The role of fine particles in the stability of emulsion in the naphthenic froth treatment (NFT) process

This study investigates the role of fine particles in stabilizing emulsion in the naphthenic froth treatment (NFT) process. The characterization results of different types of solids collected from the diluted bitumen froth indicate that kaolinite is the dominant clay mineral in the composition of NFT solids. There were differences in the mineralogy of the fine samples depending on the phase (carrier fluid) from which the samples were collected. FTIR analysis shows that the fines that remain in the diluted bitumen even after several hours of sample retention time are mainly kaolinite, though the presence of other minerals such as siderite is very likely. Moreover, the presence of organic functional groups on the surface of the particles is confirmed for all types of solids in the FTIR analysis, regardless of the washing and drying procedures employed. Inspection of the different layers of the diluted bitumen via micrography and measurement of the solids concentration shows higher fine content and smaller particles in the top layer, a dire situation for destabilizing the emulsion in the top layer, supported by the observation that the water droplets in this layer are tiny. Solid partitioning tests revealed the solid particles migrate to the interfacial region and the aqueous phase. The concentration of particles increased in the interfacial region with the presence of asphaltene in the oil phase (dominant effect) and the increased polarity of the oil. The wettability measurements show that without the coverage of solid particles with organics (asphaltene-resin molecules), the fine particles are extremely hydrophilic. The adsorption of asphaltene-resin matter on the fine particles increased the hydrophobicity of the fines, a situation that promotes the partitioning of the fine particles at the interfacial region and the stability of the droplets. It was observed that the contact angle increased with the decreasing polarity of the oil phase. In the interfacial tension measurements, the fine solids with minimal asphaltic matter coverage did not remain suspended in the oil phase and either sedimented rapidly or migrated to the air-oil interface, unlike the organics-covered solids which remained immersed in oil. No decrease in the interfacial tension was recorded for the water-oil systems in the presence of fine solids. Interfacial rheology measurements illustrate the viscoelastic behavior of the interfacial film at lower frequencies and higher fine particle concentrations. We conclude that if not for the interaction between the asphaltic matter and the fine particles, the emulsion stability by fine particles would have been very unlikely.