There are two main processing routes for the production of iron from iron oxides, these are smelting and direct reduction.
Smelting processes produce a molten iron product and slag containing gangue material. The molten product can be used directly in the steel making process or solidified into pig iron for sale as a merchant product. As the smelting processes go through a melting phase, gangue materials are eliminated from the iron product with the use of fluxes to produce a slag. The iron may contain impurities which are soluble in iron, e.g. sulfur and phosphorus, which may require further processing before being suitable for the production of steel. Some steel making processes, eg Q-BOP, can handle elevated levels of phosphorus.
Direct Reduction processes produce a solid product which substitutes for residual scrap in the EAF process. Most Direct Reduction processes produce either Direct Reduced Iron (DRI) or Hot Briquetted Iron (HBI). DRI and HBI is generally a cleaner and more consistent product than residual scrap for use in the Electric Arc Furnace (EAF) process, but depending on the purity of the iron oxide used to produce it, tends to contain more gangue material.
DRI can be used directly in the EAF as either a hot or cold charge, but cannot be traded easily as a merchant product due to its pyrophoric nature. For this reason the DRI is “compressed” to reduce its porosity using a hot briquetting process to produce HBI. In the form of HBI the porosity of the material has been reduced to a level where it is no longer pyrophoric and can be safely transported as a merchant product.
Another product being developed as a merchant product is iron carbide (Fe3C). Iron Carbide is relatively inert in atmospheric conditions, requiring no further treatment once it is produced. The carbide is also a source of energy which can be used in the downstream processing of the material in the EAF.