Innovative Approaches for Effective Utilization of Washery Middling

Abstract

Coking coal plays a critical role in the iron and steel industry. It is a primary raw material for coke making. The depletion of high-grade coal reserves leads to a deterioration in the quality of raw coal, resulting in the generation of 35% - 40% middlings during the coal washing process. These middlings, known as washed power coal, are currently used by thermal power plants. However, they could be a potential source for clean coal recovery. The growing demand for cleaner coal with lower ash content presents challenges. Present investigation explored the processing of middling sample collected from the coking coal washery. Various processing techniques were employed to improve the quality of the middling sample in terms of ash content, calorific value and maceral content. Gravity separation using spiral concentrator followed by column flotation improved the product quality from 42.8% to 18% ash. The product showed improvement in the calorific value (6989.5 kcal/kg), vitrinite and inertinite contents, making the product suitable for coke production. This study highlights the potential to upgrade middlings for clean coal recovery, which could reduce coking coal imports.