Blending Strategies of Coals from Diverse Origins for Efficient Coke Making

ABSTRACT Blending of coals for coke making is a very important process for the steel industry globally. The importance of coal blend for coke making in India lies in its impact on the quality and efficiency of coke production. The coal blend composition affects crucial factors such as coke strength, reactivity, ash content, and gas generation during the coking process. This ensures optimal performance, cost-effectiveness, and environmental compliance in the steelmaking process and is critical for the sustainability of the steel industry in India. Globally, attempts have been made to prepare suitable blends for coke making and several models have been developed. This also depends on requirement of desired types of cokes and availability of domestic and imported coals for different countries. Presently, in most cases, the Indian coke and steel industry uses 80–85% imported coals and 15–20% domestic coals for blending. Here, six coals from different domestic local mines and three imported coals have been tried in different blend proportions, to show the feasible options to use domestic coals in higher proportions and use lesser proportions of imported coals. In this study, two case studies are presented, demonstrating the blending of indigenous and imported coals in various proportions based on weighted average. Imported coals from Australia, New Zealand and domestic coals from domestic mines i.e. Dugda 1, Kathara, Kargali, Argada Sirka, Jamadoba and Bhujudih mines in Damodar Valley basin were used. The proximate analysis, petrographic studies and properties of these coal blends, including caking index, swelling index, fluidity, plasticity, CRI, CSR, M40 & M10 values have been discussed. The strategies of these blends depended on reactive macerals, inerts, coal rank, mineral matters and other critical parameters. The findings of the paper indicate that, given the constraints of the Indian coke industry, the cokes produced using the blending strategy outlined in the study have achieved optimal values. On meticulous blending, high proportion of domestic inferior coals can be blended up to 38% to prepare suitable coke, while about 50% of imported coal can be blended with domestic coals. This suggests, through a carefully designed blend strategy, the Indian steel industry may address the challenges of coking coal scarcity and reduce reliance on costly coal imports.