Enhancing the Strength of Formed Coke from Woody Biomass\nwith the Addition of Biomass Extracts

The replacement of coal with lignocellulosic biomass as feedstock\nfor blast furnace coke is a crucial approach to decarbonizing the\nsteel industry, which is a sector that is difficult to abate. Unlike\nthe addition of a small amount of biomass or its charcoal to blended\ncoal for conventional coke, the use of 100% biomass as a raw material\nis possible with formed coke, while its practical application requires\nan improvement in strength. Here, we report that the addition of a\nlow-molecular-weight fraction obtained from degradative solvent extraction\nof biomass, called Soluble, is highly effective in enhancing the strength\nof the formed coke from softwood biomass. When used alone as a raw\nmaterial, Soluble foams during carbonization, preventing coke formation.\nHowever, when mixed with woody biomass, it disperses within and between\nbiomass particles during pelletization (hot press at 130 °C)\nor carbonization (cold press). Soluble has a minimal impact on the\npyrolysis of biomass and dimensional changes of the biomass-derived\ncarbonaceous substrate during carbonization, but it acts as a binder\nto sustain the strength of the resulting coke. As a result, the tensile\nstrength of formed coke from biomass alone, which was 1.2 MPa with\na cold press and 7.5 MPa with a hot press, improved with the increasing\naddition of Soluble, reaching around 25 MPa at 30 wt % addition. The\neffect of addition varied significantly depending on the preparation\nmethod and properties of Soluble, particularly highlighting the importance\nof the resolidification temperature during the carbonization process.\nThis method was also effective for formed coke derived from lower-quality\nraw materials such as rice husk and lignite compared to softwood,\nbut the optimal addition amount varied due to differences in the Soluble\nretention capacity.