DETECTION OF WEATHERING IN STOCKPILED COALS BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

The process of natural oxidation of two low-rank coals exposed to the atmosphere for 11 months has been studied by Fourier transform infrare d (FT-IR) spectroscopy. The study was carried out on samples taken at different time intervals and additionally from zones where signs of hi gh oxidation and self-ignition were detected. The aliphatic hydrogen ( 3000-2800 cm(-1)) and oxygen-containing structures (1800-1500 cm(-1)) regions of the spectra were examined by curve-fitting analysis and a s eries of structural parameters based on ratios of integrated absorbanc e areas of curve-fitted bands were established. The aliphatic hydrogen content of samples tended to decrease with increasing time of storage and carboxyl groups only increased slightly under conditions of low p ile activity. When oxidation and self-ignition processes took place, t he structural changes were more significant. Aliphatic structures decr eased drastically and net production of oxygen-containing structures w as observed. Aliphatic hydrogen content evaluated from integrated abso rbance measurements of normalized spectra and the CO/aliphatic hydroge n ratio seemed to be very sensitive in detecting signs of weathering e ven at very low levels of activity.