GB1099856A - Granulation process and apparatus - Google Patents

Abstract

Nitrogenous fertilizer compounds, e.g. ammonium nitrate or urea, are produced in granular form by apparatus comprising a drum 10 which rests on rollers 11 and is separated b a ring 15, of adjustable width, into a granulating zone A of between one half and the full length of a cooling zone B and which is inclined at 1-3 degrees to the horizontal and is rotated, by gear engagement with ring 14, at between 4 and 12 r.p.m whereby solid particles of fertlizer, supplied through pipe 20, are advanced in a bed through zones A and B whilst being raised therefrom by lifting elements (22) Figs. 3 and 4, not shown) to form a continuous cascading curtain <PICT:1099856/C1/1> which, in zone A, is sprayed via pipe 21 with an anhydrous nitrogenous melt of at least 98% and preferably 99 to 99.5%, ammonium nitrate or urea, at 5 DEG to 25 DEG C., and preferably 10 DEG C., above its crystallization teperature whilst cooling air, supplied at outlet 31, is exhausted through duct 23 and is always at least 60 DEG C. below the temperature of the molten spray. The ammonium nitrate or urea is automatically formed in a reactor (40) (Fig.1, not shown) as an aqueous solution which is concentrated in an evaporator (41) and supplied to the drum (10) along a heated pipe line (21). Granules discharged from the drum (10) are screened in a unit (43) with correct sized material passing via a cooler (42), to a unit for coating, e.g. with diatomite, oversize material passing for incorporating into the solution and for recirculation via a cursher (45) and undersize material, together with material collected at a drum inlet hopper (46) being fed back to the drum inlet pipe (20). Fines are collected from the drum cooling air exhaust 23 and the exhaust from the cooler 42 in a separator (44) and returned for concentration in the evaporator (41). Ammonium nitrate and urea granules are produced predominantly in the size range of 0.131 to 0.065 inch diameter, the nitrate having a bulk density greater then 50 lb./cubic feet and both the nitrates and urea granules being characterized by their hardness.ALSO:Nitrogenous fertilizer compounds, e.g. ammonium nitrate or urea, are produced in granular form by apparatus comprising a drum 10 which rests on rollers 11 and is separated by a ring 15, of adjustable width, into a granulating zone A of between one half and the full length of a cooling zone B and which is inclined at 1-3 degrees to the horizontal and is rotated, by gear engagement with ring 14, at between 4 and 12 r.p.m., whereby solid particles of fertilizer, supplied through pipe 20, are advanced in a bed through zones A and B whilst being raised therefrom by lifting elements (22) (Figs. 3 and 4, not shown) to form a continuous cascading curtain which, in zone A, is sprayed via pipe 21 with an anhydrous nitrogenous melt of at least 98%, and preferably 99 to 99.5%, ammonium nitrate or urea at 5 DEG to 25 DEG C., and preferably 10 DEG C., above its crystallization temperature whilst cooling air, supplied at outlet 31, is exhausted through duct 23 and is always at least 60 DEG C. below the temperature of the molten spray. The ammonium nitrate or urea is automatically formed in a reactor (40) (Fig. 1, not shown) as an aqueous solution which is concentrated in an evaporator (41) and supplied to the drum <PICT:1099856/C2/1> (10) along a heated pipe line (21). Granules discharged from the drum (10) are screened in a unit (43) with correct sized material passing, via a cooler (42), to a unit for coating e.g. with diatomite, oversize material passing for incorporating into the solution and for recirculation via a crusher (45) and undersize material, together with material collected at a drum inlet hopper (46), being fed back to the drum inlet pipe (20). Fines are collected from the drum cooling air exhaust 23 and the exhaust from the cooler 42 in a separator 44 and returned for concentration in the evaporator (41). Ammonium nitrate and urea granules are produced predominantly in the size range of 0.131 to 0.065 inch diameters, the nitrate having a bulk density greater than 50 lb./cubic feet and both the nitrates and urea granules being characterized by their hardness.