Development and Application of a Correlation of ¹³C NMR Chemical Structural Analyses of Coal Based on Elemental Composition and Volatile Matter Content

Abstract

13C 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 13C NMR spectral analysis of coal. Solid-state 13C 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 13C 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 13C NMR data are not available for most coals. A non linear correlation has been developed that predicts the chemical structure parameters of both U.S. and non-U.S. coals generally measured by 13C NMR and often required for advanced devolatilization models. The chemical structure parameters correlated include (i) the average molecular weight per side chain (M δ ); (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 (σ + 1). The correlation is based on ultimate and proximate analysis, which are generally known for most coals. 13C 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 13C 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.

Process Development and Reactor Analysis of Coal Pyrolysis to Acetylene in Hydrogen Plasma Reactor

“…The CPD model is based on the chemical structure of coal and treats coal as a lattice of aromatic rings and models coal thermal decomposition approximating the breakdown of the macromolecular network. In this paper, the chemical structure parameters are obtained by nonlinear correlations (Genetti et al, 1999) between data from chemical analysis of coal and those from 13 C NMR analysis. The proximate and ultimate analysis of the coal used in the 2 MW pilot plant is shown in Table 3.…”

Modelling the relationship between carbon aromaticity of lignite pyrolysis chars and the process temperature with petrographic parameters

“…Furthermore, with a variation between 0 and 6% its range of tolerance is even smaller than the error of the 13 C CP-MAS NMR being between 2 and 15 mole carbon % as estimated by Snape et al (1989). Genetti et al (1999) applied the carbon content as described in equation (5). But in comparison to the measured aromaticity values it becomes apparent, that this method results in considerably too low values for both raw coal and pyrolysis residues.…”

“…So, later on further research by Retcofsky and Link (1978) revealed that this method results in too high carbon aromaticity values. Apart from van Krevelen (1953), further work was done for calculating the carbon aromaticity by Jones et al (1986), Carr and Williamson (1989), Rentrop (1989), Maroto-Valer et al (1994), Mazumdar (1999) and Genetti et al (1999). All of their models have the advantage that they were verified by NMR-spectroscopy.…”

Numerical simulation of MILD (moderate or intense low-oxygen dilution) combustion of coal in a furnace with different coal gun positions

“…Through the C NMR spectroscopy is possible to obtain the chemical structure of the coal [16]. The CPD model requires five input parameters, which can be determined from the C NMR spectroscopy, which is a very complex procedure.…”

“…Schaffel et al [9] utilized the IFRF experimental data in order to characterize both devolatilization and charcombustion processes, and thus determine the five parameters of the CPD model. Since this procedure are expensive and time consuming, in this work has been used the Genetti correlations [16], which correspond to a series of non-linear correlations able to estimate the five parameters. These parameters are: Mdel, Mcl, σ+1, p0 and c0.…”