Oxygen enrichment in steel and foundries

Basic oxygen furnace

The EU Best Available Techniques reference document (BREF) for iron and steel production, published in 2013, describes the LD converter as a pear-shaped, refractory-lined reactor into which a water-cooled oxygen lance is lowered; through this lance, pure oxygen (over 99%) from an air separation plant is blown onto the liquid hot metal. A cycle covers charging scrap and molten hot metal, oxygen blowing, sampling and temperature recording, and tapping, and the document reports that modern steelworks produce up to 380 tonnes of steel in a 30 to 40 minute cycle.

Electric arc furnace and blast furnace

For electric arc furnaces, the same BREF says that oxygen lances and oxy-fuel burners are used more and more to assist the early stages of melting. Oxygen injected together with granular carbon generates a foamy slag; oxygen also decarburises the melt and removes undesired elements such as phosphorus and silicon; and oxygen injected into the top of the furnace reacts with CO and hydrocarbons (post-combustion).

At the blast furnace, the BREF describes a hot air blast, enriched with oxygen, injected at tuyère level with auxiliary reducing agents, and records oxygen enrichment of the hot blast and oxy-coal injection at the tuyères in EU blast furnace plants.

Cupola furnaces in foundries

The 2024 BREF for smitheries and foundries describes oxygen enrichment of the cupola combustion air, made directly in the blast supply, by injection into the coke bed or through the tuyères. In the cold blast cupola, it gives a higher combustion temperature of the coke, and compared with normal operation its continuous use enables one of these improvements: a higher metal temperature for the same coke consumption, a lower coke consumption for a given metal temperature, or an increased output from an existing cupola through a higher melting rate.

• Oxygen level, for cold blast cupolas: the oxidising air mixture usually contains 22% to 25% oxygen, an enrichment of 1% to 4%.
• Expected increase in tapping temperature for a given coke charge, compared with conventional cold blast operation with one row of tuyères: 15 °C with blast enrichment, 85 °C with injection into the coke bed (the well) and 40 °C with tuyère injection.
• Divided blast cupolas: the melting rate increases by around 6.8% and the tapping temperature by about 20 °C for each 1% of direct oxygen enrichment.
• Practice: almost all European hot blast cupolas inject oxygen through the tuyères, and for cold blast cupolas the BREF says oxygen enrichment can be considered the standard technique.

The BREF adds that the economic case for using oxygen has to be established case by case.

Oxy-fuel burners

In oxy-fuel combustion, the combustion air is replaced fully or partially with pure oxygen. The 2024 foundries BREF reports that full oxy-fuel combustion may offer energy savings of up to 50% and reduce the exhaust gas volume by up to 72%. It also describes one German foundry with a 24 t/h hot blast cupola where six oxy-fuel burners raised the melt rate by 20% and cut coke consumption by 6%, based on long-term results.

ULTRAOX VSA and industrial furnaces

The Ultra Controlo Industrial 2026 catalogue counts metallurgy among the more than 40 industries its compressed air, gas and vacuum systems serve. ULTRAOX VSA, the Ultra Controlo industrial oxygen plant, lists industrial furnaces among its applications. It delivers 75% to 95% oxygen at 50 kPa, with an additional oxygen booster on demand for higher pressures, and its seven models deliver 18 to 240 m³/h at 93% oxygen. That purity range is below the over 99% oxygen that the iron and steel BREF describes for the LD converter; see industrial oxygen generators.