Override control of furnace combustion system

The furnace combustion system of circulating fluidized bed boiler (CFBB) must ensure the steam pressure as a constant via controlling the coal quantity and wind flow. Another important role is to avoid the temperature varying excessively which will result in the high temperature agglomeration or low temperature agglomeration in boiler. Based on the model and characteristic analysis of combustion system, this paper presents an override control solution which can satisfy the various control tasks requirement. In this design, the control strategy is selected automatically according to the furnace temperature value. When the temperature is normal, abnormal or unsafe, the conventional control, limiting control or shut-down devices with warning will be triggered respectively. The dynamic control process is simulated on an object model, and the quiver phenomenon that often occurs in override control is analyzed and improved. The simulation result shows that this design can deal with the control task of both steam pressure and the agglomeration at the same time, and ensure the device safety and system continuous. Whatpsilas more, the design is proved to be effective in the Wangjiazhai power plant, mining bureau of Shuichen, Guizhou province.