Method for burning granular or pulverous materials and kiln plant thereof

Abstract

A kiln plant for burning raw materials such as cement raw materials and the like includes a single-string, multi-stage suspension preheater, a suspension precalciner, a rotary kiln and a cooler. The single-string preheater includes at least a lowermost preheater stage and a penultimate preheater stage each having a gas flow inlet and outlet. The precalciner gas outlet is coupled to the gas inlet of the penultimate preheater stage. The gas outlet of the lowermost preheater stage is also coupled to the gas inlet of the penultimate preheater stage. The materials are precalcined in the precalciner solely by means of spent cooler air from the cooler while the materials are preheated in the lowermost preheater stage solely by means of kiln exhaust gases. The pressure drops arising in the two gas flows through the precalciner and the lowermost preheater stage are equalized before the union of the two gases flows entering the gas inlet of the penultimate preheater stage. The equalization of the pressure drops in the two gas flows is provided by a movable damper mounted in the respective gas flow duct before the juncture in the duct which permits the union of the two gas flows. Preferably, the two gas flows are equalized so that the pressure drop across the precalciner is of the order of twice the pressure drop through the kiln and lowermost preheater stage. A method of practicing the present invention is also disclosed.