Enhanced zircon recovery through centrifugal jigging

Abstract

Indian Rare Earths Ltd, Chavara is engaged in the mining and processing of beach sand heavy minerals from the costal belts of Kerala. IREL produces minerals like Ilmenite, Rutile, Garnet, Zircon, Sillimanite and monazite that find use in various applications like paint industry, welding electrodes, ceramics, foundry and for the production of different types of rare earth compounds. Feed to Zircon circuit consists about, 20–25% of Zircon (sp. gravity: 4.7, size range 150–106 microns), 25–30% Sillimanite (sp. gravity: 3.25, size range 250–150 microns), 4–6% of Kyanite (sp. gravity: 3.5, size range 250–150 microns), 20–25% of Quartz and other minerals. The recovery of Zircon through conventional process equipment like spiral and wet table is in the range of 60 to 65%. Due to the identical physical and chemical properties and close sp. gravity range of the minerals present in the feed, it becomes very difficult to get higher recoveries with conventional separation techniques like spiraling, tabling, etc. So we have employed a radically new technology called centrifugal jigging in the zircon circuit by installing a Centrifugal Jig wherein the feed mineral particles are elevated to higher g-field to substantially amplify the sp. gravity difference among the feed particles to effect clean separation. A suitable ragging bed is introduced as hindering bed to obtain required separation. The general operating variables to optimize the recovery and grade are jig spin speed, pulse stroke length, pulse frequency, elutrition water rate, depth of operating bed, jig screen aperture size and ragging size. Multiple tests were conducted to study the performance by altering the parameters to fine tune the process. As evidenced by our operating results, a smaller stroke and faster spin rate gives rise to tight ragging bed and that was found optimal to facilitate production of high quality concentrate. A trade off between recovery and grade can be achieved by optimizing spin speed and stroke length to prevent the escape of fine high specific gravity particle to tailings. The ragging size distribution and its effect on recovery and purity were studied separately for better performance.