Effect of interstitial air pressure and voidage during the spouting of fluidized cohesive powder

摘要

We experimentally investigated the spouting of fluidized cohesive powder bed of the soft wheat flour through a circular orifice of 4mm at the bottom of vessel, where the mean diameter is 46μm and the powder density is 1493kg/m3. Air is introduced at the three ways as the following, (1) only at the top, (2) only at the bottom, (3) at the top and bottom of bed where the flow rate of air is changed. The cumulative mass of powder through an orifice, the interstitial air pressure at the top of bed and the height of bed has been measured. The voidage of bed is estimated by the remained mass of powder in the vessel, the powder density, the height of bed and the inside diameter of vessel. We found that the steady flow of the fluidized cohesive powder as well as mass flow region is obtained when the same flow rate of air is simultaneously introduced at the top and bottom of the bed. Then, its tendency showed that the interstitial air pressure and voidage increases with decreasing the height of bed. And then, we confirmed that the mass flow rate of powder is in proportion to a square root of the voidage and the interstitial air pressure during the gush of cohesive powder.