Emile Scheepers

Abstract:

Among the many initiatives being developed to recover and reuse mineral waste at Vale mining sites, the new business solution presented here uses silica-rich tailings as a substitute for primary silica to produce engineering stone products like kitchens countertop, bathroom vanities and floor tiles in a booming, multi-billion dollar industry. Engineering stone is an alternative to natural stone like granite. It is manufactured from approximately 93% primary silica, 7% resin, colour pigments and selected aesthetic additives, with the recipes varying depending on desired colour and aesthetic properties. Using primary (typically white) silica allows engineering stone manufactures to produce products with a wide colour range, so when used, residual (darker) iron ore in tailings can somewhat decrease colour control. Through innovative technological advances combined with a skilled and highly motivated workforce, Vale has been able to systematically improve separation efficiency of its concentration/beneficiation processes (primarily aimed at maximizing the recovery of iron ore). Fortuitous laws governing mass balances have ensured that increased recovery of iron ore in one stream has meant an associated increase in silica content of the other stream (tailings), in some strategic process streams as high as 90-96% SiO2. Such a systematic increase in the silica content (becoming whiter) has meant an increase in the colour control Vale silica-rich tailings can deliver the industry. Since 2014 Vale has been working closely with leaders in the engineering stone manufacturing industry to develop recipes. This collaboration is delivering engineering stone that not only meet EN 14617 industry standards for resistance to stain, strength and impact but also have colour ranges able to satisfy market needs.