Role of Caustic Addition in Bitumen–Clay Interactions

Abstract

Coating of bitumen by clays, known as slime coating is detrimental to bitumen recovery from oil sands using the warm slurry extraction process. Sodium hydroxide (caustic) is added to the extraction process to balance many competing processing challenges which include undesirable slime coating. The current research aims at understanding the role of caustic addition in controlling interactions of bitumen with various types of model clays. The interaction potential was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). After confirming the slime coating potential of montmorillonite clays on bitumen in the presence of calcium ions, interaction of kaolinite and illite with bitumen was studied. To make our study more closely related to industrial applications, tailings water from bitumen extraction tests using Denver flotation cell at different caustic additions was used. At caustic dosage up to 0.5 wt.% of oil sands ore, a negligible coating of kaolinite on the bitumen was determined. However, at lower level of caustic addition illite was shown to attach to the bitumen, with the interaction potential decreasing with increasing caustic dosage. Increasing concentration of humic acids as a result of increasing caustic dosage was identified to limit the interaction potential of illite with bitumen.2 This fundamental study clearly shows that the critical role of caustics in modulating interactions of clays with bitumen depends on the type of clays, guiding the multi-billion dollar oil sands industry to identify clay type as a key operational variable.

Studying bubble–particle interactions by zeta potential distribution analysis

“…Sub-micron size gas bubbles were generated by hydrodynamic cavitation in the BHIA cell at a fixed agitation speed of 2200 rpm and agitation time of 40 min. The sub-micron size gas bubbles generated using this method have a bubble size of d 50 ~ 350 nm which remain stable for up to 24 hr with the presence of surfactant. [38] A Rushton impeller 5.7 cm in diameter and 1.2 cm in blade width was used throughout the study.…”

“…However, it is clear that the zeta potential distribution technique is not applicable to the systems in which the individual components do not have their own distinct zeta potential distributions. For such systems, the quartz crystal microbalance (QCM) could be a good complementary technique, [50] provided that one of the components could be made as the surface of quartz crystal sensor.…”

Analytical Electron Microscopy of Carbon-Rich Mineral Aggregates in Solvent-Diluted Bitumen Products from Mined Alberta Oil Sands

“…13−18 Clay particles may arise in bitumen products owing to the formation of water-in-oil emulsion during the extraction process, 18 which reduces the recovery of bitumen and increases the water content in the final bitumen product. 19 Adsorption of organic matter onto clay surfaces 20−22 may also result in a biwettable character for the platelets, and an emulsion can then be stabilized by an accumulation of these platelets at the bitumen−water interface. 23 The extent to which bitumen droplets are covered by fine particles is commonly referred to as slime coating.…”

“…23 The extent to which bitumen droplets are covered by fine particles is commonly referred to as slime coating. 19 Through carryover (entrainment), other types of solids may also report to the bitumen products, such as soluble salts. Zircon and titanium-bearing minerals are known to float to the bitumen froth.…”

Determination of clay content in Canadian oil sands using x‐ray florescence spectroscopy for diagnosis of ore processability

“…Ding et al showed the negative effect of illite on bitumen recovery. Using the QCM‐D method, Bakhtiari et al confirmed the slime‐coating of illite on bitumen without or at low caustic addition. Mercier et al developed an x‐ray diffraction (XRD)‐based method to characterize clays in unextracted oil sands and found that the amount of ultrathin illite was critical in bitumen extraction.…”