The Research On Control Strategy Of Circulating Fluidized Bed Boiler Combustion Process

Circulating fluidized bed biler (CFBB) are increasingly used as superior coal burning systems due to their higher efficiency,lower emissions,wider fuel adaptability and better performance of load regulation. However, because of the characteristic of the circulating fluidized bed boiler is a distribution parameters, non-linearity, large time-delay and multi-variable coupling. therefore, it is difficult to realize the automatic control with conventional control method. In view of the above question of circulating fluidized bed boiler, the main works of this dissertation are as follows:Firstly, This paper introduces the structure and technological process of circulating fluidized bed boiler (CFBB), then it analyzes the coupling relationship among various parameters and the control tasks of the circulating fluidized bed boiler. Concerning the characteristics of time-varying, coupling and large time delay, this paper introduces a new method of fuzzy decoupling,in which fuzzy rules were used for compensation. And it was put forward for the strongly multivariable coupling of the combustion control system. From the simulation of the Circulating Fluidized Bed Boiler by using MATLAB/SIMULINK, the new method overcome defect of PID controller which is very difficult to adjust parameters, and proved to be effective with good dynamic characteristic and static characteristic.Secondly, Bed temperature, which influences boiler overall combustion efficiency and the rate of pollutants emission, is one of the most significant parameters in the operation of the circulating fluidized bed boiler. In this paper four kinds of controllers is designed, including SMITH controller, decreasing time delay controller, the self-adjusting weighted coefficient fuzzy controller and BP neural network compound controller. All models of the system were generated by using MATLAB. The simulation results showed that the BP neural network compound controller has better control effect, strong robustness and certain adaptive ability.At last, the program of temperature control system is designed, the ordinary PC is upper computer and single-chip is subordinate computer, visual c++ as development platform in this program. What's more, the design of the hardware and software are described in detail. In addition, in upper computer, The main screen of temperature monitoring system, historical data screen, intelligent temperature control screen, parameter setting screen and temperature curve are designed for monitoring center in temperature control system. And also introduces the communication scheme of upper and subordinate computer serial connection.