Patent GB-1234562-A (GB)
IPC: B01J2/00
Filed: 1967-04-04
Abstract: 1,234,562. Granulating fertilizers. FISONS FERTILIZERS Ltd. 1 May, 1968 [4 April, 1967 (2)], Nos. 15361/67 and 15362/67. Heading B5A. [Also in Divisions B2 and C1] Granular fertilizers are produced by feeding fertilizer particles to an upwardly flowing gas stream e.g. air at ambient or elevated temperature, in which they are suspended and coated by spraying downwardly thereonto a liquid e.g. a melt, solution or slurry which may be the same as or different from the particles. The liquid may be sprayed by either a gas or pressureatomized nozzle and one or more spray nozzles may be employed giving a rectangular or full cone spray distribution. The particles may comprise potassium chloride, phosphate or nitrate; monammonium phosphate; urea; ammonium sulphate; or a mixture of one or more thereof. In the production of compound fertilizers, a fertilizer containing N, P 2 O 5  and K 2 O may be produced by spraying a liquid mixture of ammonium nitrate and phosphate (the latter preferably having an N: P atomic ratio of 1: 1 to 2: 1 and the mixture having a N: P 2 O 5  weight ratio of 5:1 to 3:1) on to seed particles of potash. Granules containing N and P 2 O 5  are produced by spraying the same materials on to recirculated solid particles thereof. Granules containing only N and K 2 O are produced by spraying liquid ammonium nitrate on to potash particles. Granules of single salts e.g. ammonium nitrate or sulphate; or urea, may similarly be produced. The upwardly flowing gas stream may be a fluidized air bed from which particles are removed at a point laterally opposed to the inlet, and of shallow depth e.g. 1 to 6 inches, to minimize mixing, with the apertured distributer plate thereof (through which the air is introduced) sloped down towards the outlet to accommodate increasing granule size or, alternatively, by using a bed of trapezoidal vertical section with the particles introduced at the narrow end thereof. The air velocity should be increased along the bed as the particle size increases e.g. by increasing the open area of the distributer plate towards the bed outlet. The space beneath the bed may be divided into a number of valved chambers whereby, after starting up, the air flow is progressively increased from the seed inlet. Alternatively, commencing with equilibrium air flow conditions, the particle size feed may be varied to different bed position. The upwardly flowing gas stream may be a spouted bed comprising an inner spout maintaining a vertical circulation of the particles and an outer concentric stream of gas maintaining only particles of less than the desired size in circulation. In a spouted bed apparatus, the particles are introduced by a screw feed 3, and the liquid through a spray 13 comprising an inner liquid tube 11 and an outer hot air tube 12. Air injected through tube 5 maintains the spout, and an outer stream of classifying air through which the granules drop out of suspension is provided by tube 6 from tube 8. Granules are discharged through rotary valve 9. A tube 10 prevents continuous circulation of the particles therein which are diverted to the bottom end of the apparatus towards the classifying air. Examples are given of the use of the apparatus employing molten mixtures of ammonium nitrate and phosphate sprayed on to potash particles, and of a mixture of molten ammonium chloride and nitrate sprayed on to potassium chloride particles.