Solution loss behavior of cokes and its kinetics under hydrogen-enriched atmosphere

Abstract

Hydrogen-enriched ironmaking presents a promising approach to mitigate coke consumption and carbon emission in blast furnace (BF) operations. This work investigated the relationship between the structural features of cokes and their reactivity towards solution loss (SL), especially under hydrogen-enriched atmospheres. Six cokes were characterized, and their SL behaviors were examined under varying atmospheres to elucidate the effects of hydrogen enrichment. The results indicate that an increase in fixed carbon content leads to a decrease in the coke reactivity index (CRI) and an increase in coke strength after reaction (CSR), in the CO₂ atmosphere, the CSR of coke increases from 35.76%−62.83%, while in the 90CO₂/10H₂ atmosphere, the CSR of coke increases from 65.67%−84.09%. There is a good linear relationship between CRI and microcrystalline structure parameters of coke. Cokes with larger crystalline size, lower amorphous content, and smaller optical texture index (OTI) values show enhanced resistance to degradation and maintain structural integrity in BF. Kinetic analysis performed with the shifted-modified-random pore model (S-MRPM) reveals that alterations in pore structure and intrinsic mineral composition significantly influence the reaction rate. The introduction of a small amount of water vapor raises SL rates, whereas a minor addition of hydrogen (<10%) decelerates SL due to its incomplete conversion to water vapor and the reduced partial pressure of the gasifying agent. Thermodynamic calculations also indicate that the introduced hydrogen does not convert into the same fraction of water vapor. The shift from chemical reaction control to gas diffusion control as the rate-determining step with rising temperatures during SL process was confirmed, and the introduction of hydrogen does not notably alter SL behavior. This result demonstrated that introducing a small amount of hydrogen (<10%) can mitigate SL rates, thereby enhancing coke strength and reducing coke consumption and carbon emissions.