Effects of Blast Furnace Representative Temperatures and Gas Compositions on Coke Reactivity

Abstract

The effects of coke mineralogy on coke reactivity under conditions representative of the blast furnace were studied. Coke samples were reacted under coke reactivity index (CRI) like conditions (1100°C, 100% CO₂) and at higher temperatures and atmospheres designed to replicate conditions lower in the blast furnace.

The effects of the minerals on reactivity changed as the temperature increased and the atmosphere was modified. At the lower temperatures investigated (1100–1350°C) with CO₂ present in the gas, gasification of the coke by CO₂ dominated. The effects of minerals in the coke on gasification by CO₂ under these conditions were similar to their reported effects on reactivity in the CRI test. At the highest temperature investigated, (1600°C), with no CO₂, the mineral-carbon reactions dominated. The main reaction was the reduction of the silica in the coke. These results show that when coke-gasification is dominant, CRI data can be related to conditions beyond the temperature and gas environment the data were obtained, to the higher temperatures and less oxidising conditions of the blast furnace. At higher temperatures, mineral-carbon reactions are dominant, and more data in addition to that of the CRI, may be required to understand coke behaviour in the blast furnace.

IMDC and RMDC within the coke were identified with the aid of the CGA technique, and the changes in the carbon structures within the coke studied using Raman spectroscopy. The carbon structures within the coke became more graphitic at 1600°C, with the change in RMDC greater than that in IMDC.