The effect of coal properties on carbonization behaviour and strength of coke blends

The composition of a number of coals with varying rank was characterized by a number of means with emphasis on petrographic examination. The petrographic data of coals was processed with special emphasis on quantifying vitrinite sub macerals and their association with coal carbonisation parameters as well as coke strength. The association between coal petrography data with coke strength of binary blends as well as industrial blends was also examined. Coke strength parameters including drum index and CSR were found to be predominantly influenced by coal rank with few exceptions of high rank and low fluidity coals. The study showed the association between coke strength and coke micro-texture such that coke strength after reactions was related to increased anisotropic texture. On the basis of vitrinite sub-components a new coal parameter was devised. The new parameter, the ratio of difference of collinite and telinite to the mean vitrinite reflectance, is found to predict coke strength of single coals with high confidence. However, the same parameter could not predict coke strength of binary coke as well as coke made in industrial processes. The study suggested that interaction of sub-vitrinite during carbonisation could be responsible for the limitation of application of the new parameter to predict coke strength of blends. Further investigations relating to the interaction of sub-macerals during carbonisation as well as the role of minerals may improve the confidence of coke strength prediction using the proposed new index