Hydrogen reduction of iron oxides in shaft furnaces

One strategy to decarbonize the ironmaking sector is the hydrogen direct reduction of iron oxides. However, unlike carbon, which is purely mine-derived, the production of hydrogen requires energy. The energy balance of the hydrogen direct reduction of iron oxides in shaft furnaces is presented in this paper. Since reduction is not isothermal as in a blast furnace, I have modified the Rist diagram to represent these circumstances. A two-zone model could be useful in predicting the top gas temperature and other furnace operating conditions; it has been used to specifically address two issues: the high top-gas temperature, which reduces the process’s heat efficiency, and the dense iron layers in the final reduction stage, which act as a barrier and cause only partial oxide reduction. Burden quality such as low temperature reducibility or high temperature properties is therefore a key factor for the overall efficiency of the process.