The use of magnetic resonance parameters in the characterization of premium coals and other coals of various rank

Abstract Eight premium coals and twelve Polish coals were investigated by means of e.s.r., 1 H n.m.r., 13 C CP-n.m.r. and dynamic nuclear polarization (DNP). The following parameters were studied: the concentration of free radicals, N e ; the 1 H Zeeman relaxation rate, W Z H ; the 1 H rotating-frame relaxation rate, W ρ H ; the 1 H DNP enhancement factor, P H ; and the CP-determined carbon aromaticity, ( f a ) CP . The results generally agree with the patterns established in an earlier study of the same parameters of 60 other coals. The following relationships have been found between the above parameters and parameters obtained via proximate and ultimate analyses: N e versus percentage volatile matter, W Z H versus oxygen content, W ρ H versus N e , P H versus carbon content and ( f a ) CP versus percentage volatile matter. For the premium coals it was observed that exposure to air prior to degassing resulted in irreversible changes in N e , W Z H and P H .