Numerical Study On Fluidization Characteristics Of Multi Component Particles In Circulating Fluidized Bed

The circulating fluidized bed(CFB) boiler is a coal combustion technology developed in recent 20 years, it has been widely concerned and researched for its high efficiency, clean and wide adaptability in fuel. Because of random flow, coupling and polydisperse particles, the simulations about dense gas-solid two-phase flow inside CFB is very difficult.As a result of the limitation of simulation conditions and the complexity of particles’ property, people always simplify the components of polydisperse particles recently. Most simulations about the CFB saw polydisperse particles as mono-component particles by ignoring the differences between particles. But mono-component particles is too simple and can’t obtain exact simulation results. Even the study of multi-component particles was conducted, it was about binary mixture adapting simple math model, and ignored the momentum exchange between different particles, So it is necessary to adapt a proper simulating model for the flow of multi-component particles, and use it to simulate the gas-solid two-phase flow inside the CFB. It is important for the development of the CFB and some chemical equipments.According to the Rosin-Rammler distribution of coal particles’ diameter, we divide the polydisperse particles into three typical particles: fine particles, medium particles and coarse particles. Starting from the kinetic theory of particles, a model was developed with considering the complex exchange between all phases by two-fluid model(TFM), The open source program was choosed for its advantage at models developing. After introducing the solid phase stress model and the kinetic theory of particles, and consider the major chemical reactions of combustion, I wrote the code and debuged it lastly.In the paper, a 3D fluidized bed riser simulation, a 2D cold CFB simulation and a combustion simulation were conducted. The fluidized bed riser simulation verify the model, and find the multi-component particles was much better than the mono-component, and contrasted two solids phase stress model. The simulation of the CFB obtained the concentration distribution, the velocity field, the turbulent degree and so on, and still explored the effects of gas velocity, particles’ density and particles’ diameter. Lastly, the combustion simulation analyzed the species field, the rate of chemical reactions and the temperature field of the flow field, and then explored the effect of the ratio of primary air and the chemical composition to coal combustion.