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CHEMISTRY OF
SODIUM CARBONATE ( Na2CO3 )
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Soda Ash
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INDUSTRIAL
PREPARATION OF
SODIUM CARBONATE |
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On
industrial scale sodium carbonate is prepared by Ammonia Solvay Process.
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Raw
Materials
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1. Sodium
Chloride |
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Details
of the process
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first stage a saturated solution of sodium chloride is prepared which is
also known "BRINE". Composition of solution of NaCl (brine) is 28% m/m. |
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Steps
of preparation
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Ammoniation
of Brine
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| In this stage saturated brine is allowed to flow down an ammoniating tower. This tower is fitted with mushroom shaped baffles. These baffles control the flow of brine and ensure the proper mixing and saturation of ammonia. | |||
| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||
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Carbonation
of ammoniated brine
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| In the second step, ammoniated brine is allowed to trickle down a carbonating tower known as solvay tower. This tower is also fitted with baffle plates. Here brine is mixed with carbon dioxide gas, produced by heating lime stone in a separate chamber called "kiln". | |||
| CaCO3 èCaO + CO2 | |||
| the baffle plates ensure the flow of solution and breaks up carbon dioxide into small bubbles to produce good conditions for reaction. | |||
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Flow
Chart
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Chemistry
of Solvay tower
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| CO2 reacts with ammonia to form ammonium carbonate. | |||
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2NH3 + CO2 + H2O
è(NH4)2CO3
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| Ammonium carbonate further reacts with CO2 to form ammonium bicarbonate. | |||
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(NH4)2CO3 + CO2
+ H2O è2NH4HCO3
(aq.)
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| Ammonium bicarbonate then react with NaCl to form sodium bicarbonate. | |||
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NH4HCO3 + NaCl èNaHCO3
+ NH4Cl
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| Due to exothermic nature of above reactions, solubility of NaHCO3 increases. To counter this effect , lower part of Solvay tower is cooled , ppt of NaHCO3 are separated by vacuum filtration and washed to remove ammonium salts. | |||
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Conversion
of NaHCO3 to Na2 CO3
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| Dry sodium bicarbonate is heated in rotary furnace called "CALCINER" to give anhydrous sodium carbonate or soda ash. Carbon dioxide is recirculated to carbonation tower. | |||
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2NaHCO3 èNa2
CO3 + CO2 + H2 O
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Ammonia
recovery process
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| When CaCO3 is heated, CaO is obtained along with CO2 . CaO is treated with water to form Ca(OH)2 . | |||
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CaO + H2 O èCa(OH)2
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| Quick lime is heated with NH4 Cl to form NH3 and calcium chloride (by product) . Ammonia is used again in this process. | |||
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2NH4 Cl + Ca(OH)2 èCaCl2
+ 2NH3 + 2H2 O
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| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||