Industrial Manufacture of Sodium Carbonate

Industrial Manufacture of Sodium Carbonate

Industrial Manufacture of Sodium Carbonate 

Introduction

On industrial scale the sodium carbonate or soda ash (Na₂Co₃) is prepared by Solvay’s process and is was developed by the Belgian chemist Ernest Solvay (complete name is Ernest Gaston Joseph Solvay) during 1860s.

Explanation

 In 2005 the amount of soda ash was 42 billion kilograms about where three fourth of which was prepared by Solvay’s process and he remaining amount was mined overt (directly).

Raw materials for Solvay’s process

 this is very successful method because it is very simple and utilizes cheap raw material such as concentrated aqueous solution of NaCl (brine), lime stone or calcium chloride and .the ammonia gas etc.  This process is minimized by one reaction that is

                  2NaCl _(aq)    +   CaCO3 _(aq)           è        Na₂Co_{3 (aq)}      + CaCl_{2 (aq)}  

Preparation

In Solvay’s process for the soda ash preparation different steps are involved and is as follow

1 . Ammonia Absorber

when ammonia gas is dissolved in concentrated NaCl solution (brine) a mixture known as ammonical brine is obtained. This ammonical brine is then taken to ammonia absorber tower. Where ammonia gas and carbon dioxide react to form ammonium carbonate which then reacts with brine to form precipitate sodium bicarbonate and ammonium chloride where only sodium bicarbonate is very useful. Such reaction is as follow. 

              NH₃    +    H₂O    + CO₂    è     NH₄HCO₃  

 Now this ammonium carbonate reacts with brine to form precipitates like sodium bicarbonate and ammonium chloride. That is 

             NH₄HCO₃    + NaCl   è     NaHCO₃    +  NH₄Cl

2 . Carbonating Tower or Solvay’s tower

 In this tower more carbon dioxide is passed through ammonical brine. This tower contains iron plates having small pores in the center and helps to prepare sodium bicarbonate. Such as 

              NH₃    +    H₂O    + CO₂    è     NH₄HCO₃  

 Now this ammonium carbonate will further reacts with brine to form precipitates like sodium bicarbonate and ammonium chloride. That is 

             NH₄HCO₃    + NaCl   è     NaHCO₃    +   NH₄Cl

3 . Vacuum filter (CALCINER)

Due to exothermic nature of above reactions solubility of sodium bicarbonates increases to count this effects. Lower part of Solvay’s tower is cooled and precipitates of sodium bicarbonates are separated by vacuum filtration and washed to remove ammonia salts. Finally the sodium bicarbonate is dried and heated in a furnace called CALCINER to give anhydrous sodium carbonate or soda ash or sodium carbonate. Such a reaction is as follow

4 . Kiln

 Here calcium carbonate is decompose by heating to form the carbon dioxide and calcium oxide. Such reaction of this step is as follow. 

               CaCO₃       Heat è      CaO    + CO₂  

now this formed CaO is then treated with water to form Ca (OH) ₂ (lime stone). That is                      CaO    +    H₂O     è     Ca (OH) ₂  

5 . Ammonia recovery tower

This Calcium hydroxide (lime stone) is produce in last step is then treated with ammonium chloride solution which is produced in carbonating tower to recover ammonia in this tower. Such reaction of this step is as follow.

     

               2NH₄Cl   +    Ca (OH) ₂     è      CaCl₂     +   2NH₃    +   2H₂O

Importance of Soda ash

 It is almost use in every part of our life that’s why has a lot of importance. The following importance due to usage is as follow;

1 .Due to high solubility it is used in many industrial chemical reactions.

2 . It is also use in the household detergents and also in medicines etc.

3 . It acts to reduce the acid content of power plant emissions. 

4 . It is an important component of glass, and is used to reduce the melting point of silica.

5 . It is used to remove sulfurs and phosphates from some ferrous and non-ferrous ores etc.

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