Evaporative Weathering of Diluted Bitumen Films

Abstract

Summary One of the issues for the pipeline transportation of diluted bitumen (dilbit) is the fate and behaviour of the dilbit if it is spilled in freshwater systems; in particular, the evaporation rate and the change in physical properties of the film after evaporation and exposure to water (weathering). In this study, the evaporative weathering of dilbit Cold Lake Winter Blend (CLWB) and light crude oil Alberta Sweet Blend (ASB) films were compared. Evaporation rates were measured for films on glass over time (up to 30 days) at different air-flow rates and at temperatures of 5, 15, and 25C. The solvent content, density, and viscosity of the films were measured after different weathering times. A second set of tests at 15C was performed on both dilbit and light-crudeoil films on water. As expected, the mass-transfer rate increased with increasing temperature and decreasing film thickness in all cases. The evaporation of the dilbit was found to be limited by the diffusion rate of the lighter components through the film while that of the light crude oil was limited by convective mass transfer to the air above. The density and viscosity of both the CLWB and ASB films correlated to the amount of evaporated material at all conditions examined, including different film thicknesses, temperatures, and air-flow rates. It appears that the volatile components evaporate in the same order at any conditions; therefore, film composition, density, and viscosity are only functions of the amount evaporated. The evaporation rates, density, and viscosity of CLWB and ASB films weathered over water were identical to those corresponding films weathered on glass, within the error of the measurements; that is, contact with still water had no effect on weathering.

Diluted Bitumen: Physicochemical Properties, Weathering Processes, Emergency Response, and Recovery

“…The results indicated that the highest evaporated portion of CLWB was about 22% at 25 °C, which was lower than ASB (40%) under the same condition. Furthermore, the diluents could evaporate at all temperatures, while the heavier compounds started to evaporate when the temperature reached 60 °C (Yarranton et al, 2015). Similar results of evaporation rate were found by Environmental Canada (2013).…”

“…Temperature has a profound impact on the evaporation rate of spilled oil (Environment Canada, 2013;Yarranton et al, 2015;Johannessen et al, 2020;Ortmann et al, 2020). Yarranton et al (2015) conducted several tests to investigate and compare the evaporation rate and the physical property changes of dilbit and light crudes in freshwater.…”

“…Temperature has a profound impact on the evaporation rate of spilled oil (Environment Canada, 2013;Yarranton et al, 2015;Johannessen et al, 2020;Ortmann et al, 2020). Yarranton et al (2015) conducted several tests to investigate and compare the evaporation rate and the physical property changes of dilbit and light crudes in freshwater. The Cold Lake Winter Blend (CLWB, dilbit) and Alberta Sweet Blend (ASB, light crude oil) were selected to measure the evaporation rates at temperatures of 5 °C, 15 °C, and 25 °C with different air flow rates.…”

“…No sediment was observed when cleaning the tank (Zhou et al, 2015). Furthermore, the study from Yarranton et al (2015) indicated that the weathered dilbit could afloat on freshwater for at least 10 days. This was in agreement with experimental results from SL Ross Environmental Research Limited (2012) that the weathered dilbit continued to float on the freshwater surface during the whole experiment duration (13 days).…”

“…Accurate prediction of the spilled diluted bitumen's transport and behavior is of importance to local authorities and oil companies for quick and efficient response to diluted bitumen spills. Some studies have been carried out regarding the physicochemical properties of diluted bitumen and the investigation/simulation of its weathering processes (Yang et al, 2011;Banerjee, 2012a;Environment Canada, 2013;Menzies and Thomas, 2014;Tsaprailis et al, 2014;Dew et al, 2015;Fingas, 2015;Yarranton et al, 2015;Hounjet and Dettman, 2016;Wu et al, 2016;Sereneo, 2017;Ortmann et al, 2020;Li et al, 2022). For instance, Menzies and Thomas (2014) investigated the physical properties of diluted bitumen and compared them with the conventional crude oils.…”