Promising prospects of thermal partial upgrading in reducing diluent requirements for bitumen transportation

Diluent addition and partial upgrading are two distinct techniques aimed at reducing the viscosity of bitumen and enhancing its transportability to refineries. Nevertheless, each method has its own limitations. A practical solution to overcome these challenges, which constitutes the primary objective of this research, is to integrate thermal partial upgrading with diluent addition. The first step of the study entailed thermal partial upgrading of bitumen at 420 °C with no residence time at target temperature. The process notably reduced bitumen viscosity from 169,000 cSt to 752 cSt at 21 °C with minimal coke formation of only 0.03 wt% and gas production of 2.16 wt%. Analysis of the bitumen and upgraded oil compositions revealed that around 20 % of the vacuum residue fraction in the bitumen was converted into the light cut fraction during the upgrading process. Additionally, the total acid number (TAN) decreased from 2.5 to 1.09 mg KOH/g. Asphaltene contents decreased by approximately 3 %, while nitrogen and sulfur contents reduced by around 35 % and 15 %, respectively. However, the olefin content in the upgraded oil (1.89 wt%) slightly exceeded the limit allowed for pipeline transportation (1.0 wt%). In the subsequent step, diluent was added to the partially upgraded oil to meet the viscosity requirements, and the solvent needed for feed bitumen was quantified. The thermal partial upgrading reduced the need for diluent from approximately 33 vol% to 9 vol%. Eventually, acid-catalyzed hydration was suggested as a potential technique for reducing the olefin levels to address the issue of high olefin content. As olefins generated through thermal cracking tend to accumulate in lower boiling fractions such as naphtha (boiling point ≤ 175 °C), acid-catalyzed hydration was examined on a naphtha sample obtained from a thermal partial upgrading process. The proposed approach in this study holds promise for enhancing bitumen processing capacity through no residence time at target temperature while diminishing the need for diluent.