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Blast furnaces differ from bloomeries and reverberatory furnaces in that in a blast furnace, flue gas is in direct contact with the ore and iron, allowing carbon monoxide to diffuse into the ore and reduce the iron oxide. The blast furnace operates as a countercurrent exchange process whereas a bloomery does not.
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Earlier processes for this included the finery forge, the puddling furnace, the Bessemer process, and the open hearth furnace. Modern steel mills and direct-reduction iron plants transfer the molten iron to a ladle for immediate use in the steel making furnaces or cast it into pigs on a pig-casting machine for reuse or resale.
Consequently, the structure of the granules becomes reinforced and can expand to two or three times their original volume. This expansion, or "swelling," of the granules can lead to blockage or significant damage to the blast furnace, highlighting the challenges associated with using pellets in blast furnace operations. [15]
As blast furnaces re-equipped after World War II, the favoured power source was either the diesel engine or the electric motor. These both had a rotary output, which worked well with contemporary developments in centrifugal fans capable of handling the huge volumes of air. Although the reciprocating steam blowing engine continued where it was ...
Blast furnace gas (BFG) [1] is a by-product of blast furnaces that is generated when the iron ore is reduced with coke to metallic iron. It has a very low heating value , about 3.5 MJ/m 3 (93 BTU /cu.ft), [ 2 ] because it consists of about 51 vol% nitrogen and 22 vol% carbon dioxide , which are not flammable.
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 ...
The traditional Japanese tatara furnace uses charcoal and ironsand to produce a mixture of iron and steel. Small quantities are still made by the Nittoho Tatara in Japan. The tatara smelting process involves direct reduction and—unlike a blast furnace—at no time is the product fully molten.