Coke formation during thermal cracking of a heavy crude oil
Notice bibliographique
Résumé
A pseudo-mechanism for the production of coke during the thermal cracking of a Colombian heavy crude oil was proposed based on thermal cracking experiments carried out at TGA and at horizontal tube furnace at atmospheric conditions. In-situ combustion (ISC) is a thermal method that improves the recovery of heavy crude oils and involves complex phenomena such as heat and mass transfers, low-temperature oxidation of the liquid phase (LTO), and cracking reactions that yield coke, a carbonaceous residue that, after high-temperature oxidation (HTO) produces the heat that reduces the oil viscosity increasing the recovery factor. During cracking experiments, Ottawa sand was mixed with crude oil, or with a mixture of maltenes and asphaltenes extracted from that oil, and placed under nitrogen atmosphere and heated at 2oC/min up to di_erent reaction temperatures (300oC, 350oC, 400oC and 450oC) at atmospheric pressure conditions. Even tough atmospheric pressure conditions is not a realistic condition as oil reservoirs operate above atmospheric pressure, this study as part of a bigger project to study ISC it was the _rst that develop a setup and a methodolody able to study ISC reactions. After the _rst approximation that this study made, further work will be carried out to study ISC process at more realistic conditions. This study found that the main cracking products were volatiles that could be condensables and non-condensables and a solid residue. Proximate, elemental, GC-MS and SIMDIS analysis were performed to establish the composition of the cracking products, and to determine the advance in the cracking reactions. During cracking experiments each oil fraction yielded lower- and heavier-molecular weight products. e.g. maltenes yielded gas (mainly composed by methane CH4), distillables (a condensable fraction with maximum 18 carbons), low-molecular-weight maltenes (LMWM, a condensable fraction with maximum 28 carbons, that results from the cracking of maltenes and asphaltenes), and asphaltenes. Whereas asphaltenes leaded to coke formation and to LMWM and gases. The proposed pseudo-mechanism considers the formation of lower- and heavier molecules, separates the evaporation process from the thermal cracking, and proposed new pseudocomponents such as Maltenes* that represents the maltenes fraction after the evaporation process and the one available for thermal cracking, and LMWM that is an upgraded cracking product of the cracking of maltenes* and asphaltenes that had a yield of 0.28 g/gtot. Furthermore, the proposed pseudo-mechanism proposes kinetic parameters for the thermal cracking of a Colombian heavy crude oil under in-situ combustion conditions at atmospheric pressure. The kinetic parameter were optimized by minimizing the sum of square error (SSE) between the experimental and calculated yields. A good coe_cient of determination was obtained, (R2=0; 97), using _rst order kinetic parameters. The physical interpretation of the value of kinetic parameters is complicated given the rather empirical approach used to find the kinetic parameters, it is important to note that most parameters in particular activation energies have values typical for chemical-controlled process, exceptions to this are the activation energies 26.4 and 9760 kJ/mol that are too low and too high that involve the decomposition of asphaltenes and are accompained by very low pre-exponential factor.Future work may focus on reducing the empirical nature of this mechanism.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| 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 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
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 ».