Process for calcination of cement-clinker

Abstract

A process is disclosed for calcining cement-clinkers by using a calcination apparatus having a generally cylindrical calcining furnace which is composed of (a) a throat part, (b) a spouted bed and (c) an uppermost chamber longitudinally connected in series with an upper part of a combustion chamber having a separate heat source. The calcining apparatus is disposed between a suspension type raw material preheating device and rotary kiln or a fluidized bed calcining device wherein, cement raw materials, which have been partly calcined in the said raw material preheating device, are fed in the vicinity of the upper end of the said spouted bed while a jet fluid of a high temperature flue gas passing through the throat part under high speed from the said combustion chamber and rising upwards is admixed with a tangential flow of a high temperature exhaust gas introduced into the vicinity of the upper end of the said spouted bed from the said rotary kiln or from the fluidized bed calcining device. This forms a vigorously admixed and dispersed tangential flow zone where the calcination and heat exchange of the cement raw materials are carried out in the central part of the said calcining furnace and a returning swirl flow zone of a relatively low temperature falling downwards together with non-calcined cement raw materials in the vicinity of the surface of the inner wall of the said calcining furnace; and powders of completely calcined cement raw materials are selectively exhausted together with the exhaust flue gas from the vicinity of the top part of the said calcining furnace and are transported to the rotary kiln or the fluidized bed calcining device.