Evidence for two-site model of char gasification by carbon dioxide

A new method for the measurement of solid fuel reactivity towards carbon dioxide has been developed. This new method takes into account high-pressure and temperature effects. Three devolatilized carbonaceous materials have been used in experiments: chars derived from lignite, bituminous coal and blast furnace coke. Processes were carried out at temperatures of 800, 850 and 900°C and pressures of 1.52, 2.5 and 3.4 MPa. Analysis of the product gas composition was carried out with the maximum degree of conversion of CO 2 (a m ) proposed as a representative reactivity parameter. Arrhenius and Eyring relationships have been analyzed, and values of the activation energy and activation volume have been calculated.

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“…For the non-catalytic reaction according to the LangmuirHinshelwood (L-H) mechanism, the kinetic equation most often proposed is [25][26][27]:…”

Section: Gaseous Phase Analysismentioning

confidence: 99%

The Boudouard–Bell reaction analysis under high pressure conditions

Mianowski

Robak

Tomaszewicz

et al. 2012

J Therm Anal Calorim

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“…Recent studies on CO 2 gasification confirmed that the kinetic description of the process based on the composition of gaseous products is more complicated when compared with one based on the composition of a solid phase [6,7,28]. Three typical relations of [CO] versus time depending on temperature and relationships between kinetic constants of the reactions are shown in Fig.…”

Section: Short Summarymentioning

confidence: 99%

“…(4) and (7), the well-known Langmuir-Hinshelwood equation (L-H) can be obtained [4][5][6][7][8][9][10][11][12][13][14][15].…”

Section: Introduction Ergun Considerations and Their Consequencesmentioning

confidence: 99%

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The reactivity of cokes in Boudouard–Bell reactions in the context of an Ergun model

Mianowski

Radko

Siudyga

2015

J Therm Anal Calorim

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In previous studies, a kinetic equation based on the Ergun mechanism and concept presented in 1956 was applied to Boudouard-Bell reactions for granular coke (1-3 mm) in the temperature range T = 1173-1423 K. In contrast to several other works on this subject, the proposed equation was based on only three kinetic constants: k 1 , the rate constant for the Boudouard reaction; k -1 , the rate constant for the Bell reaction; and k 3 , which is related to the oxy-carbon decomposition and CO desorption process. The dependence of these constants on temperature allows certain values characteristic of the aforementioned processes to be calculated, including activation energy of gasification reaction, enthalpy of disproportionation reaction of gasification and activation energy of desorption process. When k -1 [ 0, i.e., the Bell reaction and inhibitory effects occur, the kinetic constant k 3 can be determined using a portion of the experimental [CO] versus time data normalized to the maximum contribution of CO in the outlet gases.

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“…It is widely accepted that the pressure dependence of the gasification rate can be expressed as a Langmuir-Hinshelwood type expression, whether the reaction is catalyzed (e.g., Kapteijn and Moulijn, 1983) or not ); i.e., kl CtPco, r= where C, is total number of active sites, and PCO and PCO are the partial pressures of CO and CO,, respectively. Even though the single-site oxygen exchange mechanism has been questioned 2 (e.g., see Turkdogan and Vinters 1969;Strange and Walker, 1976;Koenig, et al, 1985;Freund, 1986), the experimental results all show that the C-C02 reaction rate varies monotonically with C02 partial pressure.…”

Section: Temperature Programmed Desorption (Tpd)/reduction (Tpr) Ofmentioning

confidence: 99%