretically required for the production of metaphosphate: the air should be 20-30 times that theoretically required; up to say 900 per cent excess water may be added; and the ratio of ammonia to phosphorus should be between 0.65 : 1 and 2 : 1 by weight. The rate of feed of ammonia and air is measured respectively by manometers 13, 15 showing the pressure drop across orifices 12, 14. In Fig. 3, molten phosphorus is burned with air from fan 9 in combustion chamber 47 formed by partition 46 in drum 40 which is connected by pipe 41 with reactor 1 of the type shown in Fig. 1. Drum 40 is cooled by water from spray pipe 45 connected to coil 19. Ammonia gas could be added with the air from fan 9 or outside the flame zone through pipes 48 at the entrance to pipe 41. The gases from reactor 1 are passed through U-bend 42 into hopper 43 p which has six canvas filter bags 44 from which the collected metaphosphate may be shaken into the hopper as product. A large scale continous operation apparatus is also described where the combustion chamber is enclosed in a fire tube boiler and the filter bags have automatic shaking means. The gases may be forced through the apparatus under pressure or sucked through by vacuum.