Oxygen dynamics in smouldering combustion: Impacts on reaction zones and biochar production
Bibliographic record
Abstract
Smouldering has been widely applied as a cost-effective technology for soil remediation and waste treatment. However, its potential as a thermochemical process for producing high-value products (e.g., biochar), remains underexplored. In particular, the mechanisms governing reaction zone dynamics and the competition between oxidation and pyrolysis for biochar production in self-sustained smouldering require further investigation. This study addresses this knowledge gap through: (1) smouldering experiments across a range of inlet oxygen mass fractions, i.e., = 0.02 – 0.23, using a mixture of sand and crushed walnut shell as the fuel bed and (2) various analytical models to predict smouldering and cooling velocities based on energy distribution, leading to self-sustained biochar production. Altogether, this study demonstrates how oxygen strongly influenced key parameters such as smouldering velocity, temperature profile evolution, and energy distribution. The smouldering experiments were self-sustained at ≥ 0.03. By increasing from 0.03 to 0.23, the average smouldering velocity increased from 0.22 to 0.78 cm min -1 , respectively, and the average cooling velocity increased from 0.13 to 0.25 cm min -1 , respectively. Oxygen dilution led to a super-adiabatic condition near ≈ 0.06. At < 0.06 biochar production was achieved due to the limited availability of oxygen, which altered the energy distribution and shifted oxidation reactions behind peak temperatures. Altogether, this study provides valuable insights into key dynamics that further our understanding of smouldering science, which can be used to harness applied smouldering for sustainable production of high-value products like biochar.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".