Study of heat exchange processes in a screw ash cooler installation

The paper presents an example of the thermal-flow analysis of a bottom ash cooler cooperating with a circulating fluidized bed (CFB) boiler. The authors present the methodology of the conducted studies and examples of thermal balance calculations basing on measurement results. The comparison of two different ash coolers indicates a significant relationship between the outlet temperatures of the ash and cooling water depending on the construction and arrangement of the analysed ash coolers. The analysis presented in this paper enables determining the optimal rotation speed of the screw in order to achieve the required temperature of the slag depending on the actual working parameters of the CFB boiler. It provides an opportunity to optimize the heat exchange conditions in order to obtain the highest acceptable water temperature at the outlet of the ash cooler while adhering to safety regulations. The hot water could further be used for internal sanitary purposes or to support heating systems operating in the power plant.