Carbon dioxide emissions from iron and steel production are estimated at about 3 Gt per year – approximately 9%of global energy-related CO2 emissions. Global production in 2016 is recorded at about 1630 million tonnes of crude steel, with approximately half coming from China.
Iron and steel making processes are energy and carbon intensive as a result of large requirements for fossil fuels, mainly carbon, both as feedstock and energy source. 70% of steel is produced today via the Blast Furnace – Basic Oxygen Furnace (BF-BOF) process, where coal is used as main reductant for iron ore at high temperature. This route produces about 2.3 tonnes of CO2 per tonne of crude steel for all direct and indirect emissions.
Among the various options that steel companies are evaluating to reduce their carbon footprint (eg. switching from coal to clean hydrogen), CCS remains one of the most effective and less invasive method to achieve deep emission cuts. CO2capture technologies are mature and can be retrofitted today on existing assets, maintaining the existing equipment (ie. blast furnaces), without disrupting current BF-BOF production processes.
Therefore, in synergy with other low, more innovative, carbon approaches, CCS can make a significant contribution to achieving large CO2 emission cuts in steel production. Recent IEA projections indicate that by 2060 CCS needs to be installed on about 21% of global crude steel production capacity. This corresponds to 506 Mt of CO2 captured annually.
However, on a global level, the current financial incentives and regulatory frameworks have not been sufficient to spur multiple large scale projects in this industry. With the exception of the Abu Dhabi CCS project (Emirates Steel Industries) no other steel plant has yet implemented CCS at a large scale (ie. above 0.5 Mt/y).
Enabling CCS in the steel industry
The European steel sector has been active for more than 10 years in exploring CCS opportunities. The largest effort is represented by the ULCOS (Ultra Low CO2 Steelmaking) programme where various CCS concepts where developed. Much has been achieved in this program but the proposed large scale CCS facility at the steel plant in Florange (FR) was not realized due to early closure of the site.
In Europe, CCS in this industry is still under consideration as demonstrated during several events around the steel sector that were held earlier this year, like the ECN/CATO event “Reducing the Carbon Footprint of the steel industry” or the seminar organized by the European Commission “The Future of European Steel Industry”.
In the current policy scenario, the European steel industry is reluctant to invest and bear liability for the transport and storage components; a full chain project would generate a financial risk for companies that is too high in a market where strong international competition doesn’t leave much margin for error.
Steel companies call for the public sector to take a leading role in financing transport and storage infrastructure, as this would greatly facilitate the development of CCS projects. Once the infrastructure is in place CCS projects are expected to follow as the steel plant owners could be more willing to accept bearing the cost for CO2 capture at their sites.
The Chinese steel sector is increasing its interest in CCS solutions. One of the main drivers for CCS in China is Enhanced Oil Recovery (EOR), which represents a significant incentive for a steel company to engage in a large scale CCS project. EOR is also the incentive in the Middle Est; the Abu Dhabi CCS project has been realized because of the positive business case based on using the captured CO2 for EOR purposes (replacing natural gas).
Significant EOR opportunities exist also in North America thanks to CO2 transport network already developed and there is large experience with this practice. The New Steel International Iron Power‐Steel (IPS) Projects plan to realize two new steel plants in Ohio and Michigan each producing 4.5‐5 million tons of steel and 8 million tons of pipeline‐quality CO2 per year for EOR purpose.
How do you capture CO2 produced in BF-BOF plants?
An integrated iron and steel mill has multiple flue gas stacks (ie. hot blast stove, lime kiln, cogeneration plant) as well as units generating combustible gases (ie. coke oven, blast furnace, basic oxygen furnace). A simple scheme is illustrated below.
These streams contain CO2 in different concentrations, however the most effective way from a techno/economic perspective is to target the stream with highest volume of CO2, namely the fuel gas generated by the blast furnace and the flue gas emitted by the cogeneration plant. The two options are described in the sections below.
- Capturing CO2 from the blast furnace gases
The gas produced by the blast furnace contains up to 60%of the total CO2 produced by the plant mixed with hydrogen and carbon monoxide. It has high CO2 concentration compared to the coke oven and basic oxygen furnace. The direct capture of CO2 from combustible gases would employ similar separation techniques as the ones employed in commercial hydrogen production processes.
A more innovative technology to separate CO2 from blast furnace gas is the Sorption Enhanced Water Gas Shift technology, or SEWGS process. This process combines the CO2 adsorption and the water-gas shift (WGS) in one reactor with advantage for the overall energy consumption; although it was designed for application at coal gasification plants, it can be adapted for blast furnace gas to increase hydrogen yield and facilitate CO2 removal. As part of the STEPWISE project a 14 t/d pilot SWEGS unit is currently being installed at Swerea MEFOS in Lulea (SE) and will be operational before the end of the year.
- Capturing CO2 from the cogeneration plant flue gases
Most steel plants usually combine the gases leaving the coke oven, the basic oxygen furnace and the blast furnace in a collection system and burn them together in the co-generation plant, producing electricity and heat needed for the facility. For the gas stream exiting the co-generation plant, the most likely capture approach would be chemical solvent-based CO2 separation.
CO2 separation with chemical absorption using an MEA-based solvent is well-know and commercially available from several vendors, therefore it would be the first technology of choice. There are also examples of steel companies developing their own technologies - Nippon Steel (within the COURSE 50 consortium), China Steel Corporation, Baosteel and POSCO for instance conducted pilot experiments to capture CO2 using proprietary processes optimized for steel mills.
Partial capture approach, currently being investigated in the CO2StCap project, could offer more economically attractive CCS approaches by designing smaller capture unit that are operated using only waste heat available at the steel facility, therefore reducing significantly its OPEX. 
Alternative CCS approaches in steel-making
Direct Iron Reduction (DRI) and HIsarna represent alternatives to BF-BOF steel making routes that are advantageous for CCS applications as they generate gas streams with increased concentration of CO2, up to 90%.
Direct Iron Reduction (DRI) and the Abu Dhabi full scale CCS facility
Iron ore can also be converted to steel through the Direct Reduced Iron (DRI) process by directly reducing iron ore with a reducing gas (eg. H2 and CO - commonly produced by reforming natural gas). The DRI process uses 20%more energy overall than the BF-BOF process, but has 20%lower CO2 emissions, resulting from the use of natural gas rather than coke.
It is usually applied in regions where there is abundant natural gas, such as the US and the Middle East. In some DRI plant configurations the CO2 separation step is inherent to the process and CO2 is simply vented to the atmosphere. DRI plants located nearby a storage or EOR site represent great CCS opportunities.
The Abu Dhabi CCS Project - also called Emirates Steel Industries (ESI) CCS project - is the world’s first iron and steel project to apply CCS at large-scale. It is located in the United Arab Emirates and since 2016 captures around 0.8 Mt/y of CO2 from gases produced by the DRI reactor. The CO2 is transported through a 43 km pipeline to the Rumaitha oil field for the purpose of EOR.
Innovative steelmaking process with CCS: HIsarna
HIsarna is an innovative steelmaking process developed by Tata Steel as part of the international ULCOS programme. HIsarna is a smelting reduction process in which iron ore is directly converted into liquid iron. This technology does not require the preparation of iron ore agglomerates or the production of coke. Without these preparatory steps, the HIsarna process can use the raw materials more economically. It also requires less energy to operate. Compared to blast furnace steel production, it can reduce CO2 emissions by 20%.
This technology produces flue gas with very high CO2 concentration (above 90%) because pure oxygen is used instead of air to feed the reaction. It does not require CO2 separation beyond simple water removal. This can lead to significant savings in capital and operating costs associated to CO2 capture. Therefore it is extremely attractive for CCS equipped steel plants of the future.
Pilot-scale testing of the HIsarna process started in 2011 at Tata Steel’s site in Ijmuiden, the Netherlands. Since 2011 there have been four test campaigns. The 5th campaign, starting in 2017, will be a so called “endurance test” lasting about 3-6 months to test long-term operational and maintenance aspects of the process and equipment. HIsarna is a very promising technology that could be soon deployed as substitute to BF-BOF process after demonstration at commercial scale will be executed.
- The steel sector, as other carbon intensive sectors, is facing increasing pressure to reduce its carbon footprint. Looking at the size of the problem, CCS is one of the few options to achieve deep CO2 emission reductions.
- CCS is a mature technology that can be retrofitted today on existing iron and steel production plants, maintaining the existing production equipment (ie. blast furnaces).
- Commercial examples already exist. Ongoing R&D effort, and the application of CCS to innovative production routes like DRI and HIsarna can result in significant cost reductions.
- In some part of the world like China, UAE or North America, EOR can be a real driver for large scale CCS project.
- Where EOR is not possible and other financial incentives are missing, the public sector needs to ease industrial CCS by taking the lead in facilitating CO2 transport and storage infrastructures.
- As the timeframe for action is getting tighter we need to start now with concrete action towards effective policies and incentives in order to guarantee the implementation of large scale projects in the next decade.