On the microstructure and CO2 reactivity of tar–impregnated charcoal for cokemaking

Abstract

Using charcoal in coke production offers a potential solution to mitigate CO2 emissions in the steel industry. However, incorporating charcoal into the cokemaking process encounters significant challenges, primarily due to its high reactivity towards CO2. The primary objective of this study was to gain a comprehensive understanding of the approach of blending charcoal with coal tar as a means of enhancing this material addition in cokemaking. The impact of tar impregnation on charcoal was assessed using optical and scanning electron microscopy, as well as CO2 reactivity. Results show that charcoals produced from impregnation followed by pyrolysis were significantly less reactive towards CO2, mainly due to pore filling and surface area reduction. Furthermore, charcoal's effect on coke quality was evaluated from laboratory coke samples produced without charcoal (reference) and with additions of 5 wt% (as received and tar-impregnated). Results from CRI/CSR tests showed that coke quality was sharply degraded due to as-received charcoal characteristics, while in contrast, coke with tar-impregnated charcoal achieved much better results, close to reference coke. This enhancement is primarily attributed to the reduced surface area resulting from impregnation and the inherently low reactivity of the pyrolyzed tar, which effectively acts as a barrier against material gasification.