Pinning phenomenon is a bottleneck constraining operation flexibility of moving bed reactor. Pinning phenomenon and pressure drop were investigated in a trapezoidal cross-flow moving bed model under different operating conditions. The trapezoidal bed model was 1.3 m in height and 0.185 m in top width while 0.299 m in bottom width

the distance between two perspex plates was 0.04 m. Experiments results indicated that pinning appeared before formation of cavity. Pinning thickness and cavity size increased with increasing superficial gas velocity. Their variation with particles mass flux was not evident. Base on the force balance

a mathematical model of pinning was established. The critical pressure drop and pinning thickness could be predicted by this model. The calculation results agreed basically with the experimental data.