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In a blast furnace, fuel , ores, and flux are continuously supplied through the top of the furnace, while a hot blast of air (sometimes with oxygen enrichment) is blown into the lower section of the furnace through a series of pipes called tuyeres, so that the chemical reactions take place throughout the furnace as the material falls downward.
This used a blast furnace to make pig iron, which then had to undergo a further process to make forgeable bar iron. Processes for the second stage include fining in a finery forge. In the 13th century during the High Middle Ages the blast furnace was introduced by China who had been using it since as early as 200 b.c during the Qin dynasty.
The process starts by charging solid sinter and heated coke into the top of the blast furnace. Preheated air at 190 to 1,050 °C (370 to 1,920 °F) is blown into the bottom of the furnace. Zinc vapour and sulfides leave through the top and enter the condenser. Slag and lead collect at the bottom of the furnace and are tapped off regularly.
The Chinese are thought to have skipped the bloomery process completely, starting with the blast furnace and the finery forge to produce wrought iron; by the fifth century BC, metalworkers in the southern state of Wu had invented the blast furnace and the means to both cast iron and to decarburize the carbon-rich pig iron produced in a blast ...
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 ...
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The blast furnace method is expected to survive into the 22nd century because of its efficient rate of iron production at competitive costs compared with other iron-making methods. Blast furnaces keep on improving with adaptations arising from new technologies driven by rising global demand, yet the main chemical process remains the same. But ...
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