Two different radial solids concentration distributions in downer have been reported, i.e. the ˄ shape combining with reverse-core-annulus and the core-annulus structures. The occurrence of these two patterns has not been quantitatively interpreted. In this paper, the aerodynamic theory is used in two-phase flow analysis. A transverse force on the particles, i.e. the Kutta-Joukowski transverse force, is introduced to explain and quantify the formations of these two radial solids concentration distributions in downer. This force is the function of the particle velocity gradient, the slip velocity and the gas density. Based on the available experimental data proposed in the published literatures, the distribution of the Kutta-Joukowski transverse force in downer is discussed. The results show that this force is the main factor for these two profiles occurrence.

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In the cross-flow moving bed, the gas-solid cross-flow pattern facilitates its high gas process capacity under relatively low pressure drop. In this paper, a structural optimization of gas-solid baffles, is proposed to enhance the bed operating flexibility by controlling the abnormal phenomena of cavity, pinning and air lock. According to experimental data, the relevant equations for predicting the occurrence of the abnormal phenomena are derived to explain the effects of the gas-solid baffles. It turns out that, with this proposed optimization, the cavity and pinning are weakened in both rectangular and radial beds; the air lock can be easily controlled by increasing the height and diameter of feed tube. The preferred gas-solid baffles is in the middle position (x/L=0.5) of the rectangular bed and/or (r-r1)/(r2-r1)<0.5 of the radial bed under different gas superficial velocities, particle diameters and bed voidages.