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Iron Ore Information
Aluminium Information.
Aluminium
Small amounts of aluminium (Al) are present in many ores (often as clay)
and some limestone. The former can be removed by washing the ore prior
to smelting. Until the introduction of brick lined furnaces the amounts
are small enough that they do not have an effect on either the iron or
slag. However, when brick is used for hearths and the interior of blast
furnaces, the amount of aluminium increases dramatically. This is due to
the erosion of the furnace lining by the liquid slag,
Aluminium is very hard to reduce. As a result aluminium contamination of
the iron is not a problem. However, it does increase the viscosity of
the slag. This will
have a number of adverse effects on furnace operation. The thicker slag
will slow the descent of the charge, prolonging the process. High aluminium will also make it more difficult to tap off the liquid slag.
At the extreme this could lead to a frozen furnace.
There are a number of solutions to a high aluminium slag. the first is
avoidance, don't use ore or a lime source with a high aluminium
content. Increasing the ratio of lime flux will decrease the viscosity.
