Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng Using DEM to investigate how shell liner can induce ball segregation in a ball mill Ngonidzashe Chimwani a, ⁎ , Murray M. Bwalya b a Institute for the Development of Energy for African Sustainability (IDEAS), A Research Centre of the University of South Africa (UNISA), Florida Campus, Private Bag X6, Johannesburg 1710, South Africa b School of Chemical and Metallurgical Engineering, University of Witwatersrand, Johannesburg, Private Bag 3, Wits 2050, South Africa ARTICLEINFO Keywords: Discrete element method Segregation Liner conﬁguration Liner proﬁle Ball size ABSTRACT Sometimes it is desirable to segregate the ball load in a mill so as to allow for the possibility of larger balls dealing with coarser particles at the feed end and ﬁner product being ground more eﬃciently at the discharge end. The Hardinge mill with cylindrical and conical sections has been used to achieve segregation quite eﬀec- tively. The cylindrical section tends to retain the biggest balls while the smaller balls drift to the conical section. However, this is a complex design and we use the discrete element method (DEM) model to investigate if simply altering liner conﬁguration on an ordinary cylindrical mill can lead to similar success. The study involves si- mulating a mill with 4 sections. Each section can be conﬁgured with distinct liner proﬁles. Three ball size classes are tracked for evidence of segregation at 75% and 60% of critical mill rotation speed. The ball distributions in the various segments at the end of 80 mill revolutions suggest that varying axial liner proﬁle conﬁguration can aﬀect ball segregation, particularly for the mill running at 75% of critical speed. The convenience of using computer simulations to avoid costly plant trials is highlighted. 1. Introduction The tube remain the most utilised piece of milling equipment de- spite the well-known fact that it is grossly ineﬃcient. It is however a very ﬂexible piece of equipment which can be manipulated to achieve diﬀerent results. It is in the interest of any particular designer to maximisereturnswithinanyapplicableconstraints.Thisdoesnotimply that the best solution possible can be arrived at nor does it mean that the best solution for today will still be the best solution for tomorrow as mill feed or product speciﬁcation may also change. One of the more desirable aspects of grinding is to match the right ball size to the particles being comminuted. This was one of the main reasonbehindthedevelopmentoftheHardingemill,whichcomprisesa cylindrical and conical section. This arrangement naturally causes the balls to segregate with smaller balls ending up in the conical section while the large balls remain in the cylindrical section. With the feed being from the cylindrical end, the feed ideally encounters coarser balls and as particles get ﬁner towards the discharge conical end, they are eﬀectively dealt with by smaller balls. In the cement industry, the mill is compartmentalised using diaphragms to keep balls of diﬀerent sizes within the diﬀerent compartments and can similarly deal with particles eﬀectively according to their size. However both the Hardinge and cement mill are more complex. In our study, we use the discrete element numerical modelling (DEM) tool to see if ball segregation can be achieved in a tube mill by simply using appropriate liner proﬁles. Liners/lifters are known to have strong inﬂuence on the load tra- jectory and ultimately breakage eﬃciency of the mill (Toor et al., 2013). Their size, shape and quantity in a mill has strong impact on the tumbling action of the mill content (King, 2001),andalsotheirmodeof energy transfer to the grinding media determines the rate of breakage, owing to the mechanical link that exists between them and the load (Makokha et al., 2006). Optimising liner proﬁle has received con- siderable attention and multiple operational conﬁgurations have been proposed to achieve mill productivity (Rezaeizadeh et al., 2010). Some among other studies have focused on; the eﬀect of wall lifters on the slurry ﬂow (Cleary and Morrison, 2012) and, ﬁnding optimum liner conﬁguration for a given milling duty in order to develop a liner design which balances liner life and milling performance (Powell et al., 2012). From this wealth of research, important and substantial progress has been achieved in the design and optimisation of mill liners. However, we are not aware of any work that explores design of liners that pro- motes axial segregation of ball mills. Therefore, DEM is used in this work to explore how axial liner conﬁguration can be used to promote https://doi.org/10.1016/j.mineng.2020.106311 Received 12 July 2019; Received in revised form 22 February 2020; Accepted 1 March 2020 ⁎ Corresponding author. E-mail address: ngodzazw@gmail.com (N. Chimwani). Minerals Engineering 151 (2020) 106311 0892-6875/ © 2020 Elsevier Ltd. All rights reserved. T