Direct iron smelting processes have been under development for more than 15 years, and several have reached the pilot plant scale. For the American Iron and Steel Institute (AISI), Direct Iron Ore Smelting (DIOS) and Hlsmelt processes, adequate data are available for useful comparisons. In this article, reaction mechanisms are briefly discussed, followed by an evaluation of several critical performance parameters. The major operating difference between AISI-DOE and Hlsmelt is the charging method. Hlsmelt uses deep injection of coal and ore, while AISI-DIOS uses gravity feeding. Hlsmelt uses air plus oxygen, while AISI-DIOS uses oxygen. These differences affect reduction, dust generation and post combustion. The reduction rates in all three processes are similar, but with Hlsmelt, some reduction occurs as the injected ore particles pass through the iron carbon melt. The carbon content of dust and the amount of dust generated when using high volatile coals are lower in Hlsmelt due to more efficient combustion of the volatiles. This may also be one of the reasons they achieve higher post combustion. Sulfur and phosphorus appear to reach slag-metal equilibrium in all three processes. Hlsmelt obtains somewhat higher sulfur and phosphorous distribution ratios (i.e., lower metal contents) probably because they operate at lower and more uniform temperatures.
展开▼
