CO2 Gasification Kinetics and Structural Characteristics of Tri-High Coal Char Prepared at Elevated Temperature.

Abstract

The combined effects of surface area, pore structure, degree of graphitization, and number of carbon functional groups on the gasification kinetics of tri-high coal char prepared at an elevated temperature were studied by a thermogravimetric analyzer and various characterization methods [scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) theory, X-ray diffraction (XRD), Raman spectroscopy, and Fourier transfer infrared spectroscopy]. In the kinetic analysis, the CO2 gasification of high-ash coal was not adequately described by the random pore model because ash influenced the char structure during pyrolysis and gasification. Meanwhile, the SEM and BET results indicated the promotion of micropore formation and mesopore expansion of the coal char during pyrolysis. The XRD, Raman, and FTIR results evidenced a significant increase of large aromatic groups during the pyrolysis process, attributable to the cracking of aliphatic groups and the polycondensation of the cracking residues. Overall, the porous structure and aromatic groups of coal char developed during the pyrolysis process improved the CO2 gasification kinetics of the tri-high coal char.