Physical degradation of coke in blast furnace.

Abstract

Fbeen concluded that the thermal degradation and the attack by inorganic compounds contribute considerably to the drastic degradation at the position of 3-5m above the tuyere level, and that the contribution to the deteriorations by CO2 reaction is smaller than the former.On the base of these findings, the coke degradation through blast furnace has been tried to determine by measuring the difference of coke size between before charging and at the tuyere during the operation with very low fuel rate (396kg/pig-t). The result obtained implies that the less thermal level of the lower part of blast furnace brings the less degradations of coke through blast furnace.Another blast furnace trial has been conducted with the low CSR (coke strength after CO2 reaction) cokes with enough JIS drum strength (more than 92.0 in DI3015) which are produced mainly by lowering the flue temperature of coke ovens. Any serious problems have not been encountered such as frequent slips and scaffold formations during the operation. A clear relation is recognized between the slag discharging speed and the hot drum index (1500°C) of charged coke.To confirm what kind of coke shows the less thermal degradation, the apparatus for measuring the indirect tensile strength at high temperatures (2300°C) has been developed. It is found that the optimum inerts and the high micro strength are indispensable to get the coke with less thermal degradation.