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Iron / Steel (Ferrous): Ladles / Ladle Drying / Ladle Pre-Heating

Ladles are used to transport molten metal from the BOF or EAF to the secondary steel refining station and then on to the casting operation.

Ladles are dried slowly after new refractory linings are installed. They're heated from cold condition prior to molten metal being poured into them. They are also re-heated between molten metal casts. In addition to re-heating, burners are used to remove any slag or residue from the previous pour. Modern ladle drying and pre-heating equipment can be configured to heat ladles in either a horizontal or vertical position.

The benefits of ladle pre-heating include the fact that heating ladles to high temperatures prevents a rapid decline in molten steel temperature during transfer to the ladle refining station or directly to the casting step. Also a well-pre-heated ladle allows the tapping temperature to be lowered which saves energy and costs.
Both natural gas / air and oxy-fuel ladle heating systems are employed. However, oxy-fuel ladle pre-heating users report that the time required to heat ladles is reduced by as much as 40% compared with air / fuel systems.

The firing rates of ladle drying, pre-heating and heating systems will vary depending on the ladle size. However, consumption for a 100 ton ladle has been reported, as follows:

  • 3.3 Mcf (3,300,000 MMbtu) natural gas consumption (air / fuel) to heat a 100 ton ladle in one hour to 2,100°F.
  • 1.4 Mcf (1,400,000 MMbtu) per hour required to hold the ladle at 2,100.
  • Oxy-fuel will decrease this use.

Other Notes on Ladle Heating:
A ladle with refractory walls preheated to 2300°F will allow an approximate 20°F reduction in metal tapping temperature (from the BOF or EAF). This saves energy at the melter, melting time, and can reduce the amount of alloy or carbon additions in the melter to compensate for increased losses at higher temperatures. Higher ladle heating temperatures also provide a longer period of time before temperature of the molten metal falls below specification. This increases the time operators have to transfer ladles with molten materials to the ladle refining station or direct to a caster. The flexibility this increased time can offer can be extremely important to prevent costly "pour-backs" in case of process upsets.