investigation of effect of number of lifters on performance of pilotscale sag mills using discrete element method

The number of lifters of mill shell liners, mill rotation speed, and filling percentage of grinding media are three of the most important parameters influencing the charge behavior and the trajectory of ball motion inside the sag mills, and consequently, their performance. in this paper, the milling operation of pilotscale sag mills using the discrete element method (dem) is investigated. first, a pilotscale sag mill with dimensions of 3.0 m × 1.5 m with no lifter is simulated. then by adding, respectively, one, two, four, eight, sixteen, and thirtytwo rectangle lifter(s), six other independent simulations are performed. the effects of the number of lifters on the two new parameters introduced by the authors, i.e. ‘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 the simulation results, a laboratoryscale sag mill is simulated. the results obtained indicate that the optimum number of lifters for pilotscale sag mills is between 16 and 32 lifters with medium thickness. liners with the number of lifters in this range require less mill speed to create cataract motions. however, liners with the number of lifters less than this range require a higher mill speed. also liners with the number of lifters beyond this range require less mill speed, and can cause centrifugal motions in the balls. comparison of the simulations related to the laboratoryscale sag mill with experimental results demonstrates a good agreement, which validates the dem simulations and the software used.