Decarbonisation Technology - November 2022

24 soaking pit furnaces is scheduled to be commissioned at Ovako Steel in Sweden during the first half-year of 2023. Scale and cost of green power supply To enable the last step of this transition to H₂- DRI for full decarbonisation, DRI-based steel production will require very large-scale green hydrogen and green power. Considering 63 kg/t of green hydrogen required per tonne of DRI and 12 kg/t for other heating applications in the plant, a 2 Mt/a DRI-EAF plant will require about 1.1 GW of green power to produce the required green H₂, as shown in Figure 4. For reference, the largest PEM electrolyser in operation today is 24 MW. Hydrogen suppliers like Linde are preparing for this scale-up and supply, but the progress is expected to take time. Considering an order of magnitude estimate on the power required to convert all 95 Mt/a of blast furnace-based ironmaking in Europe to DRI based, the power required for the hydrogen electrolyser, as well as the power for the EAF and other plant operations, would lead to a green power requirement for integrated steel production of about 400 TWh/y. Adding the power requirement for 65 Mt/a of current EAF steel production, the EU28 green power requirement for steel will total 470 TWh/a (54 GW), or around 17% of Europe’s current power consumption. In addition to large-scale hydrogen supply, the economics of this transition will require green hydrogen prices to drop significantly below current levels. Naturally, the higher the cost of CO₂ emissions (taxes, allowances), the higher the price that makes the economics of this transition to H₂-DRI favourable. Indeed, a combination of increasing cost of CO₂ emissions and decreasing H₂ pricing will be necessary to achieve economical decarbonisation. For green hydrogen from electrolysis, the cost is predominantly dependent on the cost of renewable energy. With a stable, low-cost supply of renewable energy, a viable supply of hydrogen can be put in place using electrolyser technology. We can then conceive a plant producing green steel, including hydrogen-based DRI production, EAF steelmaking supplied with renewable power, and all combustion processes using energy-efficient oxyfuel with hydrogen

Figure 3 Hydrogen is an ideal fuel for the CoJet system

arc furnaces, ladle preheating (40-60% fuel savings), reheat furnaces (batch and continuous), and heat treatment furnaces. Oxyfuel combustion, producing a much smaller flue gas volume with a high concentration of CO₂, also supports CCUS. Use of stove oxygen enrichment is a proven option that can be comparatively easily deployed at integrated steel mills, saving high calorific fuel and CO₂ emissions. In melting, preheating, and reheating, proven oxyfuel technologies are available to successfully create decarbonisation, using hydrogen now or later. Oxyfuel solutions can be applied immediately, and at many steel mills with very short payback periods. Numerous tests have been made over the past 3-4 years using hydrogen as a fuel in combination with oxyfuel combustion. It has been concluded that those proven and well- established solutions, both for conventional oxyfuel and flameless oxyfuel, work very well with hydrogen as a fuel. This has been confirmed in full-scale tests in operation. For example, to decarbonise the chemical energy input into EAFs, Linde has developed CoJet injectors with hydrogen fuel with excellent results (see Figure 3) . Hydrogen extends the coherent jet length, increases heat transfer, and reduces maintenance of the injectors. These features make hydrogen an ideal fuel for the CoJet system and pave the way to fully decarbonise the EAF. Looking at reheating furnaces, several full- scale tests have been carried out in production, and now those flameless oxyfuel technologies are all hydrogen-ready. The first permanent installation using 100% hydrogen as fuel in


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