CFD study of hydrogen injection through tuyeres into ironmaking blast furnaces

Hydrogen can be injected into blast furnaces (BFs) via tuyeres and fully replace pulverised coal injection (PCI) for lowering carbon emission, but hydrogen combustion in the raceway may affect raceway shape and size considerably. In this study, a three-dimensional (3D) transient CFD model is used for describing the complicated multiphase flow and thermochemical behaviours related to hydrogen combustion in the raceway of BFs, including the combustion of hydrogen and coke and dynamic raceway evolution under industry-scale BF conditions. The typical in-furnace flow and thermochemical phenomena related to hydrogen injection (HI) are illustrated. Then the effects of hydrogen injection rate on raceway evolution are studied by comparing the combustion performance between HI and PCI, in terms of raceway volume, gas temperature and species distribution. The simulation results indicate that in comparison with PCI, HI operation results in a much larger raceway volume and produces more reducing gas, but the gas temperature is significantly decreased due to the existence of coke gasification reaction; and moreover, higher HI rate results in the formation of a larger raceway and producing more reducing gas. This study provides a cost-effective way to understand and optimise HI via tuyeres in BFs for lower carbon footprint in steel industry.