Design Of Computer Control System For Industrial Coal-Fired Boiler

The problem of automatic control in industry coal-fired boiler is discussed in this thesis. First of all, the technological process and characteristics of industry boiler is analyzed. The task of boiler regulator is expounded. And then the system scheme of control is presented.The dynamic characteristic of loops for water level is analyzed especially the reason of ostensible water level. On the basis of these a routine PI controller is designed to control the water level. But for the complexity of boiler, it is difficult to obtain accurate mathematical model, the controller is not so effective. Then a fuzzy control system is designed on the basis of the characteristic of boiler , though the dynamic quality is improved, there is static error. After that combining the excellency of routine PI controller and fuzzy controller an fuzzy-Pi controller is designed. It works well in practice. According to the same method an fuzzy-Pi controller is designed used to steam pressure.The problem of computer control for coal-fired boiler combustion system is mainly discussed in this thesis. The optimal control system of economical combustion is simulated by computer. And the theory of economical combustion and the reasons causing low heat efficiency are discussed in the paper. The sub-optimal feedback control system is proposed in which oxygen setting is controlled by a fuzzy controller.According to the principle of thermal equilibrium and considering the complexity of combustion system a new standpoint of representing coal-measurement by heat signal is put forward. Then a self-searching optimal control method for enhancing thermal efficiency is obtained through the optimal wind-coal ratio. Then a computer control system for economic combustion in coal-fired boiler is designed. And itsresult is compared with traditional PID controller. The influence of parameters of optimal controller on the system is studied.The hardware and software block diagrams of SHL-20 coal-fired boiler computer control system developed are presented at the end of the thesis .The program flow chart is given also.