(c) Most aluminum reduction plants manufacture their own carbon electrodes
from petroleum coke.
In the carbon electrode and paste plant (Annotation 8)
purified petroleum coke is melted and poured into molds to form the electrodes.
(d) The petroleum coke can be stored either in open stockpiles or within a
petroleum coke storage building (Annotation 9).
(e) Cryolite is usually synthetically produced either at a separate
facility or in a facility collocated with the aluminum reduction plant.
If
cryolite is shipped to the reduction plant, it is unloaded at the receiving and
handling building (Annotation 7) and conveyed to a series of small silos
(Annotation 5) for storage.
(f) Alumina is transported from the alumina plant and
unloaded at the
receiving and handling building and from there conveyed into
the large silos
(Annotation 4).
(g) Electric furnaces, called pot lines or rooms, are the heart of the
aluminum reduction plant (Annotation 3). These furnaces consist of insulated steel
boxes, lined with carbon.
Cryolite is the first raw material to be charged into
the electrolytic furnace.
Cryolite melts as the current is introduced; then
alumina is added.
As the alumina melts, it gives up its oxygen which, in turn,
combines with the carbon electrodes to form carbon dioxide gas. The gas is vented
out of the furnace while the liquid aluminum metal sinks.
(h) Periodically, the molten aluminum is tapped from the furnaces into a
ladle and then poured into ingot molds in the casting building (Annotation 6).
Once cooled, these ingots (or pigs) can be shipped to a mill or foundry for further
processing.
(i) A fluorine recovery facility and a small internal combustion and/or
thermoelectric power plant may be present.
Cryolite releases fluorine gas during
the reduction of alumina.
This gas may be recovered and reused in the synthetic
production of cryolite.
IT 0673
28
Previous Page
