Document Type : Research Paper
Faculty of Mining, Petroleum & Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran
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. 70% and 80% 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 240.13, 283.40, 306.47, 278.12, 274.42, 274.42, and 278.12 cm at the simulations performed with Smooth, Wave, Rib, Ship-lap, Lorain, Osborn, and Step liners at 70% of NC. The corresponding values at 80% of NC are as follows: 256.08, 264.56, 313.54, 298.45, 313.54, 311.60, and 283.40 cm. On the other hand, the impact zone lengths are respectively about 33.14, 22.11, 38.63, 35.86, 38.63, 38.63, and 49.59 cm at the simulations performed with above-mentioned liners at 70% of NC. The corresponding values for impact zone lengths at 80% of NC are as follows: 35.86, 27.63, 49.59, 38.63, 33.14, 52.32, and 41.38 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.