CFB boiler bed temperature´s improved fuzzy control

Keeping the regular bed temperature is the key point of making the circulating fluidized bed boiler work stably. The difficult part of the CFB bed temperature control system lies in: there are many influence factors, little tunable factors, large time delay, big inertia and strong coupling between bed temperature and the main steam pressure. According to the feature of CFB boiler, this paper analyzed the dynamic characteristic of bed temperature control system and the reasons leading to low automation utilization ratio of the combustion system, and designed a bed temperature control system which takes advantage of feed coal quantity for rough tone, primary air flow for precision adjust, by using the cooperation of feed coal and primary air flow times without number to achieve the goal of stabilize the bed temperature. Base on the limitations of fuzzy controller for large time delay system, using controller´s output history to replace the deviation change ratio as one of the inputs of the fuzzy controller, the new controller reduces the overshoot of the system, speeds up the settling time, gets better suitability for the changed parameters and solves the CFB bed temperature control problem well.