Scaling inline static mixers for flocculation of oil sand mature fine tailings

Abstract

in Wiley Online Library (wileyonlinelibrary.com) Operations to reclaim mature fine tailings (MFT) ponds involve flocculation using high-molecular-weight polymers, for which inline static mixers are suited. Three different commercial static mixers were utilized to determine mixing parameters corresponding to optimal dewatering performance of flocculated MFT. MFT was treated with polymer solution under different mixing conditions. The dewatering rates passed through a peak with increasing mean velocity, V and Reynolds number, Re of the fluid. The greater the number of mixer elements, the lower the V and Re at which the peak dewatering rate occurred. Mixing parameters such as G-value, residence time, and mixing energy dissipation rate of the most rapidly dewatering flocculated MFT were dependent on mixer type and setup. In contrast, peak dewatering rates converged when scaled with respect to specific mixing energy, E, demonstrating that E is a suitable scale-up parameter for inline static mixing to produce optimally dewatering MFT. V C 2015 American Institute of Chemical Engineers AIChE J, 61: [4402][4403][4404][4405][4406][4407][4408][4409][4410][4411] 2015

Impact of preflocculation on scroll decanter centrifuge separation performance

“…Pressure drop, ΔP , across the static mixers increases linearly with the number of mixing elements, much like the length effect in regular pipe flow. The slopes of log ΔP verses log Q were 1.6 and 1.8 for the KMS and Koflo static mixers, respectively, indicating that the preconditioning conditions are such that the flow is turbulent and the mixing corresponds to orthokinetic flocculation …”

“…Just as considerable mechanical shear is needed to mix the feed and create large flocs, shear can also rupture the flocs when the hydrodynamic stress exceeds the floc strength. Steady shear and dynamic oscillation rheological measurements, as well as stereo microscopic images, reveal that mixing intensity and mixing duration determine the floc sizes and the network structure of the flocculated FFT . Structural changes caused by excessive mixing lead to poor dewatering rates in systems that rely on overflow or drainage water release .…”

“…Combinations of Chemineer‐Kenics KMS™ and Koflo 275™ commercial stainless steel static mixers were utilized to mix the FFT and flocculant . The inline static mixers and the feed piping were 25.4 mm (1 inch) nominal diameter.…”

“…Since a significant fraction of the solids in oil sand tailings ponds is smaller than 2 μm, the use of flocculants is necessary. Field observations and laboratory studies have shown that combinations of mixing time and mixing intensity can be found that yield optimally flocculated FFT corresponding to the disposal method …”

Monitoring tailings flocculation performance using hyperspectral imagery

“…Several engineering techniques have been proposed and tested to accelerate the dewatering of tailings and increase the performance of the consolidated deposit such as thin lift drying, centrifugation, composite tailings, and freeze‐thaw drying . In‐line flocculating and drying of tailings has been tested by several oil sands operating companies . In this method, tailings are mixed with polymer flocculants or inorganic coagulants to form large aggregates that improve the settling velocity.…”