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

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 U_in,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 U_in,g and the axial solids holdup of the heavy particles changes with heavy particle loadings. The light particle U_in,g varies with the total amount of binary particles.