气泡驱动液固流化床内二元颗粒的流化行为

Flow behaviors in bubble-driven liquid-solid fluidized-bed adopting binary particles

采用密度稍重于和稍轻于流体的两种颗粒,研究了气泡驱动液固流化床内二元颗粒的流化行为。通过测量压差和拍摄视频的方法确定了初始流化气速Uin,g、固含率和气含率。重颗粒的Uin,g通过流化床底部的压差变化确定,轻颗粒的Uin,g则通过观察得到。研究表明,在气泡驱动的液固流化床内,重颗粒和轻颗粒的初始流化气速都随藏量的增加而增加,但重颗粒增加幅度更大。完全流化后,重颗粒固含率在轴向上分布不均匀,而轻颗粒则分布较为均匀。在二元颗粒体系内,上部轻颗粒的流化受到下部重颗粒的影响而底部重颗粒的流化不受轻颗粒影响,导致重颗粒Uin,g和固含率分布主要受自身藏量影响,而轻颗粒Uin,g随二元颗粒的总藏量变化。

Adopting two kinds of particles whose density is a little higher and lighter than fluid,the fluid dynamics in a bubble-driven liquid-solid fluidized-bed was studied.Air was introduced into the bottom as driving force and the liquid was continuous phase at the stationary phase.Pressure drops were measured and the videos were taken between different heights to estimate the initial fluidization gas velocity U,in,g solid holdup and gas holdup.The initial fluidization gas velocity of heavy particles could be obtained by the variation of pressure drops at the bottom of the bed near gas distributor.While that of the light particles was determined by observation.The results showed that Uin,g of both the heavy and the light particles increase with solids loadings.The increasing tendency of the heavy particles at higher loadings becomes steep while that of the light particles is gentle.After fully fluidization,the axial distribution of solids holdup of the heavy particles is non-uniform comparing to the uniform distribution of the light particle solids holdup.When using binary particles,the fluidization of the upper light particles is influenced by the lower heavy particles.However,the heavy particles are not affected by the light particles.Thus Uin,g and the axial solids holdup of the heavy particles changes with heavy particle loadings.The light particle Uin,g varies with the total amount of binary particles.