Research on the Post-reaction Strength of Iron Coke Hot Briquette Under Different Conditions

Abstract

The utilization of iron coke hot briquette (ICHB) prepared by carbonizing iron ore–coal composite agglomerate made from hot-pressing the mixture of iron ore and blended coal has been considered to be an effective countermeasure to improve blast furnace ironmaking reaction efficiency and to reduce carbon emissions. The strength of ICHB after gasification reaction is overestimated by the Chinese National Standard (GB/T 4000/2008, equivalent to the Nippon Steel Corporation method) and should be evaluated by different methods. In this study, the post-reaction strength of ICHB with the addition of different ratios of iron ore under various conditions was experimentally investigated to illuminate the degradation mechanism of ICHB reacted with CO2. The results showed that, with increasing the iron ore addition ratio from 0% to 20%, the reactivity of ICHB reacted with CO2 at 1100°C for 2 h is remarkably increased, due to the catalytic effect of metallic iron in ICHB, while the post-reaction strength is distinctly decreased. Furthermore, stopping at the weight loss ratio of 20%, the strengths of ICHB after reaction at 1100°C under a CO2 atmosphere and a CO2/CO=1/1 atmosphere are clearly reduced, from 89.74% to 75.93% and from 85.24% to 73.65%, respectively. Meanwhile, the post-reaction strength of ICHB under CO2 is greater than that obtained under CO2/CO=1/1 atmosphere, since there is more time for the reaction gas to diffuse from the exterior to the interior of the ICHB under the latter condition. Additionally, the post-reaction strength of ICHB decreases with increasing weight loss ratio regardless of the reaction gas composition; however, it can be maintained at a high level.