During Hindalco’s copper production process, by-products such as sulphuric acid and copper slag are formed. Sulphuric acid is partly converted into phosphoric acid, which is then made to react with ammonia to make di-ammonium phosphate (DAP) fertiliser. During the process of making phosphoric acid, phosphogypsum and hydrofluosilicic acid (HFA) are formed. HFA is partly utilised to make aluminium fluoride, and rest is sold in the market.
Sulphuric acid
Hindalco produces sulphuric acid of IS 266/1993 technical grade. The sulphuric acid plants use the double contact double absorption (DCDA) process, and are designed by Monsanto Envirochem (USA).
Phosphoric acid
Hindalco’s phosphoric acid plant is based on the Prayon Mark IV dihydrate technology provided by SNC Lavalin (Belgium).
Phosphogypsum
Phosphogypsum is a by-product of Hindalco’s phosphoric acid plant.
Copper slag (iron silicate)
Copper slag is produced during the smelting process at Hindalco’s copper smelter located at Dahej.
Aluminium fluoride
Hindalco produces aluminium fluoride by reacting HFA (a by-product of the phosphoric acid plant) with aluminium hydroxide (from Hindalco’s aluminium manufacturing facilities).