Simulation of Structural Relaxation of Coal Aggregates Using the Molecular Dynamics Calculation

摘要

A molecular dynamics (MD) computer simulation method was used to study the structural relaxation behaviors by heat treatment for Upper Freeport coal (Argonne Premium Coal Sample) and its two fractions obtained from solvent extraction and fractionations. The calculation was carried out at 373 ― 723 K, in order to see changes in various properties by heat. For the extract fractions (acetone-insoluble and pyridine-soluble (PS) and pyridine-insoluble and mixed solvent soluble (PI) fractions), the temperature at which the average volume of unit cell discontinuously changed was observed. The DSC thermograms of PS and PI showed a reversible endothermic peak at 623 - 713 K and 673 - 713 K, respectively, corresponding to the temperature ranges in which the structural relaxation was estimated by simulation. While, for the raw coal an irreversible endothermic peak was observed around at 623 K on the DSC thermogram. The simulation suggested that irreversible structural changes have occurred during heating, which results from thermal stabilization of anisotropic structure of the raw coal.