Experimental And Computational Study On Flaky Particles Fluidization Characteristics In A Fluidized Bed

Presently, the global emission reduction pressure is grim with the increasing of fossil fuel consumption. The unconventional solid fuels for the combustion of boiler, such as oil shale, biomass and garbage, have great development potential due to its rich reserves. The circulating fluidized bed combustion(CFBC) technology has been widely used because of its good adaptability to low-grade fossil fuels, low-temperature combustion, and very low SO2 and NOx emissions, etc, which makes CFB boiler suitable for burning these solid fuels. However, these solid fuels often exhibit flaky or lump characteristics after broken or extruded so that they are easy to cause the undesirable fluidization phenomena such as channel flow, etc. An experimental study was carried out in a small fluidized bed to investigate the combined effects of particle size, density and air distributor structure on fluidization features of flaky particles. And the hydrodynamics of 3D gas-solid flaky particles fluidized bed were studied computationally. the simulation results are in good agreement with experiments phenomenon, it proved the correctness of the selected model. The conclusions are as follows:Based on the experimental found that, the average relative error between experimental and calculated results is 6.73%. The experimental correlation of flaky particles u was derived according to regression analysis of our experimental data. 15°?-shaped air distributor can enhanced the particles lateral diffusion, and improve the channel flow phenomenon of the flaky particles, while particles cannot enter the steady fluidization status with 15°?-shaped air distributor. The u of 15°?-shaped air distributor is smaller than the rest of air distributor. And with the increase of the ?-shaped air distributor angle, the particle trends to gather on one side, which is more likely to cause the phenomenon of bed-overturn. Therefore, the ?-shaped air distributor with smaller inclination angle can improve the channel flow phenomenon.Based on the numerical simulation found that, the simulation and experimental results of bed pressure drop are in good agreement, proved the accuracy of the nonspherical particle drag force model. The particle radial distribution show a core-annular flow structure, and the particles axial velocity shows the internal circulation pattern that the particle move upward in the core area and move downward in the annilus area. Bed expansion of spherical particles is significantly less than the height of the flaky particles, the larger the diameter of the particles, the easier deposited in the bottom, the smaller the particle size of the particles, the greater elutriation in the central region. Bubbles appear from the central region with 15°?-shaped air distributor while bubbles appear from the side wall region with 15°?-shaped air distributor. The internal circulation pattern wsa not obvious in the bed with 15°?-shaped air distributor, and core-annular flow structure not show in the bed with 30°?-shaped air distributor. The particles deposited on the left side of the bed with 30°?-shaped air distributor.