Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands—II. Flotation hydrodynamics of water‐based oil sand extraction

Abstract

Bitumen flotation hydrodynamics in water‐based oil sand extraction is critically reviewed by comparing aeration of oil sand slurries with mineral flotation. The role of the two‐stage particle‐bubble attachment model in flotation is emphasized as a means to accelerate bitumen flotation recovery. It involves the generation of micro/nanobubbles and their frosting on hydrophobic bitumen droplets, followed by their attachment to a flotation‐size bubble via its coalescence with the nanobubbles frosted on the bitumen. Nanobubble generation by hydrodynamic cavitation demonstrates that the size of nanobubbles can be reduced, and the number of nanobubbles increased by fast liquid flow, intensified agitation, high dissolved gas content and surfactant concentration. The mechanism of pre‐existing gas nuclei in enhancing nanobubble generation by cavitation is utilized to produce a large volume of stabilized nanobubbles for practical flotation, by continuously recirculating the stream through a gas saturation tank or a cavitation tube. The aeration of oil sand slurries in hydrotransport pipelines is analyzed based on its similarity to dissolved air flotation. Bitumen extraction recovery increased significantly with the presence of nanobubbles in the system. The role of improved flotation hydrodynamics in bitumen recovery is briefly discussed in terms of the Suncor operation using flotation columns to process oil sand middling streams. Future research should be directed at understanding bitumen flotation kinetics, optimizing size ranges of nanobubbles for maximized flotation recovery, minimizing wearing of cavitation tubes in industrial operations, and intensifying the role of in‐situ nanobubble nucleation on hydrophobic particles/bitumen droplets in flotation, especially for bitumen extraction from underperforming oil sands.

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands III. Next generation of water‐based oil sands extraction

“…The importance of manoeuvring the amount of air and the method of air addition (including entrained air and injected air) was addressed by Clark [15,20,[22][23][24] ; Too much air could carry fine solids/clays along with bitumen to the froth, and too little air may not be able to float all the bitumen. In addition, only small air bubbles that are a few millimetres or less in diameter are effective in floating liberated bitumen droplets.…”

“…The development of oil sand slurry hydrotransport in pipelines to replace the transportation of raw oil sands F I G U R E 3 Classification of oil sands extraction technologies by belt conveyors in the early 1990s has made the expansion of oil sands exploration feasible. [24] It has revolutionized the traditional ore slurry conditioning in rotating tumblers, leading to the reduction of extraction temperature from 80 C to~50 C or lower. The corresponding heat requirement was reduced from 300 to 180 MJ/t oil sands.…”

“…[ 25 ] Bitumen recovery from the middling streams has been modified from using mechanical flotation machines to flotation columns in Suncor and Fort Hills Mine operations. [ 24 ] Jameson cells are used to recover residual bitumen from coarse tailings in tertiary recovery. [ 39 ] Caustic is still the only chemical process aid used for boosting bitumen extraction performance if necessary, although Syncrude recently patented a secondary process aid by adding citrate to combine with caustic, [ 40,41 ] and InnoTech Alberta developed caustic replacement for non‐caustic extraction processes.…”

“…In addition, with the mining site far away from the extraction plant, the traditional transport of oil sands by belt conveyors, followed by the oil sands digestion in tumblers is far from efficient for large‐scale operations. Hydrotransport pipeline:The development of oil sand slurry hydrotransport in pipelines to replace the transportation of raw oil sands by belt conveyors in the early 1990s has made the expansion of oil sands exploration feasible. [ 24 ] It has revolutionized the traditional ore slurry conditioning in rotating tumblers, leading to the reduction of extraction temperature from 80°C to ~50°C or lower. The corresponding heat requirement was reduced from 300 to 180 MJ/t oil sands.…”

“…This includes both flotation chemistry and flotation hydrodynamic conditions, as have been discussed in the first and second parts of this technical series. [ 24,89 ] They are briefly summarized below: Feed requirement:Simple mineralogy and particulate surface properties. Suitable particle size distribution (say, 20‐200 μm, depending on the density of the particulates); relatively dilute feed slurries (say, <20‐30 wt% solids); lower content of clays and fine solids to reduce slurry viscosity, and minimize slime coating. Water chemistry requirement:Low concentrations and few types of ionic species (especially multi‐valent metal cations) and suitable slurry pH.…”