WORKING :
The Iron Ore, Coke and Limestone, (the Charge), is conveyed to the top of the Furnace.
The Charge is stored in Bells till the timing is right for the charge to be dropped into the Furnace.
Hot air is then blown through pipes called Tuyers, to fire the mixture.
The Coke burns to increase the temperature in the Furnace.
The Limestone attracts the impurities in the Iron Ore and forms Slag. This Slag is lighter than the molten Iron and so floats on top of it.
As the Furnace fills, the molten Iron is tapped off. The Slag is also tapped off at regular intervals.
Most Iron is taken straight from the Blast Furnace to the Steel Mill however some is poured into buckets called Pigs. This Iron is called Pig Iron and is used to make Cast Iron.
The Charge consists of 3 parts:
Iron Ore
Coke
Limestone
IRON ORE :
The Iron Ore is first mined so brought to the Blast Furnace. It contains impurities that have to be removed.
Hematite and Magnetite are the foremost common ores. It takes about two tons of Iron Ore to produce one ton of iron however this varies with different types of ores.
COKE :
Coke is made by heating soft coal in the absence of air. As Coke is burned in the Blast Furnace it raises the temperature to about 2000°C which is enough to melt the Iron Ore.
The Carbon in the Coke chemically reacts with the Oxygen in the Iron Ore to form Carbon di oxide, and Carbon Monoxide, that escapes through the Gas Outlet.
LIMESTONE :
The Limestone is mined then crushed before being brought to the Blast Furnace. It combines with the impurities in the Iron Ore to form Slag. A material which removes unwanted materials or cleans another material is called a Flux.
THE EXHAUST GAS OUTLET :
The Exhaust Gas Outlet collects any gaseous emissions from the chemical reactions that are taking place in the Furnace.
These gases are hot they are reused to save energy. They are piped to nearby Stoves in order to heat them.
The gases are then 'cleaned' before being let into the atmosphere.
CHARGING BELLS :
There are in fact two Bells in the system called the Small Bell and the Large Bell. The Small Bell is filled directly from the Conveyor System when it is close to being full it is opened to allow the Charge drop into the Large Bell.
The Large Bell is then opened when it is nearly full and the Charge can drop into the Furnace.
By use of this system, reduces the amount of heat that is lost to the atmosphere.
Gas Outlet :
The Gas Outlet is an array of holes in the furnace that allows the escaping gases to get to the Exhaust Gas Outlet.
Melting Iron Ore, Coke and Limestone :
At the top of the Furnace the Iron Ore, Coke and Limestone is at a temperature of about 200°C.
At this stage the materials are gone through the pre-heating stage.
Close to the middle of the Furnace the temperature has increased to approximately 480°C, where the raw materials have started to melt. The temperature increases rapidly to about 2000°C at the bottom of the Furnace where the molten Iron is situated, waiting to be removed.
TUYERS
These are small pipes that permit hot air from the bustle pipe to enter the furnace. The tuyers are located all around the furnace.
They also have valves so that nothing can escape from the Furnace.
TAP HOLE
It is used to draw off the molten Iron at regular intervals of about 5 to 6 hours.
Tap hole is located below the Slag hole. This is because the Slag is lighter than the molten Iron and so sits on top.
The molten Iron leaves the tap hole and is either poured into moulds termed as pigs.
SLAG HOLE :
It is located above the tap hole because slag is lighter than molten iron.
The Slag is scraped off every 3 or 4 hours and is then used for road beds, fertilizer or cement.
BUSTLE PIPE :
The Bustle Pipe is a large diameter pipe that circles the base of the furnace.
It carries the hot air from the Stoves, where the air is heated, to the tuyers which allow the hot air to enter the Blast Furnace.
CONVEYOR SYSTEM :
The Conveyor System takes the Charge from the area where it is maxed together to the top of the blast furnace.
The Charge is carried in skip cars which run on a rail track.
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