Structural analysis of chars generated from South African inertinite coals in a pipe-reactor combustion unit

• Published in: Fuel processing technology Vol. 92; no. 4; pp. 743 - 749
• Main Authors: Malumbazo, N., Wagner, N.J., Bunt, J.R., Van Niekerk, D., Assumption, H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2011; Elsevier
• Subjects: 13C Solid State NMR; Applied sciences; Aromaticity; atmospheric pressure; carbon; coal; Coal structure; combustion; drying; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fourier transform infrared spectroscopy; Fuels; nitrogen; nuclear magnetic resonance spectroscopy; Pyrolysis; stable isotopes; Structural ordering; temperature; X-ray diffraction; 13C Solid State NMR; Pyrolysis; Coal structure; Aromaticity; Structural ordering; Combustion; Inertinite; Infrared spectrometry; Char; Ash; Nuclear magnetic resonance; X ray diffractometry; Bituminous coal; C Solid State NMR; Structural analysis; Drying
• ISSN: 0378-3820; 1873-7188
• DOI: 10.1016/j.fuproc.2010.09.009

An inertinite-rich medium rank C bituminous South African coal was utilized to generate chars in a pipe-reactor combustion unit. This unit generates chars at atmospheric pressures and temperature was controlled with N 2 to a maximum of 1250 °C. Chemical structural changes were investigated at different reaction zones identified in the pipe-reactor combustion unit. A combination of FTIR, XRD and Solid State NMR experiments were used to characterize the coal/char/ash fractions produced in the reactor. These techniques revealed that the coal structure becomes disordered in the drying zone as well as in the beginning of the pyrolysis zone in the reactor. As the temperature increases towards the base of the reactor the coal structure becomes more ordered and well aligned until char is formed and converted. Major structural changes were seen to occur in the drying to the pyrolysis zones. Structural changes within the molecular core were observed with FTIR and XRD results obtained from samples taken from the drying zone to the combustion zone. However, 13C CP/MAS and dipolar dephasing experiments were not able to corroborate these structural changes of the coal/char/ash fractions produced in the reactor occurring in the reduction and combustion zones.