Soda ash manufacturing and process flow diagram

1. SODAASH AND BAKING SODA
INDUSTRY
USAMA PERVAIZ
BS CHEMICAL ENGINEER
Department of Chemical Engineering, CIIT Lahore

2. PRODUCTION OF
SODIUM CARBONATE/BICARBONATE
• Uses and History
• Raw materials
• Process flow diagram
• Steps involved in production
•

3. Uses of Sodium Carbonate
Use Process Notes
Glass Making
A mixture of Na2CO3, CaCO3 and SiO2(silicon dioxide
sand) is used for window or bottle glass.
Water Softening Agent
CO3
2- 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.
Paper Making
Na2CO3 is used to produce the NaHSO3necessary for
the sulfite method of separating lignin from cellulose.
Baking Soda Production
Baking soda (or sodium hydrogen carbonate or sodium
bicarbonate), NaHCO3, is used in food preparation and
in fire extinguishers.
Sodium Hydroxide Production
for Soaps and Detergents
Na2CO3 is reacted with a Ca(OH)2, slaked lime,
suspension.

4. RAW MATERIALS
• SALT(SODIUM CHLORIDE)
• LIME STONE
• COAL
• AMMONIA
• DEIONIZED WATER

5. THE OVERALL
REACTION
NaCl+CaCO3 Na2CO3 +CaCl2
However……..

6. PROCESS FLOW
DIAGRAM

7. STEPS INVOLVED IN THE PRODUCTION
OF NA2CO3 /NAHCO3 BY SOLVAY
PROCESS
1- Ammonia absorption
Saturation of salt solution with ammonia
bubble and cap absorber

8. 1.Trayed towers (plate columns). 2.Packed columns.

9. perforated valve cap Bubble cap

10. SOLVAY
PROCESS……….CONTD.
2- Burning of limestone to produce carbon dioxide and
lime
• Combustion of C to CO2 (highly exothermic and produces
96.5 Kcal/mole of C burnt)
• Decomposition of 1 mole of CaCO3 need 43.44 Kcal
Thus mixing lime with coke…….

11. SOLVAY PROCESS
CONTD.
3- The Solvay tower/carbonation of ammoniated brine

12. SOLVAY
PROCESS………..CONTD.
4- Separation of Sodium Bicarbonate
Filtering and washing of precipitated bicarbonate
5- Thermal decomposition of NaHCO3 to Na2CO3
(Calcination)

13. SOLVAY
PROCESS……….CONTD.
6- Production of milk lime (calcium
hydroxide)

14. SOLVAY
PROCESS……….CONTD.
7- Regeneration of ammonia

15. LIGHT VS HEAVY
SODA ASH
Soda ash can be classified into two forms –
heavy and light.
Product after calcination is called light form is obtained first and some is then converted into
the heavy form containing less than 0.5% sodium chloride.
Heavy sodium carbonate is obtained by hydrating light sodium carbonate to the monohydrate
(Na2CO3.H2O) and then dehydrating it to give a product with an increased crystal size and
density.
The two grades have different uses.
The major uses of heavy sodium carbonate are as a solid, particularly in making glass, where
it is used as a flux in the melting of silica (sand).
The uses for light sodium carbonate are traditionally where the chemical is required in
solution.

16. Sodium carbonate, is used
In the manufacture of glass, paper, rayon, soaps, and
detergents.
As a water softener
To control pH (carbonate solutions neutralize acids,
producing only carbon dioxide and water).
In the chemical industry to synthesize many different
sodium compounds, including sodium bicarbonate (baking
soda), sodium silicate (used in detergents), sodium
tripolyphosphate (a detergent builder), sodium hydroxide
(lye), sodium chromate and sodium dichromate (used in
chrome plating), sodium aluminate (used in refining
aluminum), and sodium cyanide (for electroplating).

17. Q-1
Why sodium carbonate called as washing soda?

18. Q-2
Identify the raw materials used in the Solvay process and
name the products

19. Q-3
Describe the uses of sodium carbonate

20. Q-4
Identify the sequence of steps used in the Solvay process
and describe the chemistry involved in:
brine purification
hydrogen carbonate formation
formation of sodium carbonate
ammonia recovery.

21. Q-5
ICI soda ash at khewra, Punjab province, Pakistan, produces
350 000 tons per year of soda ash (sodium carbonate). How
many tons of calcium carbonate are needed to produce
this? Take the overall equation as,
CaCO3(s) +2NaCl(aq)
Na2CO3(aq) +CaCl2(aq)

22. Q-6
Evaporative basins at Dry Creek near Adelaide produce an
average of 650 000 tons per year of salt. This is purified,
then dissolved to form a saturated brine solution that is
pumped to the Solvay plant.
Ammonia is dissolved in the brine solution and then the
ammoniated brine is reacted with carbon dioxide.
I. Write an equation for this reaction.
II. If 50% of the original salt is sodium chloride, what mass
of ammonia will be needed to react with it?

23. Olympia chemicals limited (OCL), is the second largest producer
of soda ash in Pakistan. Based on the available evidance,
determine the criteria used to locate a chemical industry using
OCL as an example. The answer should include
Proximity to supply of raw materials
Proximity to market
Availability of raw materials- for raw materials and finished
product
availability of housing, transport, schools & shops for workers &
family
facilities for waste disposal

24. CO3
2- 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.

25. Brine purification
Salt water (brine) is pumped into shallow ponds, where the water is
evaporated by the sun leaving salt. This is a mixture of calcium and
magnesium salts as well as sodium chloride. The Ca and Mg ions must
be removed.
Calcium salts are precipitated by the addition of sodium carbonate.
Ca2+(aq) + CO3
2–(aq) CaCO3(s)
Magnesium salts are precipitated by the addition of sodium hydroxide.
Mg2+(aq) + 2OH–(aq) Mg(OH)2(s)
A flocculant is added (this causes suspended particles to clump
together and fall out of solution) and the precipitates are skimmed off
the brine.

26. Production of hydrogen carbonate and sodium carbonate
Calcium carbonate is heated in a kiln to form carbon dioxide
& calcium oxide
The calcium oxide is removed, to be used in ammonia
recovery.
Coke is also present in the kiln, producing more carbon
dioxide when heated, as well as providing heat to decompose
the calcium carbonate.
C(s) + O2(g) CO2(g)

27. Ammonia is dissolved in the purified brine (NaCl) and carbon dioxide is
dissolved in this
solution.NaCl(aq) + NH3(g) + H2O(l) + CO2(g) NH4Cl(aq) + NaHCO3(
aq)
Sodium and chloride ions are spectator ions, so this equation may be
written as the following ionic equation:
NH3(g) + H2O(l) + CO2(g) NH4
+(aq) + HCO3
–(aq)
This reaction is carried out at a low temperature (0°C) so that sodium
hydrogen carbonate, which is relatively insoluble at low temperatures,
precipitates out. The mixture is filtered. Sodium hydrogen carbonate is
washed, dried and used to make sodium carbonate. The ammonium
chloride filtrate is sent to the ammonia recovery plant so that ammonia
can be recovered and reused.
Sodium hydrogen carbonate is heated to about 300°C and decomposes
into sodium carbonate and carbon dioxide. Sodium carbonate is
removed and sold. Carbon dioxide is reused.

28. Ammonia Recovery
Calcium oxide (from the first step) is dissolved in water to
form calcium hydroxide.CaO(s) + H2O(l) Ca(OH)2(aq)
Ammonium chloride is reacted with this calcium hydroxide
forming calcium chloride and ammonia. The ammonia is
reused, but calcium chloride is waste.
2NH4Cl(aq) + Ca(OH)2(s) 2NH3(g) + CaCl2(aq) + 2H2O(l)

29. Calculate moles
From the periodic table, molar mass of Na2CO3 = 2 x 22.99
+ 12.01 + 3 x 16.00 = 105.99 g
no mol in 325 000 tonnes = 325 000 x 1 000 000/105.99 =
3066 327 000 mol
From the equation:
1 mol Na2CO3 produced from 1 mol CaCO3
3 066 327 000 mol Na2CO3 produced from 3 066 327 000 mol
CaCO3
Moles to mass
1 mol CaCO3 = 40.08 + 12.01 + 3 x 16.00 = 100.09 g
3 066 327 000 mol CaCO3 = 100.08 x 3 066 327 000 = 306 878
006 200 g = 306 878 tonnes CaCO3

30. Q6
NaCl(aq) + NH3(g) + H2O(l) + CO2(g) NH4Cl(aq) +
NaHCO3(aq)
50% 650 000 = 325 000 tonnes
Calculate moles
1 mol NaCl = 22.99 + 35.45 = 58.44 g
325 000 tonnes = 325.000 x 1 000 000/58.44 = 5 561 259 411
mol NaCl
From the equation
1 mol NaCl reacts with 1 mol NH3
5 561 259 411 mol NaCl reacts with 5 561259 411 mol NH3
Moles to mass

31. Moles to mass
1 mol NH3=14+3x1=17g = 17/1000 000 tons
5561259.4 mol= (17x5561259.4)/1000
= 94730.5 tons NH3