1. PRODUCTION OF SULFURIC ACID
DCDA POCESS
PRODUCTION OF SULFURIC ACID

2. PREPARED BY :
NAME EN NO:
1. PATEL VIVEK
2. PAUL SOURAV
3. PITHADIYA MAULIK
4. RADADIYA ROSHAN
5. RAVAL KUNJAN

3. COLLEGE NAME:
G.H.PATEL COLLEGE OF ENGG & TECH.
BRANCH : CHEMICAL 2nd year
SEM: 3rd
SUBJECT:
CHEMICAL PROCESS INDUSTRIES - 1

4. Sulfuric acid PURE 100% H2S04 Mol. Wt. 98.08 M.P. 10.5. C B.P. 340. C
SOLUBILITY : COMPLETELY MISCIBLE WITH H2O WITH LARGE HEAT OF SOLUTION .SO3 SOLUBLE IN H2S04 TO GIVE VARYING PERCENTAGE OF OLEUM.

5. Manufacturing by DCDA Process
Raw materials
Sulfur
Pyrites
CuS ,ZnS, PbS, MoS2
H2S Sources
Sulfur source

6. Chemical reactions Three Step Process 1) S + O2 SO2 2) SO2 + 1/2O2 SO3
2) SO /2O SO3
3) SO3 + H2O H2SO4

7. Process The process can be divided into five stages:
combining of sulfur and oxygen
purifying sulfur dioxide in the purification unit
adding excess of oxygen to sulfur dioxide in presence of catalyst vanadium pentoxide, with temperatures of 450 °C and pressure of 1-2 atm
sulfur trioxide formed is added to sulfuric acid which gives rise to oleum (disulfuric acid)
the oleum then is added to water to form sulfuric acid which is very concentrated.

8. Oxidation of Sulfur
Air
93% H2SO4
Sulfur
10-12% SO2
Steam
Water

9. Oxidation of Sulfur Process: - Air drying tower with acid
- Sulfur is injected into burner
- Reaction Temperature 2000°F
- Exothermic reaction must be cooled
- Steam recovered
Kinetic Effects
- Oxidation of sulfur dioxide is slow and reversible
- The reaction requires a catalyst and 426.7°C temperatures
The reaction is exothermic and sensitive to excessive heat
Equilibrium Constant (The degree at which the reaction proceeds is temp. dependent) 

10. log Kp = T
T = absolute temp. in kelvin
Kp = equilibrium constant as a function of partial pressure of gases
Kp = ( PSO3 ).5 /( PSO2 PO2 ).5

11. Purification unit Purification unit
This includes the dusting tower, cooling pipes, washing tower, drying tower, arsenic purifier and testing box. Sulfur dioxide has many impurities such as vapours, dust particles and arsenous oxide. Therefore, it must be purified to avoid catalyst poisoning . In this process, the gas is washed with water, and dried by sulfuric acid. In the dusting tower, the sulfur dioxide is exposed to a steam which removes the dust particles. After the gas is cooled, the sulfur dioxide enters the washing tower where it is sprayed by water to remove any soluble impurities.

12. In the drying tower sulfuric acid is sprayed on the gas to remove the moisture from it. Finally, arsenic oxide is removed when the gas is exposed to ferric hydroxide.

13. OVERALL FLOW CHART

14. DCDA
The next step to the Contact Process is DCDA or Double Contact Double Absorption. In this process the product gases (SO2) and (SO3) are passed through absorption towers twice to achieve further absorption and conversion of SO2 to SO3 and production of higher grade sulfuric acid.
SO2-rich gases enter the catalytic converter, usually a tower with multiple catalyst beds, and are converted to SO3, achieving the first stage of conversion. The exit gases from this stage contain both SO2 and SO3 which are passed through intermediate absorption tower

15. where sulfuric acid is trickled down packed columns and SO3 reacts with water increasing the sulfuric acid concentration. Though SO2 too passes through the tower it is unreactive and comes out of the absorption tower.
This stream of gas containing SO2, after necessary cooling is passed through the catalytic converter bed column again achieving up to 99.8% conversion of SO2 to SO3 and the gases are again passed through the final absorption column thus resulting not only achieving high conversion efficiency for SO2 but also enabling production of higher concentration of sulfuric acid.

16. The industrial production of sulfuric acid involves proper control of temperatures and flow rates of the gases as both the conversion efficiency and absorption are dependent on these.

17. Oxidation of Sulfur Dioxide
Gas
Cooling
SO3 Gas
SO2 Gas
93% H2SO4

18. Because of the large effect temperature plays on the reaction, multiple catalyst layers are used, with cooling between each step.
Additionally, as the partial pressure of SO3 increases, further reaction is limited.
This is overcome by removing the SO3 after the third stage to drive the reaction to completion.
CATALYST:
MOST WIDELY USED CATALYST IS VENADIUM P ENTOXIDE DISPERSED ON A POROUS CARRIER IN PELLET FORM.

19. Oleum Production Sulfuric acid with additional SO3 absorbed
20% Oleum contains 20% SO3 by weight in the oleum
Common strengths of oleum are 20, 30, 40, 65 percent.
To produce 20 and 30 percent oleum, only requires an additional absorption tower.
Oleum is used in reactions where water is excluded
SO3 + H2SO H2S2O7 (disulfuric acid)

20. Reaction By-products / Heat Integration
57 to 64% of the energy input generates steam
Steam energy is used to drive the turbine that supplies power to the main air blower
Additional steam remaining is tolled internally for other plant operations
SO2/SO3 is vented in small amounts and is federally regulated.
Heat Integration
Steam is used to pre-heat and vapor from the absorption towers used to cool
Minimizes the cost of manufacturing to maximize the profit.

21. Production Considerations
Metal corrosion is a big issue in the manufacture of sulfuric acid.
Special alloy metals must be used to guard against excessive corrosion.
Nickel, chromium, molybdenum, copper, an silicon are the most important elements that enhance corrosion resistance of alloys.
important variables for corrosion
Concentration of the acid
Temperature of service
Speed of flow in pipes and equipment
Alloy element make-up

22. THANK YOU 