Formation of Metallurgical Coke within Minutes through Coal Densification and Microwave Energy

Abstract

This paper shows how feedstock densification gives rise to a step change in the time required to create a metallurgical grade coke using microwave energy. Five densified coking and noncoking coals were heated in a multimode microwave 2450 MHz cavity for varying treatment times (2–20 min) with a fixed power input (6 kW). Proximate analysis, intrinsic reactivity, coke reactivity, dielectric properties, and petrographic analysis of the coals and microwave-produced lump cokes were compared to a commercial lump coke. Densifying the sample prior to microwave treatment enabled a dramatic acceleration of the coking process when combined with targeted high microwave energy densities. It was possible to form fused coke lump structures with only 2 min of microwave heating compared to 16–24 h via conventional coking. Anisotropic coke morphologies (lenticular and circular) were formed from noncoking coal that are not possible with conventional coking, and increasing the treatment time improved overall coke reflectance. Three of the coals produced coke with equivalent coke reactivity index values of 20–30, which are in the acceptable range for blast furnaces. The study demonstrated that via this process, noncoking coals could potentially be used to produce high quality cokes, potentially expanding the raw material options for metallurgical coke production.