Gas Cleaning Systems in Ironmaking Blast Furnaces

In a blast furnace, iron ore and coke are charged into the top of the furnace. The molten iron is removed near the bottom of the
furnace. Combustion air is supplied through tuyeres at a level just above the iron tap hole. The combustion air is called wind. Wind is
air that has been preheated, compressed and may contain added oxygen, natural gas, pulverized coal or other additives. One of the
limiting factors of increasing production of an ironmaking blast furnace is the velocity of the wind in the furnace. If the wind
velocities become too high, the normal downward flow of the charge materials is inhibited.1 One technique used to increase the
amount of wind available for combustion is to increase the pressure at the top of the furnace. This increase in top pressure increases
the pressure of the incoming wind, which increases the gas density, and lowers the wind velocity. Because of the resulting
improvement in blast furnace performance, top pressures above 15 psig are becoming more common and some furnaces are operating
at top pressures as high as 30 psig. 2,3
Blast furnace gas has a modest heating value from the carbon monoxide and hydrogen that it contains. The gas is burned to recover
this heat and to reduce the carbon dioxide emissions from the process. Some of the gas is used to preheat the blast furnace wind in
stoves that are normally located adjacent to the furnace. For efficient operation and longevity of the stoves, the blast furnace gas must
be clean and dry.