THE INFLUENCE OF RANK UPON CHAR MORPHOLOGY AND COMBUSTION

This study is based upon nine vitrinite-rich coals of increasing rank (subbituminous to anthracite) and investigates the relationships between coal structure, rank, char formation and the combustion of char using a laboratory-based entrained flow reactor at 1273 K, providing a rapid rate of heating estimated to be 10(4) K s-1. Results show that it is impossible to ascribe any one char type to vitrinite. Char characteristics such as optical texture, the degree of vesiculation, char wall porosity, CO2 surface area and thermoplasticity are related to aspects of the molecular structure of the original vitrinite and vary as a function of rank. Those char characteristics in turn influence the char burn-out during combustion at 1273 K. The study discusses the relevance of both inverse and normal relationships between the elemental oxygen of the parent vitrinite-rich coal and the generation of cenospheres and network chars, respectively, such relationships possibly provide experimental evidence for current theories on the pyrolysis of coal and the formation of char.