Some new insights into the kinetic compensation effect in different diffusion-controlled domain for char-CO2 gasification

Kaiwei Sun, Meiqin Cui, Bo Zhang, Yongjun Li, Ping Geng, Peng Fu, Weiming Yi and Yan Zhang

Renewable Energy, 2023, vol. 217, issue C

Abstract: The CO2 gasification reaction of lignite and coffee char are conducted at 1098–1173 K and 0.025–0.1 MPa CO2 via thermogravimetry analysis (TGA). The calculation methods of the activation energy and pre-exponential factor are further compared and analyzed. The activation energy and pre-exponential factor in the chemical-controlled domain, the external diffusion-controlled domain and the bed diffusion-controlled domain are measured to investigate the relationship between the kinetic compensation effect and mass transfer limitations. Results reveal that the normalized power-law rate equation can provide reliable kinetic parameters due to PCO2n ≠ constant (PCO2n represents the partial pressure term) at different temperatures and f(X) ≠ constant (f(X) represents the mechanism function term) at different char conversion. In the chemical-controlled or the external diffusion-controlled domains, coffee grounds char (CGC) and lignite char (LC) exhibit similar activation energies and pre-exponential factors in the char conversion range of 0.2–0.8. In the bed diffusion-controlled domain, the activation energy and pre-exponential factor increase and then decrease during the reaction process. An evident kinetic compensation effect was observed between E and ln(A0) throughout the conversion process with bed diffusion and among data from experiments with and without diffusional limitations, showing its dependence on mass transfer limitations.

Keywords: Char gasification; Activation energy; Pre-exponential factor; Mass transfer limitation; Kinetic compensation effect (search for similar items in EconPapers)
Date: 2023
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Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:217:y:2023:i:c:s0960148123012703

DOI: 10.1016/j.renene.2023.119355

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