Patent GB-1069454-A (GB)
Title: Pan granulation process
IPC: B01J2/14
Filed: 1965-05-04
Abstract: <PICT:1069454/C2/1> Urea granules are produced, preferably in an apparatus shown in Fig. 1, by a process comprising the following steps:  a sloping slow-moving bed of solid nuclei particles of urea 17 (preferably at 40-70 DEG  C. below m.pt.) and a zone of fast-moving particles are diametrically opposed in an inclined (e.g. 60 degrees to horizontal) circular pan 10 which is rotated about its axis at a rate (e.g. 20-40 r.p.m.) sufficient to transfer small particles from the bed under the scraper 18 to the upper fast moving zone to which is also fed, via hopper 9, cooled solid nuclei particles of urea forming a layer ( 1/2 -\ba3/4 inch thick) of closely packed particles; molten, anhydrous urea (at 5-15 DEG  above its m.pt.) is sprayed at 20-45 p.s.i.g. on to the layer by sprays 24; large granules are discharged from the bed 17 over the rim 16, cooled to 50-70 DEG  C. by passing in counter-current to air and screened, selecting a predetermined size range as product and crushing oversized granules which are returned with the undersized granules to the zone via hopper 9 as said cooled solid nuclei particles; the particle fines entrained in the cooling air are collected, dissolved in a solution of urea which is concentrated to provide anhydrous melt of urea (at least 99%) for spraying. The ratio of the weight of cooled particles returned to pan via hopper 9 to the weight collected as product is between 0.9: 1 and 3: 1.  The urea granules produced contain less than 0.15% by wt. moisture after conditioning with an anti-caking agent (e.g. diatomaceous earth).ALSO:Ammonium nitrate granules are produced in an apparatus shown in Fig. 1 by a process with the following steps: a sloping slow moving bed of solid nuclei particles of NH3NO3 17 (at 40-70 DEG  C. below melting point) and a zone of fast moving particles are diametrically opposed in an inclined (e.g. 60 degrees to horizontal) circular pan 10 which is rotated about its axis at a rate (e.g. 20-40 r.p.m.) sufficient to transfer small particles from the bed under the scraper 18 to the upper fast moving zone to which is also fed, via hopper 9, cooled solid nuclei particles of NH4NO3 forming a layer ( 1/2 -\ba3/4 inch thick) of closely packed particles; <PICT:1069454/C1/1> molten, anhydrous, ammonium nitrate (at 5-15 DEG  C. above its melting point) is sprayed at 20-45 p.s.i.g. on to the layer by sprays 24; large granules are discharged from the bed 17 over the rim 16, cooled to 50-70 DEG  C. by passing in countercurrent to air and screened, selecting a predetermined size range as product and crushing oversized granules which are returned with the undersized granules to the zone via hopper 9 as said cooled solid nuclei particles; the particle fines entrained in the cooling air are collected, dissolved in a solution of NH4NO3 which is concentrated to provide anhydrous melt of NH4NO3 (at least 99%) for spraying.  The ratio of the weight of cooled particles returned to pan via hopper 9 to the weight collected as product is between 0.9 : 1 and 3 : 1.  The NH4NO3 granules produced contain less than 0.15% by weight, moisture after conditioning with an anti-caking agent (e.g. diatomaceous earth).