Development of a spiral-flow jet mill with improved classification performance

Our group has proposed a jet mill equipped with a particle-trap ring at the exit of the comminution zone to prevent the escape of large particles entrained by shortcut flow. The visualized swirl flow compares favorably with simulation results obtained by CFD. Experimental results reveal that a trap ring with a height of 4 mm is the most effective for attaining high classification performance. Yet the classification efficiencies measured at various ring heights are much lower than the classification efficiencies calculated by the CFD. This discrepancy may be attributable to the particle-flow interaction and the change in particle size during the particle movement.

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► Flow visualization was performed for improving jet mill classification performance.
► Flow visualization revealed short cut flows in jet mill degrade the performance.
► The performance is improved by stopping the shortcut flows with a trap ring.
► The ring height is optimized by particle trajectory analysis with CFD.