Experimental study of the blockage boundary for dense-phase pneumatic conveying of powders through a horizontal slit

• Blockage boundary of dense-phase pneumatic conveying in a horizontal slit was studied.
• A minimum solid loading ratio existed for slit blockage at a given conveying pressure.
• A higher conveying pressure led to a greater minimum solid loading ratio.

The estimation of the blockage boundary for pneumatic conveying through a slit is of significant importance. In this paper, we investigate the characteristics for blockage of powder (48 μm average diameter) through a horizontal slit (1.6 m × 0.05 m × 0.002 m). The results show that the required critical solid mass flow rate increases as the superficial air velocity increases superficial air velocity. The solid loading ratio and superficial air velocity displayed a decreasing power law relationship. This finding agrees with existing theory and experimental results. However, a minimum inlet solid loading ratio exists. When the air velocity is greater than the corresponding air velocity of the minimum solid loading ratio, the solid loading ratio exhibits an increasing trend in power law. We also found that when the inlet conveying pressure increased, the critical solid mass flow rate required for blockage, the inlet solid loading ratio, and the minimum inlet solid loading ratio increased.

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