ANALYSIS OF THE ARGONNE PREMIUM COAL SAMPLES BY THERMOGRAVIMETRIC FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

We have developed a TG-FTIR instrument that combines thermogravimetric analysis (TGA) with evolved product analysis by Fourier transform infrared (FT-IR) spectroscopy. FT-IR analysis of evolved products has advantages over mass spectroscopy in allowing analysis of very heavy products and over gas chromatography in speed. This paper describes the most recent improvements in the apparatus and presents its application in characterizing the Argonne premium coal samples. The TG-FTIR apparatus for pyrolysis, oxidation of pyrolysis products, and oxidation of the sample is described. To analyze coal, a sequence of drying, pyrolysis, and combustion is employed to obtain proximate analysis, volatile composition, volatile kinetics, and relative char reactivity. Pyrolysis results are presented for the eight Argonne coals, several demineralized coals, and two oxidized samples of Pittsburgh Seam coal. A kinetic analysis was applied to species evolution data collected at several different heating rates. There is a systematic variation in rate with rank. The rate for tar evolution from Pittsburgh Seam coal is in good agreement with that of Burnham et al. using a similar set of data. Analysis of the amounts of evolved products also show a systematic variation with rank consistent with the coal’s elemental and functional group comositions. Postoxidation of the volatile products has been successful in providing elemental composition information on the volatile products as well as showing the evolution of H2, which is not infrared active, and H2S (in the postoxidized SO2 profile), which is a weak infrared absorber. Oxidation of the char yields an ash amount as well as two measures of the char’s reactivity, the oxygen absorbed by the char and the temperature at which significant oxidation of the char occurs. © 1990, American Chemical Society. All rights reserved.