Petrographic observations of Gieseler semi-cokes from high volatile bituminous coals

Semi-cokes from Gieseler plastometry experiments on high volatile bituminous coals conducted under both ASTM 2639 (3 degrees C/min temperature ramp) and isothermal conditions, the latter run at both varied temperatures and at fixed times at a single temperature, were studied for their optical texture. There is some relationship between semi-coke texture and coal rank, with semi-cokes from higher rank coals showing a greater tendency towards the development of a Bow texture and, in certain cases, the progression from isotropic to anisotropic semi-coke. Increases in both time and temperature promote a similar tendency towards the development of a how texture and, in the case of an eastern Kentucky coal, the progression from isotropic to anisotropic semi-coke. Vitrinite types with a greater initial organic sulfur content exhibit flow textures at shorter times than comparatively low-sulfur vitrinite. (C) 1999 Elsevier Science Ltd. All rights reserved.