The mechanism of the carbon dioxide-carbon reaction

Gadsby, J.; Long, Frank; Sleightholm, P.; Sykes, Keith

doi:10.1098/rspa.1948.0051

Cited by 68 publications

(10 citation statements)

References 3 publications

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“…[11,12,15,19]), CO has been reported to have a stronger effect than H 2 [48,49]. This trend is correctly reproduced by the kinetic expression used in this study, as shown in Figure 8, where the predicted inhibitory effect of CO and H 2 are compared at different temperatures for a fixed partial pressure of the gasifying agents.…”

Section: Co Inhibitionsupporting

confidence: 64%

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Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed

et al. 2013

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Coal-CO 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 2 capture and CO 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 2 slurry feeding on gasification kinetics and ultimately on carbon conversion and oxygen consumption in a pressurized, single-stage entrained-flow gasifier processing Illinois 6 coal is studied here using a 1-D reduced order model. Results show that the CO 2 gasification reaction plays a dominant role in char conversion when the feeding system is CO 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 2 slurry feed has a 7%-point lower carbon conversion for a given outlet temperature. The gasifier exit temperature must be raised by 90K in order to achieve the same conversion as in a water slurry-fed reactor; the peak reactor temperature increases by 220K as a result. Net oxygen savings of 8% are estimated for a system with a CO 2 slurry-fed gasifier relative to one with water slurry and the same level of conversion.

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Section: Co Inhibitionsupporting

confidence: 64%

“…Other, more complex, mechanisms which consider additional steps as well as inhibition through different routes such as direct adsorption of the products onto active sites have also been proposed [11][12][13][14].…”

Section: Mechanismmentioning

confidence: 99%

Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed

et al. 2013

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“…A well-accepted Langmuir–Hinshelwood-type reaction model for CO 2 gasification is given as follows: − where C f represents a free active carbon in the porous char matrix, C(O) is a carbon–oxygen complex as the CO precursor, and n is an integer of 0, 1, or 2, while n = 1 is normally used. , The equilibrium of the CO 2 chemisorption and desorption is the origin of the CO inhibition effect. Insufficient mass transfer results in the accumulation of CO in the char matrix and results in the inhibition.…”

Section: Resultsmentioning

confidence: 99%

Re-examination of Thermogravimetric Kinetic Analysis of Lignite Char Gasification

et al. 2019

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Kinetic analysis of CO2 gasification by thermogravimetry was examined employing chars from a Victorian lignite. The gasification of char from the rigorously acid-washed lignite was extremely slow. More than 600 min was required for the complete gasification as a result of a near absence of inherent alkali and alkaline earth metallic (AAEM) species. It was nonetheless necessary to strictly choose the following conditions for eliminating the mass transfer effect: an initial mass of char of <1.3 mg, a particle size of char of <125 μm, and a total gas flow rate of ≥1000 mL standard temperature and pressure min–1. Such requirement arose from the inhibition of non-catalytic gasification by CO within the char particle. On the other hand, the char from the original lignite was gasified much faster than the non-catalytic gasification and completed within 50 min by catalysis of the inherent AAEM species. The measured rate of catalytic gasification was, unexpectedly, independent of the initial char mass and particle size and gas flow rate. This was reasonably explained by no or little importance of CO inhibition in the catalytic gasification. This study has also drawn another important conclusion that the non-catalytic gasification obeyed first-order kinetics with respect to the char mass. The rate constant was steady over the entire range of char conversion, while both the specific surface area and carbon-type distribution of the char varied along with the conversion.

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“…As the temperature increased, the reaction time in the mixture exceeded the time in H 2 Og radually.W hent he gasificationa gents were 30 %H 2 Oa nd 15 %C O 2 + 30 %H 2 O, the reaction times [16,17] It was supposed that the reactionso fc har-H 2 O and char-CO 2 proceeded through different reaction mechanisms at different temperatures.S ome researchers proposed mechanisms to describe char gasification; one of them was the Langmuir-Hinshelwood (L-H) mechanism. [18,19] There were two probable mechanismsfor char gasification in amixture of CO 2 and H 2 O. One assumed that the reactions of char-CO 2 and char-H 2 Oo ccurred on common active sites, whereas the other assumed these two reactionso ccurred on separate active sites.…”

Section: Resultsmentioning

confidence: 99%

Influence of Reactant Atmospheres and Temperature on Mechanism of Gasification of Coal Char Derived from Lignite

Wang

Luo

et al. 2016

Energy Tech

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The structural characteristics and reactivity of char derived from lignite were studied to explore the mechanism of char gasification and existence of a maximum reaction rate under an atmosphere of CO2 and H2O in a pressured thermogravimetric analyzer system. Gasification was carried out at temperatures of 1123, 1173, and 1223 K. When the temperature was below 1173 K, the mechanism of char gasification in the mixture of H2O and CO2 proceeded through the separate active sites assumption, whereas if the temperature was higher than 1173 K, it favored common active sites. The reaction rate increased and then decreased during the remaining time, which was in agreement with the total surface area. The existence of a maximum reaction rate depended highly on the surface area: a larger surface area resulted in a higher reaction rate. The total surface in H2O was the largest and the addition of CO2 inhibited the formation of pores. The reaction of char with CO2 mainly took place on the microporous surface first, and then took place on a mesoporous surface, and the reaction of char with H2O took place on both the micro‐ and mesoporous surfaces simultaneously.

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The mechanism of the carbon dioxide-carbon reaction

Cited by 68 publications

References 3 publications

Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed

Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed

Re-examination of Thermogravimetric Kinetic Analysis of Lignite Char Gasification

Influence of Reactant Atmospheres and Temperature on Mechanism of Gasification of Coal Char Derived from Lignite

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