One of the steps when producing bitumen by surface mining is the recovery of bitumen from the oilsands using hot water extraction. The product from this process is a froth that consists of a mixture of bitumen (~60 wt%), water (~30 wt%) and minerals (~10wt%). In order to obtain a clean bitumen product, a paraffinic or naphthenic solvent is added during the froth treatment to reduce bitumen viscosity and density to facilitate separation. Past studies on froth treatment focused on the separation efficiency and solvent recovery. The froth treatment is operated at a temperature range 30-80 °C, and at this low temperature the reactivity behavior of bitumen attracted little study. Previous studies performed at lower temperatures than the ones used for bitumen upgrading showed that bitumen visbreaking at 250 °C led to a slightly lower viscosity product, and that hydrogen transfer reactions were observed on heating asphaltenes at a temperature range 100-150 °C. Furthermore, at a higher temperature (400 °C), there was evidence that the presence of mineral matter when heating bitumen delayed the onset of coking. These observations led to the following questions: 1) Is it possible to partially upgrade bitumen by increasing the temperature of the froth treatment process to 250 °C? 2) What are the benefits of upgrading bitumen in the presence of water and minerals during thermal treatment of froth? Thermal treatment of froth diluted with kerosene (1:0.75 w/w) was performed at 250 °C in order to evaluate the possibility of partial upgrading of bitumen during froth treatment. Additionally, reactions at 400 °C and 25 minutes were performed to investigate the potential benefits of having water and minerals during bitumen visbreaking. Control reactions were performed to decouple the effect of the presence of water, solids and solvent over the physical chemical properties of interest (viscosity, density, aliphatic/aromatic hydrogen content and free radical content). The results showed that at 250 °C there was a slight increase of the viscosity and density probably due to addition reactions favored at this temperature, while reactions at 400 °C indicated that the interaction among bitumen, water and minerals might influence the hydrogen transfer reactions during bitumen conversion.

Potential for partial upgrading by thermal treatment of bitumen froth

ACS Spring Meeting 2021

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