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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)).
Plants for the production of pre-reduced iron ore are known as direct reduction plants. The principle involves exposing iron ore to the reducing action of a high-temperature gas (around 1000 °C). This gas is composed of carbon monoxide and dihydrogen, the proportions of which depend on the production process.
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 Flodin process is a direct reduction process for manufacturing modern iron and steel, developed by Gustaf Henning Flodin from Sweden and patented in 1924. It has been used in Norway , Sweden , and the United States.
Direct reduction is the fraction of iron oxide reduction that occurs in a blast furnace due to the presence of coke carbon, while the remainder - indirect reduction - consists mainly of carbon monoxide from coke combustion. It should also be noted that many non-ferrous oxides are reduced by this type of reaction in a blast furnace.
In a blast furnace, iron oxides are reduced by a combination of CO, H 2, and carbon. Only around 10% of the iron oxides are reduced by H 2. With H 2 enrichment, the proportion of iron oxides reduced by H 2 is increased, consuming less carbon is consumed and emitting less CO 2. [47] This process can reduce emissions by an estimated 20% ...
The process was later adopted in Europe, particularly in Sweden, to facilitate the production of pre-reduced iron ore. [4] Pellet production saw substantial growth between 1960 and 1980 but eventually plateaued at approximately 300 million tons annually. The following data illustrates pellet production over several years: [5]
The reduced iron agglomerates into 3 to 8 mm metal nodules called Luppen. If the infusibility of the gangue is high, the temperature must be increased, up to 1,400 °C for a basic charge. [22] It is crucial to control the gangue's hot viscosity. [9] Among rotary drum direct reduction processes, it stands out for using high temperatures.