Recuperator

Recuperator is a counter current heat exchanger in which hot gases at  from the scrap preheater enters and exit gases leave at  and oxygen enters at  and preheated oxygen enters the furnace. The efficiency of the heat exchanger depends on the flow velocity of hot gas and oxygen. For a given cross section of the flow passage of the recuperator, the length of the recuperator must be optimized so that heat transfer from the furnace gases is maximum to preheat the incoming oxygen. The efficiency of the recuperator can be defined as



Furnace operation

A liquid heel is left in the furnace from the previous heat in proportion which depends on scrap proportion. Higher the scrap proportion, higher is the amount of heel.

The operation in this case starts with injection of carbon in the hot metal heel until 3% carbon is achieved. This is followed by charging of the preheated scrap and refining commences immediately thereafter. Oxygen injection for refining and post combustion begins simultaneously. Slag is allowed to form so that it can flow over the sill down the pit.

The refractory consumption is kept within the limits by using water cooled panels and scrap supporting bass. To increase furnace life and effective preheating, maximum and minimum size of scrap are controlled.

Important Features

• Oxygen is blown by a lance submerged in the melt for refining and simultaneously oxygen is also injected for post combustion.
  
  
• Utilization of sensible heat of furnace off-gases by preheating scrap and  
  
  
• Flexibility to use hot metal  and scrap in any proportion
  
  
• Wet de-dusting system
  
  
• Liquid steel with low levels of phosphorus and sulphur
  
  
• Low noise level
  
  
• An average of 42 heat/ day is possible.

With the above features EOF presents a low cost alternative for steelmaking combined with flexibility in terms of metallic charge mix.