Asphaltene Precipitation From Bitumen Diluted With n-Alkanes
Notice bibliographique
Résumé
Introduction Some heavy oil and bitumen production processes involve the precipitation of asphaltenes upon the addition of a paraffinic diluent. For example, in a new oil sands process, a paraffin solvent is used to treat the froth generated in bitumen extraction. The recently proposed VAPEX process is also based on a paraffinic solvent. To optimize these processes, data is required on asphaltene precipitation from heavy oils or bitumens diluted with n-alkanes. In this work, the onset and amount of asphaltene precipitation from Athabasca bitumen were investigated in a PVT cell using three different methods over a range of temperatures and pressures. Results are presented for the precipitation of asphaltenes from the bitumen diluted with nalkanes, including n-heptane, n-pentane, n-butane, and propane. Experimental Chemicals and Materials Two batches of Athabasca coker feed bitumen were obtained from Syncrude Canada Ltd. This oil sand bitumen had been processed to remove water and solids, such as sand and clays, and was ready for upgrading. Table 1 shows the SARA analysis of the two samples. n-Heptane and npentane were obtained from Aldrich Chemical Company and were 99%+ pure. n-butane and propane were obtained from Praxair and were 99.5% pure. PVT Experiments A mercury-free PVT cell was used to study the effect of pressure and temperature on asphaltene precipitation for bitumen-alkane systems. The cell capacity is approximately 100 cm3 and a typical sample size was 35 cm3. The precipitation experiments in the PVT cell were performed using three different methods: the "premixing method", the "heating method", and the "bench-top method". Premixing Method The development and testing of the premixing method is described in detail elsewhere 1,2 and is outlined below. The bitumen was premixed with solvent at a low solvent-to bitumen ratio to reduce viscosity sufficiently to flow the bitumen. The premixed solvent-to-bitumen ratios were 0.51, 0.32, and 0.24 wt/wt for n-heptane, n-pentane, and n-butane, respectively. The bitumen and solvent were premixed in a sample cylinder, sonicated, and shaken for 2 hours for the nheptane- bitumen mixture and for 10 hours for the other bitumen-solvent mixtures. The final solvent-to-bitumen ratio was determined from the mass of solvent in the bitumen plus the mass of solvent initially charged into the cell. Note that a potential source of error is that the premixed bitumen/solvent mixture may not be homogeneous. If the mixture is not homogeneous, the solvent-to-bitumen ratio of the sample displaced into the PVT cell may not be the same as the ratio in the sample cylinder. Before charging the PVT cell, it was first evacuated using a vacuum pump for 10–15 minutes. The PVT cell was then filled with the required volume of solvent. The connecting lines were drained and evacuated once again and the required volume of premixed solvent and bitumen was added to the cell. The contents of the cell were mixed continuously with a magnetic stirrer for 23 hours. The sample was then displaced from the PVT cell to a modified sample bomb.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».