Using Three-Dimensional Image Analysis Techniques To Understand the Formation of the Plastic Layer during the Heating of Australian Coking Coal Blends

摘要

The plastic layer formation is a critical step during coke formation in coke ovens, during which the physical structures of the coal change dramatically. To better characterize the pore structures of the plastic layers, the commercial GeoDict software has been employed in this study to carry out the three-dimensional (3D) image analysis on the two-dimensional (2D) cross-sectional images of plastic layers from two Australian coking coals and their blends. The plastic layer samples were prepared using a laboratory-scale 4 kg coke testing facility and subjected to the Synchrotron micro-computed tomography analysis to obtain the 2D cross-sectional images. The 3D images were then constructed and analyzed using the commercial GeoDict software. The 3D image analysis provided more detailed pore structural information, such as the total void fraction, the number of total and isolated voids, and the pore size distribution. Through the 3D image analysis, the coalescences of the pores in the thermoplastic region during coking have been elucidated. It seems that the blending of high-vitrinite coals in coal blends would result in more large and closed pores during the plastic layer stage. This would increase the chance of pore coalesce and increase the total porosity. With increasing the proportion of the high vitrinite coking coal in the blends, more channel-like types of pores with a large size tended to evolve inside the plastic layers. The 3D image analysis enables the characterization of pore connectivity that was not possible using 2D image analysis.