
CFD Review 


Site Sponsors 


Tell a Friend 



Help this site to grow by sending a friend an
invitation to visit this site.





CFD News by Email 



Did you know that you can get today's CFD Review headlines mailed to your inbox?
Just log in and select Email Headlines Each Night on your User Preferences page.




 

Hatch uses CFX for Grinding Mill Analysis 



Posted Mon February 23, 2004 @06:41PM






by Ross Haywood,
NonFerrous Metals Technology,
Hatch Australia
Hatch, a leading global engineering organization, has a reputation for the successful scaleup of process technology and the implementation of innovative solutions to technical challenges. To fulfill this reputation, Hatch’s NonFerrous Metals Technology Group uses advanced analytical tools, in particular CFD, for design evaluation and optimization, scaleup analysis and problem solving, where heat transfer, fluid flow, combustion and mass transfer are critical issues.
Recently we confronted the problem of scaleup analysis of a multiphase grinding mill – essentially a multiphase turbomachine! The mill works by vigorously “stirring” the feed material (pulp) and a coarse solid grinding media using a series of concentric disks rotating at high speed. At the discharge, a stationary separator is used to allow the pulp to flow out of the mill while retaining the grinding media. The essential features of the problem, from a modeling perspective were: complex geometry; multiple frames of reference (rotating disks and a stationary outlet), and a multiphase flow. As an added complication, the flow is strongly swirling with tangential velocities nearly three orders of magnitude greater than the mean axial velocity through the mill; this seemed like a perfect fit (or worthy challenge) for the new capabilities of CFX5.






The physical geometry and computational mesh for a typical segment of the mill were generated using CFXBuild, the native geometry/mesh preprocessor within CFX5. The mesh was generated in three sections with general grid interfaces (GGIs) between the first two sections to accommodate a pitch change and between the intermediate and final section to model the change from a rotating reference frame to a stationary frame. A “frozen rotor” treatment was used to model the interface at the GGIs.
As the interest in this work was of a general nature, the total grid was modest, using only 130,000 tetrahedral volumes (30,000 nodes) in the three grid sections. The standard Eulerian multiphase model for liquidsolid systems was employed representing the pulp as the continuous phase and the grinding media as a dispersed second phase (solid). The solutions were computed on a singleCPU PC and required typically 500 iterations to achieve convergence to a tolerance of 104 in mass and momentum residuals. Actual clock time was approximately 8 hours per solution.
The CFD analysis has provided considerable insight into the internal workings of the mill. It has been possible to begin to understand the nature of media distribution, secondary flows, and anticipate qualitatively the wear characteristics of operating and pilotscale mills. The CFD model has shown considerable promise in aiding the understanding of mill behavior, in design for scaleup, and also generally in improving operation.
Schematic diagram of a grinding mill.
Grinding Mill Installation. Photo courtesy of MIM Process Technology.
Contour plot of the grinding media volume fraction in an axial slice, showing that the grinding media is forced to the outside periphery of the mill.
Vector plot of the grinding media phase secondary flows in an axial slice.
Contour plot of the grinding media volume fraction in a rotor passage in "blade to blade" view, approx 50% span. Note the high concentration on the pressure side of the "blade". (Rotor spinning counterclockwise)




[ Post Comment ]
< CFD for Industrial Ventilation  Melting Simulation in STARCD >  

CFD Review Login 


Related Links 

