The Solvay process is the major industrial process for producing sodium carbonate. It involves purifying salt brine, dissolving ammonia in the brine, absorbing carbon dioxide in a reactor tower to form sodium bicarbonate, and heating the bicarbonate to produce sodium carbonate. The key reactions are: 1) NH3 + H2O + CO2 → NaHCO3, 2) 2NaHCO3 → Na2CO3 + H2O + CO2. The process recovers and recycles the ammonia.

1. Article written and published
By
www.worldofchemicals.com
MANUFACTURING OF SODIUM CARBONATE BY
SOLVAY PROCESS

2. INTRODUCTION
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Sodium carbonate (Na2CO3) is found naturally or is manufactured
from natural salt i.e., sodium chloride (common salt). It has many
uses but, one of the major notable applications is in making of
glass. Soda ash is a key chemical for producing soap, paper
making, baking soda production, and bleaching fabrics and paper.
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Origin of soda ash term
The name "soda ash" is based on the principal historical method
of obtaining alkali, which was by using water to extract it from
ashes. The word "soda" (from the Middle Latin) originally referred
to certain plants that grow in salt marshes; it was discovered that
the ashes of these plants yielded the useful alkali "soda ash."
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3. WHY SODIUM CARBONATE CALLED AS
WASHING SODA?
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CO32- from dissolved Na2CO3 can precipitate Mg2+ and Ca2+ ions from
hard water as the insoluble carbonates, preventing them from forming a
precipitate with soap resulting in scum. For this reason, sodium
carbonate is also known as washing soda.
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Soda ash is used to produce the NaHSO3 necessary for the sulfite
method of separating lignin from cellulose.
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Sodium carbonate removes grease from wool and neutralizes acidic
solutions.
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Na2CO3 is used to remove SO2(g) from flue gases in power stations
Na2CO3 was produced by two processes
Leblanc process
Ernest Solvay process
The Solvay Process (also known as the ammonia-soda process),
developed in 1861, is the world's major industrial process for the
production of sodium carbonate (NaCO3), or soda ash.
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4. SOLVAY PROCESS HISTORY
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In 1861, after realizing the polluting impacts of the Leblanc Process,
Belgian industrial chemist Ernest Solvay rediscovered and perfected
Augustin Fresnel's reaction. This process recovered the ammonia in the
reaction for re-use, therefore making it less detrimental to the
environment.
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In 1874, other companies had bought the right to use the Solvay
process in their own plants. Now the sodium carbonate production
market became a booming industry with several plants opening
worldwide.
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In 1890's, Solvay-based process plants produced the majority of the
world's soda ash.
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The materials needed in the Solvay process are nearly all readily
available and inexpensive:

5. SOLVAY PROCESS FEEDSTOCKS
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Salt Brine – Salt brine as one of the feedstock provides salt and
water and it can be easily sourced from both inland and the
ocean.
Limestone
Ammonia
The following steps are involved in solvay process and in this
process some amount of ammonia recycled back as feedstock to
start new round of solvay process.
Brine purification
Ammoniation of brine
Reactions in Solvay Tower
Reactions in klin / Separation of solid sodium hydrocarbonate
Formation of sodium carbonate
Ammonia Recovery

6. MANUFACTURING STEPS IN SOLVAY PROCESS

7. BRINE PURIFICATION
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Brine or brine solution is a solution of salt and water. It is mainly
used as a preservative for vegetables, fish, fruit, and meat
through a process known as brining. The high salt content in
Brine prevents the growth of bacteria and thus helps to preserve
the food for a long time without creating any difference in taste.
Brine is widely used all over the world for various food
preparations and is best suited for delicacies made from meat
and fish.
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Brine is both naturally found and artificially produced as well.
Brine has many commercial applications. Brine is be prepared by
dissolving rock salt post hydraulic fracturing of a well. The
process of creating Brine is more than simple mixing. It is done by
an electronically controlled and monitored process. Huge
quantities of Brine are extracted by installing a self-contained
hydraulic system from heavy salt concentrations areas

8. APPLICATIONS OF BRINE
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Brine is an extremely useful substance used in domestic
chores as well as commercial applications.
Brine is used for the production of salts. The brine is
generally evaporated and then processed to get the
common salt or table salt (Nacl).
Brine is widely used for food preservation.The brine can
be mixed with a wide variety of herbs and spices for
flavor.
Brine is often used for marinating meat. It makes the flesh
juicier, and tender. Apart for that, Brine kills the
microorganisms that harbor in meat. The process of
marinating the meat with brine, prior to cooking reduces
the cooking time.

9. APPLICATIONS OF BRINE CONT ..
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Brine solution is an excellent prewetting agent and
commercially used to treat the roads. The solution is noncorrosive, biodegradable, and environmentally friendly.
Brine is used to transfer heat from one place to another
place and is largely used for refrigeration.
Brine has a lower freezing point than water and can be
cooled to below zero Celsius. Hence it is effectively used
as coolant other than plain water. Brine freezes at -21ºC
(-6ºF). It is used for cooling steels and other metals.
Brine is often used for Pickling.
Brine is an important source of chlorides, sulphates of
magnesium and potassium apart from natural salt. These
salts are extracted through electrolysis.

10. APPLICATIONS OF BRINE CONT ..
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Brine solution cures Psoriasis, Osteoporosis, Arthritis,
Gout and Herpes sores.
Brine steam inhalation cures asthma, bronchitis,
acute and chronic sinus and ear infections.
Brushing teeth with concentrated Brine solution helps
to protect tooth enamel.
Brine poultice is used to sterilize open wounds.
Brine baths improves circulatory system and control
high temperature during viral fever.
Brine acts an excellent detoxification solution and
improves the metabolism. It maintains the body’s pH
Factor and eliminates heavy metals.

11. REACTIONS INVOLVED IN SOLVAY PROCESS
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The solvay process will commences with brine purification which
involves
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Brine solution is concentrated by evaporation to at least 30 per cent
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Calcium, magnesium and iron are collected as precipitants in this
reaction
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Ca2+(aq) + CO32-(aq) → CaCO3(s)
Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)
Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s)
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Following the precipitation reaction brine solution is then filtered and
passed through an ammonia tower to dissolve ammonia.
Through this process energy is released because of its exothermic
nature, thereby, the ammonia tower will get cooled by this energy.

12. COMPLETE REACTION PROCESS EXPLAINED
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The solvay process will commences with brine purification which
involves
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Brine solution is concentrated by evaporation to at least 30 per cent
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Calcium, magnesium and iron are collected as precipitants in this
reaction
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Ca2+(aq) + CO32-(aq) → CaCO3(s)
Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)
Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s)
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Following the precipitation reaction brine solution is then filtered and
passed through an ammonia tower to dissolve ammonia.
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Through this process energy is released because of its exothermic
nature, thereby, the ammonia tower will get cooled by this energy.

13. COMPLETE REACTION PROCESS EXPLAINED
CONT ..
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Types of kilns
Shaft kilns
Counter current shaft kilns
Regenerative kilns
Annular kilns
Rotary kilns
Kilns are fed with a limestone/coke mixture (13:1 by mass). The coke burns in a
counter-current of pre-heated air
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C(s) + O2(g) → CO2(g)
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The heat of combustion raises the temperature of the kiln and the limestone
decomposes
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CaCO3(s) ↔ CaO(s) + CO2(g)
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The gas, containing approximately 40 per cent carbon dioxide, is freed of lime dust and
sent to the carbonating (Solvay) towers. The residue, calcium oxide, is used in
ammonia recovery.

14. REACTIONS IN SOLVAY TOWER
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The Solvay Tower is tall and contains a set of mushroom-shaped baffles
to slow down and break up the liquid flow so that the carbon dioxide can
be efficiently absorbed by the solution. Carbon dioxide, on dissolving,
reacts with the dissolved ammonia to form ammonium hydrogen
carbonate
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NH3(aq) + H2O(l) + CO2(g) → NaHCO3(s)
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The solution now contains ions Na+(aq), Cl-(aq), NH4+(aq) and HCO3-(aq). Of
the four substances which could be formed by different combinations of
these ions, sodium hydrogencarbonate (NaHCO3) is the least soluble. It
precipitates as a solid in the lower part of the tower, which is cooled.
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NaCl(aq) + NH3(aq) +H2O(I) +CO2(g) → NaHCO3(s) + NaCl (aq)

15. FORMATION OF SODIUM CARBONATE
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Formation of sodium carbonate
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Suspended sodium hydrogen carbonate is removed from the carbonating tower
and heated at 300oC to produce sodium carbonate:
2NaHCO3(s) → Na2CO3(s) + H2O (g) + CO2 (g)
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Ammonia Recovery
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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)
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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(g)

16. REFERENCE
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[1] © From, http://www.ausetute.com.au/solvay.html
[2] © From,
http://www.essentialchemicalindustry.org/chemicals/s
odium-carbonate.html
[3] © From,
http://www2.warwick.ac.uk/fac/soc/economics/current
/modules/ec303/201011_further_details/the_solvey_p
rocess.pdf
http://www.worldofchemicals.com/wocart/440/manufa
cturing-of-sodium-carbonate-by-solvay-process.html