Blast furnaces are large towers or cylinders that have a heat-resistant lining. These furnaces force gusts of hot air and gases up through the furnace load. As air is pushed into the furnace from the bottom, ore, fuel, and limestone are pushed in through the top. This allows the chemical reaction to occur as the ore, fuel, and limestone move down the cylinder. The result is molten metal and slag at the bottom of the furnace, while flue gases move upward and exit through the top of the blast furnace. A benefit of blast furnaces is how relatively inexpensive they are when it comes to operating and maintaining the equipment.
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Applications of Blast Furnaces
Blast furnaces are used for smelting industrial metals, a process used in the production of steel and iron. They can be used to extract iron from iron ore, converting it into liquid iron, which is then used to make steel, as well as for other smelting procedures and for processing lead, copper, and other types of metals, which are eventually shaped into beams, billets, or slabs. In general, blast furnaces are used for various heat treatments of materials. Heat treating adds significant value to metal products, especially those made of steel and nonferrous materials, by imparting specific properties to the parts. These properties are often critical to the proper function of the parts.
Blast Furnace Design and Function
Blast furnaces are made with several kinds of heat-resistant (refractory) elements to withstand long-term use. The enclosed space within them holds the materials, gas, or air being heated until the desired temperature is reached. The materials used are brought to the top of the cylinder using a conveyor belt. Temperatures within the cylinders can range from 1600ºF to 2300ºF. They can come with varying temperature control options or be set for a single temperature, depending on the process for which the furnace will be used. The shape and design of the structure allows for easy control of the temperature within the cylinders. When needed, oil, tar, natural gas, coal, and oxygen can be added to increase productivity.