Hydrodynamic characterization of a Denver laboratory flotation cell
Bibliographic record
Abstract
Gas dispersion in a laboratory Denver flotation cell was characterized by measuring the superficial gas velocity (Jg), bubble size (d b) and estimating the bubble surface area flux, Sb as a function of impeller speed, frother concentration (Dowfroth 250), and solids content (-30mum silica). The cell was operated by self-aspiration or forced air. The air flow rate was measured using a McMillan meter (self-aspiration) and a mass flow meter (forced air). The bubble size was measured by a photographic technique developed at McGill. From repeat experiments, the average relative standard deviation on Jg was ca. 2% and on db was ca. 13%. No effect of location on bubble size was found. In self-aspiration mode Jg increased with impeller speed due to increased suction and decreased with increasing frother concentration and solids content. The effect of frother was attributed to increased recirculation of air as the bubble size was reduced. The effect of solids appears related to sedimentation. Bubble size increased with increasing impeller speed, which was attributed to the increase in Jg. Solids did not affect the bubble size. Bubble size decreased with frother most notably at low concentration then remained almost constant at high frother concentration. The critical coalescence concentration appeared to be close to 5 ppm for the present conditions. The bubble surface area flux Sb increased approximately linearly with impeller speed up to ca. 40s-1. Using forced air the bubble size behaved as expected: it decreased with increasing impeller speed (due to higher shear) and decreasing Jg . The Sb ranged up to ca. 80s-1, higher than values quoted for a laboratory machine. To correspond more closely to industrial cells, operation with forced air is recommended. The use of higher impeller speeds than are commonly used in laboratory testwork will give more closely fit superficial gas velocity found in industrial plant practice.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".