Blast Furnace Processing, part 2 of 2: Processing in the Blast Furnace
All modern iron making blast furnaces are built in the form of a tall chimney-like structures lined with refractory brick. Metallurgical coke, iron ore (iron oxide) and limestone flux are put into the top part of the furnace in a precise filling order, thanks to which all the chemical reactions and flowing gas are under control. Four “uptakes” allow the dirty, hot gas to exit the furnace dome. “Bleeder valves” are to protect the top part of the furnace from sudden gas pressure surges. A bleader cleaner is for cleaning the bleeder valves. The coarse particles in the gas settle in The “dust catcher” catches the coarse particles dumps them into a truck or railroad car for disposal. Then the gas itself flows through a venturi scrubber and a gas cooler reduces the temperature of the cleaned gas.
The “casthouse” at the bottom half of the furnace contains tuyeres, the bustle pipe and whole equipment needed to cast the liquid iron and slag. When a “taphole” is being drilled through the refractory clay plug, slag and liquid iron are flowing down a trough through a “skimmer” opening, which is used to separate flowing iron and slag. Modern large blast furnaces use to have two casthosues and four tapholes. When slag and the pig irona are already tapped, the taphole is plugged again with the refractory clay.
Blast furnaces of Třinec Iron and Steel Works (Třinecké Železárny, Czech Republic)
The tuyeres implement a hot blast, which can be used to increase the efficiency of the blast furnace. They direct the hot blast into the furnace through water-cooled copper nozzles (so called tuyeres), which are near the base of the furnace. The hot blast temperature is high (from 900 to 1300 Celsius degrees or from 1600 to 2300 Fahrenheit degrees) and it depends on the condition and design of the stove. The temperatures tuyeres deal with may be much higher (form 2000 to 2300 Celsius degrees or from 3600 to 4200 Fahrenheit degrees). Tar, oil, powdered coal, oxygen and natural gas may be can also injected into the furnace at tuyere level – then they are combined with metallurgy coke and this combination releases additional energy that can help in increasing a total productivity of the process.