Ingot Casting : Combustion Technology

Adapted from: “The Making, Shaping, and Treating of Steel”, 10th edition. Association of Iron and Steel Engineers, 1985, p. 844

Combustion Technology
Energy Consumption
Process Description
R&D Trends

Soaking pits are used to provide uniform heating of the ingots to a range of 2150°F to 2450°F. The hearth sizes are 100 to 300 sq ft. with capacities of several hundred tons. The figure shows a typical soaking pit furnace building with removable roof, ingot car, and cinder removal. The furnace shown uses coke breeze on the floor (called wet bottom practice) to combine with scale that flakes off the ingots and then melts. The cinders are then removed through the cinder tunnel.There are several different hearth and burner configurations used in soaking pit design including single and double top-firing, bottom firing, center firing, and tangential firing.

NOx Control

Soaking pits using cold air firing produce 0.064 to 0.069 lbs/MMBtu of NOx (0.091 – 0.104 lb/ton of steel). The use of air preheat approximately doubles the NOx produced.


NOx emissions from Iron and Steel Mills, Alternative Control Techniques Document, U.S. EPA, Sept 1994.