Direct reduced iron
From Wikipedia, the free encyclopedia
Direct-reduced iron (DRI) is produced from direct reduction of iron ore (in form of lumps, pellets or fines) by a reducing gas produced from natural gas or coal. The reducing gas is a mixture majority of Hydrogen (H2) and Carbon Monoxide (CO) which acts as reducing agent. This process of directly reducing the iron ore in solid form by reducing gases is called direct reduction.
The conventional route for making steel consists of sintering or pelletization plants, coke ovens, blast furnaces and basic oxygen furnaces. Such plants require huge capital investment and raw materials of stringent specifications. Integrated steel plants of less than one million tons annual capacity are generally not economically viable. The coke ovens and sintering plants in an integrated steel plant are highly polluting and expensive units. Installation of highly complex and expensive pollution control systems make this route highly capital intensive.
Direct reduction, an alternative route of iron making, has been developed to overcome some of these difficulties. DRI is successfully manufactured in various parts of the world through either gas or coal-based technology. Iron ore is reduced in solid state at 950 – 1050 °C either by reducing gas (H2+CO) or coal. The specific investment and operating costs of direct reduction plants is low compared to integrated steel plants.
While this is in general a more expensive process than reducing the ore in a conventional iron-making processes like blast furnace, there are several factors which can make it economical:
- Direct-reduced iron is richer in iron than pig iron, typically 90-94% total iron [1] as opposed to about 93% for molten pig iron, and an excellent feedstock for the electric furnaces used by mini mills, allowing them to use lower grades of scrap for the rest of the charge.
- Hot-briquetted iron (HBI) is a compacted form of DRI designed for ease of shipping, handling, and storage.
- The direct reduction process uses powdered ore, avoiding the sintering process otherwise necessary to use this ore in a blast furnace.
- The direct reduction process can use natural gas contaminated with inert gases, avoiding the need to remove these gases for other use.
- Supplies of powdered ore and raw natural gas are both available in areas such as Northern Australia, avoiding transport costs for the gas.
India is the world’s largest producer of direct reduced iron, a vital constituent of the steel industry.[2]
Direct reduced iron describes the method of producing metalic iron from iron ore i.e. smelting. Dietary suplements of iron include forms called "reduced iron", this is a reference to the oxidation state of the iron (reduced to improve bio-availability) and is not a reference to iron smelting process.
