Carburisation as in the blast furnace process does not occur in the DRI-process, as coke is not used as a reducing agent. In order to prevent excessive re-oxidation of the sponge iron in the ambient air, it must be cooled down in the lower region of the shaft furnace. Sponge iron is a highly ferrous ore from the direct reduced iron process! The appearance resembles a porous sponge, which is why the deoxidized and thus strongly ferrous iron ore is also called sponge iron. This causes the iron ores to crack on the surface. The reduction gases only dissolve oxygen from the iron ores. The iron ores are therefore not melted! This also applies to the gangue contained in the ore, which is why the iron ores used must be relatively low in gangue from the outset. In contrast to the blast furnace process, the direct-reduced iron process operates at temperatures of up to 1000 ☌. The reduction of iron oxides takes place according to the following chemical equations: The process gases carbon monoxide (\(CO\)) and hydrogen (\(H_2\)) are blown into the furnace at temperatures of approx. Instead, these reducing agents are produced from natural gas by catalysis outside the shaft furnace. In contrast to the blast furnace process, however, these reduction gases do not result from the combustion of coke. Carbon monoxide and hydrogen are used to dissolve out the oxygen in the iron ores. The heart of the direct reduction is the shaft furnace, which is filled from the top with lump ore and pellets. Figure: Shaft furnace for the direct reduced iron process Just think of the complex coke production, hot-blast production and the high demands placed on blast furnace materials due to the enormous temperatures and not least the harmful waste gases. Particularly in the wake of climate change, it is necessary to look for alternatives that produce less CO2 than is currently the case in the blast furnace process.įor these reasons, the DRI-process was developed, but in terms of productivity it still stands far behind the blast furnace process. The starting point for the efforts to find an alternative to the blast furnace process was the relatively high process expenditure. In addition to the process route via the blast furnace process, there is another option for extracting crude steel from iron ores using the so-called direct reduced iron (DRI) process (secondary route).
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