Crystallization and Fracture: Product Layer Diffusion in Sulfation of Calcined Limestone
Bibliographic record
Abstract
Sintered samples of calcined limestone were sulfated for extended times in a differential reactor to study the reaction kinetics after formation of a product layer. The reaction rate was controlled by product layer diffusion, except during the initial period. The product layer diffusivity increased with temperature, but decreased with increasing SO 2 concentration. The diffusivity not only depends on current conditions, but also on previous conditions that led to the formation of the layer. The results support a crystallization and fracture model and a hypothesis that the rate-limiting mechanism changes from inward gas diffusion control in the early stages to outward ionic diffusion control after formation of a continuous product layer, a change attributed to the need for the reaction to do mechanical work to displace the product layer and make room for increased solid volume at the CaO/CaSO 4 interface. A criterion is established to determine whether a product layer can be fractured. A gas containing 2250 ppm SO 2 at 900 °C cannot fracture a product layer as thick as 233 nm, while such a layer can be fractured by steam at 250 °C and a partial pressure of 1 bar.
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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) | 0.001 | 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".