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Manufacture of Sodium Carbonate by Solvay process

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Principle

↪ When carbon dioxide gas is bubbled into pure brine solution saturated with ammonia, ammonium bicarbonate is formed in cold which reacts immediately with sodium chloride to form sodium bicarbonate and ammonium chloride.

NH3 + H2O + CO2 → NH4HCO3

NH4HCO3 + NaCl → NaHCO3 + NH4Cl

↪ Sodium bicarbonate is less soluble and ammonium chloride is highly soluble.
↪ Sodium bicarbonate precipitates from the mixture due to common ion effect of spent brine and it is separated from ammonium chloride solution by filtration.
↪ Solid NaHCO3 when calcined gives sodium carbonate (light soda ash).

2NaHCO3 → Na2CO3 + H2O + CO2

↪ For the reaction, CO2 is obtaind from the calcination of calcium chloride.

CaCO3 → CaO + CO2

↪ And NH3 gas is generated by heating the mixture of NH4Cl solution and slaked lime (Ca(OH)2)

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


⁕ Flowsheet diagram of Manufacture of Sodium Carbonate by Solvay process