Characterising coals for coke production and assessing coke: predicting coke quality based on coal petrography, rheology and coke petrography

摘要

Given the high costs and general shortage of coking coals on the domestic andudinternational markets, and because the nature and qualities of many of the coking coalsudavailable on the markets are themselves mixed products, conventional mechanisms andudtried and trusted formulae for manufacturing coke products based on single coals ofudknown qualities can no longer apply. There is therefore an urgent need to develop moreudeffective techniques for evaluating and assessing the properties of individual coalsudrapidly and reliably and in a manner that could provide useful data for use in modellingudthe effect of new coal components in a coke blend. Towards this end, the current researchudhas sought to find more accurate coal characterisation techniques at laboratory scale thanudcurrently exists in industry at present.udSeventeen coking or blend coking coals from widely different sources were selected andudcokes were produced from them in as close to full scale conventional conditions asudpossible. Both coals and cokes were analysed using conventional chemical, physical,udpetrographic and rheological coking methods.udThe results indicated that, whilst all coals had acceptable chemical, physical andudpetrographic properties as evaluated on individual parameters thereby indicating theirudpotential values as prime coking coals, in fact the resultant cokes of some of the coals hadudproperties that disproved this assessment. These anomalies were investigated byudintegrating all characteristics and statistically evaluating them.udThe result [outcome] indicated that the series of coals under review fall naturally intoudthree distinct categories according to rank, as determined by the reflectance of vitrinite,udand that the coking coals in each rank category were further characterised by parametersudspecific to that level of rank. In this way more accurate predictions of coke quality wereudobtained than has been the case to date when using single set evaluations or previouslyuddevised formulae.udOn this basis it was concluded that, when selecting coals for coke making, it is essentialudto first establish the rank of the coal by vitrinite reflectance and then to apply cokeudevaluating parameters specific to that level of rank. The formulae developed for thisudpurpose held good for all coals tested, however, it remains to be seen whether this appliesuduniversally to an even wider source of coals.