Shaft furnace for direct reduction of iron bearing pellets or lump iron ore

摘要

A method for effecting direct reduction of iron oxides in the form of lumps or pellets, in which an ore burden is passed downwardly successively through prereduction and metallization zones of a shaft furnace while passing a flow of rich fuel gas produced by external partial combustion upwardly in counter current through the prereduction zone, and passing a flow of reducing gas in cocurrent though the metallization zone. The flow of reducing gas is an independent flow that has not been subject to external combustion, and an intermediate zone is provided forming a narrowed throat between the prereduction and metallization zones. The reducing gas is introduced at a boundary between the intermediate and metallization zones, such that passage of rich fuel gas from the prereduction zone to the metallization zone is inhibited. The gas flows should be controlled so that about 5% to 10% of the volume of reducing gas passes upwardly from the intermediate zone to the prereduction zone.