流化床内煤燃烧的传热过程DEM数值模拟

Numerical simulation of heat transfer process of coal combustion in fluidized bed by using discrete element method

采用离散单元法(DEM)对流化床内煤颗粒燃烧过程中的传热过程进行了数值模拟.气相湍流采用k-ε模型,颗粒相采用离散单元法(DEM).颗粒传热过程考虑了颗粒与气相的对流传热、颗粒与床层的辐射传热、煤颗粒的燃烧热以及颗粒碰撞传热;燃烧过程中化学反应包括焦炭与O2和CO2的异相反应、挥发分燃烧及CO和O2的均相反应.模拟得到了煤颗粒的加热升温和燃烧过程中各种热量对煤颗粒传热的贡献大小,并对不同颗粒刚度系数、考虑颗粒旋转与不考虑颗粒旋转以及不同颗粒摩擦系数对各种传热量的影响敏感性进行了模拟.

The stimulation of heating behaviors of coal particles combustion in fluidized beds was carried out, in which the turbulence of gas phase was described by k-ε model and the solid phase by discrete element method （DEM）. The convection heat exchange between gas and particles, the radiation heat exchange between particles and the bed, the heat release from of burning coal particles and the heat transfer due to particle collision were considered in the transfer process of particles. The heterogeneous reaction of char with oxygen and char with carbon dioxide, the homogeneous reaction of volatiles with oxygen and carbon monoxide with oxygen were included in the chemical reactions. The simulation results indicate that the four heat exchange modes contribute to the heating of coal particles on different levels. The effects of four heat exchange modes on the particles＇ different stiffness coefficients, the particles being rotated or not, and the particlesr different friction coefficients were also stimulated.