This article is comprised of an update from the SUSTAIN Future Steel Manufacturing Research Hub 2023 Annual Review.
In this article, the research team explain their approach to capturing CO2 produced during the steelmaking process and converting it into a commercially valuable product, and the progress that they’ve made in the last year towards their goal.
Steelmaking process and emission gases are a source of carbon dioxide from which to manufacture chemicals. The future availability of fossil-free chemicals is linked to hard-to-decarbonise processes including those of the foundation industries.
This is particularly true for carbon-intensive BF-BOF steelmaking emitting ca. 1.9 tCO2/t crude steel, but also for lower carbon emitting EAF still releasing ca. 0.1 tCO2/t steel (0.3 tCO2/t steel when adding electricity CO2 intensity).
The opportunity is to integrate CO2 capture and utilisation technologies in steel manufacturing processes to deliver added value in collaboration with the chemical industry.
The overall aim of SUSTAIN Task 1 is to reduce steelmaking carbon emissions by capturing and converting CO2 into commercially valuable products.
Valuable products made from CO2 will lower the overall cost of carbon capture and sequestration to create virtuous integration between steel and chemicals manufacturing.
CO2-derived chemicals and fuels are interesting for their added value and, in some cases, large market scale, allowing a future circular economy based on the recycling of carbon dioxide.
This approach is essential since steelmaking processes will continue generating CO2 while transitioning and deploying technologies with a lower carbon footprint.
A new approach
One of the original aims of the project was to tackle BF-BOF process gases and heat/power generation (combustion of natural gas) carbon emissions. Whilst the idea of obtaining higher calorific value CO/H2 enriched gas streams for use in the integrated steelworks remains a valid transitional approach, there has been a shift towards EAF emissions with substantially different gas compositions.
The direct CO2 emissions of a typical EAF are dependent on how much fossil fuel (natural gas, or even coal) is used as an energy source, accounting for 40%-70% of overall emissions. Substituting hydrogen for fossil fuel the process generates CO2 from graphite electrode consumption and from the thermal decomposition of additives such as CaCO3.
As a result, CO, CO2, SOx and NOx are present in the emission of EAF steelmaking. The impact of contaminants such as sulphur and nitrogen oxide must be considered on the carbon capture and utilisation has then to be considered.
Since the inception of Task 1, we made significant progress in developing and scaling both carbon capture and utilisation technologies.
The FluRefin carbon dioxide capture and refining system has been developed from being a small laboratory scale unit to a ca. 0.1 t/d mobile capture unit, with considerable in-king financial and engineering support from AESSEAL in Rotherham.
This has put the technology approximately 5 years ahead of schedule.
Consequently, we filed a GB Patent Application in 2022 and now a PCT Application in January 2023.
Sheffield has now issued an exclusive license to CCU International Limited in Scotland to begin the commercialisation of FluRefin. Field trials are being prepared for the deployment of the system at steelmaking sites and the refined gases will be converted to a number of value-added products including ethanol, methanol and DME foe use as synthetic transport fuels. The utilisation reactors are currently being constructed and recommissioned.
The FluRefin technology was a short-listed Finalist at The Engineer Awards: Collaborate to Innovate. The collaborators were listed as University of Sheffield, AESSEAL limited, BetterWorld.Solutions and SUSTAIN. We were awarded the only Highly Commended Award at the ceremony in London on 23 February 2023.
Our CO2 utilisation technologies have matured during the last year. We are now implementing large-scale electrochemical conversion solutions to bench-scale carbon dioxide electrolysers to generate chemical products like ethylene.
Ethylene is of great interest given its large-scale production (150Mt C2H4/year) and potential to replace the use of fossil carbon whilst avoiding vast amounts of carbon emissions (250Mt CO2/year).
We developed new CO2 electrolysers integrating technical solutions from the largest electrolysis process in the world, the chloralkali process. The purpose of this novel approach is to deliver stable CO2 electrolysis, as robust as the chloralkali process achieving the thousands of operational hours necessary for commercial implementation.
Currently, we have designed and built a 30 cm3CO2 electrolyser (10+ times scale-up) to include the falling film technology responsible for the long-term stable operation of the chloralkali process. In parallel to that, we have been making in the laboratory CO2 reduction gas diffusion electrodes following industrial manufacturing procedures in view of achieving robust and scalable ethylene production performance.
Applications in industry
The FluRefin system developed at Sheffield has now been licensed for commercial development and has had follow-on funding from Innovate UK Transforming Foundation Industries Challenge fund to develop a larger 1 t/d system, housed in a 20’ ISO shipping container.
The Flue2Chem project also includes current partners Tata as well as 12 other major global companies including Unilever, P&G, BASF, JM and others. (See this press release for further information).
The main barrier is now funding the commercialisation programme to start the rollout of systems to industry. We will also need to further develop the connectivity of FluRefin to the utilisation operations (Innovate UK TRLs), as well as develop innovative fundamental science for new capture materials and catalytic utilisation processes.
The integration of carbon utilisation technologies requires close collaboration between steelmakers and chemicals manufacturers with a shared vision of a transformed and merged industry where CO2 from steel production is in the carbon feedstock for chemicals production.
The industrial impact of this approach is transformative in the way that a sustainable circular economy is achieved whilst decarbonising steelmaking and defossilising chemicals manufacturing.
A key barrier to implementation is establishing executive communication between steel and chemicals industries to create and support a bold and forward-looking vision to grant investments in new CO2 utilisation technologies.
In the case of Task 1 CO2 electrolysis, we need to address practical issues in the laboratory with scalability in mind. For example, we are currently testing our new CO2 falling film electrolyser fully aware that the resulting technology will be transferred to the pilot scale (10-100 times larger electrodes).
To operate on a larger scale the level of investment and the required facilities are those of the chloralkali industry. For this reason, we are in direct communication with relevant partners. Currently, we work in the laboratory to de-risk the falling film technology to then embark on scale-up activities with our industry partners.
Innovate UK-funded Flue2Chem will allow us to build a 1 t/d system and then we will work with commercial partners to move to a standard 10 t/d modular capture facility.
Within Task 1 of SUSTAIN we need to develop the connectivity between the capture and utilisation units and develop new catalysts and processes.
A big challenge will be scale-matching between the volume of captured CO2 and the ability to convert it all without re-emitting any excess to the atmosphere. Therefore, we are adding a downstream liquefaction facility to allow us to store captured CO2 for subsequent use and also for public engagement activities, allowing people to see pure liquid CO2 being formed.
The next stage of the development of CO2 electrolysis is to demonstrate long-term operation with sustained production of ethylene also in the presence of gas feed impurities. We need to understand and minimise the impact of gas contaminants (SOx, NOx), optimise the process for high energy and product formation efficiency, and establish a channel of communication between steelmaking partners and the chemicals industry to participate and invest in de-risking our CO2 falling film technology.
The effects of electrification
We have always considered CCU to be a transitional technology and so it may become redundant in a fully electrified system. However, we do not see that happening any time soon.
Furthermore, there are other areas of the steel-making supply chain that will be difficult to electrify, including maritime transport and heavy-duty road transport and power generation on site.
The FluRefin system is adaptable so that it can be used in many emissions scenarios. It is for this reason that in Task 1 we have brought in additional partners in the utilisation phase looking at CCU products for the shipping industries (Dolphin N2, maritime) and synthetic carbon fuels sector (Shell). We will adapt our technology approach as the picture becomes clearer regarding potential electrification and the availability of low-carbon electricity.
The electrification of steelmaking is suitably aligned with the integration of CO2 electrolysis in the manufacturing of chemicals and fuels. The CO2 falling film technology that we are developing in Task 1 is powered by electricity and fits in naturally in the electrified industry.