A Coke Analogue for the Study of the Effects of Minerals on Coke Reactivity

Abstract

The properties of metallurgical coke are critical to the performance of the blast furnace for iron making. While extensive work has gone into understanding the relationship between the properties of coke and its behaviour in the blast furnace, the heterogeneous nature of coke makes understanding these relationships difficult. Herein we report the use of a laboratory produced coke analogue to examine the effects of minerals on the reactivity behaviour of coke in a pseudo-CRI test. The effects of a range of minerals on the reactivity of the coke analogue are demonstrated and the effects of binary combinations of silicon and iron bearing minerals are examined. The properties of the metallurgical coke used in the blast furnace for steel making have a direct effect on the quality and productivity of the steel making process. Coke provides three primary functions in the blast furnace. 1) It is fuel for the furnace, the carbon source for the CO to convert iron oxide to metallic iron and provides the structural support for the blast furnace burden. The structural support of the burden during operation of the blast furnace is critical as collapse of the burden reduces gas and liquid permeability 1) consequently reducing the efficiency of the blast furnace operation both in reducing through put and in increasing carbon dioxide emissions per unit of iron produced. A number of factors affect the performance of metallurgical coke in the blast furnace. These include carbon forms (microtextures), pore network and catalytic effects on the reactivity due to minerals present in the coke. 2) It is desirable to predict the reactivity of coke from its key characteristics. Unfortunately this is in part limited by unknown or non-quantified effects of minerals on coke reactivity. Elucidation of the effects of minerals on coke reactivity has proved difficult due to the complex heterogeneous nature of coke and potential non-additive effects of minerals on coke reactivity. Several different approaches have been taken to understanding the effects of minerals on the reactivity of metallurgical coke. Two principle methods have been utilised to study the effects of minerals on coke reactivity. Early attempts were made through doping of coke making coals with mineral additions 3,4) and studying the subsequent reactivity. Later techniques involved statistical analysis of a large range of cokes of known mineralogy and reactivity to attempt to identify the important mineral species with respect to coke reactivity. 5–8) Early studies examining doped coke reactivates 3) indicated that the mineral cations present coke could be ranked as follows in terms of their effect on reactivity: