Preparation and Characterization of Lime/Coal Ash Sorbents for Sequential CO<sub>2</sub> and SO<sub>2</sub> Capture at High Temperature
Bibliographic record
Abstract
Extensive research has been done on Ca-based sorbents as a promising way to capture CO2 and SO2 from power plants. Considerable effort has also been directed toward maintaining sorbent activity by means of sorbent modification to deal with activity decay with repeated CO2 capture cycles. Based on the principle of “treating waste with waste” and inspired by the idea that a pozzolanic reaction can enhance the surface area, this paper presents a method of hydrothermal synthesis of lime and coal ash. A small amount of CaSO4 or NaOH was added during the hydration process, and the mixture was stirred for several hours at about 90 °C. The synthesized samples were then characterized by scanning electron microscopy, nitrogen adsorption/desorption spectroscopy, and X-ray diffraction. The activity of the synthesized sorbent for CO2 and SO2 capture were then tested in a thermogravimetric analyzer. The treated samples demonstrate longer-lasting performance for CO2 cyclic capture, albeit with a slightly reduced capture ability compared to pure lime in the first few cycles due to their lower CaO content (25–81% versus 98%). The sample with a lime/ash mass ratio of 45:5 showed higher CO2 capture ability after three cycles and much greater stability in terms of its activity. The main product of the pozzolanic reaction is CaSiO3, which has a network structure, whose development is related to the ratio of CaO/coal ash, hydration duration, and the amount of CaSO4 and NaOH additives. After high temperature calcination, a new phase, namely Ca3Al2O6, is believed to serve as a skeleton preventing sintering in repeated capture cycles. After experiencing multiple cycles, the synthesized sorbents also have a high SO2 capture capacity. A small amount of added NaOH decreases the cyclic CO2 carrying capacity of the synthesized sorbent but enhances the SO2 carrying capacity dramatically. The explanation for this is that the sulfation reaction is controlled not only by gas diffusion but also by solid-state ion diffusion. Na+ ions generate more crystal lattice defects which can accelerate the ion diffusion rate in the product layer and consequentially enhance overall SO2 carrying capacity.
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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".