Manufacturing Process of chlorine Purified saturated brine is heated and electrolyzed in a diaphragm cell. The cell operating at 45-55% decomposition efficiency, discharges 10-12% solution of caustic soda with about equal concentration of NaCl. Multiple effect evaporator concentrates the cell liquor to 50% NaOH solution The opted salt is separated, centrifuged, washed, then slurried with treated brine. Salt saturator overflow is 50% caustic soda product. This further brine is again treated the mercury cell and the yield from this section is 70% of caustic soda. Chlorine is collected, dried, compressed and cooled upto-30o C and collected as liquid chlorine.
Or
Electrolytic Process:
In this process carbon dioxide is passed in the solution of sodium hydroxide obtained by the electrolysis of aqueous solution of sodium chloride.
2NaOH + CO2 Na2CO2 + H2O
The electrolysis of sodium chloride is carried in an iron box lined with bricks. A carbon rod is used as the anode and copper wire gauze covered on the inside with asbestos serves as the cathode.
A concentrated solution of sodium chloride is admitted into the cell at the bottom and the electrical current is passed through it. As the solution rises it undergoes electrolysis and finely leaves the cell from the top as spent liquor.
Thus chlorine is liberated at the anode and at the cathode sodium hydroxide and hydrogen are formed. Chlorine and hydrogen escapes from the respective outlets in the anode and cathode compartments. A mixture of steam and carbon dioxide is then blown into the sodium hydroxide solution in the cathode compartment when sodium carbonate is formed as mentioned earlier. The solution is periodically removed and concentrated to obtain pure crystalline sodium carbonate.