Liquefaction Residues Classification Working Group
|January 11, 2016||Filled under Com III||
Liquefaction is the conversion of coal to liquids and can be carried out in terms of hydrogenation (direct liquefaction), pyrolysis and Fischer-Tropsch synthesis (indirect liquefaction). Thereby, pyrolysis takes a unique position since it is not only an independent method for upgrading of solid fuels, but also the initial step of most conversion processes (e.g. combustion, gasification and even hydrogenation).
Since understanding the very complex pyrolysis behaviour of the different coal macerals enables the possibility of predicting the course and efficiency of the technological pyrolysis process, this know-ledge is of prime importance. A first approach to this can be given by a systematic examination of the micropetrography of solid residues.
In other coal utilization processes, like combustion or gasification, such applied organic petrology is already far advanced and demonstrated its high potential. And even for the hydrogenation process a classification system was developed and published by the ICCP in 1993. But although both processes – pyrolysis as well as hydrogenation – are used to generate liquids from coal in the absence of air, this classification cannot be directly transferred to pyrolysis residues. The reason for that are the highly divergent process conditions between hydrogenation (reactive atmosphere at high pressure with a hydrogen donator) and pyrolysis (inert or reactive atmosphere without any additional reaction agent at relatively low pressures).
Because of that, the published classification systems for hydrogenation residues of the ICCP (1993) should be expanded with a view to classifying the residues of hydrogenation as well as pyrolysis by the same criteria and nomenclature. Thereby, a classification system could be established, which enables the direct comparison of two technological important but very different processes.
The general objective of the Liquefaction Residues Classification Working Group is to investigate the microscopic components of coal liquefaction residues.
For this purpose the following steps should be taken in the course of the WG over a period of three years: (1) To review, all published classification systems for solid process residues, including that of the ICCP of 1993, (2) to describe the optical appearance of the microscopic components of solid liquefaction
residues and (3) to develop and establish petrographic criteria able to identify and classify solid liquefaction residues. Especially for achieving the aims of (2) and (3), two to three round robin exercises on the basis of photomicrographs taken under reflected, polarized and fluorescence light should be performed.
In addition to developing a generally nomenclature, the components can also serve as indicators for the course and efficiency of the technological process. Therefore, possible indications for process optimization using applied organic petrology should also be derived in working step (4).