Thermal Conversion of Deasphalted Oil at Low Temperature

• Author / Creator

  Castillo Lugo, Javier

• Canada has one of the largest oil reserves in the world, with around 3 trillion ultimate reserves in heavy oil. Even though, one of the major difficulties that Canadian Oil sands industry has faced over time is the transportation of bitumen due to its extremely high viscosity.

  Having this in mind, the concept of field upgrading process developed by Nexen Energy ULC suggests a middle thermal conversion process as the main conversion unit in the field upgrader in order to reduce the viscosity and enable to meet the pipeline transport specification. Thermal cracking of industrial deasphalted vacuum residue from the Nexen Long Lake upgrader were carried at low reaction temperature (280 - 408 °C) in order to gain a deeper understanding of the changes that heavy oil experiences during milder conversion processes. It was found that although there was not significant change in viscosity at thermal conversion reactions below 360 °C, an increase in the asphaltene content was observed even at low temperature, namely 280 °C. On the other hand, practically useful cracking conversion and viscosity reduction for upgrading was found only at 360 and 400 °C. The viscosity measured at 40 °C could be reduced by three orders of magnitude from 3720 Pa·s in the feed to 2 to 5 Pa·s in the product. The density of the product was not reduced by much, despite vacuum residue cracking conversions of 33 % at 360 °C and 45–47 % at 400 °C before the onset of coking. The liquid yield was 88–89 %. Vacuum residue conversion at 360 °C increased linearly with time, which indicated zero order kinetics. Vacuum residue conversion at 400 °C was non-zero order. This study showed that thermal cracking at 360–400 °C is better described by a rate equation with two terms. Temperature dependent differences in the maximum conversion before onset of coking, and the kinetic description of vacuum residue conversion, indicated that the equivalent residence time (ERT) description of visbreaking was an inadequate approximation of thermal conversion at 400 °C and below.

• Subjects / Keywords

  • Thermal conversion
  • Bitumen
  • Deasphalted
  • cracking

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3XK8561C

• License

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