Paste thickener benefits for soda ash: liquor recovery, mine backfill and surface stack

The benefit of paste and thickened tailings (P&TT) was used for decades in the trona industry with a highdensity type thickener installed as early as 1994. The extraction process produced supersaturated liquor, which makes liquor recovery paramount. The insoluble material consisting largely of clays and silts produces the common problem of safe containment of the tailings. Both mine backfill and surface stacking of the tailings are being used. This paper provides a commodity review for trona, discussing the benefit of paste-type thickeners in the soda ash circuit. The topics include recovery from counter current decantation (CCD) circuits versus dilution washing; before and after retrofit data establishing improved underflow density and clarity from the latest thickener designs and operation; and the difficulties of surface stacking and drying due to residual soda ash forming a decahydrate crust sealing the stack and preventing drying. The trona industry provides a good review of paste-type thickeners and their benefits.