In an improved process for granulation of materials wherein same is effected in an enclosed vessel by spraying particles of molten material onto rapidly moving granules of substrate such that said granules of substrate are increased in size by accretion as the sprayed particles solidify quickly on the surface of said substrate, said enclosed vessel comprising a rotating generally cylindrical drum equipped with lifting flights, the angle of the axis of which ranges upwards to about 3 degrees from the horizontal and said drum being equipped with deflector means, said deflector means comprising a plurality of deflector pans, said pans generally vertically displaced from one another wherein at least the top surface of each pan is substantially parallel with the axis of said drum;
- extends substantially throughout the length of said drum;
- is sloped downward at an angle of at least about 25 degrees with the horizontal in the direction toward the portion of the shell of said rotating drum moving in an upward direction and wherein at least said pan at the highest elevation therein is located horizontally above the axis of said drum and that portion, of each of said pans, juxtaposed its uppermost edge, with the exception of said pan at the highest elevation therein, subtends the lower edge of each succeeding pan thereabove, which improved process comprises:
- (a) alternately causing at least a portion of said granules of substrate in said enclosed vessel to be generally vertically displaced upwardly, by means of said lifting flight, from a bed of rolling discrete particles generally maintained in the lowermost section of said drum and thereafter transferred in a succession of first cascades onto the top surface of at least said pan at the highest elevation in said drum and over substantially the full top surface thereof to effect movement thereover downwardly to the lower edge thereof wherefrom said particles free fall to the top surface of the next pan vertically disposed therebeneath and move thereover downwardly to the lower edge thereof and wherein the cycle of discharge of particles from the lower edge of a pan in free-fall mode to the top surface of the next pan vertically disposed therebeneath is repeated until said particles discharge from the lower edge of the lowermost pan comprising said deflector means and eventually free fall back to said bed, the successive free-fall modes of said particles from the lowermost edge of said pans comprising an interrupted curtain, or a succession of second cascades of particles, said second cascades, having a particle density substantially greater than the particle density of said first cascades formed by discharge of said particles from said lifting flights, with the angle of the fall line of said granules of substrate in the free fall portion of the descending attitude of said vertical displacement for eventual return to said bed ranging from about 90 degrees to the horizontal to about 5 degrees greater than the angle of repose of said granules of substrate;
- (b) causing at least a portion of the air in said enclosed vessel to be utilized as cooling air and moved in a generally horizontal attitude in a manner so as to intersect said granules of substrate in a free-fall mode of their descending attitude of said vertical displacement, said generally horizontal movement of air being sufficient to at least partially penetrate at least one of said cascades of said free falling granules of substrate, with the contact angle between said air and the plane of the fall line of said at least one cascade ranging from between about -45 degrees to about +45 degrees from the direction perpendicular to the plane of said fall line;
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- (c) causing at least a portion of said air in said enclosed vessel having intersected and at least partially penetrated said at least one cascade of said granules of said substrate therein to be displaced to exhaust means;
- the improvement in combination therewith for effecting substantially improved heat transfer between the granulated material in said enclosed vessel and the air introduced therein which comprises the additional steps of:
- (1) confining the portion of said cooling air to be moved in step (b) supra within first manifold means and moving same therein generally parallel to the axis of said drum to effect introduction of same into said drum;
- (2) subsequently effecting a change in the direction of said cooling air movement, from the perspective of the planer view thereof, in the range of from about 45 degrees to about 135 degrees from the direction of said cooling air movement in step (1) supra;
- (3) subsequently causing said cooling air to move through a plurality of apertures, the total area of said apertures ranging from about 8 to about 15 times the cross-sectional area of said first manifold means with the points of origin of said cooling air exiting said apertures extending substantially throughout the length of said drum and generally defining a plane substantially parallel to the axis of said drum and angularly disposed between about -45 degrees to about +45 degrees from a vertical plane, said vertical plane substantially parallel to the axis of said drum;
- (4) substantially confining said cooling air exiting said plurality of apertures within second manifold means, said second manifold means having, as one generally planner boundary thereof, said at least one second cascade, the confinement of said air by said second manifold means substantially;
- (i) eliminating lateral short circuiting or by-passing of said at least one second cascade by said cooling air;
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- (ii) intersecting said granules of substrate in a free-fall mode of their descending attitude of vertical displacement in a manner to thereby effect total penetration of said at least one second cascade with said confined cooling air;
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- (5) removing said air to said exhaust means;
- said improved process for granulation characterized by the fact that the substantial elimination of lateral by-passing of particles comprising said at least one second cascade by said cooling air substantially increases the penetration thereof and enhances the cooling efficiency of said process to a degree such that adjustments to the enthalpy of the cooling air, subsequent to its penetration of said at least one second cascade for recycling of same for purposes of subsequent contact with particles subsequently comprising said at least one second cascade, is substantially eliminated.