Optimization criteria of heat recovery from solid beds

Heat recovery from beds of particulate solids that are cooled for process requirements is an attractive practice in many industrial areas. In this paper several heat-recovery arrangements are analyzed under the hypothesis of unsteady-state operation. Assuming a constant and uniform cooling air flow rate, solutions based on single- and double- (parallel or series) hoods have been considered. Results show that significant improvements over a single hood can be achieved with double-hood systems, especially if the second hood is used as a source of preheated air. The improvements are in terms of heat-transfer efficiency and in terms of control flexibility to match the actual running conditions.