Characterising coals for coke production and assessing coke: predicting coke quality based on coal petrography, rheology and coke petrography
Date
2008-04-15T08:41:53Z
Authors
Jordan, Pierre
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Abstract
Given the high costs and general shortage of coking coals on the domestic and
international markets, and because the nature and qualities of many of the coking coals
available on the markets are themselves mixed products, conventional mechanisms and
tried and trusted formulae for manufacturing coke products based on single coals of
known qualities can no longer apply. There is therefore an urgent need to develop more
effective techniques for evaluating and assessing the properties of individual coals
rapidly and reliably and in a manner that could provide useful data for use in modelling
the effect of new coal components in a coke blend. Towards this end, the current research
has sought to find more accurate coal characterisation techniques at laboratory scale than
currently exists in industry at present.
Seventeen coking or blend coking coals from widely different sources were selected and
cokes were produced from them in as close to full scale conventional conditions as
possible. Both coals and cokes were analysed using conventional chemical, physical,
petrographic and rheological coking methods.
The results indicated that, whilst all coals had acceptable chemical, physical and
petrographic properties as evaluated on individual parameters thereby indicating their
potential values as prime coking coals, in fact the resultant cokes of some of the coals had
properties that disproved this assessment. These anomalies were investigated by
integrating all characteristics and statistically evaluating them.
The result [outcome] indicated that the series of coals under review fall naturally into
three distinct categories according to rank, as determined by the reflectance of vitrinite,
and that the coking coals in each rank category were further characterised by parameters
specific to that level of rank. In this way more accurate predictions of coke quality were
obtained than has been the case to date when using single set evaluations or previously
devised formulae.
On this basis it was concluded that, when selecting coals for coke making, it is essential
to first establish the rank of the coal by vitrinite reflectance and then to apply coke
evaluating parameters specific to that level of rank. The formulae developed for this
purpose held good for all coals tested, however, it remains to be seen whether this applies
universally to an even wider source of coals.
Description
Keywords
coal, coke, coal-petrography, coke-petrography, coke quality prediction