Influence of impeller configuration and operating parameters on granular mixing: a DEM investigation

Résumé fourni par la source

Granular mixing with bladed mixers is widely used across various industries. This study employed the Discrete Element Method (DEM) to explore the effects of rake angles (30° (150°), 45° (135°), 60° (120°), and 90°), rotational speeds (25, 50, 75, 100, and 150 rpm), and fill levels (1, 2 and 3) on the flow and mixing efficiency of 2- and 3-bladed impellers. The Lacey mixing index, granular temperature, circumferential velocity, diffusion coefficient, and void percentage were used to evaluate mixer performance. Results showed that for rake angles ≥ 90°, the highest values for the Lacey mixing index, granular temperature, and diffusion coefficient were achieved, although particle circumferential velocity decreased. The mixing efficiency improved significantly with 2-bladed impellers at rake angles of 135° and 150° and 3-bladed impellers at 120° and 135° rake angles. The void percentage increased linearly with rake angle. Rotational speed and fill levels were found to strongly affected the Lacey mixing index, with optimal rotational speeds < 100 rpm. Increasing rotational speed raised particle granular temperature, circumferential velocity, diffusion coefficient, and void percentage. For 3-bladed impellers, performance improved at fill levels where H/h > 1, although granular temperature and diffusion coefficient decreased with increasing fill levels. Granular temperature and diffusion coefficient were found to be reliable indicators of pre-mixing performance. It is recommended to use 3-bladed impellers at H/h > 1 and rotational speeds < 100 rpm, while 2-bladed impellers perform better at lower fill levels.

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