8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Ferro-coke is a highly reactive coke and considered a promising advanced burden material for blast furnace ironmaking due to a potential of decreasing RAR and CO2 emission. The essential reason is it reacts with CO2 in BF gases at lower temperatures, which is resulted in by the catalytic effect of metallic iron, and leads to a lower temperature of the thermal reserve zone. However, since iron ores are an inertial material, the mechanical strength of ferro-coke is commonly inferior to the coke prepared without iron ore addition. This violates the requirement for coke in providing mechanical support to the large charge column and in permitting the gases to ascend through the voids. In this work, focused on ferro-coke, a great effort has been made to clarify the influencing factors of reactivity as well as mechanical strength at the room temperature as well higher temperatures after reaction and to determine the quantitative relationship between the quality indices and the productive parameters. Two processes can be applied in the production of ferro-coke, i.e. the traditional battery cokemaking process and the briquetting/shaft process. The briquetting/shaft furnace process is superior to the former in higher iron ores blending ratio, and the traditional battery cokemaking process is superior to the later in higher process maturity, higher production capacity, no need in binders. For this reason, the traditional battery cokemaking process was selected for the preparation of ferro-coke. Further, the stamped coke battery route was tried in this study in order to obtain ferro-coke products with higher mechanical strengths at a same blend ratio of high quality cokemaking coals. It was revealed by this work that the main factors influencing on the reactivity (also the starting gasification temperature) and mechanical strength of ferro-coke are the coking capacity (Vadf, G and Y values) of coal blend, the quality (gangue materials content, combined water content, size distribution) and blend ratio of iron ores, carbonization conditions (heating speed, carbonizing temperature, soaking time, etc.), and the bulk density of coal charge in particular. A mathematical model has been built up based on the results of a systematical experimental study. This model can be used either for forecasting the reactivity and mechanical strength of ferro-coke under a specified production condition, or for determining the productive conditions for achieving a specified quality standard of ferro-coke. In the 6 kg experimental coke oven of Wuhan University of Science and Technology, a ferro-coke sample with quality indices that are comparable to the industrial coke fed into 2300 m3 BF has been produced; its declining rate of mechanical strength with the reactivity increasing is as small as that of the formed ferro-coke sample prepared in laboratory by the hot-briquetting/shaft process.