The aluminium product manufacturing process typically undergo through two stages; the Bayer process and the Hall-Heroult process. There are 9 stages of aluminium manufacturing process that needs to be completed in order to come up with a finished product. Here are stages:
The Bayer Process
- The bauxite ore needs to be crushed. The crushed ore will be mixed to caustic soda and sent to a grinding processor. The result would be water suspension or slurry containing fine ore particles.
- The slurry will be pumped to a digester. It will be heated at 230-520°F (110-270°C) with pressure of 50 lb/in2 (340 kPa). The heating process takes from 30 minutes to several hours depending on the design of the product.
- The hot slurry is processed until it turns into sodium aluminate solution then it passes through a number of flash tanks.
- After the slurry is processed, it is pumped into a settling tank where impurities called red mud are eliminated.
- When the impurities are removed, the remaining liquid is pumped through cloth filters. The remaining impurities will be removed from the filters at this stage ofaluminium product manufacturing. The remaining materials will be washed and collected to gather alumina and caustic soda for reusing.
- The purified liquid is moved to precipitation tanks. Each of the tanksis added with alumina hydrate seed crystals.
- At this stage, the crystals precipitate and settle at the tank bottom for collection. They will be washed and transferred to a kiln so for them to be heated. A conveyor transfers the crystals into a cylindrical kiln. Water molecules are evaporated at2,000° F (1,100° C) temperature leaving off anhydrous or waterless alumina crystals which will be passed through a cooler.
The Hall-Heroult Process
- The alumina crystals are melted in a molten cryolite at 1,760-1,780° F (960-970° C) temperature creating electrolyte solution.
- The last aluminium product manufacturingprocess involves moving the crucible to a potline to collect molten aluminium which will be transferred to a holding kiln and cast formoulding.