The blast furnace process has been the primary method for producing iron for many decades. The blast furnace is a refractory-lined circular shaft 100 to 200 feet high, with an internal diameter between 20 and 45 feet. The refractory wall lining typically measures two feet or more in thickness and contains more than 2,500 tons of refractories. Blast furnaces produce iron by exposing iron ore, iron pellets, and sinter to high temperatures and carbon monoxide, a reducing agent. Coke is the primary fuel, although it is often augmented by injected auxiliary fuels.
Preheated air from the hot-blast stoves is also injected into the furnace through the tuyeres. The tuyeres encircle the furnace at the upper hearth elevation, where incomplete combustion of the coke occurs. The combustion liberates considerable heat and forms a very hot carbon monoxide–reducing gas that sweeps upward through the burden material. Iron oxide reduction begins when the ore comes into contact with the reducing gas and generally proceeds in stages to form metallic iron with a high carbon content. The iron collects as a molten pool in the hearth. Since the blast furnace process offers little opportunity for refractory repair during operation, the length of the blast furnace campaign is determined mainly by the life of the refractories. Today campaigns of 10 to 15 years are common, although numerous short stoppages must be planned for maintenance.
HarbisonWalker International offers a complete refractory package proven to maximize the life of the furnace. From the hearth bottom up through the bosh and stack, the refractory design will vary due to the service conditions and destructive forces in each zone of the furnace. HWI will work closely with you to ensure that all needs are addressed and that the proper materials (UFALA®, KALA®, or KX-99®-BF) are selected for each zone within the furnace. Several alternatives may be offered depending on the furnace’s cooling design and campaign goals.