Study On The Fuzzy-control In The Combustion System Of A480t/h Extreme Pressure CFB Boiler And Its Application

Circulating Fluidized Bed (CFB) boilers have been developed rapidly in China, as theyhave the unique features: fuel flexible, wide turn down ratio, high heat intensity, low NOxand SO2emission etc. However, CFB boilers’ combustion system is characterized bymultiple variable, strong coupling, large time delay and nonlinear. As a control object, thecombustion system of a CFB boiler is so complicated that traditional ways can’t offer agood performance.In this paper, fuzzy control is introduced into the combustion control system, andrespectively design fuzzy control system of coal feed quantity and primary air flow. Thecontrol system of coal feed quantity consists of two fuzzy controllers. The main controllerhas two input variables, one is the differentials between the Main Steam Pressure (MSP)setting and the measured MSP, the other one is the changing rate of measured MSP. Thevice controller’s input variables are the differentials of bed temperature and the differentialsof bed pressure. And the control system of primary air flow has only one fuzzy controller,its inputs are the differentials of coal feed quantity and the differentials of bed temperature.All fuzzy controllers’ outputs are incremental signals which will be added to the actualoperating order.The fuzzy control in the combustion system of a480t/h CFB boiler is completed in theDCS system, and the fuzzy control system is optimized through large number of tests. Andthe experiments show that this control system is valid and practicable.