Study on selection and optimization of slag cooler system for a ultra-supercritical CFB boiler

The construction of large scale CFB units with high steam parameters is the best way to make large-scale clean use of low calorific value coal such as slime and gangue. The ash and slag heat loss of CFB units burning low calorific value coal is large. Roller slag coolers widely used in in-service CFB units have a low efficiency in terms of heat recovery and utilization of ash and slag for CFB boiler, while air-water combined slag cooler can effectively recover heat from ash and slag. By analyzing and studying the influence of air-water combined slag cooler and roller slag cooler on boiler efficiency and power consumption, the coal consumption of ultra-supercritical CFB units with different slag coolers was calculated, and the technical economy of different types of slag coolers was also compared. The results indicate that the air-water combined slag cooler should be selected for the CFB unit with high price of standard coal and large amount of bottom slag, and better economy of the unit could be obtained. In order to take into account the economy and operational reliability of slag cooler system, the scheme of mixing air-water slag cooler with roller slag cooler can be adopted to optimize the selection of slag cooler system for a ultra-supercritical CFB unit. These results can provide referential materials for the selection and optimization of slag cooler system of large-scale CFB boiler.