Notice bibliographique
Résumé
Kraft batch and continuous digesters are used to react wood chips with an alkali based liquor to remove lignin from the wood and release individual pulp fibres for further processing. Current operating strategies rely on contacting chips with liquors of different temperatures and compositions throughout the cook to optimize pulp quality and strength. This requires uniform liquor flow through the chip column. For batch digesters liquor must reach all chips in a timely manner as cooking conditions are changed. For continuous digesters this requires creation of distinct reaction zones (liquor flow zones) in the descending chip mass where effective chipliquor contacting is made. However, recent findings have shown that the liquor flow is likely non-uniform, particularly in larger digesters. Indications of this in continuous digesters include corrosion in the lower digester, temperature non-uniformity around the vessel circumference, and variation in kappa number produced as a function of time. A key parameter affecting liquor flow is the flow resistance through the chip bed as a function of operating conditions. In order to understand this, pressure drop was measured as a function of superficial velocity, void fraction, kappa number, and compacting pressure. White spruce chips were used in this study. The chips were characterized and cooked into four different furnishes defined as follows: 100% accepts, 87.5% accepts + 12.5% pins, 75% accepts + 25% pins, and 100% pins. The main results of these experiments are as follows. First, chips are more easily compressed as the lignin content (kappa number) of the chips decreases. The void fraction of the chip column decreases with decreased kappa number and increased compaction force applied to the chip column. Second, the flow resistance increases with decreased kappa number, increased superficial velocity, and increased compacting pressure. Furthermore, pressure drop was a function of the particle size distribution of the chips. The addition of pin chips to the accept chips could dramatically increase the pressure drop in the chip column. Indeed a mixture of chip types (75% accepts + 25% pins; 87.5% accepts + 12.5% pins) had a pressure drop greater than either pure pin or accept chips alone. Third, it was found that while a modified Ergun equation (according to Harkonen (1987)) could be used to correlate our experimental data, the predicted constants of Ri and R2 were larger than those predicted by the Harkonen equation and differed depending on the chip mixture and kappa number. Further, the use of d.32 (Sauter mean diameter of particle) for the chip particle size distribution did not permit the pressure drop to be correlated by the Ergun equation with constant values of A and B. These difficulties are likely due to the compressibility of the chip column, which is not accounted for in this analysis.
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 | 0,001 | 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 ».