Development and application of a correlation of 13C NMR chemical structural analyses of coal based on elemental composition and volatile matter content

C-13 NMR spectroscopy has been shown to be an important tool in the characterization of coal structure. Important quantitative information about the carbon skeletal structure is obtained through C-13 NMR spectral analysis of coal. Solid-state C-13 NMR analysis techniques have progressed beyond the mere determination of aromaticity and can now describe features such as the number of aromatic carbons per cluster and the number of attachments per aromatic cluster. These C-13 NMR data have been used to better understand the complicated structure of coal, to compare structural differences in coal, tar, and char, and to model coal devolatilization. Unfortunately, due to the expense of the process, extensive C-13 NMR data are not available for most coals. A nonlinear correlation has been developed that predicts the chemical structure parameters of both U.S. and non-U.S. coals generally measured by C-13 NMR and often required for advanced devolatilization models. The chemical structure parameters correlated include (i) the average molecular weight per side chain (Md); (ii) the average molecular weight per aromatic cluster (M-cl); (iii) the ratio of bridges to total attachments (p(0)); and (iv) the total attachments per cluster (sigma + 1). The correlation is based on ultimate and proximate analysis, which are generally known for most coals. C-13 NMR data from 30 coals were used to develop this correlation. The correlation has been used to estimate the chemical structure parameters generally obtained from C-13 NMR measurements, and then applied to coal devolatilization predictions using the CPD model and compared with measured total volatiles and tar yields. The predicted yields compare well with measured yields for most coals.