Numerical Simulation Of Flow Characteristics Of Coal Gangue And Coal Bed Methane In CFB

Coal gangue with the characteristics of lower valotile, high ash, lower heat value and hard-to-burn is one of the most quantity industrial solid residues. Coal bed methane with the characteristics of strong greenhouse effect and easy-to-burn and explode, is released methane in the process of exploitation of coal, and it is harmful to the coal exploitation.Emission of coal residue and coal bed methane not only cause environmental pollution, but also waste the resources. The gas-solid combustion technology in the fluidized beds has been considered clean and efficient. So it is a new way for synthetically utilizing coal residue and coal bed methane. It has very high economic and social benefits.CFB combined combustion technology is adopted to retrofit NG-35/3.82-M chain grate stroke in the paper. The influence of the gas burner height to the flow characteristics in the CFB is simulated, and the mixed combustion ratio of the two fuels influence to flow characteristics in the CFB is also investigated. According to different entrance of coal bed methane, different velocity of the secondary air and different particle size, the flow characteristics are studied.According to changing different disposed position and different velocities of the secondary air, the flow characteristics are studied. Distribution of velocity field shows that different entrance of coal bed methane doesn't influence axial velocity field, particles in the centre of the boiler move upward and particles near the wall move downward. Among four layout formations, when the gas burner layout corner tangentially and the height of the burner is 4m, fluctuations of the particles are the smallest in different height of the boiler, air vortex is formed in the level cross-section of gas entrance. This will strengthen the mixing between air and particle, so this layout formation is the best. Distribution of particle-concentration field shows that, layout formation of the gas burner and velocity of the secondary air will influence axial velocity field of the particles. When the height of the burner is 4m, the secondary air is about 35m/s, higher particle-concentration will be formed above the dense phase zone.The proportion of the two fuels influences flow characteristics in the boiler. When amount of coal bed methane increases, disturbance in the boiler increases and particle velocity increases, then stay time of the particles in CFB decreases. When the mixed proportion is 8:2, turbulent kinetic energy of the particles are the biggest, the distribution of velocity field and concentration field are the best. The study results in this paper have important reference and application value, and pave the way for exploring the mixed combustion technology of coal residue and coal bed methane in CFB.