This article is comprised of an update from the SUSTAIN Future Steel Manufacturing Research Hub 2023 Annual Review.
In this article, the research team provide an update on their work to produce useful and valuable products from the waste material that’s created during the steelmaking process.
Net zero carbon does not mean zero. For example, the Earth has used CO2 as an energy vector for 4 billion years by using non-fossil carbon as a chemical fuel source and recycling the CO2 by-product using renewable (solar) energy through photosynthesis. The key to this success is that CO2 production and recycling are balanced in nature.
The problem is that, since the Industrial Revolution, energy production for heat, electricity, transport and manufacturing has operated as an almost exclusively linear economy using fossil fuel carbon as the fuel source and generating huge amounts of CO2 by-product.
However, the scale, extreme environments (high temperature/pressure, reactive gases) and complexity of process chemistries, allied to the significant, long-standing industrial expertise in fossil fuel raw materials makes decarbonisation non-trivial.
Task 2 considers alternative carbon sources for fossil fuel carbon based either on waste and/or on “recent” which can displace “ancient” fossil fuel carbon in iron and steelmaking. This decarbonises the process because “recent” carbon arises from CO2 which has recently been removed from the atmosphere. In this way, any CO2 which is released does not add to atmospheric CO2 concentrations.
Zero carbon steelmaking is very unlikely because carbon is still required even for EAF remelting processes.
Task 2 initially focussed on reprocessing non-recyclable waste. But the scope has extended to other non-fossil fuel carbon and associated life cycle analysis.
Task 2 also initially focussed on blast furnace ironmaking but has extended the scope to also consider slag recycling, the decarbonisation of sinter production, carbon within EAF processing and CO2 recycling.
Whilst the manufacturing processes may differ, the central theme remains – i.e., if you input non-fossil fuel material and recycle the CO2 by-products, you achieve net zero.
Key findings to date
Key parameters for non-fossil fuel carbon have been identified in comparison with the significant, long-term understanding related to fossil fuels (coke, coal, natural gas etc).
A range of non-recyclable waste and fossil fuels have been studied in the context of different iron and steelmaking processes. Parameters include reaction rates, kinetics and thermodynamics for devolatilization, burn-out, gasification and in-process reactions, in situ chemical speciation and reactivity and pilot scale simulation.
Iron and steelmaking contexts studied include blast furnaces, iron oxide sintering, EAF simulation, along with circular economy/recycling. We have also assisted steelmakers with regulatory approvals and carbon manufacturing issues.
Applications in industry
The risks to implementation are the same as they would be for the introduction of any new raw material into the process (e.g. composition, reactivity and side reactions). But these risks are exacerbated by potential additional technological changes to materials handling and the manufacturing processes themselves.
These risks can be mitigated, and the impact generated by tests at increasing scale towards plant-scale tests. Government support for full-scale plant tests would help remove barriers to impact.
Energy is at the heart of all decarbonisation issues. It is the reason that fossil fuels or any alternative raw materials are used in any industrial process, and it will become, if anything, more important as we move, stepwise towards net zero.
The next stages are to consider the de-fossilisation of carbon raw materials and the decarbonisation and recycling of exhaust gases but all within the quantum yield (i.e., energy in versus energy out) of these processes.
The effect of electrification
Firstly, electrification is not a solution for steelmaking unless electricity production is also decarbonised. In fact, electricity produced using carbon (even biomass) will make the net carbon equation worse partly because of the well-known transmission and distribution inefficiencies associated with large-scale electricity generation alongside processing issues.
Hence, developing a better understanding of non-fossil fuel carbon inputs and CO2 recycling remains vital however wide you throw the circular economy loop.
Blast furnaces are large-scale gasification reactors which have the potential to be developed into multi-million tonne per year CO2 recycling units, i.e., industrial-scale atmospheric gas cleaning.
So, if iron and steelmaking become net carbon positive, this offers the potential for the steel industry to be the solution to climate change rather than part of the problem.