‘ Closed loop ’ to reduce CO 2 emissions
Birmingham researchers have devised a ‘ closed loop ’ carbon recycling system that could radically reduce carbon dioxide emissions from the steelmaking industry .
Text by the University of Birmingham
Researchers from the University of Birmingham have designed a novel adaptation for existing iron and steel furnaces that could reduce carbon dioxide ( CO 2 ) emissions from the steelmaking industry by nearly 90 %. This radical reduction is achieved through a ‘ closed loop ’ carbon recycling system , which could replace 90 % of the coke typically used in current blast furnace-basic oxygen furnace systems and produces oxygen as a biproduct . 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 EUR 1.45 billion in 5 years while reducing overall UK emissions by 2.9 %.
Professor Ding 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 EUR 1.1 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 CO 2 , and the cost savings , are seen immediately .”
Steel production 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 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 CO 2 . The top gas from the furnace contains mainly nitrogen , CO and CO 2 , which is burned to raise the air blast temperature up to 1200 to 1350 ° C in a hot stove before blown to the furnace , with the CO 2 and N 2 ( also containing NOx ) emitted to the environment .
The novel recycling system captures the CO 2 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 ° C ) that can be powered by renewable energy sources and / or generated using heat exchangers connected to the blast furnaces . Under a high concentration of CO 2 , the perovskite splits CO 2 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 . Iron and steelmaking is the biggest emitter of CO 2 of all foundation industrial sectors , accounting for 9 % of global emissions . According to the International Renewable Energy Agency ( IRENA ), it must achieve a 90 % reduction in emissions by 2050 to limit global warming to 1.5 ° C . 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 .
46 Stainless Steel World March 2023 www . stainless-steel-world . net