Microstructural analysis of metallurgical cokes and intercalated species

Abstract

The microstructure of metallurgical cokes has been investigated using high resolution electron microscopy (HREM) and complementary techniques. The object of the study was to evaluate the role of recirculating alkali, present in blast furnaces, in the weakening and subsequent degradation of the coke. It is shown that the microstructure of cokes charged to the furnace markedly differs from samples removed from the high temperature regions of the furnace. The feed cokes show a turbostratic structure of short range order, whereas the ex-tuyere cokes show two distinct, additional microstructural species, viz. an intercalated material retaining the turbostratic disorder and an extensively ordered carbon structure. It has also been found that the nature and distribution of the mineral matter inherent in metallurgical cokes is that of randomly dispersed alumino-silicates. Successful replication of the ex-tuyere microstructural forms has been achieved by reaction of the feed coke with potassium carbonate in laboratory experiments. The major factors contributing to the degradation of metallurgical coke are discussed.