Research And Applications On The Advanced Process Control System Of Circulating Fluidized Bed Boilers

Circulating fluidized bed (CFB) combustion is a new technology of coal cleaning combustion with high burning efficiency, low pollution and wild fuel adaptability. It has received wildly application in cogeneration industry. CFBB is a complex system of distribution parameters, nonlinear, time-variation, strong delay and multivariable coupling. It's hard to build a precise mathematic model, and some conventional method which is well operated on general boiler can not yield ideal result. The automatic control of CFBB has become the main obstacle for its commercial application. In view of above questions, this dissertation does some research on modeling and advanced process control of CFBB. The main works of this dissertation are as follows:The principle, development and dynamic performance of CFBB are briefly introduced, and the research and application of advanced process control for circulating fluidized bed boiler at home and abroad are summarized systemically.On the basis of combustion characteristic of CFBB, a model of its combustion system is developed. The model is composed of three sub-models: hydrodynamic sub-model, coal combustion sub-model and heat transfer sub-model. With the reasonable hypothesis and simplicity, bed temperature model and main steam pressure model are established and are validated with the industrial data.Aiming at solving the time-variation of CFBB, a pattern recognition based self-tuning PID is given. The structure, evaluation and principle of the pattern recognition based self-tuning PID controller are introduced in detail.The pattern recognition based self-tuning PID controller is used for the control of bed temperature and main steam pressure. The simulation results show the self-tuning PID controller has good adjustability on the characteristic changing of controlled process. Based on this, a coordinated control system of bed temperature and main steam pressure is developed. The control system can not only satisfy the demanding of control in bed temperature and main steam pressure, but also assure the stabilization of primary air. The simulation proves the feasibility and validity of this control system.The works of this thesis are summarized and some prospects are made in the end.