Mathematical Model And Numerical Simulation Study Of Circulating Fluidized Bed Boiler

In the case of conflict of coal combustion and environment protection, the Circulating Fluidized Bed (CFB) combustion technology is largely developed in two decades, because it is a new kind of clean coal technology with high combustion efficiency and low pollutant emissions. Developing an overall mathematical model of circulating fluidized bed (CFB), it can provide important data and instruction for design and operation of circulating fluidized bed.In this thesis a summary is made to describe advantages and disadvantages of CFB. It introduces the previous research works and achievements. Based on previous research works, an overall mathematical model of circulating fluidized bed (CFB) boiler is put forward to simulate phenomena of the combustion of the coal that has wide particle size distribution. Because of the complicated physical and chemical process in the furnace, some proper simplifications are introduced in the model.The model divides the furnace into two parts: a dense one at bottom part that is a bubbling bed and a dilute one at up part which is a core-annulus flow structure. On the hydrodynamics model, a Particle Cluster Renew mechanism is adopted to describe the heat transfer. The coal combustion model includes four submodels: devolatilization and volatilization combustion, char combustion, homogeneous reaction, pollutant emission formation and reduction. In the model, the performance parameters and features of CFB boiler are obtained by changing temperature, fuel and sulfur retention.In comparison with the experiment data of Chalmers University of Technology, the predictions agree well with the experiment results. It proves that the overall model is a useful tool to research and design the circulating fluidized bed boiler.