Effect of volatile matter and thermoplastic components on softening and swelling behavior in carbonization of coal

To investigate the dominant factors that affect carbonization process of coal, behaviors of caking and low-quality coals (i.e., non- or slightly caking coal) during carbonization were examined. The release of volatile matter of pulverized coal samples in carbonization was evaluated using thermogravimetric analyzer, and the fluidity of coal particles was measured by the Gieseler plastometry method. Furthermore, a single coal particle was heated under a nitrogen atmosphere, and the images of the samples were acquired. From the images, swelling onset temperature, maximum swelling temperature, and maximum swelling ratio were evaluated. The carbonized coal particles were imaged using X-ray Computed Tomography (CT), and their internal structure was investigated. Although the release behavior of volatile matter, fluidity, and swelling of each coal were different according to kinds of coal, many of the parameters associated with those behaviors would correspond to coal rank. Combined with the carbonization behavior of coal and pore structure of carbonized coal, the amounts of thermoplastic components and volatile matter may affect the softening and swelling of coal particles.