Visbreaking of Bitumen Froth: Influence of Minerals, Water, and Solvent on the Physicochemical Changes in the Bitumen Phase

Thermal treatment of oil sand bitumen froth has the goalof notonly improving the separation process during froth treatment but alsoaccomplishing bitumen upgrading. There is evidence that both waterand minerals have an effect on the physicochemical transformationsthat take place during the treatment. However, little is known aboutthe nature of these transformations and whether the presence of mineralsolids and water can be beneficial. The current study investigatedthe visbreaking of froth at 400 & DEG;C with an average equivalentresidence time of 30 min. The froth elements (mineral solids and water)were either separated or maintained in the mixture to assess theireffects during visbreaking. Visbreaking was performed in the absenceand presence of hydrocarbon solvents (n-hexane andkerosene). Viscosity, density, refractive index, elemental composition,persistent free radical content, and nature of the hydrogen and carboncontent were evaluated before and after the treatment. The productsfrom froth visbreaking on a solvent-free bitumen basis had a kinematicviscosity in the range 1-4 x 10(3) mm(2)/s at 7.5 & DEG;C and a density in the range 990-1000 kg/m(3) at 15.6 & DEG;C. When visbreaking was performed in the presenceof n-hexane, the products had a lower increase inaromatic C, lower viscosity, and lower density on solvent-free basiscompared to the products from visbreaking performed in kerosene orwithout a solvent. The presence of mineral solids and/or water duringbitumen visbreaking consistently yielded a bitumen product with numericallyhigher viscosity and density compared with visbreaking of bitumenalone. Mineral solids and water affected hydrogen transfer reactionsduring visbreaking, which could be seen in terms of the relative changein the aromatic H and C content in the products. When mineral solidswere present, some products were adsorbed on the solids, which alsoaffected the H/C and free radical contents of the liquid product.

Automated summary

The thermal treatment of oil sand bitumen froth aims to improve the separation process and upgrade the bitumen. The current study investigated the effects of mineral solids and water on visbreaking at 400°C. It was found that the presence of mineral solids and water consistently yielded bitumen products with higher viscosity and density. The presence of hydrocarbon solvents also influenced the product characteristics.