Lead Refining Process

This Process involves purifying of Crude Lead produced in the Smelting section. The Crude lead is charged in to the Refining Kettles and is melted. At low temperature and stirrer is introduced to mix the molten lead.

Dross / crystals floating on the top of the surface is skimmed off. The well-dried dross is black powder of Lead Oxide and copper with Nickel, Iron, Cobalt etc. During the process Copper is removed as CU2S.

The chemical reactions involved during removal of Copper and other associated elements and sulfur treatment are as follows.

For the next process temperature is increased to oxidize the selective impurities. Antimony, Arsenic and Tin are removed by oxidation method by adding Caustic Soda, Sodium Nitrate and Lead chloride to the Lead bath at different temperatures with stirrer in operation. Few chemical reactions that take place during this Refining Process are given below.

2 As + 2 NaNO3 + 4 NaOH ---- --- 2 Na3AsO4 + 2H2O + N2

2 Sb + 2 NaNO3 + 4NaOH ------- 2 Na3SbO4 + 2H2O + N2

5Sn + 4 NaNO3 + 6NaOh -------- 5 Na2SnO3 + 3H2O + 2N2

5Pb + 2NaNO3 + 8NaOH ---------- 5Na2PbO2 + N2 + 4H2O

During Refining Process drosses are skimmed off, and are collected in the Steel Trays/drums. These drosses are stored separately and are treated for the manufacture Lead alloys.

For manufacturing of Pure Lead all the impurities are brought down to trace level or to below the specified limits

For the Manufacturing of Lead Alloys to required Specifications, calculated quantity of Pure Metals such as Antimony, Tin, Copper, Arsenic, Calcium or Selenium are added either in Virgin form or in Master Alloy form.