GB1367898A - Methods of and apparatus for transmitting heat between a powdered material and gas - Google Patents

Abstract

1367898 Preheating and cooling powdered material F L SMIDTH & CO AS 6 Dec 1971 [25 Feb 1971] 5452/71 Headings F4B and F4U A preheater for cement raw meal being fed to a rotary furnace 1 comprises a narrow casing 3 with walls 23, 24 enclosing four channels 16, 17, 18 and 19 arranged in zig-zag fashion, each channel being formed by downwardly and inwardly inclined side walls 26, 27 merging into vertical skirts 28, 29 defining a continuous restricted opening 30 along the bottom of each channel, hot gases from the furnace offtake 2 passing through each opening 30 in turn to a waste pipe 4. At the end of each channel is a small chamber 14 with an outlet 25 controlled by a flap valve 15. Raw material fed by pipe 12 to the uppermost chamber 14 is released in batches by its valve 15 over channel 16 above which are eddies created by the passage of gases through the opening 30. These eddies carry the material downwardly until contact with the next lower chamber 14 destroys the eddy depositing material on the valve 15. From the lowest stage material enters the furnace via pipe 20. Hot gases from pipe 4 pass in turn through a cyclone separator 5, a fan 7 and an electrostatic precipitator 9. The chambers 14 may be dispensed with except at the material entry and exit points (Fig. 5) and said material may be introduced into pipe 4. Cement discharged from a mill or alumina from a rotary furnace may be cooled in the apparatus of Fig. 7 in which a single channel is formed in an elongated casing 49 with material inlet 58, outlet 60, and air offtake 62, the lower part of the casing being divided by partitions 50 into plenum chambers supplied with cooling air by a fan 57 via a main 55 and branch pipes 54. Two coolers may be disposed in series, one at a slightly lower level than the other (Fig. 10).