Power point on data analysis

1. DCDA POCESS
PRODUCTION OF SULFURIC
ACID

2. • PREPARED BY :
• NAME Roll No:
1. Amir Latif 33
2. Shan Salahudin 16
3. Muhammad Ammar 35

3. • COLLEGE NAME:
Institute of Chemical Engineering and
Technology, University of the Punjab, Lahore
• SEM: 1st
• SUBJECT:
ADVANCED CHEMICAL REACTION
ENGINEERING

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
•
• 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 = 4.956 - 4.67
• 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
SO3 Gas
SO2 Gas
93% H2SO4
SO2 Gas

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 + H2SO4 H2S2O7 (disulfuric
acid)

20. Reaction By-products / Heat
Integration
• By-products
• 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