In-Situ Observation of Heavy-Oil Cracking using Backscattering Optical Techniques Open Access
- Other title
- Type of item
- Degree grantor
University of Alberta
- Author or creator
Dinh, David Q.
- Supervisor and department
McCaffrey, William (Chemical Engineering)
Gray, Murray (Chemical Engineering)
- Examining committee member and department
Semagina, Natalia (Chemical Engineering)
Department of Chemical and Materials Engineering
- Date accepted
- Graduation date
Master of Science
- Degree level
An investigation was conducted on heavy oil cracking using polarized hot stage microscopy and laser dynamic backscattering. Both of these in-situ techniques were used to monitor cracking reactions through the use of backscattering. The use of hot stage microscopy resulted in a series of micrographs that were analyzed using the mean grey value (MGV). MGV is a parameter that reflects the average brightness of micrographs taken. Laser dynamic backscattering was also used and reported results using the depolarization ratio (DPR). DPR is the quotient of the parallel and perpendicular components of light after the initial incoming linearly polarized light is backscattered. Both optical techniques allowed for an examination of cracking kinetics, fouling behavior, mesophase onset and the effect of added water.
The activation energies of low conversion cracking for several feeds (Cerro Negro crude oil, Safaniya vacuum residue (VR), Cold Lake VR, Athabasca VR, Gudao VR and Columbian VR), were calculated from several experiments at various temperatures (420°C to 450 °C) using both apparatus.
Mesophase are anisotropic materials that appear as light domains on the micrographs, and were observed for all feeds given sufficient time for reaction. A second type of fouling only observed for Gudao VR and Columbian VR was dark film fouling which appeared as dark deposits and was observed before mesophase onset.
Finally, water in the range of 12.9-23.4 wt% was added to Athabasca VR to investigate if water had any effect on cracking. It was found that the added water introduces phase instability and causes Athabasca VR to exhibit dark film fouling.
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