A STUDY ON ECONOMIC VALUE ADDED of HINDALCO INDUSTRIES LTD
MANUfACtUrING PrOCESS: Production of Alumina primarily involves two important raw materials Bauxite and Alumina bearing ore and electric for which an abundant supply is necessary. Bauxite is an ore formed by the weathering of Aluminum – bearing rocks. The ore us obtained by a quarrying operation, which includes ripper dozer. About 2.8 tones of Bauxite are required to make one tone of alumina. This involves chemical processing of the or into Alumina by a method called the BAYER PROCESS. At the Alumina Plant, the crushed Bauxite is mixed with a solution of Caustic Soda and then digested in large pressure vessels.
Caustic Soda
dissolves the Alumina present in the Bauxite. This process is called DIGESTION. Classification the solution containing Alumina is separated, by setting filtering, from insoluble solid impurities such as Iron Oxide, Titanium and Silica.
The resulting residue commonly called red mud is discarded and
sent to the red mud pond. During PRECIPITATION, the clear liquor is pumped into large tanks called precipitators.
After ‘seeding’ with fine
crystalline particles of Hydrated Alumina produced earlier, circulation is started through airlift pipes.
During circulation, new crystals formed by
cooling separate out of the solution. After sufficient Alumina has separated, the crystals are settled and washed free of Caustic liquor. The final stage in refining is called CAlCINATIONS. After precipitation the Hydrated Alumina contains approximately 1/3 of its own weight of combined water, which is removed to obtain alumina free from water molecules. This dehydration process is achieved by heating the Alumina on
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