Steel is a key material in our modern lives, powering vehicles and infrastructure. It is, however, a major global source of greenhouse gases. Decarbonizing is a big challenge. Greener alternatives still haven't proven to be viable in this highly competitive industry.
It takes large amounts of power to increase carbon content in steel. This is around 400 kilowatts per tonne. A new technology, however, could cut the energy required by up to 30% while increasing efficiency. The new technique relies on a high-performance raiser of carbon as fuel for the smelting. The raiser, dubbed recarburizer by the steel industry, is made up of finely-ground recycled steel, calcium carbide and activated carbon. The process works by increasing melting temperature and decreasing the pressure required for the metal to become molten. This allows more atoms to enter the liquid phase. The surface area increases, increasing the melting capacity. It also makes melts more fluid which allows for quicker melting and cooling times.
The recarburizer is suitable for many different applications. These include medium to high carbon (0.5 - 0.8% C) steels, ductile and austempered iron, steel cord, rails and bearing steels. The recarburizers also help increase the density in steels used for cold rolling. Carbon content is what determines mechanical properties and durability.
In the quest for a low carbon economy, many steelmakers aim to reduce emissions. OECD figures show that there is still a 26% overcapacity, but government subsidies allow inefficient plants to continue operating. The IEA believes that these subsidies should be removed in order to bring the steel industry into compliance with climate change targets. They also want to see the closure and development of new technologies, such as direct reduction iron EAF, which emit less carbon dioxide.
In the short term, the steel industry can reduce its emissions by using electricity from renewable sources. It would be more important to switch to hydrogen instead of coal as the primary raw material in steelmaking. The IEA says that developing countries will need to build significantly more renewable energy capacity, as well as develop the capacity to produce hydrogen from renewable sources. The transition to hydrogen will take time and depend on the companies that develop supplies of renewably produced hydrogen for DRI or other uses. These are not currently available in any commercial quantities.
In a world that is trying to reduce carbon emissions, the steel industry has to act quickly in order to not be left behind. But smelters are advised to avoid green-labeling anything other than electric furnaces powered with renewable energy. Big River Steel Dearborn, Michigan is the only US facility certified by ResponsibleSteel. It uses electricity from a nearby wind farm to power its blast furnaces instead of pure coal.
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