Novel coordinated control method with coal-quality correction of circulating field bed boiler
To improve the load-following capability and the coal-quality applicability of a circulating field bed boiler (CFBB), a new coordinated control method with coal-quality correction is proposed in this paper. This method takes the primary air as another new control variable into the coordinated control of CFBB, which can take advantage of the unburned carbon in bed to improve its load-following capability. Simultaneously, a multivariable predictive controller based on augmented state space model is designed to deal with the CFBB's characteristics such as time-delay and strong coupling. Finally, an improved strategy to correct coal-quality online based on the disturbance observer is provided. Compared with the conventional control scheme, the simulation results for a 330MW CFBB shows that the method proposed in this paper can significantly improve the load-following capability and the coal-quality applicability.
Application of turbine following boiler coordinated control in 300 MW CFB boiler against the great change in coal quality
In view of large grain size of fuels and long lagging of combustion in CFB boiler, the control quality of turbine following boiler CCS became deteriorated in case of great change in coal quality. The turbine following coordinated control mode was utilized on 300 MW CFB boiler in Baima Demonstration Power Station. Considering the frequent fluctuation in coal quality, the coal quality calculation logic and oxygen content correction logic were designed in CCS control loop. Base on the practical conditions in commissioning, the differential signal of drum pressure was added in the calculation of steam heat absorption to optimize the coal quality correction logic; in addition, the output of O2 controller was only performed on the coal to improve the oxygen content correction logic. The practice shows that the main steam pressure is stable, the load range can be limited within ±2% of the grid load, and the CCS can be put into long stable operation in the case of turbine following boiler coordinated control.
Predictive fuzzy controller for bed temperature system of CFB boiler based on multi-sensor information fusion algorithm
Bed temperature of circulating fluidized bed (CFB) boiler is measured by multiple sensors equally fixed around the furnace wall. Big inertia of the combustion process and the large time delay of bed temperature measure are unfavorable for thermal process control. Based on the redundant distributed measuring property of bed temperature, a new sensor signal synthesis method was proposed. The new method is based on information fusion technique, which uses multi-sensor resource to decrease the measure uncertainty, eliminate the failure sensor/sensors, so the measure result is more credible. That is very important for optimal control of combustion system. Grey modeling theory and fuzzy control strategy are combined to control the combustion process. Numerical simulation results of bed temperature measure and grey fuzzy control for a CFB boiler show that the proposed new strategy is feasible and effective.