Researchers List Steps to Decarbonize Steel Making
Strategic Research Institute
Published on :
28 Mar, 2022, 5:38 am
Imperial College London’s Department of Chemical Engineering’s Paul Fennell, Imperial College London’s Fennell Group’s Justin Driver, IDDRI.org researcher Christopher Bataille & University of California Irvine’s of Earth-system science professor Steven J Davis have highlighted nine priorities for research and action for decarbonization of steel making. Together, these steps could take steel close to being carbon neutral to becoming a carbon sink.
1. Use the latest technologies
Ensuring that production plants are fitted with the best available technology offers immediate gains. Improving insulation of industrial plants can save 26% of the energy used; better boilers cut energy needs by up to 10%; and use of heat exchangers can decrease the power demands of the refining process by 25%2. Old, inefficient plants are usually out-competed by more modern facilities, so industries become more efficient over time. However, gains diminish as industries mature and improvements become incremental. Today, the most efficient cement plants can squeeze only 0.04% of energy savings per year by upgrading technologies3. More needs to be done.
2. Use less
Smaller quantities of steel and cement can be used for the same job. Today, the world produces 530 kilograms of cement and 240 kilograms of steel per person per year. Small but significant changes to building codes and education for architects, engineers and contractors could reduce demand for cement by up to 26% and for steel by 24%, according to the International Energy Agency4. Many building codes rely on over-engineering for safety’s sake. That margin could be limited by using modern materials and computer modeling to whittle down designs to use only the necessary amount of resources. Alternative materials with a smaller carbon footprint for a given use, such as aluminium, might replace steel in some products, including cars. Professionals would have to shift their practices and re-train.
3 Reinvent steel production
Carbon is at the core of conventional steel production. Coke (derived from coal) fuels blast furnaces in which iron ores are chemically reduced to metallic iron at temperatures of up to 2,300?degree Celsius. Coke burns to produce carbon monoxide, which reduces the ore to iron and CO2. Molten iron is then refined into steel, usually in a coal-fired furnace, but sometimes (especially when recycling scrap) in an electric arc furnace. The process emits about 1,800 kilograms of CO2 or more per tonne of steel. Other substances can be used to reduce the ores. About 5% of the world’s steel is already made through ‘direct reduced iron’ (DRI) processes that don’t require coke and typically use hydrogen and CO (derived from methane or coal). By using methane-derived gas and renewable electricity to power an electric furnace, such steel plants emit about 700 kilograms of CO2 per tonne of steel, 61% less than coke-based ones. Better still, using only hydrogen for DRI should reduce CO2 emissions to 50 kilograms or less per tonne of steel, a 97% reduction. Firms in Europe, China and Australia are piloting such plants, with several slated to open in 2025 or 2026. The challenge is that this process requires a lot of hydrogen.
4. Recycle steel
Steel can be efficiently recycled using an EAF. One-quarter of steel production today is based on recycled scrap. Globally, recycled production is expected to double by 205011, reducing emissions by 20–25% from today (depending on how the electricity is produced). However, it is not currently possible to recycle steel endlessly. ‘Tramp’ species, undesirable compounds particularly copper, build up. Their accrual can be slowed by better sorting scrap and by redesigning products so that copper wiring is easier to remove.
5, Swap fuels
For steel, it is tempting to suggest replacing coal and coke with charcoal or other forms of biomass. But there are challenges. Growing biomass for energy can conflict with land needs for agriculture, and not all biomass harvests are sustainable. Wood charcoal is too weak (compared with coke) to support material layers in blast furnaces. Rethinking steel processing, as above, is a better solution.
6. Capture carbon
CCS, taking CO2 and locking it away underground, will be essential to lowering cement-production emissions, and is important for steel, too. CCS is relatively advanced in some other industries. The Norwegian state oil company Equinor has operated a CCS project since the late 1990s, burying around one million tonnes of CO2 per year. But the technology is underused; just 0.1% of all global emissions are currently captured and stored. Only a few steel and concrete plants are trialling CCS. For example, one modern DRI steel plant in Abu Dhabi has used CCS since 2016. CCS must be scaled up rapidly.
7. Subsidize changes
Together, the potential of these steps is vast. But further economic hurdles must be overcome if low-carbon heavy industries are to reach megaton-per-year scales of production. Policies should be put in place to encourage these developments. The time has come for steel and cement production to help, rather than hinder, the race to net zero.