A Mechanistic Approach To Characterize Coal Heterogeneity in Predicting High-Temperature Volatile Matter Yields

Abstract

The reflectance distribution of coal (the reflectogram), which shows the heterogeneity of coal, can be represented by several reflectance bins. In this paper, in considering the heterogeneity of coal, coal is regarded as a mixture of particles. Each particle is characterized by reflectance and is treated as being homogeneous, without considering the intraparticle heterogeneity. The chemical compositions (volatile matter (VM), carbon content (C%), ratio of hydrogen to carbon (H/C)) of a single particle have been estimated from previous works and are used to derive the 13C NMR parameters of this particle. These parameters are input into the chemical percolation devolatilization (CPD) model to predict the high-temperature VM yields of this particle. The total VM yields of the coal can be obtained by a summation of the results of all of the particles. In the experimental portion, the sink−float technique has been used to separate a series of coals into different maceral-rich fractions, which exhibit very different reflectance distributions. The high-temperature VM yields of these samples have been obtained from drop tube furnace pyrolysis experiments at 1400 °C to validate the model. The results from pyrolysis experiments and the single-particle modeling approach show that, under high temperature, the inertinite-rich fraction produces less VM than does the vitrinite-rich fraction of the same coal. The inertinite-rich fraction has a lower Q factor, which is defined as the ratio of high-temperature VM yields and proximate VM, than its vitrinite counterpart. The high-temperature VM yields also have been estimated from bulk properties of coal samples from the CPD model. These estimations do not agree with the experimental data. The model could not be applied to those coals that showed abnormal reflectance features.

Review of 30 Years of Research Using the Chemical Percolation Devolatilization Model

“…Tang et al 37 used a float−sink separation technique to obtain maceral-rich fractions of coals. Some coals had high inertinite fractions.…”

Coal Swelling Model for Pressurized High Particle Heating Rate Pyrolysis Applications

“…However, it appears that the NMR parameters predicted from correlations 26 with the ultimate and proximate analyses yield reasonable swelling trends for the data of Wu et al 2 (see Figure 13). Vitrinite and inertinite contents have also been correlated with carbon and hydrogen content, 38 which may explain why the use of chemical structure features derived from elemental analysis might yield good predictive results for Southern Hemisphere coals.…”