New Furnace Adaptation Could Decarbonise Steel Production

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01 March 2023

Researchers from the University of Birmingham have designed a novel adaptation for existing iron and steel furnaces that could reduce carbon dioxide (CO₂) emissions from the steelmaking industry by nearly 90 per cent.

This radical reduction is achieved through a closed-loop carbon recycling system, which could replace 90 per cent of the coke typically used in current blast furnace-basic oxygen furnace systems and produces oxygen as a by-product.

Devised by Professor Yulong Ding and Dr Harriet Kildahl from the University of Birmingham’s School of Chemical Engineering, the system is detailed in a paper published in the Journal of Cleaner Production, which shows that if implemented in the UK alone, it could deliver cost savings of £1.28 billion in 5 years while reducing overall UK emissions by 2.9 per cent.

The UK only has two steel companies left, however, the government recently approved the building of a new coal mine to supply the steel industry. The government’s Climate Change Committee (UKCCC) have stated that 85 per cent of the coal will be exported, negating concerns of significantly adding to the UK's carbon emissions. That said, it's still not favourable in terms of the UK's global impact or image. 

"The system we are proposing can be retrofitted to existing plants, which reduces the risk of stranded assets, and both the reduction in CO₂, and the cost savings, are seen immediately.”

 

– Professor Yulong Ding
Founding Chamberlain Chair, Chemical Engineering, Birmingham University

Why is Steel Currently Carbon Intensive?

Most of the world’s steel is produced via blast furnaces which produce iron from iron ore and basic oxygen furnaces which turn that iron into steel. The process of steel production is inherently carbon-intensive, using metallurgical coke produced by destructive distillation of coal in a coke oven, which reacts with the oxygen in the hot air blast to produce carbon monoxide. This reacts with the iron ore in the furnace to produce CO₂. The top gas from the furnace contains mainly nitrogen, CO and CO₂, which is burned to raise the air blast temperature up to 1200 to 1350^oC in a hot stove before being blown to the furnace, with the CO₂ and N₂ (also containing NOx) emitted to the environment.

Professor Yulong Ding, Founding Chamberlain Chair of Chemical Engineering said: “Current proposals for decarbonising the steel sector rely on phasing out existing plants and introducing electric arc furnaces powered by renewable electricity. However, an electric arc furnace plant can cost over £1 billion to build, which makes this switch economically unfeasible in the time remaining to meet the Paris Climate Agreement. The system we are proposing can be retrofitted to existing plants, which reduces the risk of stranded assets, and both the reduction in CO₂, and the cost savings, are seen immediately.”

The Breakthrough

The new novel recycling system captures the CO₂ from the top gas and reduces it to CO using a crystalline mineral lattice known as a ‘perovskite’ material. The material was chosen as the reactions take place within a range of temperatures (700-800^oC) that can be powered by renewable energy sources and/or generated using heat exchangers connected to the blast furnaces.

Under a high concentration of CO₂, the perovskite splits CO₂ into oxygen, which is absorbed into the lattice, and CO, which is fed back into the blast furnace. The perovskite can be regenerated to its original form in a chemical reaction that takes place in a low-oxygen environment. The oxygen produced can be used in the basic oxygen furnace to produce steel.

Making a Difference

Iron and steelmaking is the biggest emitter of CO₂ of all foundation industrial sectors, accounting for nine per cent of global emissions. According to the International Renewable Energy Agency (IRENA), it must achieve a 90 per cent reduction in emissions by 2050 to limit global warming to 1.5°C.

The University of Birmingham Enterprise has filed a patent application covering the system and its use in metal production and is looking for long-term partners to participate in pilot studies, deliver this technology to existing infrastructure, or collaborate on further research to develop the system.

Picture: a steel mill/factory. Image credit: Pixabay.

Article written by Bailey Sparkes | Published 01 March 2023

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