Viscosity and Stability of Visbroken Fractionated Oils

One challenge facing Western Canada is the limited capacity to transport bitumen through pipelines. Bitumen has a high density and viscosity that both exceed pipeline specifications. It must be diluted for transport, but the diluent occupies a capacity that would otherwise be available for the bitumen. One possible solution is to reduce the amount of diluent by decreasing the density and viscosity of the bitumen through a combination of de-asphalting and visbreaking processes. Visbreaking reduces the viscosity of the oil, however, if carried too far, this process can destabilize the oil (cause asphaltene precipitation and coke formation). De-asphalting decreases the oil density and can allow more intensive visbreaking without destabilizing the oil. These processes can be applied to both bitumen and vacuum bottom feeds. In all cases, it is necessary to predict the product properties and stability to optimize the process design. This thesis aims to measure and model the effect of visbreaking on the density, viscosity, and stability of a bitumen, a vacuum bottom, and a de-asphalted oil. Each oil was visbroken at two different severities (combinations of temperature and residence time) in an in-house continuous visbreaker. The feeds and their products were separated into distillates, saturates, aromatics, resins, and asphaltenes, and the properties (molecular weight, density, viscosity, and solubility) of each fraction were measured. Previously developed correlations for molecular weight, density model parameters, viscosity model parameters, and solubility parameters were updated. The density of the oils was determined with a volumetric mixing rule and their viscosity with the Expanded Fluid viscosity model. Their stability versus asphaltene precipitation was determined with the Modified Regular Solution phase equilibrium model. The average deviation of the modelled densities and viscosities were 2 kg/m³ and 19%, respectively. The average deviation in the modelled onset of asphaltene precipitation (solvent content at which precipitation first occurred) was 4.4 wt% n-heptane. The average deviation of the modeled asphaltene yield (mass of precipitated asphaltenes divided by the mass of feed oil) was 2.3 wt%.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Engineering – Chemical & Petroleum

Grantor dc:publisher.institution

Schulich School of Engineering

Year dc:date.issued

2021

Author dc:creator

• Abbaspourmehdiabadi, Amirabbas

Advisor dc:contributor.advisor

• Yarranton, Harvey

Committee members dc:contributor.committeemember

• Pereira Almao, Pedro
• Sundararaj, Uttandaraman

• Visbreaking, Modified Regular Solution, Expanded Fluid, Viscosity, Phase behavior, Asphaltenes

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

eng

DOI

http://dx.doi.org/10.11575/PRISM/38799

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/113335