Mozambique coal - the uncommon petrographic quality and its consequences on the coke strength

Abstract

An ideal coal blend coke must have an appropriate maceral composition (vitrinites, exinite and inertite) to provide the right balance of fusible and non-fusible material. The coal must also be in a particular range of carbonization degree or rank. This is because these parameters are directly related to the structure and texture of coke, which will determine its strength. Sources of non-fusible material are readily available, commonly from high inertinite or weakly caking coals or even petroleum coke. Sources of fusible material however are scarcer, being limited to vitrinites and exinite in coals of coking rank. High vitrinites coals from Mozambique provide an opportunity to achieve an appropriate maceral composition to optimize coke quality. The amount of vitrinites in a coal has a strong connection with the genesis and formation of deposits. The coals formed during the Carboniferous period in Europe and Eastern USA has high content of vitrinites. On the other hand, the coals formed during the Permian period in Australian and Eastern Canada have low volumes of vitrinites that may be less than 50%. The coals deposits located in the Tete Province of Mozambique in Africa, though formed in the Permian period, have high volumes of vitrinite, above 80%. This work aims to compare the results of coke resistance between coals of different origins and therefore with different levels of vitrinite content. The cokes are produced from a 40kg pilot scale oven of a renowned research center in China, and physical testing performed by the same research centre. The results indicate that high vitrinite content can positively affect both the hot and cold strength. Mozambique coals, with the highest vitrinite content in this study, achieved the best results overall in comparison to the other studied coals.