Discrete element simulation of mill charge in 3D using the BLAZE-DEM GPU framework

Abstract

The Discrete Element Method (DEM) simulation of charge motion in ball, semi autogenous (SAG) and autogenous mills has advanced to a stage where the effects of lifter design, power draft and product size can be evaluated with sufficient accuracy using either two-dimensional (2D) or three-dimensional (3D) codes. While 2D codes may provide a reasonable profile of charge distribution in the mill there is a difference in power estimations as the anisotropic nature within the mill cannot be neglected. Thus 3D codes are preferred as they can provide a more accurate estimation of power draw and charge distribution. While 2D codes complete a typical industrial simulation in the order of hours, 3D codes require computing times in the order of days to weeks on a typical multi-threaded desktop computer. This paper introduces a 3D GPU code based on the BLAZE-DEM framework that utilizes the Graphical Processor Unit (GPU) via the NVIDIA CUDA programming model. Utilizing the parallelism of the GPU a 3D simulation of an industrial mill with four million particles takes 1.16 hours to simulate one second (12 FPS) on a GTX 880 laptop GPU. This new performance level may allow 3D simulations to become a routine task for mill designers and researchers. Furthermore the shorter compute time can elevate the physics included in the computations to a higher level wherein ore particle breakage and slurry transport can be included in the simulation. In this paper we verify our GPU code by comparing charge profiles and power draw obtained using the CPU based code Millsoft and pilot scale experiments. Finally, we show computations for plant scale mills.