There are also significant operational issues: for example, the endothermic nature of the H 2 reduction reactions of shaft furnace-based DR processes means the heat balance will be quite different than for a conventional natural gas-based configuration and likely would present operating challenges. There are significant issues to overcome before the Hydrogen Economy is a reality for steel and other industries the main one being the economical supply of ‘green’ hydrogen and electricity (4, 5). (Source: CRU Steel Metallics Monitor – 2020 Macro Trends,, “How higher CO 2 prices could shift the EU to low-carbon steelmaking”) Green hydrogen – water electrolysis using renewable electricity coupled with renewably-sourced electrical energy, which is challenged by the cost and scale of current commercial plants.Blue hydrogen – fossil fuel source with CCS or electrolysis using non-renewable electricity but at great capital cost for commercially available CCS and H 2 generation equipment.Grey hydrogen – fossil fuel source with no CCS to remove, store, and stabilize CO 2.Hydrogen is labelled according to the source of underlying energy carrier used to produce the H 2 and whether carbon capture and storage (CCS) is employed: WHAT IS MEANT BY GREY, BLUE, AND GREEN HYDROGEN? In fact, there is substantial evidence that carbon can be removed from the process and replaced by H 2, as was discussed in the first quarter 2020 issue of Direct from Midrex (4).
Carbon does not play a key role in the process however, increasing the H 2-to-CO ratio does have a significant effect on the process heat balance. In the case of shaft furnace-based direct reduction (DR) processes, such as MIDREX®, a reducing gas mixture of carbon monoxide (CO) and H 2 is produced from the decomposition of natural gas. This, of course, assumes cheaper and ‘greener’ methods of H 2 production become reality. The massive potential generation of CO 2 from industrial processes and transportation is the motivation behind the desire to decarburize and become a Hydrogen Economy (using H 2 as a fuel source).
In the case of the Iron Blast Furnace, carbon (in the form of coke) also plays a vital role by providing structure and mechanical support to the bed of materials in the reactor shaft.įigure 1 summarizes the generation and required CO 2 reductions, the anticipated increase in steel demand, and the required change in carbon intensity between 20 (3).
The great majority of this CO 2 generation is due to coal, constituting 75% of the energy used in the steel industry, predominantly in the ironmaking process, where carbon is used chemically to reduce iron oxide and provide fuel for the process. The world steel industry constitutes 8% of the overall energy demand whilst contributing 7% of the total carbon dioxide (CO 2) generated by humanity (2.6 GTonne CO 2 2020 2.8 GTe CO 2 2015).
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