Evaluation of Ball Mill Liner Wear Using Discrete Element Method

Abstract

Mainstream mining techniques in developing nations are hampered by high investment capital demand. As a result, many low-income nations with abundant mineral deposits are where small-scale mining is most prevalent. The utilization of locally made machinery is necessary due to limited funding sources. These machines, however, are frequently unreliable and ineffective, which has a detrimental effect on size reduction of mineral ores. Science must therefore increase the overall effectiveness and dependability of these machines. A ball mill is a device for grinding rocks and assisting in the liberation of minerals for additional processing in the mining industry. The machine is made up of components such as the power source, the supporting framework, the drum, and the liners. The drum, which has a cylindrical or polygonal profile, is the ball mill’s primary working component. The latter profile is highly favored for artisanal mining due to its ease of fabrication. Due to the high abrasiveness of the majority of ores used in ball mills, liners are employed to lessen drum wear. The replacement of the liners is expensive and time-consuming because of the excessive wear that causes grinding inefficiencies. To increase production and lower costs, it is crucial to determine how different drum profiles affect liner wear. In this study, the discrete element approach was used to compare the severity of liner wear on the two drum profiles. First, particle model calibration was carried out using a hollow cylinder experimental setup. The model was then validated using a rectangular container method. For the liner wear model, calibration involved a drum wear test with a sliced drum geometry. Validation of the wear model was subsequently performed using the same drum wear test method, but with a full-scale drum setup. In both cases, experimental results were compared with simulation outcomes during the calibration and validation of the two DEM models. Although the octagon, decagon, and dodecagon geometries were taken into consideration in this work, the hexagon geometry was used as a depiction of the polygon profile. Further, lifters were incorporated into the two profiles, and their impact on the wear volume was examined. It was established that wear in the cylindrical profile was primarily due to material slip over the liner surfaces. However, the polygon profile wear was caused by both material slip over the liners and concentrated compressive force at the vertices. The influence of material slip on wear was thought to be greater on all of the profiles than the effect of compressive force. Thus, the cylindrical profile’s roundness made it easier for material to slide across the liner surface, which increased the wear on its liners. Instead, the polygon profile sides prevented material slippage, which reduced wear on its liner surfaces. The result was a wear difference of 17.9% on average between the two profiles at all speeds, with the polygon profile wearing out the least. Fitting of lifters in the two profiles prevented particles from sliding, causing a reduction of wear in all the profiles. Nonetheless, the wear caused by compressive force in the polygon profile was left unresolved. Therefore, the cylindrical profile fitted with lifters experienced 32.2% less wear compared to the polygon profile fitted with lifters, at all rotation speeds. Results obtained from this work are able to scientifically inform on the drum profile with least amount of wear. Additionally, results obtained will guide the artisanal miners on the design features to consider when fabricating a ball mill. This will lead to reduction in maintenance cost and enhanced efficiency of the equipment