Study On Model Of Optimal Wind-coal Ratio In Circulating Fluidized Bed Boiler

With the rapid development of China's economy comes a number of problems about energy shortage and environmental pollution.As a clean combustion technology,circulating fluidized bed has the advantages of low pollution,high burning efficiency and wide adaptability,which has been widely used in recent decades.At present,the research on the mathematical model of circulating fluidized bed has made great progress,and the research on the optimum wind-coal ratio of circulating fluidized bed is still in the primary stage.Whether the wind-coal ratio is suitable for the economic and safe operation of the whole thermal power plant is very important,so the study of the optimal wind-coal ratio of circulating fluidized bed boiler is of great practical significance.This paper introduces the two systems: material circulation system and the combustion system,which are closely related to the optimal wind-coal ratio of circulating fluidized bed.Then the mathematic models of material balance,oxygen volume balance and energy balance in the fluidized bed boiler are described based on the three reference objects of bed temperature,flue gas oxygen content and residual carbon.The step response simulation is done by using matlab.By comparing the simulation curve with the historical trend,it is found that the trend is basically consistent,which verifies the accuracy and rationality of the mechanism model.Finally,the study of optimum wind-coal ratio is converted to a multi-objective optimization problem with three variables: bed temperature,flue gas oxygen content and residual carbon and it is optimized by particle swarm optimization in three different conditions.The optimized wind-coal ratio was applied to the simulator based on the Dalian Taishan 135 MW CFB unit and compared with the unoptimizable historical trend.It was found that the fluctuation range of bed temperature,oxygen content and unit load is smaller and the stability is improved,which proves that the optimal wind-coal ratio based on mechanism model is effective.