Research On Multi-Objective Optimal In Large-sized Circulating Fluidized Bed Boiler Combustion Process

The circulating fluidized bed boiler(CFBB) is a kind of combustion technology with high combustion efficiency, wide fuel adaptability and low pollutants emissions,so recently it has been widely used in the field of industry and electricity. The combustion process of the CFBB is nonlinear and with large inertia, strong coupling, large time delay and multi-disturbance. Towards the complex combustion process, the main works of the paper are as follows:The principle and development status of the CFBB are briefly introduced. The research work of the combustion process and operation optimization of the CFBB at home and abroad is reviewed and summarized systematically. The complex characteristics of the combustion process of the CFBB are analysed. And this paper made a detailed introduction to the generalized predictive control and artificial fish swarm algorithm. The mechanism of the combustion process of the CFBB was studied. The boiler was divided into the dense-phase region and dilute-phase region, these two regions were respectively modelled. By solving four ordinary differential equations related to the balance of oxygen concentration, the residual carbon mass balance, mass balance of the bed material and the total energy balance, the simulation platform for the combustion process of the CFBB was established. We get the linear mathematical model of the system in the95%load by doing linear processing to the step response of the parameters. Based on the discrete linear mathematical model, the multi-objective optimization strategy with a two-layer structure of the combustion process and the objective function for evaluating the economic index of the boiler were established. The first layer uses the regional control strategy based on generalized predictive control with constraints; the second layer uses artificial fish swarm algorithm to optimize the objective function of economic index of the combustion process. The results show that the multi-objective optimization strategy with a two-layer structure of the combustion process can effectively achieve the goal of energy saving under the premise of meeting the control performance of the syeterm.