A technique for measuring the reduction of yield stress of thickened tailings
Paste 2011 - 14th International Seminar on Paste and Thickened Tailings
Apr 10, 2011
The need to reduce the yield stress and viscosity of highly dewatered thickened tailings is very important to the design of pumping and transport systems over long distance pipelines to a tailings storage facility. Test work in the laboratory and pilot plant has been conducted to measure the rates of reduction of yield stress of flocculated thickened tailings, in order to determine the relationship between solids content, power consumption, time duration and shearing intensity at 180 and 950 rpm. Highest reduction rates occur during the onset of shearing, rapidly flattening off to approach a limit. Three types of flocculated tailings materials were evaluated.
An in-house designed prototype of a simple shear device with data logger was employed to characterise the rheological behaviour of the samples and generate the parameters required for design of large volumetric flows characteristic of large modern projects in the design stage in South America.
Rates of reduction of yield stress were determined for each type of tailings tested. The results will be presented as figures relating the unsheared, sheared and fully sheared samples. Such relationships are necessary in the design of tailings handling downstream of thickeners, such as the agitated receiving tank for thickened tailings, to further enhance the rheology prior to the delivery pump and distribution spigots of a tailings deposition strategy. The findings show how solids contents of the underflows can be handled, having established the yield stress as the tailings are transported to tailings storage.
Please see attached PDF.