CFD study of hydrogen co-injection through tuyere and shaft of an ironmaking blast furnace

•Effects of H2 co-injection via tuyere and shaft on the performance of an industrial scale blast furnace are quantified.•Impacts of water gas shift reaction on blast furnace performance are studied.•Interrelation between utilisation efficiencies of H2 and CO on isothermal lines is identified.•Operation strategies for H2-rich operation of blast furnaces are explored. Hydrogen (H2) can be co-injected into the tuyere and shaft into a blast furnace (BF) for reducing CO2 emissions. However, the feasible co-injection schemes and their effects on in-furnace phenomena are not well understood. In this study, a multi-fluid industrial-scale BF model is further developed to investigate the impacts of H2 co-injection through the shaft and/or tuyere on the BF internal state and overall performance in terms of temperature field, H2 and CO utilisation efficiency, and species distributions. The results show that the proposed H2 co-injection through tuyere and shaft allows H2 to be better utilized and the overall BF temperature field can be improved, compared to respective tuyere or shaft injection cases. Further, the effects of high hydrogen injection rate at tuyere (i.e., low hydrogen injection rate at shaft) are studied. It is found that with increasing H2 injection ratio at tuyere, the water gas reaction and water gas shift reaction are intensified; the temperature is decreased and the H2 utilization efficiency is suppressed; the raceway adiabatic flame temperature (RAFT) gradually decreases; the lowest coke rate is 285.8 kg-C/t-HM is found when the distribution ratio of injected H2 is 4:6 at tuyere and shaft, and the highest coke replacement ratio is 4.1 kg-C/kg-H2. Then, the possible operation strategies for H2-rich operation of blast furnaces are explored. This paper provides a cost-effective tool to understand the flow-thermal-chemical behaviours inside a BF when H2 co-injection schemes are employed.