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A cfd-dem approach to study the hydrodynamics of solid-liquid mixing in vertical stirred mills using dynamic mesh

University of British Columbia

In mineral processing industries, stirred media mills are known for achieving smaller particle size and better energy intensity in comminution. The mill consists of a rotating shaft driving discs, pins, or skews known as a stirrer powered by a motor coupled outside the mill chamber. The rotating shaft transmits the kinetic energy to the grinding media. Every mineral has its distinctive physical properties, making it hard to create general standards to cover all materials that the stirred media mills might process. Therefore, to address specific applications, different stirred media mills were built with varying stirrer designs. The mill’s performance improvements are complicated, which are related to grinding and energy efficiency, because of the lack of flow profiles inside the system, which vary based on the stirrer shapes. The lack of flow profiles is due to the high-density slurry media flow, which complicates the enhancement of stirred mills performance. However, it is necessary to increase the comminution efficiency in stirred media mills to reduce its power consumption. To overcome these flow monitoring issues, the grinding mechanisms, and fluid-particles flow mixtures for a better understanding, numerical models are commonly used in smaller particle sizes. In this study, slurry and grinding media suspension behaviour are captured using a multi- phase computational model. Media particle collisions with each other and walls are solved numerically using Discrete Element Method (DEM), while single-phase slurry flow is simulated using Computational Fluid Dynamics (CFD) and the combined effects are established through coupling these numerical methods. Media particles’ grinding efficiency is estimated using stress intensity generated by particle collision. This study focuses on developing and validating a high- performance multi-scale numerical model to simulate agitated stirred mills filled with granular media and slurry. Also, the effects of operating and design parameters on the hydrodynamics of the system and particle breakage is considered for efficiency optimization. The proposed high-fidelity CFD-DEM numerical approach with dynamic meshing helps to understand the fluid-particle flow behaviour inside the mill and optimize the design parameters for performance improvements of VXPmills, which leads to the evolution of a new design with enhanced grinding efficiency with less torque.

Text

2022-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/78019

Mining Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/