How do blast furnaces work?

Sanjeev Gupta, the businessman at the centre of efforts to salvage the Welsh steel industry, says any plan to buy Tata’s operation will do away with blast furnaces at Port Talbot. But how do they actually work?

Blast furnaces such as the two in Wales are huge steel stacks lined with brick. Iron ore, coke and limestone are dumped in the top, and preheated air is blown or blasted into the bottom of the chamber. This process, through various chemical reactions, produces liquid iron — or hot metal as it sometimes called.

It is a process invented in the 14th century to turn ore dug from the ground into a malleable metal by removing the oxygen. The liquid iron becomes the raw material for the rolling and other processes of modern steel making. In the UK, the iron ore raw material and the coal to make the coke are both imported at considerable cost.

A blast furnace also represents a huge overhead cost because, once fired up, it typically runs for six to 10 years, giving an operator little flexibility. If it is shut down prematurely, cooling damages the brick lining.

Steelmaking using electric arc furnaces, such as Mr Gupta is proposing, is a cheaper technology and uses steel scrap as its raw material. The scrap is melted using electricity. But the process is energy intensive, with an industrial-sized arc furnace consuming as much power as a town of a 100,000 people

Industry officials say it also does not produce the same quality steel as that made using blast furnaces.