GB1097135A - Improvements relating to the production of pig iron - Google Patents

Abstract

Pig-iron is produced in a stationary hearth, particularly a Siemens-Martin furnace 1 charged with iron ore, solid carbonaceous material such as coal or coke breeze, and limestone, with or <PICT:1097135/C6-C7/1> without scrap containing Fe2O3, by introducing e.g. from one or more lances or burners 3 an oxygen-containing gas stream 12 directly into the furnace chamber to impinge on to part of the charge (Zone I) and react with the carbonaceous material to produce a reducing gas such as CO and H2 (Zone II) which passes through the advancing part of the charge to heat and reduce it (Zone III), and to produce heat to melt the pig-iron formed. The gas stream may be oxygen of at least 95% purity or formed by combustion products of oxygen and heating oil burnt on introduction into the furnace chamber. 20 to 80% by weight of the total carbon required may be contained in either the burner fuel or solid carbonaceous material. The oxygen to fuel ratio of the gas stream is preferably at least 0.7. 10 to 50% by volume of the gas stream may be directed on to the molten pig-iron. Before passing into the hearth furnace, the charge may pass through a rotary tube furnace 8 where 40 to 70% by weight of the ore is pre-reduced (Zone IV) by waste gases from the hearth furnace, any remaining burnt by additional air. To reduce the amount of solid carbonaceous material in the charge, gaseous or liquid carbonaceous material may be introduced into the solid charge near its junction with the molten pig-iron; high carbon pig-iron may thus be produced.