Bitumen processing reduces diluent content of pipeline-transportable products and can mitigate impacts of spills into various water types

Abstract

Diluted bitumen (DB) consists of viscous bitumen that is blended with light, hydrocarbon-based diluent, so that it can flow through transmission pipelines from production sites to upgraders and refineries. However, diluent usage incurs substantial expense and occupies pipeline capacity. To minimize diluent usage, bitumen “partial upgrading” processes are being developed to generate processed bitumen products (PBPs) that contain less diluent than DB while meeting pipeline transportation specifications. In this work, bitumen was subjected to six different partial upgrading processes, involving visbreaking and/or solvent deasphalting. Processed bitumen types were then blended with minimal diluent such that the resulting PBPs met specifications for density and viscosity. Bitumen that was visbroken then solvent deasphalted met these specifications without dilution. Diluent also contains acutely toxic, volatile, and water-soluble components that are released into the environment when DB is spilled. Although the aquatic behaviour of DB has recently been investigated in response to growing public concern, little is known about that of various PBPs, and such information is needed to help mitigate spill impacts. In response to this need, PBPs were independently mixed with fresh and salt waters in the presence and absence of fine-grained mineral sediment. The PBPs prepared by solvent deasphalting with a high pentane-to-feed ratio alone or after visbreaking formed relatively unstable floating water-in-oil emulsions. Conversely, PBPs prepared by visbreaking alone or after low-ratio solvent deasphalting produced highly stable emulsions having higher water contents. These results can inform recommendations and policies for transporting Canadian oil sands bitumen products, and the development of strategies to prevent, prepare for, and respond to their spillage based on product quality.