Gases for Melting and Casting in Iron and Steel Production

Technologies include: oxygen fuel (oxy-fuel) and oxygen-enhanced (air/oxy-fuel) combustion systems; nitrogen and argon blanketing (shrouding / inerting); stirring using gases; and other industrial gases applications. These offer significant financial benefits for preheating, melting, holding and casting in the iron and steel production industry.

Offerings applicable to:

Oxygen is injected into the blast furnace to increase production rate and to support the combustion of alternative fuels. The cost of oxygen is offset against fuel savings.

Blast Furnace (BF) - BF Blowdown

Oxygen is injected into the furnace to increase productivity, reduce flue gas volume and allow a more stable flame. The cost of oxygen is offset against fuel savings.

The Basic Oxygen Furnace is a highly efficient item of equipment for converting pig iron into steel by injecting oxygen. Air Products can supply the gas, advanced flow and process control systems and technical expertise (in, eg, positioning of lances).

Basic Oxygen Furnace (BOF) - Scrap Preheating

Complete burner and control packages have been developed to efficiently preheat ferrous scrap using non-water-cooled oxy-fuel burners. 70% fuel savings and 50% reductions in heat-up rates are typical.

Basic Oxygen Furnace (BOF) - Slag Splashing

By injecting nitrogen down an existing BOF oxygen lance to splash a protective coating of molten slag
on the inner refractory wall, gunning consumption is considerably decreased and campaign life extended.

Basic Oxygen Furnace (BOF) - Bottom Stirring

The melt is stirred by using high-pressure gas injection to improve steel yield and alloy recovery,
and extend campaign life.

The electric arc method of melting metal is inefficient until a flat bath is achieved. By using a fuel-efficient oxy-fuel flame at the beginning of the melting process, a greater overall melting efficiency is achieved with a faster melt rate. Further temperature homogeneity benefits can be achieved by using these burners to direct thermal energy at cold spots caused by uneven energy distribution from the electrode arcs. Additionally, the burners can be positioned in front of the slag door to enable early, efficient oxygen lancing, or over the tap hole area to promote quick, trouble-free tapping. Electrical savings of 80kWh/tonne and 20% production increases have been achieved.

Electric Arc Furnace (EAF) - Foaming Slag Practice

Lances are hydraulically manipulated through the slag door to inject oxygen, carbon and lime into the surface slag layer during the electric arc melting process. This action decarburises the melt and aids formation of an insulating foamy slag layer which decreases heat loss from the melt surface and therefore reduces energy costs.

Electric Arc Furnace (EAF) - Post-Combustion

Oxygen is injected into the post-combustion zone of electric arc furnaces to promote combustion of carbon monoxide inside the furnace rather than in the off-gas handling system. This reaction produces heat that is transferred to the charge, reducing energy consumption (typical electrical savings of 10-20 kWh/tonne) and increasing productivity by up to 4%. Additionally the post-combustion injectors reduce loading on the EAF baghouse and improve environmental compliance with respect to carbon monoxide.

Complete burner and control packages have been developed to efficiently preheat ladles or torpedo cars using non-water-cooled oxy-fuel burners. 70% fuel savings and 50% reductions in heat-up rates are typical.

Ladle or Torpedo Car - REHeat® heating

Our patented technology (with Bethlehem Steel) for chemically reheating steel by simultaneous injection of fuel (aluminium and silicon) and oxygen achieves temperature gains of 5 to 8°C/min. Subsequent stirring with inert gas ensures that steel cleanliness is not adversely affected. This technique is used to reheat cold ladles or torpedo cars of metal to avoid expensive pourbacks and subsequent casting interruptions.

Using nitrogen to displace the oxygen in a holding furnace atmosphere reduces the formation of oxides at the melt surface providing a higher yield and improved quality.

Holding Furnace - Pressurising

Shrouding molten metal streams with an inert argon atmosphere minimises oxide and nitride formation to decrease alloy wastage, reduce production rejects and increase product quality. Typical applications are ladle-to-tundish, tundish-to-mould and ingot teeming processes.