BigPatents India

Method and apparatus for the extraction of gibbsite (Al2O33H2O) from bauxite. A double extraction method is used wherein the first extraction constitutes any low temperature digestion technology with solid-liquid separation temperature below atmospheric boiling point of the liquor, and the separated solids, after mixing with Spent liquor are subjected to a second extraction followed by a second solid-liquid separation at a temperature below atmospheric boiling point. The second extraction is carried our at a temperature between 120 and 1600C. In the second extraction step spiral hear exchangers are used to transfer hear from the extraction vessel discharge flow to the extraction vessel feed flow.