Mills play a critical role in the manufacturing processes of granular materials. After several years of joint research in the simulation of granular media single phase granular flow processes – or those that can be considered as a simplified single phase – are now manageable as a simulation. The next challenge is the simulation of multi-phase flows with at least one granular or powdery phase.
Of these, the simulation of the flow in bead mills presents a special challenge. The calculation of complex flows within a simulation links several areas of current research:
- Two-phase suspension flows of powder and water, modeled as a non-Newtonian fluid
- a third phase modeled as granular beads, fast moving components
- and a fourth phase of the surrounding air.
The modeling and numerical difficulties that this presents are huge. The interaction of four, full resolution, spatial and temporal phases must be modeled, not only among themselves but also with the fast moving components. The resulting phase-specific requirements for the numerical simulation process are met with an extended time-step control.
The FLUID component, a multiphase, non-Newtonian model together with a third Newtonian phase, was combined here for the first time with the GRAIN component – for the simulation of the mixing beads in such a complex problem. In collaboration with the project partners, subsequent simulation results were successfully compared with available measurements.
Project example with KRONOS:
Project partner: KRONOS INTERNATIONAL, INC.
Task: Simulation of the flow of a TiO2 suspension by granular agitator balls in a vertically rotating disk mill.
- Dynamic calculation of local variables
- density distribution of the suspension and agitator balls
- velocity fields
- pressure distribution
- shear forces and power loss in all phases
- Virtual tests of the performance of the mill in relation to:
- local load and local power loss to characterize the grinding performance
- local shear forces on the plates and cylinder walls to show the abrasive wear