Lecture Outline - Sulfuric Acid

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Lecture Outline - Sulfuric Acid
- History of Manufacture Development -
Manufacture - Oleum Production - Heat Integration
Issues / By-products - Markets - Usage in
Caprolactam Manufacture
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History of Manufacture of Sulfuric Acid

• One of the oldest industrially applied processes.
  Discovered by a Persian alchemist in the tenth
  century.
• Saltpeter and sulfur were mixed in a glass
  container and burned in a moist atmosphere. Acid
  was collected from the condensed vapors.
• In England, 1746, the lead chamber reactor was
  invented. This invention allowed for higher
  production rates (lt78).
• In England, 1831, a patent was filed that
  described the oxidation of sulfur dioxide over a
  platinum catalyst, the Contact Process. This new
  process increased yields of reaction from 70 to
  above 95.
• In 1913, BASF was granted a patent for the use of
  vanadium pentoxide as a catalyst for the Contact
  Process
• By the 1930s, vanadium pentoxide was becoming
  the dominate catalyst used because of
  insensitivities to poisons and lower cost.
• In 1960 a patent application was filed by Bayer
  using the so called double-catalyst process
  (double absorption).

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Manufacture
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Oxidation of Sulfur
Process - Air drying tower with acid - Sulfur is
injected into burner - Reaction Temperature
2000F - Exothermic reaction must be cooled -
Steam recovered

• Primary Generation of SO2
• 79 Combustion of Sulfur
• 9 Recovery from Metallurgic Processes
• - 5 Regeneration of Spent Acids

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Oxidation of Sulfur Dioxide
Contact Process -Vanadium pentoxide
catalyst - Exothermic Reaction - Multiple Steps
with cooling in between - Double
absorption - Heat integration
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Oxidation of Sulfur Dioxide

• 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.

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Oxidation of Sulfur Dioxide

• Kinetic Effects
• - Oxidation of sulfur dioxide is slow and
  reversible
• - The reaction requires a catalyst and 426.7C
  temperatures
• The reaction is exothermic and sensitive to
  excessive heat
• Equilibrium Constant (The degree at which the
  reaction proceeds is temp. dependent)
• log Kp 4.956 - 4.678
• T
• T absolute temp. in kelvin
• Kp equilibrium constant as a function of
  partial pressure of gases
• Kp ( PSO3 )
• PSO2 PO2

0.5
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Oxidation of Sulfur Dioxide

• Temperature Profile

510 C
75 C
430 C
200 C
125 C
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Oxidation of Sulfur Dioxide

• Temperature Profile

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Oxidation of Sulfur Dioxide
Typical Catalyst Distribution
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Overall Production Scheme
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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)

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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.

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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

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World Production of Sulfuric Acid
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World Supply / Demand for Sulfuric
Acid(thousands of metric tons, 100 H2SO4)
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Markets for Sulfuric Acid

• The fertilizer market is the largest U.S. single
  use for sulfuric acid and consumes 50-65 percent
  of all produced.
• Second is the organic chemical industry.
  Production of plastics and synthetic fibers are
  examples.
• Production of TiO2 consumes large quantities of
  sulfuric acid. TiO2 is a white pigment used in
  paints and plastics.
• In the metal industry, sulfuric acid is used for
  pickling ferrous and non-ferrous materials and in
  the recovery of copper, nickel, and zinc from
  low-grade ores.
• Finally, the petroleum industry uses acid as a
  catalyst for various reactions.

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Acid Strengths Associated End Uses
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Usage in Caprolactam Manufacture
Production and consumption figures for
caprolactam manufacture