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.
Iron production in India has seen rapid growth over the last few years, significantly exceeding forecasts. This growth has accentuated several issues regarding management of the slimes, dewatering, and tailings storage facilities (TSF). The number of slime pelletising beneficiation plants has increased to produce pellets for domestic use and exports. Pellet plants vary in size from 1 to more than 8 Mtpa pellet production. Slime beneficiation can produce tailings with more than 90% passing 20 microns (µm). In light of recent world iron tailings disasters, there has been a focus on much lower risk tailings storage systems. Plants have significant obstacles to overcome in the management of these slime tailings; the tailings very fine particle size distribution (PSD) is notorious for poor filtration rates, small TSF areas are available, stream variability can greatly affect dewatering efficiency, and water management at the TSF in high rainfall, to name a few. Paste thickener technology, which provides solutions to several of these challenges, has entered the Indian iron market. The first installation was in 2015 at Shri Bajrang Power and Ispat Ltd Tilda pellet plant. This paper features additional Indian paste thickener sites, discussing dewatering variable feed streams, thickener operation and results, and methods of TSF management.