TEST WORK ON HIGH THROUGHPUT DIAMOND TRACER RECOVERY FROM ALLUVIAL RECOVERY TAILINGS WITH A CONTAINERISED OPTICAL SORTER UNDER REAL PRODUCTION CONDITIONS

摘要

Worldwide alluvial diamond deposits are traditionally processed with dense media separationand XRF sorters, hand picking or grease tables. The test work conducted verifies the performanceof an optical sorter detecting the transparency of particles for diamond recovery from the DMSconcentrate, eg XRF-sorter and handpicking tailings. The containerised setup enables economicallyfeasible, high throughput, semi-mobile setups to retreat recovery tailings from alluvial and alsoprimary deposits. The test work has been conducted with quartz and glass particles, which are lesstransparent or comparably transparent, under realistic production conditions on a 600 mm beltmachine with an installed electrical power of only 21 kW. The results show that 99 per cent recoverycan be reached at a throughput of 10 t/h in the -8 + 2 mm fraction and at 22 t/h in the -25 + 8 mmfraction. At a throughput of 18 t/h a recovery of 88 per cent has been assessed. At a further escalationof the throughput, dust in the sorter container made sorting impossible in the coarse fraction andthe recovery decreased significantly in the fine fraction. Analysis of the belt coverage indicates thathigher throughputs of the coarse fraction can be fed onto the optical sorter if the dust extractionsystem is improved. The results are basis for the decision to conservatively feed 20 t/h of the coarsefraction and 17 t/h of the fine fraction in day to day production. The settings have been applied to sortalluvial recovery tailings in South Africa and will be applied to sort the recovery tailings of a primarydeposit in Lesotho.The test work has shown that an optical sorter can be used to retreat recovery tailings with highthroughputs. The compact setup of a screen and a 9 m standard container enables semi-mobile,temporary setups for small recovery tailings dumps and remote areas. In addition, sorting ontransparency ensures the recovery of high value low-fluorescent diamonds.