The purpose behind the testwork
By performing thickener testwork, we determine the optimum feed solids, settling rate, flocculant dose, underflow density and mud residence time to correctly size a thickener for the required duty.
The MissionZero testing looks at the implications of treating coarse tailings from the CoarseAir flotation much earlier in the flowsheet, meaning water is recycled after the grinding circuit. A thickener process step is not required to treat the coarse tailings so the water will also be free from flocculants, although still may require Max-R treatment.
From the testwork done so far on the coarse tailings, it also indicates that vacuum filtration will be the process route, rather than pressure filtration. For the fine tailings, both Eco Paste and a traditional thickener and pressure filter process route will be evaluated.
Kyle talks about the direct filtration on a vacuum filter to test moisture levels and water recovery. “Particle size is a critical element in determining how a material will thicken or filter. Typically, the finer the particle size, the more difficult it is to thicken. The lower underflow density means less water recovery,” says Kyle.
“With MissionZero being a coarser material, the idea is to have lower energy consumption and higher water recovery. A filter will be in the flowsheet and we’ll test various technologies, such as pressure filtration, vacuum filtration and pneumapress, to determine which is the most suitable.”