Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed
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Ghoniem_Impact of finite.pdf
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Author(s)
Botero, Cristina
Field, Randall
Ghoniem, Ahmed F
Herzog, Howard J.
Date Issued
December 2012
Journal
Applied Energy
Publisher
Elsevier
Citation
Botero, Cristina, Randall P. Field, Howard J. Herzog, and Ahmed F. Ghoniem. “Impact of Finite-Rate Kinetics on Carbon Conversion in a High-Pressure, Single-Stage Entrained Flow Gasifier with coal–CO2 Slurry Feed.” Applied Energy 104 (April 2013): 408–417.
Version
Original manuscript
Abstract
Coal--CO[subscript 2] slurry feed has been suggested as an attractive alternative to coal–water slurry feed for single-stage, entrained-flow gasifiers. Previous work demonstrated the system-level advantages of gasification-based plants equipped with CO[subscript 2] capture and CO[subscript 2] slurry feed, under the assumption that carbon conversion remains unchanged. However, gasification in carbon dioxide has been observed to be slower than that in steam. In view of this, the impact of CO[subscript 2] slurry feeding on gasification kinetics and ultimately on carbon conversion and oxygen consumption in a pressurized, single-stage entrained-flow gasifier processing bituminous coal is studied here using a 1-D reduced order model. Results show that the CO[subscript 2] gasification reaction plays a dominant role in char conversion when the feeding system is CO[subscript 2] slurry, increasing the CO content in the products by up to a factor of two. CO inhibition of the gasification reaction and a higher degree of internal mass transport limitations lead to an up to 60% slower gasification rate, when compared to a system based on coal-water slurry. Accordingly, a gasifier with CO[subscript 2] slurry feed has 15% less oxygen consumption but a 7%-point lower carbon conversion for a given reactor outlet temperature. The gasifier outlet temperature must be raised by 90 K in order to achieve the same conversion as in a water slurry-fed reactor; the peak reactor temperature increases by 220 K as a result. Net oxygen savings of 8% are estimated for a system with a CO[subscript 2] slurry-fed gasifier relative to one with water slurry and the same level of conversion.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
MIT Energy Initiative
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DOI of Published Version
https://doi.org/10.1016/j.apenergy.2012.11.028
