A novel approach for coal characterization by NMR spectroscopy: global analysis of proton T1 and T2 relaxations

1H NMR spectroscopy is a potentially useful technique for the characterization of coals. It has been shown that it is possible to determine important coal properties (e.g. detailed information on moisture and hydrogen content) from solid state measurements on a low field (20 MHz) NMR instrument. The measurement consists of the combined determination of spin–lattice (T1) and spin–spin (T2) relaxations resulting in a unique response surface. The overall measurement time is approximately 30 min. Appropriate numerical analysis of the relaxation surface, based on a global, nonlinear least-squares fit, results in detailed information about several different types of protons in the coal. Five different classes of proton containing components have been distinguished, characterized and quantitatively determined. Two classes could be assigned to water in the coal and water in the mineral structure. Three classes have been assigned to different types of organic components.