GB491877A - Improvements relating to the burning of cement - Google Patents

Abstract

491,877. Cement. AHLMANN, N. March 11, 1937, No. 7218. [Class 22] Cement raw materials are sintered by forming a porous layer of fine granules of the raw material on a gas permeable support and passing gases at a temperature equal or substantially equal to the sintering temperature, i.e. about 1400-1500‹ C., through the layer. The raw material may be made porous as described in Specification 407,077 ; the average size of the granules should be about 1 mm. in diameter and should not exceed 3 mms. The raw materials may be preheated and even substantially calcined by mixing them with fuel, igniting and drawing air therethrough to effect combustion. The heating gases may be continuously circulated through the layer of raw material and reheated, e.g. electrically and /or by mixing with hot furnace gases ; a fraction of the gases may be continuously bled off and carbon dioxide isolated therefrom. In the apparatus shown, two hoppers 4, 5 respectively supply a heat resistant material such as clinker and raw material to form layers 6 and 7 on a chain grate 1 moving around rollers 2, 3. The hot gases are circulated by a fan 8 and after being heated by an electric furnace 16, pass first into a hood 9, then through the layers 7, 6 and the grate 1 into a space 10 which is sealed relatively to the grate 1, thence they pass upwards through the grate and layers 6, 7 to a pipe 11 connected to the suction side of the fan 8. Additional gases may be admitted through a pipe 13 having an adjustable damper 12 and gases may be removed through a pipe 15 having an adjustable damper 14.