Dynamic Elemental Thermal Analysis: A technique for continuous measurement of carbon, hydrogen, oxygen chemistry of tar species evolved during coal pyrolysis

摘要

A novel technique is described which provides quantitative and continuous analysis of light gas and condensable tar components as they are evolved in terms of carbon, hydrogen and oxygen. The technique has also been used to directly characterise the total tar sample in terms of carbon distribution and boiling point. It has been found that changes to the dynamic tar-H/C ratio correspond well with particular temperatures measured by Geiseler Plastometer for softening, maximum fluidity and re-solidification. This technique can enhance the chemical understanding of mechanisms occurring during de-polymerisation and cross-linking of coal (i.e. metaplast development and the transfer of hydrogen) while also monitoring tar evolution. A tar collection and re-vaporisation method provides a means of identifying tar groups that contribute towards the metaplast phase and temperatures at which they evolve. Both methods are unique in studying chemical aspects of coal and tar behaviour with heating, in a field based on thermo-physical techniques (e.g. H~1 NMR, high temperature rheology, Geiseler plastometry, dilatation). Overall, the Dynamic Elemental Thermal Analysis (DETA) technique can give new insight into the fundamental mechanisms prevalent in coal pyrolysis and provides quantitative chemical assessment of tar nature (i) during the heating of coal and (ii) as a final (total) condensed product.