Evolution of carbon dioxide storage properties of coal during pyrolysis: Implications for geological carbon dioxide sequestration after underground coal gasification
Bibliographic record
Abstract
Deep unmineable coal seams are a potential target for geological sequestration of greenhouse gases (GHGs). The primary objective of this study is to evaluate the effects of thermal treatment of coal on coal properties and CO2 storage. Specifically, CO2 adsorption isotherms were measured for Mannville coal samples (western Canada) after heating the samples over a wide temperature range (30-1000°C) in order to understand how CO2 storage capacity changes with distance from an in-situ gasification chamber. A controlled-atmosphere (N2) furnace was used for thermal treatment (pyrolysis) of the Mannville coal samples at 300 °C, 700 °C and 1000 °C. The furnace enabled pyrolysis of a large sample mass (75 grams), which was required for the CO2 sorption tests. In addition to high-pressure, high-temperature (HPHT) CO2 adsorption, various post-pyrolysis characterization methods were performed to evaluate the impact of pyrolysis. The CO2 adsorption isotherms for the thermally-treated Mannville coals were measured using a HPHT gas adsorption apparatus at 55 °C (simulated reservoir temperature) and at pressures up to 2610 psi. Complementary characterization methods, including low-pressure gas (N2/CO2) adsorption (LPA) and helium porosity, were combined with HPHT CO2 adsorption testing to evaluate the impact of pore network attributes (e.g., surface area, porosity) on CO2 adsorption capacity. Maximum vitrinite reflectance (Ro) increased from % 0.71 to % 5.67 after pyrolysis from 300 °C to 1000 °C, suggesting that the pyrolysis experiments were successful in artificially increasing the rank (thermal maturity) of the coal. Density Functional Theory (DFT) model was used to derive pore size distributions from LPA data after each thermal treatment step. After pyrolysis at 700 °C, a significant amount of microporosity was generated in the coal, yielding the highest CO2 adsorption capacity (1.98 mmol/g). In contrast, after pyrolysis at 1000 °C, the amount of mesoporosity increased, leading to a decrease in surface area, and a reduction in CO2 adsorption capacity (from 1.98 mmol/g to 1.82 mmol/g). A direct relationship between microporosity and CO2 adsorption capacity of the coal was observed (excluding data at 300 °C). Coal exposed to 700 °C can adsorb twice the amount of CO2 compared to untreated coal.
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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".