Soda ash manufacturing and process flow diagram

Soda ash manufacturing and process flow diagram

1. Soda Ash 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 Na 2 CO 3 , CaCO 3  and SiO 2 (silicon dioxide sand) is used for window or bottle glass. Water Softening Agent CO 3 2-  from dissolved Na 2 CO 3  can precipitate Mg 2+  and Ca 2+  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 Na 2 CO 3  is used to produce the NaHSO 3 necessary for the sulfite method of separating lignin from cellulose. Baking Soda Production Baking soda (or sodium hydrogen carbonate or sodium bicarbonate), NaHCO 3 , is used in food preparation and in fire extinguishers. Sodium Hydroxide Production for Soaps and Detergents Na 2 CO 3  is reacted with a Ca(OH) 2 , slaked lime, suspension. Wool Processing Na 2 CO 3  removes grease from wool and neutralises  acidic solutions. Power Generation Na 2 CO 3  is used to remove SO 2(g)  from flue gases in power stations.

4. Raw materials SaLT (Sodium Chloride) Lime stone Coal Ammonia Deionized water

5. The overall reaction NaCl+CaCO 3 Na 2 CO 3 +CaCl 2 However……..

6. Process flow diagram

7. Steps involved in the production of Na 2 CO 3 /NaHCO 3 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 B ubble cap

10. Solvay process……….Contd . 2- Burning of limestone to produce carbon dioxide and lime Combustion of C to CO 2 (highly exothermic and produces 96.5 Kcal/mole of C burnt) Decomposition of 1 mole of CaCO 3 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 NaHCO 3 to Na 2 CO 3 (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 (Na 2 CO 3 .H 2 O) 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. S odium carbonate, is used In the manufacture of glass, paper, rayon, soaps, and detergents. A s a water softener To control pH (carbonate solutions neutralize acids, producing only carbon dioxide and water). I n 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 I dentify 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 , CaCO 3 (s)  +2NaCl( aq )     Na 2 CO 3 ( aq )  +CaCl 2 ( 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 . Write an equation for this reaction. 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. CO 3 2-  from dissolved Na 2 CO 3  can precipitate Mg 2+  and Ca 2+  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.  Ca 2+ ( aq )   +    CO 3 2– ( aq )      CaCO 3 (s) Magnesium salts  are precipitated by the addition of sodium hydroxide.  Mg 2+ ( 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)   +   O 2 (g)           CO 2 (g)

27. Ammonia is dissolved in the purified brine  ( NaCl ) and  carbon dioxide is dissolved  in this solution.NaCl ( aq )  +  NH 3 (g)  +  H 2 O(l)  +  CO 2 (g)      NH 4 Cl( aq )  +  NaHCO 3 ( aq ) Sodium and chloride ions are spectator ions, so this equation may be written as the following ionic equation: NH 3 (g)   +   H 2 O(l)   +   CO 2 (g)        NH 4 + ( aq )   +   HCO 3 – ( 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)   +   H 2 O(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. 2NH 4 Cl( aq )  +  Ca (OH) 2 (s)    2NH 3 (g)  +  CaCl 2 ( aq )  + 2H 2 O(l)

29. Calculate moles       From the periodic table, molar mass of  Na 2 CO 3  = 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 Na 2 CO 3  produced from 1 mol CaCO 3  3 066 327 000 mol Na 2 CO 3  produced from 3 066 327 000 mol CaCO 3 Moles to mass  1 mol CaCO 3  = 40.08 + 12.01 + 3 x 16.00  = 100.09 g  3 066 327 000 mol CaCO 3  = 100.08 x 3 066 327 000 = 306 878 006 200 g = 306 878 tonnes CaCO 3

30. Q6 NaCl ( aq ) + NH 3 (g) + H 2 O(l) + CO 2 (g)    NH 4 Cl( aq ) + NaHCO 3 ( 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 NH 3  5 561 259 411 mol NaCl reacts with 5 561259 411 mol NH 3 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