Investigation of the effect of industrial ball mill liner type on their comminution mechanism using DEM

The mill shell liner type, rotation speed and the amount of its loading are the key factors influencing the charge behavior, consequently the comminution mechanism. In this paper, milling operation of industrial ball mills using Discrete Element Method (DEM) is investigated. First, an industrial scale ball mill with a Smooth liner type is simulated. Then, by changing liner type, i.e. Wave, Rib, Ship-lap, Lorain, Osborn, and Step liners, six other independent simulations are performed. Effects of mill shell liner type on charge shoulder, toe, impact, and head points, also on head height and impact zone length as well as on creation of cascading, cataracting, and centrifuging motions for balls at two different mill speeds, i.e. ۷۰% and ۸۰% of its critical speed (NC) are evaluated. Also, in order to validate simulation results, a laboratory scale mill is simulated. The results indicate that the charge heads are respectively about ۲۴۰.۱۳, ۲۸۳.۴۰, ۳۰۶.۴۷, ۲۷۸.۱۲, ۲۷۴.۴۲, ۲۷۴.۴۲, and ۲۷۸.۱۲ cm at the simulations performed with Smooth, Wave, Rib, Ship-lap, Lorain, Osborn, and Step liners at ۷۰% of NC. The corresponding values at ۸۰% of NC are as follows: ۲۵۶.۰۸, ۲۶۴.۵۶, ۳۱۳.۵۴, ۲۹۸.۴۵, ۳۱۳.۵۴, ۳۱۱.۶۰, and ۲۸۳.۴۰ cm. On the other hand, the impact zone lengths are respectively about ۳۳.۱۴, ۲۲.۱۱, ۳۸.۶۳, ۳۵.۸۶, ۳۸.۶۳, ۳۸.۶۳, and ۴۹.۵۹ cm at the simulations performed with above-mentioned liners at ۷۰% of NC. The corresponding values for impact zone lengths at ۸۰% of NC are as follows: ۳۵.۸۶, ۲۷.۶۳, ۴۹.۵۹, ۳۸.۶۳, ۳۳.۱۴, ۵۲.۳۲, and ۴۱.۳۸ cm. Comparison of the simulations related to the laboratory scale mill with experimental results demonstrates a good agreement which validates the DEM simulations and the software used.

Keywords:

DEM simulation , Industrial ball mills , Liner type , Head height , Impact zone length