Bibliographic record
Abstract
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%.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".