An innovative flake graphite upgrading process based on HPGR, stirred grinding mill, and nanobubble column flotation

Abstract

Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade. An innovative grinding and column flotation process has been developed for efficient graphite upgrading to substantially simplify the process flowsheet and reduce operating costs. In this process, a high-pressure grinding roller (HPGR) and a stirred mill were employed as primary comminution techniques and a nanobubble flotation column as a key separation process. The results obtained with a crystalline flake graphite sample with a carbon grade of 11.15% show that the novel process can produce a concentrate with 94.82% carbon grade and 97.89% recovery from an open circuit of one rougher and two cleaner flotation stages. Scanning electron microscope (SEM) microphotographs indicate that HPGR offers the advantage of more effective protection of graphite flakes during crushing. Grinding test results show that stirred mill could not only protect graphite flakes but also promote the efficient liberation of graphite. Compared with the traditional flotation process, nanobubble flotation can effectively recover ultrafine graphite. The new process possesses a number of important advantages over the traditional method, including substantially higher graphite recovery, greatly simplified process flowsheet, better protection of flake size, reduced reagent consumption and process costs, etc.