Effect of Coal Rank on Coking Property of HyperCoal Blends

Abstract

Coke making is becoming more expensive because of the sudden rise in the price of caking coals due to the decreasing supply, and so a technology to manufacture good-quality coke from coal blends containing low-quality slightly caking or non-caking coals is strongly required. "HyperCoal" (ash-free coal, HPC) is produced by thermal extraction using cost-effective industrial solvents below 400 °C in an inert atmosphere. It has originally a wider temperature range of thermoplasticity during heating than ordinary caking coals. HPC can be produced from various ranks of coals including lignite and subbituminous coal, however, the chemical property of HPC is different depending on the coal rank. HPCs produced from low-rank coals such as lignite and subbituminous coal, showed a high thermoplasticity from lower temperature range than those from high-rank bituminous coals. In addition, HPCs from low-rank coals possess a higher permeability due to the lower viscosity in the thermoplastic region. As a result, the addition of HPCs from low-rank coals to a coal standard blend showed a higher effect on the tensile strength of cokes produced by carbonization of the HPC-blending coals at 1000 °C, than that of HPCs from caking coals.