In recent years, DEM ( discrete element method) software, along with 3D laser measuring equipment, have become powerful tools to describe mill charge behavior, as well as forces acting on the liners of SAG mills. With the aim of contributing to streamline this application of the advanced technologies ME Elecmetal and Universidada Federal do Rio de Janerio, UFRJ, proposed a new approach to improve the design of mill liners using elements from mechanistic modeling of grinding.
This paper presents a methodology for continuous improvement of liner design, which uses information from the DEM collision energy spectra in the mill discriminated for the different components (ore and steel balls) as well as information on the breakage properties of the ore being ground. From these it proposes the concept of “effective collisions” , which corresponds to the collisions that are of sufficient magnitude to cause breakage, thus allowing to discriminate from impacts that do not cause breakage either in a first impact or after repeated loading. It also tracks the collision of steel balls against the shell in order to assess their potential damage to the liners.
An industrial case study is presented of a 38″ diameter SAG mill, which was experiencing challenges associated to liner breakage and low efficiency with the old liner design. Through a modification of the liner design, simulations demonstrated the potential benefit associated to reduction in ultraprojection and improvement in mill capacity. Implementation of the new design in the SAG mill was carried out, resulting in an increase in daily throughout from 6-12%. Further, the time spent in liner change was reduced by 47% given the reduction in the number of parts. This operation also benefited from having no stops due to unplanned shutdowns to replace broken tiles. These demonstrate the benefit of coupling advanced computational tools to sound engineering principles in continuous improvement of liners.