GB404018A - Improvements in processes of and apparatus for treating solid materials with gases - Google Patents

Abstract

In a process and apparatus for treating a layer of fine granular material of relatively high specific gravity, such as minerals, with a gas which is caused to pass through the layer, the material is charged in a layer on to a moving grate or sieve part of which serves to support the layer but from part of which it tends to fall, and the layer is held to the grate or sieve by setting up a sufficient difference of gas pressure on the two sides thereof. The material is finally discharged from the grate or sieve by reducing or eliminating the pressure difference <PICT:0404018/III/1> <PICT:0404018/III/2> <PICT:0404018/III/3> <PICT:0404018/III/4> at the point of discharge. The treatment may be for the purposes of effecting chemical reactions, heat exchange, or the removal of solid matter from the gas. Suitable granulation of the initial material may be effected by treatment with water, insufficient to form a slurry, in a crushing mill, grinding drum, or like mixing or pulverising apparatus, with subsequent drying if necessary. In one arrangement, Figs. 1 and 2, the granular material is supplied through a shoot 4 to form a layer upon the outer surface of the perforated wall of a rotary cylindrical drum 1 mounted within a fixed casing 3 and the material is prevented from falling from the underside of the cylinder by the pressure of air supplied through an opening 5 in the casing 3 and extracted axially of the cylinder through a pipe 6. At the point of discharge is provided a hood 7 connecting by a pipe 8 with the atmosphere or with a supply of compressed air. In a modified arrangement the material forms a layer upon the inner surface of the perforated wall and the air is supplied to the inside of the drum. Fig. 5 illustrates the use of the apparatus of Figs. 1 and 2 for preheating by means of the hot gases from a rotary kiln 12, granular material being fed to the kiln, the material being supplied to the drum 1 by a shoot 4 and worm conveyer 10 and held to the drum by the chimney draught, preferably increased, until it arrives beneath the hood 7 and falls into a shoot 13 delivering it into the kiln. Alternatively, the rotary grate may be built into the enlarged inlet end of the kiln, the material falling from the grate being transferred to the kiln by scoops. In this case the grate preferably rotates more rapidly than the kiln. Fig. 7 shows a modification of this arrangement in which the material is supplied by a shoot 4 and worm conveyer 10 to the inner surface of the perforated drum and on leaving the drum is delivered into the kiln by a shoot 13.