A Numerical Study on Hydrogen Reduction of Iron Oxide Pellets in a Shaft Furnace with Internal Retrieval of Thermal Energy

In the current study, the hydrogen shaft furnace (HSF) process with a special focus on internal retrieval of thermal energy via injecting room-temperature hydrogen (H₂) from the furnace bottom is investigated. A validated 2D computational fluid dynamics model is employed to clarify how and to which extent the flow rate of bottom-injected H₂ affects the thermochemical state and overall performance indicators of the HSF. In the results, it is indicated that the thermal energy retrieved by adopting the bottom injection operation can well compensate for the reduction in the total sensible heat of feed H₂ under the conditions considered. Therefore, the furnace shows a better overall performance because the system requires less total supply of sensible heat while achieving a higher solid outlet reduction degree compared to a reference scenario with no bottom injection. Since the central gas flow is enhanced and local species transport of H₂ is facilitated, the radial uniformity of solid reduction degree is also improved effectively. Moreover, the fluidization factor is well below unity, indicating no substantial particle fluidization will take place within the furnace incorporating the operation of bottom injection. In these findings, the potential of internal thermal energy retrieval in achieving a more suitable and efficient HSF process is highlighted.