Quantitative characterization of coal properties using bidirectional diffuse reflectance spectroscopy

The 0.3–26 μm (33,000–385 cm−1) reflectance spectra of the <45 μm fractions of a series of coal samples ranging from lignite to anthracite were analyzed in conjunction with compositional information to derive spectral–compositional–structural relationships. The reflectance spectra, particularly in the 1.8–4 μm (5500–2500 cm−1) region exhibit a number of absorption features attributable to both the organic and inorganic components. Quantitative spectral–compositional relationships were found which permit the derivation of properties such as aromaticity, total aliphatic, aromatic content, moisture content, volatile content, fixed carbon abundance, fuel ratio, carbon content, nitrogen abundance, H/C ratio, and vitrinite reflectance. In general, all absorption bands become less intense, and overall reflectance decreases with increasing rank.