Analysis of coal by diffuse reflectance near-infrared spectroscopy

Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) in the near-infrared (NIR) range is a technique able to determine moisture, ash, volatile matter, fixed carbon, heating value and percentage of carbon, hydrogen, nitrogen and sulfur in coal samples. In this paper, spectra from 142 coal samples of different origins were acquired in absorbance, reflectance and Kubelka-Munk units. Physical effects due to particle size were minimized after applying different pre-treatments to each spectra. The resultant spectra were correlated to the above mentioned coal properties using partial least squares regression (PLS). Moreover, a principal component analysis (PCA) of the full set of samples suggested the use of more homogeneous sample sets. The results obtained for a homogeneous set improved the prediction ability of the procedure.