Why does British Steel need to be rescued by the government and what happens next?

As the UK government took control of the British Steel site at the weekend after it was put at risk of imminent closure, some of our experts help explain what a blast furnace is and how they work.

What is a blast furnace?

John Patsavellas, member of the Institution of Engineering and Technology’s (IET) Sustainability and Net Zero Policy Centre, in conjunction with Professor Mark Jolly of Cranfield University said: “Blast furnaces reach temperature of more than 1,700 degrees Celsius for smelting iron. Iron ore, coke and limestone are melted: the ore provides the iron, while the coke acts as fuel and a reducing agent that imparts carbon into the iron, reducing its melting point and, coupled with the limestone, removes its impurities. These removed impurities then form slag, a glassy residue which can be used to make cement.

“This process reduces iron oxide into iron using carbon monoxide generated by the coke; it’s therefore important to have the right type of ore and coke to ensure high quality steel is produced with a minimal amount of slag and ensuring low energy use. Lower quality materials will lead to higher energy consumption, higher emissions, and higher costs to make a lower quality product.”

Can we just turn it off and turn it on again?

Professor John Loughhead CB OBE CEng, Fellow and energy expert at the Institution of Engineering and Technology (IET), said added: “If the furnace cools, the slag will solidify into a hard substance and block the furnace, so would need to be removed mechanically, which itself can damage the furnace. We need to maintain these supplies of materials to keep the furnaces running and stop them getting cold. We need to use a particular type of coal, coking coal, to make steel.”

Prof Patsavellas explained: “Blast furnaces are designed to run continuously for their 10–20-year lifecycle, with just the occasional re-linings needed for maintenance. If a furnace cools down, the brick linings and refractory materials – including bricks in the furnace – may crack due to the changing temperature, leading to an expensive and time-consuming process to complete the repairs and make them useable again.

“Restarting a cooled furnace can take months, involving a lot of hot, dirty, and risky work that will be very expensive and is entirely avoidable. You’re essentially looking at a complete rebuild of the inside of the furnace. Maintaining a continuous supply of fuel, ore and power is therefore essential to our national steel capability to ensure industrial resilience.

“The steel-making process has been optimised around the use of specific materials, which needs to be maintained to keep the high quality. Using other materials or lower quality ones can make the economics of the plant not viable.”

What happens next?

Prof Loughhead commented: “Protecting the plant will mean we need to assure a market price at a rate that Scunthorpe can achieve. To do this while achieving net zero ambitions will mean either supporting carbon capture and storage developments at the plant, or moving to reprocessing scrap metal with electric furnaces; the latter does not produce high quality ‘virgin’ steel though, so we’d still be reliant on imports.

“High electricity costs in the UK, coupled with carbon pricing, mean the plant incurs high running costs, which hinders its ability to be competitive on the export market. A reduced market for the product then makes it hard to achieve efficiencies through volume.”

Prof Patsavellas continued: “Keeping the blast furnaces going at Scunthorpe should be a temporary measure to maintain the production of high quality ‘virgin’ steel in the UK. This is essential for a number of industries, mainly defence and infrastructure.

“We also need to invest in developing the new technology of direct reduction of steel, which uses hydrogen or ammonia to cut out the interim stage of using pig iron with high carbon which then has to be reduced in the refining process using oxygen. Both the blast furnace and the refining stages produce huge amounts of CO2, while direct reduction avoids this; the challenge with it at the moment is the supply and cost of the chosen reducing gas. Research into this technique is underway at the Materials Processing Institute.

“The coke from the Cumbrian coal mine was never of the quality high enough for the Scunthorpe plant; it was destined to be exported for processes in other parts of the world, which would have increased global carbon emissions.”

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