The Physical Parameters of Different Rank Coals Related To Their Degree of Cross-Linking and the Caking Ability

Physical parameters such as true density, porosity, ultrasonic velocity, dynamic elastic modulus, spin concentration, widths of the Lorentzian EPR lines, and maximum optical reflectance were determined for 15 coals of a wide rank and of a wide caking ability. Coals were characterized by carbon content ranging from 83.1 to 94.9 wt % C and by the Roga Index (RI) in the range of 0−76. Single monolithic blocks of these coals were applied for production of the single-coal cokes in the Jenkner's retort furnace. The same physical properties as for coals were also studied for cokes. The physical parameters studied were discussed in relation to the degree of cross-linking and the caking ability of coals. Cokes were found to be characterized by the higher degree of cross-linking than those of initial coals, except for the cokes from the lowest rank coals. The Roga Index was found inversely proportional to the degree of cross-linking of coals. The lowest cross-linked coals exhibited the highest RI values. Optical reflectance was found independent of the degree of cross-linking, unlike the EPR parameters. Both spin concentration and the width of the EPR lines determined in coals decreased with increasing molecular weight per cross-linked unit (Mc). It was found that cokes produced from coals with RI values between 40 and 55 were characterized by elastically isotropic structure.