UK researchers devise a way to reduce carbon emissions from steel by 90%

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Researchers at the University of Birmingham in the U.K. have devised a new system that can be retrofitted on existing steel furnaces and help reduce carbon emissions of the process by as much as 90 percent, a university press release said.

The iron and steel-making industry is one of the world's largest producers of carbon dioxide, accounting for nearly nine percent of all global emissions. As per estimates of the International Renewable Energy Agency (IRENA), the industry must reduce its emissions by as 90 percent by 2050 if the goals of the Paris Climate Agreement are to be met.

So far the plan to reduce emissions has involved switching to an electric arc furnace powered by renewable electricity. However, building an electric arc furnace costs over US$1.24 billion, making it difficult for industries to switch. The novel retrofit can be used in existing facilities and is expected to deliver financial savings and reduce carbon emissions.

Conventionally, steelmaking involves using blast furnaces to extract iron from iron ore and then using oxygen furnaces to convert it into steel. The distillation of coal produces the first metallurgical coke in a coke oven. The coke then reacts with the iron ore to produce carbon dioxide.

The top gas from the furnace contains nitrogen, carbon monoxide, and carbon dioxide, which is then burnt to raise the air blast temperature to 2192 - 2462 Fahrenheit (1200 to 1350oC) in a hot stove before being blown into the furnace. After manufacturing steel, carbon dioxide and nitrogen are released into the environment.

A team led by Yulong Ding, a professor of chemical engineering at the University of Birmingham, has now devised a new system that captures the carbon dioxide from the top gas and then reduces it to carbon monoxide using a perovskite, a crystalline mineral lattice.

Using the material also ensures that steel-making reactions can now occur within a temperature range of 1292-1472 Fahrenheit (700-800oC), which can be achieved using renewable energy sources or heat exchanges connected to blast furnaces.

In the presence of high amounts of carbon dioxide, the perovskite splits the gas into oxygen which its lattice structure absorbs, and carbon monoxide is fed back to the blast furnace. The reaction between the perovskite and oxygen is also reversible. In a low-oxygen environment, the crystal lattice releases the absorbed oxygen, which can then be used in the oxygen furnace to make steel.

The press release said that this system's closed loop of carbon recycling could replace 90 percent of the coke typically used in blast furnaces. "Current proposals for decarbonizing the steel sector rely on phasing out existing plants and introducing electric arc furnaces powered by renewable electricity. 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 Ding added.

The research was recently published in the Journal of Clean Production.

Abstract

We present here a first-principles study of the sector coupling between a thermochemical carbon dioxide (CO2) splitting cycle and existing blast furnace – basic oxygen furnace (BF-BOF) steel making for cost-effective decarbonisation. A double perovskite, Ba2Ca0.66Nb0.34FeO6, is proposed for the thermochemical splitting of CO2, a viable candidate due to its low reaction temperatures, high carbon monoxide (CO) yields, and 100% selectivity towards CO. The CO produced by the TC cycle replaces expensive metallurgical coke for the reduction of iron ore to metallic iron in the blast furnace (BF). The CO2 produced from the BF is used in the TC cycle to produce more CO, therefore creating a closed carbon loop, allowing for the decoupling of steel production from greenhouse gas emissions. Techno-economic analysis of the implementation of this system in UK BF-BOFs could reduce steel sector emissions by 88% while increasing the cost-competitiveness of UK steel on the global market through cost reduction. After five years, this system would save the UK steel industry £1.28 billion while reducing UK-wide emissions by 2.9%. Implementation of this system in the world's BF-BOFs could allow the steel sector to decarbonise in line with the Paris Climate Agreement to limit warming to 1.5 °C.