Economical Iron Production in the Submerged Arc Furnace

摘要

In examining the historical past for iron making using a submerged arc furnace (SAF), a primary reason that this method of iron making has not dominated the industry was the cost of electricity. Submerged arc furnace production of pig iron and foundry iron has been practiced in some industrialized countries as late as the 1950's. This was especially true where coking coals were scarce, and hydroelectric power was abundant and cheap. These electric furnace iron processes used combinations of ores and fluxes to produce iron with compositions and metal to slag ratios similar to those produced in a blast furnace. Nevertheless, the quantity of electricity consumed to produce the iron was on the order of 2,300 kilowatt hours per net ton (kWH/NT). With the strong growth in the demand for electricity for other uses, and the availability of cheap iron from blast furnaces, it became apparent that only producers in countries having readily available ores and abundant hydroelectric power, such as Norway or Venezuela, were capable of economical electric iron making. Although research to improve SAF performance continued vigorously with new process developments, such as Tysland-Hole, Strategic-Udy, and New Zealand Steel, the improvements were focused on pre-reduction and pre-heating of the iron oxides prior to charging. Electricity used for those ore-based processes remained above 900 kWH/NT. With a few exceptions, none of those processes were able to demonstrate viable economics for competing with the blast furnace for steel making or the cupola for iron castings. This paper will introduce the Alabama Power Company (APC) process for making foundry iron and hot metal. This process is scrap-based and has produced foundry iron with an average of 3.4% carbon, 2.0% silicon, and 0.06% sulfur (by weight). Average energy consumption was 474 kWH/NT for foundry iron. Hot metal (4.7% C, 0.6% Si, and 0.002% S) was produced from DRI at an energy consumption of 580 kWH/NT.