GB857218A - Improvements in or relating to the production of white cement - Google Patents

Abstract

857,218. White cement clinker. DYCKERHOFF ZEMENTWERKE A.G., and METALLGESELLSCHAFT A.G. Jan. 29, 1959 [March 18, 1958], No. 3259/59. Class 22. White cement clinker is produced from green pellets of the raw material of particle size 2 to 15 mm. diameter on the moving grate of a band sintering apparatus 1 by passing the pellets successively through zones 8, 9, 12, 14, 15, 16 where the sinter bed is preheated and dried, sintered, " after treated " in a reducing atmosphere above 900‹C., cooled to below an oxidising temperature and finally cooled to atmospheric temperature, the heating and cooling being by gas. The sinter bed consists of a lower grate protecting layer 3 of inert material coarser in size then the raw material green pellets in layer 5, and a top layer 7 of preburned pellets. Under hood 8 drying is at 300‹C. to 400‹C., sintering under oxidising conditions at 1000‹C. to 1400‹C. under hood 9 and before sintering at 1400‹C. to 1460‹C. in a reducing gas under hood 12 a layer 19 of finished clinker up to 4 mm. size is placed on layer 7 by hopper 11. In the " after treatment " zone 14 reducing gases at 1050‹C. are drawn through the bed at a reduced speed and in the reducing cooling zone 15 reducing gases decreasing in temperature from 400‹C. to 200‹C, are drawn through the bed at an increased speed to reduce the temperature of the upper layer to below 500‹C. A further protective layer 20 of finished clinker is added to the bed from hopper 16 before the final cooling to 100‹C. by atmospheric air in zone 17. The coarse grate particles from layer 3 are sieved and recycled to hopper 2, the fines from layer 5 are returned to hoppers 11 and 16 and the layer 5 is separated from the finished white clinker 7 and returned to hopper 6 for refeeding. The exhaust gas from hood 9 is recycled to hood 8, gas from hood 12 to hood 15, and gases from 14 and 15 are mixed with the gas in hood 9.