høyovnen

The høyovnen, or blast furnace in English, is a tall, vertical furnace used for smelting iron ore. It is a key component of industrial iron production. Raw materials, typically iron ore, coke (a fuel derived from coal), and limestone (a flux), are loaded into the top of the furnace. Air is then blown in from the bottom through tuyeres, hence the term "blast." This process creates extremely high temperatures within the furnace.

The coke serves as both a fuel and a reducing agent, reacting with the iron ore to remove oxygen and extract molten iron. The limestone reacts with impurities in the ore and coke to form a molten slag, which is lighter than the iron and floats to the top. Periodically, the molten iron and slag are tapped off from separate outlets at the bottom of the furnace. The iron produced in a blast furnace is known as pig iron and is high in carbon content, making it brittle. Further refining is usually required to produce steel or other iron alloys. The design and operation of the blast furnace have evolved significantly since its invention, leading to much larger capacities and higher efficiencies.