Study On Key Parameters Control Of Lignite Drying System

The lignite is important energy and chemical raw materials.Its higher moisture content and lower calorific value leads to low prices, low utilization rate and forming lots of waste residue fuel and air pollution.If it is dried and controled the moisture content reasonablely,whice can ascend coal quality and increase the lignite market dosage and economic benefits greatly.As a result, QinYe heavy industry and Northeastern University designed large vibration fluidized bed lignite drying system. Given this background,this paper deals with the study of control for key parametres in lignite drying system.Through mathematical model of lignite drying and dust explosive mechanism,this paper acqiured three key parametres influencing lignite drying which are gas temperature,gas flow and oxygen concentration.In the process of lignite drying, control plant is lagging, nonlinear time-varying and can’t make accurate mathematics model.Key parameter control system of lignite drying system is decomposed into three control circuit, namely the flue gas temperature control circuit, gas flow control loop and oxygen concentration control circuit. According to the characteristics of the controlled objects, put forward the fuzzy control strategy,adesigned fuzzy controller to the three control circuit,and simulated the two control loops by Matlab. Compared with traditional PID control method, The simulation confirmed the superiority of fuzzy control algorithm.The monitoring system of the key parameters composed by the two levels of computer. Host computer used industrial computer, showing timely and clearly work status of dry system and failure message and display msc setting; Inferior computer used PLC, finishing all kinds of parameters testing, information processing and control function. Based on the virtual instrument software Lab VIEW realized the human-computer interface and context of the communication between a machine. We designed all the component elements of the fuzzy PID controller which include the fuzzy algorithm process,fuzzy reasoning and anti-process in PLC.The fuzzy controller was used to choose the reasonable parameters of PID.In this paper, the key parameters in the system lignite dry control adopted fuzzy control and the traditional PID control combination of control plan,which improved the system robustness and adaptability, at the same time, inherited the PID control the advantages of high steady precision. Thus,the control system not only guaranteed lignite dry can result expected effect, but also ensure the drying system worke safely and reliably.