Volatility and Speciation of Mercury during Pyrolysis and Gasification of Five Chinese Coals
Bibliographic record
Abstract
The fate of mercury in coal gasification systems is closely relevant to its transformation in fuel gases and subsequent release into the environment. This paper presents a study of the volatility and speciation of mercury during pyrolysis and gasification of five typical Chinese coals commonly used in gasification stations. Experiments were conducted on a bench-scale fixed bed under atmospheric pressure at final temperatures from 400 to 1200 °C, in 200 °C increments. The mercury concentration in coals ranged from 0.259 to 8.339 μg/g. The gas-phase mercury was analyzed by an atomic fluorescence mercury analyzer according to the Ontario Hydro Method. It was observed that mercury volatility increased monotonically with temperature over 30 min. Hg 0 (g) was the dominant species at most of the temperatures and holding times examined. It was also observed that high temperatures and long times enhanced mercury oxidation. With the temperature increasing from 800 to 1200 °C, Hg 2+ (g) increased from 5% to 35% during pyrolysis, and from 20% to 60% during gasification. The ratio of Hg 2+ /Hg T reached its minimum at 800 °C for one coal (GZA) during pyrolysis, whereas for two other coals (BS and SF) the maximum value of that ratio was higher than the other coals and occurred during high temperature steam gasification at 1200 °C, respectively. The maximum value of the ratio of Hg 2+ /Hg T was achieved during the high temperature steam gasification. Comparative studies on mercury emission under different conditions indicated that the volatility and speciation of mercury may correlate with the halogen concentration in the coals. However, no obvious correlation between Hg 2+ /Hg T and basic oxides or acidic oxides in the ash was observed.
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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 | 0.000 |
| 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) | 0.000 | 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".