Realization and performance evaluation for long-term low-load operation of a CFB boiler unit

Abstract As one of the pivotal aspects for the flexible generation, the technique of long-term stable low-load operation plays an important role in the increasing scale of renewable energy power connected into grid, but it is still unable to be fully realized. Based on the unique capacity of circulating fluidized bed (CFB), including huge energy storage capacity and combustion method, the research on the long-term low-load operation may lead to a breakthrough in this area. With reasonable retrofits on a 330 MW CFB unit, several low-load operation tests are successfully carried out, and a performance evaluation framework for CFB low-load operation is structured in this paper. The framework is based on the use of process data that can represent the fluidization and combustion stability as well as the boiler efficiency. It is found that the key of long-term stable operation is to maintain compatible fluidization and heat distribution in the CFB boiler, which is controlled by the adjustment of primary air volume. With reliable data analysis and research, a novel low-load control strategy for primary air volume has been proposed and verified by actual operation.