The operation control and application of CFB boiler unit with high blending ratio of coal slurry

Abstract

In China, a large amount of coal slurry is produced every year as the by-product of coal washing. If all these slurry were utilized, it could not only bring huge economic benefits but also solve the environmental pollution caused by coal slurry storage. As one of the most important devices to burn the coal slurry, circulating fluidized bed (CFB) boilers needs to improve the control level to consume more slurry. In this paper, the characteristics of CFB boiler with large blending ratio of coal slurry are investigated from both the operation and control aspects. The energy fluctuation caused by long-term coal slurry combustion in CFB boiler is analyzed, which would influence the operating stability of the unit and restrict the blending ratio of coal slurry. Based on the analysis and boiler energy storage theory, a novel control strategy is proposed to improve energy conversion and stabilize energy fluctuation caused by co-combustion of coal slurry. Finally, the control strategy is applied to an actual 300 MW CFB boiler unit. The long-term operation shows that the improved control system can reduce the energy fluctuations, raise the control stability and increase the coal slurry blending ratio, bringing huge economic benefits to power plant.