Approaches for large-scale green steel production

The pilot plant was put into operation on 2 December 2021 (Source: Paul Wurth/SMS)

The carbon intensity of steel production has reduced in recent years, which is a positive development. However, the high demand for steel has led to an increase in global emissions from steel production. It is expected that the demand for steel will continue to rise, possibly by one-third by 2050, making it all the more important to be able to produce green steel not just in pilot plants but on an industrial scale.

The primary blast furnace route is still the most important source of iron and steel (Source: Kateryna Babaieva/pexels)

What are the options for nearly CO₂-neutral steel production at an industrial scale?

Steel can be produced either from recycled scrap or from iron ore, with 70% of the steel produced worldwide being extracted from ore – usually in blast furnaces. The high temperatures required for this process are traditionally generated using carbon-intensive coke. The processing of recycled scrap is less emission-intensive as it is based on electricity. However, this does not reduce CO2 emissions in the overall system.

But emissions can be reduced by replacing coke with natural gas.

Due to the long investment cycles for metallurgical plants, time-consuming and cost-intensive new project developments that are built on greenfield sites are likely to be the exception. Instead, a large proportion of future CO2 savings will come from retrofitting existing smelting works (brownfield). There is no patent remedy for the "best" option here. However, companies such as the Düsseldorf-based SMS group offer customised solutions for different customer scenarios.

EasyMelt is designed to operate with a fifth of the current consumption of 300 kg of coke and 200 kg of pulverised coal injection, as long as sufficient hydrogen is not available (source: think.steel)

Brownfield example: Upgrade with EASyMelt

The search for ways to achieve virtually CO₂-neutral steel production on an industrial scale has driven SMS group to enhance the emission reduction potential of the 'Blue Blast Furnace' using the EASyMelt process. The Blue Blast Furnace is characterised by the production of synthesis gas (carbon monoxide and hydrogen) and its introduction at the bottom of the blast furnace shaft to replace coke as a reducing agent.

The EASyMelt process is based on electrically assisted syngas smelting and is seen as a promising alternative to direct reduction. In the electrified direct reduction and metallisation process, the hot blast is replaced by coke oven gas, natural gas, hydrogen, or ammonia. A minimal amount of coke is sufficient for this process. This approach is expected to achieve emission savings of over 60% compared to the conventional integrated primary blast furnace (BF-BOF process), depending on the energy input. Carbon Capture and Storage (CCS) or the utilization of biomass or biogas as raw material could be considered to further decrease emissions. Remarkably, when it comes to producing emission-reduced iron, the EASyMelt technology could be less CAPEX-intensive than other technologies for current factories.

An impressive aspect of this process is that it can be easily adapted to different scenarios and is more resilient to supply shortages. Most importantly, EASyMelt can continue to use conventional sintered material, which avoids intense competition for the limited supply of high-quality pellets. Similar to the implementation of the 'Blue Blast Furnace', EASyMelt will also be realised step by step, with various technological elements working together. The central components include the shaft injection of reducing gas, the plasma-assisted superheating of the nozzle injection and finally the efficient separation and utilisation of the remaining emissions.

Greenfield example: direct reduction in the electric arc furnace

If green hydrogen is available in sufficient quantities at competitive prices, the key to decarbonisation according to the state of the art lies in the combination of direct reduction and electric steel production.

In this model, decarbonisation is achieved through the complete electrification of production, i.e. the replacement of blast furnaces powered by coke or natural gas with electric arc furnaces. So-called direct reduction plants can then be operated in electric arc furnaces. These work on the basis of hydrogen and, depending on how the hydrogen is produced, emissions from primary steel production could be reduced by up to 90%. A certain amount of residual emissions and purchased emissions in the course of the supply chain are unavoidable according to the current state of the art. However, green hydrogen, produced solely through renewable energy sources, is expected to be scarce in Germany over the coming years. As a result, natural gas is necessary as a bridging technology.

Iron production with MIDREX technology

The MIDREX direct reduction facilities in Paul Wurth's portfolio offer three main technologies for bridging the transition from 100% natural gas to 100% hydrogen:

- MIDREX NG enables the substitution of up to 30% natural gas with hydrogen, without the need to modify equipment

- MIDREX Flex is compatible with all natural gas and hydrogen combinations, up to operating solely with hydrogen

- MIDREX H2 is purpose-built for employing hydrogen concentrations of up to 100% in a MIDREX shaft furnace

Operation of a blast furnace using the Midrex process (Source: Midrex Technologies Inc.)

The federal government and the state of North Rhine-Westphalia are subsidising the construction and operation of thyssenkrupp Steel's first direct reduction plant to the tune of 2 billion euros. (Source: thyssenkrupp)

In natural gas-based direct reduction plants, pre-reduced iron ore pellets undergo reduction in a MIDREX shaft prior to being fed as hot DRI directly into an electric arc furnace. The material is melted in the electric arc furnace, producing liquid steel. No intermediate step is required and, depending on the MIDREX technology used, only a small amount of carburisation is needed to reduce the nitrogen content of the steel.

The carbon content of low-carbon to carbon-free DRI from hydrogen reduction can be changed in the lower cone of the shaft furnace, also known as the cooling zone. Scrap can also be charged into the electric arc furnace. The required degree of purity of the scrap is only determined by the quality requirements of downstream processing stages. For greenfield initiatives, this approach is a compelling solution.

One example of the application of this process is the H2 Green Steel project in Boden in northern Sweden. The world's first virtually carbon-neutral steelworks is being built there. The plant is set to produce green steel from 2025 and demonstrate the feasibility of producing high-quality DRI using 100% hydrogen.

"tkH2Steel": thyssenkrupp sets course for green steel

In August of this year, Vice Chancellor and Federal Minister for Economic Affairs and Climate Protection Robert Habeck confirmed the funding commitment for the "tkH2Steel" decarbonisation project amounting to around two billion euros. The state of North Rhine-Westphalia is contributing up to 700 million euros to the total funding. thyssenkrupp's own investment amounts to just under one billion euros. This marks the start of one of the world's largest decarbonisation projects.

Ambitious hydrogen ramp-up

The key to the transformation project is the ambitious ramp-up of the use of hydrogen, which will quickly save large amounts of CO2. It is the first plant combination of its kind in the world. The core of the concept is the integration of a technologically new plant combination into Europe's largest steelworks. The coal-based blast furnaces will be replaced by a 100% hydrogen-capable direct reduction plant with two smelters and a production capacity of 2.5 million tonnes of directly reduced iron per year. The iron produced there will be liquefied into pig iron in specially developed downstream melting units. All subsequent production steps can take place in the existing plant structure, including the steelworks.

The plant for the direct reduction of iron ore is scheduled for completion in 2026, but will initially run on natural gas. Annual savings of up to 3.5 million tonnes of CO2 are expected - that is already just under five percent of the Ruhr region's emissions. Hydrogen is expected to be available from 2029 so that the plant can then be operated with around 143,000 tonnes of hydrogen per year – the electricity required to produce this amount corresponds to the generation of around 500 wind turbines. The necessary prerequisites for achieving this ambitious goal are therefore a massive expansion of renewable energies and the rapid ramp-up of a functioning hydrogen market.

The transformation to climate neutrality depends on the availability of green electricity and climate-neutral hydrogen. Technologies for emission-reduced steel production already exist. Plant manufacturers can already incorporate them into a large number of existing and future plants.

Find out more about the possibilities of emission-reduced steel production and visit wire & Tube in Düsseldorf from 15–19 April 2024! Here you can experience SMS group, thyssenkrupp, Paul Wurth and H2 Green Steel live and learn more about the current status of their decarbonisation projects.