Straw combustion in circulating fluidized bed at low‐temperature: Transformation and distribution of potassium
Bibliographic record
Abstract
Abstract Potassium in straw is relatively high and exists mainly as readily available potassium (K r ). The release and transformation of the K r during biomass combustion mean a decrease or loss of potash fertiliser value. The purpose of this work is to quantify the transformation and the distribution of the K r under conditions that can obviously reduce the loss of it, and then to try to offer some suggestions for new biomass projects. A pilot‐scale circulating fluidized bed (CFB) combustor (0.5 MW th ) has been applied to combust rice straw. The combustion temperature was kept at a low level (lower than 700°C) to reduce the transformation of potassium. The K r and the total potassium (K t ) in the rice straw, the bottom ash, and the flyash were determined after chemical fractionation and wet acid digestion, respectively. The mass balance of the biomass ash, the K r and the K t in stable operation were quantified. The experimental results showed that the flyash accounted for more than 95% of the total straw ash. The flyash contained around 92% of the K t and 86% of the K r of the straw. In the flyash about 3% of the K r of straw was transformed to unavailable potassium (K u ) during combustion. On the basis of the obtained results, four suggestions that reduce the loss of the K r are given for the better development of biomass‐fired power plants. Le potassium contenu dans la paille est relativement élevé, environ 1 à 3% du poids à sec, et existe principalement sous la forme de potassium rapidement utilisable (K r ). La libération et la transformation du Kr pendant la combustion de biomasse à température élevée entraîne une diminution ou une perte de valeur de l'engrais potassique. Le but de ce travail est de quantifier la transformation et la répartition du Kr dans des conditions qui peuvent visiblement en réduire la perte, et par la suite essayer d'apporter quelques suggestions pour les nouveaux projets de biomasse dans l'optique de la protection de la durabilité de l'agriculture. Une chambre de combustion à lit fluidisé circulant (CLFC) à l'échelle pilote (0,5 MWth) a été utilisée pour brûler la paille de riz, biomasse agricole la plus commune. La température de combustion a été maintenue à un bas niveau (en dessous de 700) afin de réduire la transformation du potassium. Le Kr et le potassium total (K t ) contenus dans la paille de riz, les cendres résiduelles, et les cendres volantes ont été déterminés après le fractionnement chimique et la digestion à l'acide humide, respectivement. Le bilan de masse de la cendre de biomasse, le Kr, et le Kt en régime de fonctionnement stable a été quantifié. Les résultats expérimentaux ont démontré que les cendres volantes constituaient plus de 95% de la totalité des cendres générées par la paille. Les cendres volantes contenaient environ 92% du teneur en Kt et 86% du teneur en Kr de la paille. Environ 3% du teneur en Kr de la paille a été transformé en potassium inutilisable (Ku) dans les cendres volantes pendant la combustion. Sur la base des résultats obtenus, quatre suggestions résultant dans la réduction de perte du Kr sont proposées pour le développement de centrales d'énergie alimentées à la biomasse. Can. J. Chem. Eng. © 2010 Canadian Society for Chemical Engineering
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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".