Analysis and Design of Control Systems of Circulating Fluidized Bed Boilers
YANG Jin-qi1, ZHAO Wei-jie2, GUO Rong1, ZHANG Wei-jie1(1.Shanghai Power Equipment Research Institute, Shanghai 200240, China; 2.Shanghai Petrochemical's General Cogeneration Power Plant, Shanghai 200540, China)
In connection with the example of the control system of operating 2×310 t/h circulating fluidized bed power sets, the respective relationship between control magnitudes and bed temperature, oxygen content, bed pressure, steam flow, fresh steam pressure as well as sulfur content in the flue gas are analyzed on the basis of tests, performed on fluidized bed boilers, with respect to disturbance of fuel, primary air, secondary air and limestone feeding. A way of how the fresh steam pressure controller controls combustion, oxygen amount and bed pressure by allocation of primary and secondary air is being explained emendation of the oxygen amount by adjustment secondary air is further elucidated. Functional relationships between boiler output and primary air, secondary air and fuel feeding have been obtained by tests. With an eye on often met occurrences of coal bin plugging, bridging, coal feeder racing and tripping, an automatic self-emendation fuel feeding loop has been designed which warrants steady operation of the control system even in case of fuel plugging, coal sliding or feeder stripping, which in turn helps a lot to warrant safe and steady operation of the circulating fluidized bed boiler. Figs 7 and refs 2.