This presentation will help you in the conceptual understanding of commercial and industrial preparation of washing soda, also known as soda ash.

2. Commercial Production of Sodium Carbonate
By
Mr. Muhammad Ullah Afridi
Institute of Chemical Sciences, University of Peshawar.

4.  Sodium carbonate (molecular
formula: Na2CO3), is the
water soluble sodium salt of
carbonate.
 The pure product appears as a
white, odorless powder with a
strong alkaline taste.

5. o Strong electrolyte
o Density 2.532 g/cm3
o Melting point 851 C
o Boiling point1600C
o Weak acid slightly soluble in ethanol
o Insoluble in alcohol

6.  Solvay process
 Labnac process
 Dual process(modified solvay process)
 Electrolytic process

8.  In 1861,labnac process failed as it proved to
have polluting impacts to environment
 Belgian industrial chemist Ernest Solvay
introduced Solvay process in which ammonia
recovered in reaction for re-use, which
reduced the polluting impacts.
 1874 is a year which forced to set up
industries of sodium carbonate after success
Solvay process and 1890 was a dominant year
of soda ash production worldwide.

9. PROCESS FLOW DIAGRAM

10.  Ammoniation tower(ammonia absorber)
 Solvay tower(carbonation tower)
 Lime kiln
 Ammonia recovery tower

11.  Sodium chloride ( NaCl)
 Lime stone(CaCO3)
 Ammonia (NH3)
 Coal for fuel/coke

13. Ca2+
(aq) + CO 2- → CaCO3 (aq) 3(s)
Mg2+ + 2OH- → Mg(OH)
Fe
3+
(aq)
-
(aq) 2(s)
(aq) + 3OH (aq) → Fe(OH)3(s)
 PREPARATION OF BRINE
 First of all saturated solution of NaCl is made called as
brine
 PURIFICATION OF BRINE
 As metal impurities present in water
such as calcium, magnesium and iron are removed by
precipitation, eg,

14.  AMMONIATION TOWER
 Brine solution is then filtered and passed through an
ammonia tower to dissolve ammonia.
 This process is exothermic, releases energy, so the
ammonia tower is cooled.

15. Carbon dioxide is produced by the thermal
decomposition of limestone, CaCO3(s), in the lime
kiln:
CaCO3(s) → CO2(g) +CaO(s)

16. SOLVAY TOWER
 Carbon dioxide is bubbled through the ammoniated brine
solution in the carbonating tower.
The carbon dioxide dissolves to form a weak acid:
 CO2(g) + H2O(l) --------- HCO -
3 (aq) + H+
(aq)
+
The ammonia in the brine reacts with H to form ammonium
ion:
NH3(aq) + H+
(aq) NH +
4 (aq)
-
The HCO3 then reacts with the Na+ to form a suspension of
(aq) (aq)
sodium hydrogen carbonate:
HCO3
- + Na+ NaHCO3(s)

17. SOLVAY TOWER
-
NaHCO3 precipitates because of the large excess of
Na+ present in the brine
The overall molecular equation for the formation of sodium hydrogen
carbonate in the carbonating tower is:
NH3(aq) + CO2(g) + NaCl(aq) + H2O(l) → NaHCO3(s) + NH4Cl(aq)
The net ionic equation for the formation of sodium hydrogen carbonate in
the carbonating tower is:
NH3(aq) + CO2(g) + Na+
(aq) + H2O(l) → NaHCO3(s) +NH +
4 (aq)

18.  Suspended sodium hydrogen carbonate is removed
from the carbonating tower and heated at 300oC to
produce sodium carbonate:
2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
 The carbon dioxide produced is recycled back
into the carbonating tower.

19.  When CaCO3 is heated, CaO is obtained along with
CO2 .
 CaO is treated with water to form Ca(OH)2 .
CaO + H2 O Ca(OH)2
 Quick lime is heated with NH4 Cl to form NH3
and calcium chloride (by product) .
 Ammonia is used again in this process.
2NH4Cl + Ca(OH)2 CaCl2 + 2NH3 + 2H2O

20.  CaO is formed as a by-product of the thermal
decomposition of limestone in the lime kiln. This
CaO enters a lime slaker to react with water to form
calcium hydroxide:
CaO(s) + H2O(l) →Ca(OH)2(aq)
 The calcium hydroxide produced here is reacted
with the ammonium chloride separated out of the
carbonating tower by filtration:
Ca(OH)2(aq) +2NH4Cl(aq) →CaCl2(aq) +2H2O(l) +2NH3