Co-injection of hydrogen and biochar (CoHB) in a simulated blast furnace: A univariate and multivariate study

Both hydrogen and biomass have been considered renewable fuels, and the co-injection of hydrogen and biomass (CoHB) in blast furnaces (BF) is an emerging ironmaking technology to bridge the transition to full hydrogen ironmaking as the global focus on decarbonisation intensifies. Their combustion efficiency within the raceway is a key to this technology. In this study, a three-dimensional (3D) computational fluid dynamics (CFD) model was employed to investigate the process under a range of operating conditions. The key parameters include hydrogen content in cooling gas, blast temperature, blast oxygen content, biochar mean particle size, and biochar injection rate. In particular, the combustion behaviour was investigated comprehensively with a combination of one-factor-at-a-time (OFAT) and design of experiment (DoE) approaches. Collectively, the simulation results indicate that the combustion efficiency of biochar particles was generally controlled by local particle temperature and oxygen availability. An empirical response surface model statistically significant at a 95% confidence level was successfully developed to represent the overall biochar burnout across multiple varying factors. The optimum conditions to maximise the biochar burnout were explored, such that a maximum overall burnout of 51.71% was predicted. The findings from this study propose a guideline for the tuning of parameters crucial to the CoHB process in BF operations.