JPH0310587B

Cement clinker is produced in that raw cement powder is preheated in a suspension-type heat exchanger and is de-acidified in a precalcining apparatus and clinkered in a fluidized bed and the clinker is subsequently cooled. An de-acidification of at least 95% is effected at a temperature above 85 DEG C. in a circulation system comprising a fluidized bed reactor, a cyclone separator and a recycling duct. The carbonaceous fuel required for the calcining and clinkering processes is fed in an amount of at least 65% (related to the total heat requirement) to the de-acidifying fluidized bed reactor and in an amount of at least 10% (related to the total heat requirement) to the clinkering fluidized bed reactor. The fuel supplied to the fluidizing bed reactor is burnt near stoichiometrically in two stages with fluidizing gas and secondary gas. The ratios of the rates and volumes of fluidizing gas to secondary gas are so selected that a means suspension density of 100 to 300 kg/m3 is maintained in the zone between the inlet for fluidizing gas and the inlet for fluidizing gas, and a mean suspension density of 5 to 30 kg/m3 is maintained above the inlet for secondary gas.