New retrofit for existing blast furnaces could reduce emissions from steelmaking by 90%

A factory for the production of steel
Iron and steel production is the largest CO2 emitter of all basic industrial sectors, accounting for 9% of global emissions.

Researchers from the University of Birmingham have designed a new retrofit for existing iron and steel furnaces that could reduce carbon dioxide (CO2) emissions from the steel production industry by almost 90%.

This radical reduction is achieved by a ‘closed-loop’ carbon recycling system, which could replace 90% of the coke commonly used in current blast furnace oxygen furnace systems and produce oxygen as a by-product.

Designed 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 savings of £1.28 billion over 5 years while reducing total UK emissions by 2.9%.

Professor Ding said: “Current proposals to decarbonise the steel sector rely on phasing out existing plants and introducing electric arc furnaces powered by renewable electricity. However, an electric arc furnace can cost more than £1 billion to build, making this change economically unfeasible in the time left to meet the Paris climate agreement. The system we propose can be retrofitted into existing plants, thus reducing the risk of stranded assets, as well as reducing CO2and the cost savings are immediately visible.”

Most of the world’s steel is produced through blast furnaces that produce iron from iron ore and basic oxygen furnaces that convert that iron into steel.

The process itself is carbon intensive, using metallurgical coke produced by the destructive distillation of coal in a coke oven, which reacts with oxygen in a blast of hot air 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 CO2which is burned to raise the air blast temperature to 1200 to 1350onC in a hot furnace before blowing into the furnace, with CO2 and N2 (also contains NOx) emitted into the environment.

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

Current proposals to decarbonise the steel sector rely on phasing out existing plants and introducing electric arc furnaces powered by renewable electricity. However, an electric arc furnace can cost more than £1 billion to build, making this change economically unfeasible in the time left to meet the Paris climate agreement. The system we propose can be retrofitted into existing plants, which reduces the risk of stranded assets, and the CO2 reduction and cost savings are immediately visible.

Professor Yulong Ding, Faculty of Chemical Engineering

Under high CO concentration2perovskite cleaves CO2 into oxygen, which is absorbed into the grate, and CO, which is returned back to the blast furnace. 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 a basic steelmaking oxygen furnace.

Iron and steel production is the biggest emitter of CO2 of all major industrial sectors, accounting for 9% of global emissions. According to the International Renewable Energy Agency (IRENA), a 90% reduction in emissions must be achieved by 2050 to limit global warming to 1.5°C.

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

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