Modeling And Optimization Control On The Combustion System Of Circulating Fluidized Bed Boiler

Energy-saving and ejection-decreasing is a hot topic in modern world. Energy consume are most come from coal and petroleum, and wastes comes from them too. Boiler as the main equipment to generate electricity, on one side, it consume a lot of coal every year, on the other side, it ejects so much exhaust gas which can extremely waste the energy and affect the environment. In order to save energy and reduce the ejection of exhaust gas, it is necessary to improve combustion efficiency of boiler. Circulating Fluidized bed boiler is just developed in this situation. However, because the flowing and heat transfer in boiler is so complexity that the characteristic of boiler traps a lot of researcher all the time. Besides, it is a distributed parameter, nonlinear time-varying and multivariate coupling system which also brings some difficult problem as well. To solve these problems have greatly significance, which may enhance the design of boiler, improve the combustion efficiency, make proper regulations, and design good control system.The main research work of this dissertation can be summarized as the following aspects:1. According to the investigation of a 150t/h CFB boiler in a power plant and based on the historical data collected from it and the exiting mathematical models, MATLAB Identification Toolbox is used to develop transfer function models. The developed models are then used to study the dynamic behavior of the combustion system through simulation. This paper is mainly focused on the relationship between the coal feed rate, primary air feed rate, secondary air feed rate as inputs and the material bed temperature, main steam pressure, main steam temperature, flue-gas oxygen concentration as outputs. Furthermore, a transfer function matrix is presented which can be used in the design of control system for the combustion system of a CFB boiler. The simulation results indicate that the model can reflect the dynamic performance of the boiler properly. The factors affecting the dynamic behavior have been also discussed, which establishes a platform for the study on the control strategy of combustion system of the CFB boiler.2. It is necessary to verify the controller's validity and rationality before it used to the real plant, so there should be construct a model of plant which include some nonlinear characteristic and can get close to the real plant. As a result, with the MATLAB toolbox, a nonlinear model is developed using wavelet network.3. Set the nonlinear model as a real plant, based on the linear model, there develops a multivariable DMC controller to control the nonlinear model. At last, the simulation results and detailed analysis have been demonstrated.