Number concentration of slender particles in gas-solids circulating fluidized bed
Circulating fluidization of slender particles is used widely in industrial production,for example,combustion of biomass stalks and drying or wetting of cut-tobacco.The movement attitude of slender particles is more complicated than that of the spherical particle owing to the slender particles'six degrees of freedom,and thus there are some differences in fluidizing behavior between slender particle and spherical particle.Number concentration is one of the most important features of fluidizing behavior of slender particles.Based on the direct simulation Monte Carlo(DSMC) method,rigid body dynamics and momentum conservation law,a three-dimensional motion model of slender particles,including the inter-particle collision mathematical model,was established.The gas-solids flow in an actual circulating fluidized bed was simulated by using the current model,and some number concentration features of slender particles were captured.In the experimental riser,among all the slender particles,the slender particles with less slenderness firstly arrived at the exit from the near wall regions of the riser.There existed such evident phenomena as floc,migration and so on in the process of fluidization.In the fluidization state,the number concentration of slender particles did not change evidently with entrance air speed.