What is Chlor-Alkali
And what does it’s industrial manufacturing process produce?
What is Chlor-Alkali
The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride solutions.
The balanced process looks like this:
2NaCl +2H2O => 2NaOH + Cl2 + H2
When using potassium chloride, the products contain potassium instead of sodium.
Another process or production method:
While the mercury cell method produces chlorine-free sodium hydroxide, the use of several tonnes of mercury leads to serious environmental problems.
For reference: https://en.wikipedia.org/wiki/File:Chloralkali_membrane.svg
Few related references:
About CPP’s Chemical Business Unit [CBU]
The CBU focuses on conveying highly corrosive fluids.
The unit cover the following industries:
- Chlor-Alkali Membrane Cell Plants
- SO2 / SO3 Gas Cleaning Plants
- Power Plants ( Flue Gas Desulphurization systems – FGD)
The business unit is equipped with several Helical Filament Winding ( HFW) lines to manufacture piping as per ASTM , AWWA, IS, DIN and AS standard.
To manufacture caustic soda consists of following steps:
- Saturation of raw salt to form brine solution.
- Primary brine purification which includes removal of calcium,magnesium,sulphates & insoluble by dosing of certain chemicals & sedimentation through clarifier.
- Secondary brine purification which includes S.S removal by candle filters & hardness removal to ultra pure level by ion exchange method.
- Electrolysis of ultra pure brine by passing D.C current through membrane cells. This process will lead to formation of Cl2 gas , H2 & caustic soda (32%), depleted brine.
- Treatment of depleted brine by dechlorination which includes removal of free Cl2 from brine by vaccum & addition of sodium sulphite.This brine sents for saturation.
- Treatment of Cl2 which include washing, cooling & drying of Cl2 by sulphuric acid.
- Compression & liquefaction of Cl2 to form liquid Cl2 which is stored in chlorine storage tanks.
- Treatment of H2 which include washing & cooling.
- After liquefaction of Cl2 some amount of non condensable gases left which is burnt with H2 to form HCl in HCl furnace.
- For emergency like leakage in Cl2 lines , start up of plant & during shut downs residual Cl2 is absorbed with 18% caustic soda solution in Cl2 gas absorber under vacuum & thus sodium hypo chlorite is formed.
- H2 treated is further compressed & filled in H2 cylinders.
- 32% NaOH is further concentraterd by evaporator to form 48% caustic. This 48% caustic is further converted to caustic flakes using flaking unit.
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