Effect of suspension conductivity and fines concentration on coarse particle settling in oil sands tailings

Abstract

Sedimentation of coarse particles in mature fine oil sands tailings (OST) was studied by varying the fines concentration and aqueous phase conductivity to determine under which conditions the coarser particles will settle and when they will not. An OST sample was desalinated, separated into finer and coarser fractions, then recombined for settling tests. The isolated finer fraction was predominately phyllosilicate clays (>87 wt%) while the coarser fraction was mostly quartz (<77 wt%). From optical backscattering (OBS) height scan measurements, complete sedimentation of the coarse particles was observed at low conductivity values and fines concentrations, but a sufficient increase in suspension conductivity or fines concentration caused a reduction in coarse particle settlement. Samples with lower fines concentration, 0.5 wt% and 2.4 wt%, exhibited coarse settlement over a wider range of conductivity values; whereas samples with higher fines concentration, 5.9 wt% and 8.2 wt%, exhibited decreased sedimentation even at low suspension conductivity values. At similar conductivity values and fines concentrations, increased sedimentation of pure quartz was observed compared to the coarse OST particles. This difference in settling behaviour was partially attributed to the presence of residual organics on the surface of the OST coarse particles. In addition to typical metallurgical assay methods (x‐ray diffraction and scanning electron microscopy), a synchrotron‐source computed tomography scan of the untreated OST sample was obtained to visualize the distribution of the fine, coarse, and fluid phases within the sample.

Experimental Study on Tailings Deposition Distribution Pattern and Sedimentation Characteristics

“…Some scholars analyzed the influence of initial water content on the soil sedimentation property and discovered that the sedimentation stabilization time and the initial water content exhibited good power exponent relationship. , Meanwhile, temperature and pH value also affect the pore water pressure and cohesion of tailings. , However, tailing particle size distribution has a relatively more significant influence on sedimentation and consolidation. Some scholars carried out static sedimentation tests of ultrafine tailings to investigate the sedimentation time-history effect of tailings and compare the sedimentation and consolidation properties of sandy and viscous tailings in still water. − With regard to numerical simulation, numerous studies simulated the grain flow based on the discrete element method to analyze the motion rules of different particles under water power. − To sum up, the change in tailings particle size will affect the self-weight sedimentation and consolidation processes, which may lead to changes in tailings pond parameters, such as dry beach surface and saturation line height.…”