Aspects of SOx Reduction

1
Aspects of SOx Reduction

• Presented by
• Ken Sourisseau
• Shell Canada Limited

2
Sulfur Pathways

• Fossil fuels contain sulfur
• Natural gas H2S, COS, mercaptans
• Oil, chemical bound in heavy hydrocarbons
• Sulfur recovered as H2S from processing
• H2S converted to elemental sulfur and recovered
• Unrecovered sulfur oxidized before release to
  atmosphere
• Sulfur released as SOx (Majority SO2, unusual
  operation SO3)

3
Sulfur Recovery Options

• Very Small (lt250 kg/d) Use Adsorbents
• 99.9 recovery
• Small (1/4 20 t/d)
• 99.9 recovery
• Biological Shell Paques,
• Liquid Redox LoCat, CrystaSulf, Sulferox,
• Medium to Large
• 96 - 99.8 recovery
• Modified Claus (Thermal Catalytic)
• Claus Extensions
• Claus plus Tail Gas Treating

4
Sulfur Recovery Efficiency

• Modified Claus (92 to 97)
• Claus Extensions (98 to 99.3/-)
• SCOT Tail Gas Treating (99.8)

5
Modified Claus (95 Recovery)

• Catalytic stages operate at 240 oC to 345 oC
• Third stage increases recovery to 97

6
Modified Claus Recovery Limits

• Equilibrium in last stage means some reactants
  not converted
• Non conversion of COS and CS2
• Sulfur vapour from last condenser
• Sulphur droplet mist from last condenser

7
Claus Extension (99 Recovery)

• Direct catalytic partial oxidation SUPERCLAUS
• Sub dewpoint CBA, Sulfreen, MCRC
• New units less common

8
Claus Extension Recovery Limits

• SO2 in tail gas
• Minimized by selecting operating conditions
• Non conversion of COS and CS2
• Sulfur vapour from last condenser
• Sulphur droplet mist from last condenser

9
SCOT (99.8 Recovery)

• Shell Claus Offgas Treatment (SCOT)

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SCOT (99.8 Recovery)
11
SCOT Recovery Limits

• H2S equilibrium at the top of the absorption
  column
• Determined by temperature and residual amine
  loading
• Tail gas may contain 250 ppmv H2S

12
Costs of Increased Efficiency

• Significantly more equipment than Claus
  extensions
• Increased capital
• Increased ongoing operating and maintenance costs
• Energy requirements
• Fuel for reduction burner (CO2 emissions)
• Steam for regeneration
• May be available as surplus
• Generation will result in energy consumption and
  CO2 emissions

13
Sulfur Recovery Efficiency Improvement Costs

• Relative capital cost
• Claus (3 stage) 100
• Claus Extension (2 Plus 1) 120
• Claus SCOT (2 plus) 130 - 170
• Costs are relative and indicative. Actual cost
  differences require detailed engineering

14
SCOT Improvements

• Low temperature SCOT
• Improved catalyst operates at lower temperature
• Reduced fuel requirements
• Reduced CO2 emissions
• Steam reheater
• Utilize available steam for reheat
• Simplified system reduces capital and operating
  costs
• Reduced CO2 emissions if surplus steam is
  available

15
SCOT Integration Opportunities

• Integrate SCOT amine with primary treating or
  enrichment
• One regenerator with higher flow rates
• Reduced capital cost
• Reduced steam consumption
• Cascade SCOT amine to primary treater
• Amine from SCOT reused in high pressure absorber
• One regenerator with lower flow rates
• Reduced capital cost
• Further reduction steam consumption

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SCOT Unit Upsides

• Cooling
• Winter conditions improve cooling and provide
  seasonal improvements in recovery
• Regeneration
• Deeper regeneration has the potential to also
  improve overall recovery
• Increased energy consumption
• Increased capital cost

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Sulfur Capacity/Efficiency
SO2 emission 2 x sulfur emission
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Recovery Efficiency vs Technology
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Claus Reaction Furnace
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Claus Converter
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SCOTReactor
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SCOT Unit Vessels
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Thank You

• Questions?