The Research And Design On The Automatic Control System Of The Dowtherm Burner

The Dowtherm burner is one of the important equipments in the polyester process. This thesis mainly discusses the control principle of the whole system,including the hardware and software design with the background of one project in Hainan.The thesis discusses first the main process of the system and the traditional control strategy. But the dowtherm boiler is a big lag-time and big inertial system with multi-non-liner variables. It is very difficult to obtain ideal control quality with the traditional control methods, such as simple PID controller, especially to solve online automatic adjustment problem. So we introduce the fuzzy control, a branch of intelligent control ,into the dowtherm boiler control system to make up the disadvantage of the PID control.The thesis describes in detail the hardware and software design of the whole control system. The control system consists with 3 parts: the level control system,the load control system and the firing control system. It applies the fuzzy and PID two method in the load control system to guarantee the accuracy of the system, and increase the response speed at the same time. The firing system is to regulate the air quantity depending on the quantity of the nature gas to make it burning fully with the help of the fire-management-system(FMS).At first, we inputs the best firing curve according to the load, then the FMS will control action of the air valve and the gas valve to let gas fully burning automatically. We use another regulator to control the level of the flash tank to ensure the safety of the system.We also draws the process based on the touch panel with the configure software.At last, it draws a conclusion of the system, and figure out the advantages and disadvantages of the system.