Solid Phase Hydrodynamics of Three-Phase Fluidized Bed Reactors -- A Convective/Dispersive Phenomena
Bibliographic record
Abstract
The objective of this work was to investigate the relative contribution of the convective and dispersive mixing mechanisms to the overall solid phase mixing mechanism for three-phase fluidized bed reactors. Noninvasive Radioactive Particle Tracking (RPT) data were obtained at various operating conditions, reactor diameters and particle systems. The structural wake model was updated and consists of three sub-phases: the particle wake and downflow-emulsion phase following the convective mixing mechanism and the vortex-emulsion phase following the dispersive mixing mechanism.The particle velocity mean and STD increased with the superficial liquid and gas velocity as well as the reactor diameter for each particle phase. Therefore, the extent of mixing increased under these operating parameters. The particle phase's holdup and a new Mixing Mechanism Indicator (MMI), however, exhibited a much more complex trend. For the larger reactor (Dc = 0.292 m), the convective mixing mechanism dominated and at low superficial liquid velocity the contribution of the convective mixing mechanism increased with superficial gas velocity. This trend, however, was reversed when the superficial liquid velocity increased. For the smaller reactor (Dc = 0.10 m), the random movement of the solid dominated. Therefore, the extent of mixing and the mixing mechanism did not follow the same trend. The CFD and the mixing model have to follow both those hydrodynamic properties.Relations to estimate mean and STD particle velocity distribution as well as particle phase holdup were developed. Solid in the established region mainly followed the convective mixing mechanism. Random movement of the solid was mostly observed at the top of the bed, but it was also present in the established region and at the bed bottom. The volume of each region depended on the operating conditions, reactor diameter and particle system. Furthermore, the particle wake expulsion frequency range was similar to the wake shedding frequency found in literature. It is, thus, possible to assume that wake shedding was mainly responsible for the solid exchange between particle phases.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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".