02/02/2024
Can copper and zinc production make steel green? There’s more routes to Green Steel than the one heavily depending on hydrogen... The majority of the initiatives related to reducing CO2 emissions from steel production rely on a DRI route involving hydrogen gas. If the hydrogen itself is green, that indeed can be a CO2-neutral route. The production of H2 is however energy-intensive as well, so the overall energy footprint can be relatively high.
Other metals, like aluminum, copper and zinc are produced since ages using an approach called “electrolysis”. The same process that can be used to produce hydrogen out of water. Recent advances show that a similar approach might be an option to be used in the production of iron as well. The technology hasn’t reached full industrial scale yet, but today 2 routes are being pursued:
⏩ A low-temperature one using an aqueous solution, like is the case in the production of copper and zinc
⏩ A high-temperature one using a molten salt, like in the case of aluminum
In the first one iron ores are first dissolved in a water-based liquid. Subsequently, using an electrical current, the iron is collected out of the liquid on one of the electrodes. Temperatures remain comfortably below 100°C. In the latter one the iron ore is molten into a liquid salt. Again an electrical current is used to reduce Iron ions into almost pure iron. In this case the temperatures need to be at least 1600°C.
Both techniques have advantages and disadvantages, but initial signs show that both can indeed serve as a viable alternative to a DRI-based production route. In order to evaluate properly, real numbers are required, and these are currently being generated by amongst others Boston Metal (molten salt) in the US and projects related to the SIDERWIN SPIRE project at the European side of the Atlantic (aqueous route). Again the availability of continuous power and or the ability to cope with increased fluctuations in green power sources will play a role in deciding what the most viable options are as well as where best to locate the plants.
The route to green steel 💚 is challenging, interesting, by far not finished, but essential. Let’s keep on moving forward! 🚀
