Drying plant for industrial and sewage sludges, includes stages recirculating and condensing drying gas, and transferring condensation heat to following stage

摘要

The sludge passes through one or more drying stages for treatment by drying gas in closed-circuit recirculation. Condensation heat evolved in this stage, is used in one or more further drying stages, to heat the drying gas. Between drying stages, sterilization is undertaken by heating the sludge to a given temperature. During this operation, no waste gas is removed, and no condensate is produced. In later stages, some of the drying gas is removed, following drying. Waste heat, e.g. from a power station, is used to heat the drying gases in one or more drying stages. In a drying stage with gas recirculation, the maximum temperature of the sludge reaches 70degreesC. In no drying stage does the temperature of the drying gas exceed 102degreesC. The temperature of the drying gas decreases from stage to stage. The dried sludge is cooled by a fresh air supply. An Independent claim is included for the corresponding sludge drying plant.