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Direct reduction processes can be divided roughly into two categories: gas-based and coal-based. In both cases, the objective of the process is to remove the oxygen contained in various forms of iron ore (sized ore, concentrates, pellets, mill scale, furnace dust, etc.) in order to convert the ore to metallic iron, without melting it (below 1,200 °C (2,190 °F)).
The coking plant that feeds a battery of blast furnaces is just as expensive as the blast furnace and requires a specific quality of coal. [ 64 ] [ 65 ] Conversely, many direct-reduction processes are disadvantaged by the costly transformation of ore into pellets: these cost on average 70% more than raw ore. [ 66 ]
For blast furnaces, direct reduction corresponds to the reduction of oxides by the carbon in the coke. However, in practice, direct reduction only plays a significant role in the final stage of iron reduction in a blast furnace, by helping to reduce wustite (FeO) to iron. In this case, the chemical reaction can be trivially described as follows ...
Blast furnaces used in the ISP have a more intense operation than standard lead blast furnaces, with higher air blast rates per m 2 of hearth area and a higher coke consumption. [ 79 ] Zinc production with the ISP is more expensive than with electrolytic zinc plants, so several smelters operating this technology have closed in recent years. [ 80 ]
The HIsarna ironmaking process is a direct reduced iron process for iron making in which iron ore is processed almost directly into liquid iron ().The process combines two process units, the Cyclone Converter Furnace (CCF) for ore melting and pre-reduction and a Smelting Reduction Vessel (SRV) where the final reduction stage to liquid iron takes place.
The hot blast pumps hot air into the blast furnace. The hot blast temperature ranges from 900 to 1,300 °C (1,650 to 2,370 °F) depending on the design and condition. Oil, tar , natural gas, powdered coal and oxygen can be injected to combine with the coke to release additional energy and increase the percentage of reducing gases present ...
In 1960, a Krupp-Renn furnace using low-grade ore yielded 100 kilotons of iron annually, [28] while a contemporaneous modern blast furnace produced ten times as much cast iron. [ 31 ] Direct reduction processes employing rotary furnaces frequently face a significant challenge due to the localized formation of iron and slag rings, which sinter ...
Iron ore, coke, and flux are fed into the blast furnace and heated. The coke reduces the iron oxide in the ore to metallic iron, and the molten mass separates into slag and iron. Some of the iron from the blast furnace is cooled, and marketed as pig iron; the rest flows into basic oxygen furnaces, where it is converted into steel.