Research On Optimal Control Of Multi-Objective In Circulating Fluidized Bed Boiler Combustion Process

Circulating fluidized bed boiler(CFBB) combustion is a clean coal technology developed recent years, with high burning efficiency, low pollution and wild fuel adaptability. It has received widely application in power and cogeneration industry. CFBB is a control object of distribution parameters, nonlinear, time-variation and multivariable coupling, general control method cannot yield ideal results. From these problems, this dissertation does some researches on CFBB combustion process dynamic control and optimization of reducing its operation cost and emissions. The main works of the dissertation are as follows:1. The principle,advantages and present status of circulating fluidized bed boiler are briefly introduced. The research and application of advanced process control for CFBB at home and abroad are summarized systemically.2. The dynamic mathematic model and modeling status of circulating fluidized bed boiler combustion process are introduced. The control objects and difficulties of CFBB combustion process are simply analyzed. Mainly, the coupling relationship,characteristics between bed temperature and main steam pressure are discussed.3. An overview of model predictive control(MPC) algorithms is given. After particular analyzing the fundamental modes of the generalized predictive control (GPC), a two-layered multi-objective optimal control strategy based on the GPC is proposed. The structure,evaluation and principle of the strategy are introduced.4. To deal with the dynamic characteristics in the process of CFBB combustion, a two-layered GPC optimal control strategy which faces consumption of coal is proposed. The strategy includes the dynamic control layer for zone control of the bed temperature and main steam pressure along with the steady state optimization layer for the economic target optimization. The simulation results demonstrate that the proposed two-layered control strategy can decrease the coal consumption effectively while assuring the steady of the bed temperature and main steam pressure compared with only zone control. 5. Based on the optimization of coal consumption in the process of CFBB combustion, an integrative optimal control strategy which achieves the desulfurization efficiency and operation cost optimization is proposed. The simulation results demonstrate that the proposed two-layered strategy can achieve different operation conditions and reach integrative optimum effects through changing the weight coefficients emphasize particularly on the different requirements between CFBB desulfurization efficiency and operation cost, while ensuring the steady of the bed temperature and main steam pressure.The last part is summary and perspective.