What is Chlor-Alkali

And what does it’s industrial manufacturing process produce?

frp piping grp pipes chlor alkali process

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 chlor-alkali industry uses brine (salt water) to produce chlorine, sodium hydroxide (NaOH or caustic soda), and hydrogen  also called: Cl2, NaOH, chlorine, sodium hydroxide.

An electric current is passed through the brine, to form hydrogen gas at the negative electrode and chlorine gas at the positive electrode, leaving a solution of sodium hydroxide.

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.

Membrane cell

The most common chloralkali process as shared above is by the electrolysis of aqueous sodium chloride (a brine) in a membrane cell.

Chloralkali membrane process

For reference:  https://en.wikipedia.org/wiki/File:Chloralkali_membrane.svg

The interests of chloralkali product manufacturers are represented at regional, national and international levels by associations such as Euro Chlor and The World Chlorine Council.

Few related references:

FRP, GRP Piping for Soda Ash, Chlor-Alkali, Bromine, Power and Desalination projects

For Chlor – Alkali Membrane Cell plants

About CPP’s Chemical Business Unit [CBU]

The CBU focuses on conveying highly corrosive fluids.

The unit cover the following industries:

The business unit is equipped with several Helical Filament Winding ( HFW) lines to manufacture piping as per ASTM , AWWA, IS, DIN and AS standard.

We can manufacture alone FRP as well as Thermoplastic lined FRP piping . For eg : PVC-FRP , CPVC-FRP, PP-FRP , PVDF-FRP , FEP-FRP etc.

Process Description 

To manufacture caustic soda consists of following steps:

  1. Saturation of raw salt to form brine solution.
  2. Primary brine purification which includes removal of calcium,magnesium,sulphates & insoluble by dosing of certain chemicals & sedimentation through clarifier.
  3. Secondary brine purification which includes S.S removal by candle filters & hardness removal to ultra pure level by ion exchange method.
  4. 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.
  5. 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.
  6. Treatment of Cl2 which include washing, cooling & drying of Cl2 by sulphuric acid. 
  7. Compression & liquefaction of Cl2 to form liquid Cl2 which is stored in chlorine storage tanks.
  8. Treatment of H2 which include washing & cooling.
  9. After liquefaction of Cl2 some amount of non condensable gases left which is burnt with H2 to form HCl in HCl furnace.
  10. 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.
  11. H2 treated is further compressed & filled in H2 cylinders.
  12. 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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