NOx Reduction Using Selective Catalytic Reduction … · Experienced People – Advanced Thinking 1...
Transcript of NOx Reduction Using Selective Catalytic Reduction … · Experienced People – Advanced Thinking 1...
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AIChE Meeting
May 20, 2005
New Orleans, LA
NOx Reduction UsingSelective Catalytic Reduction (SCR)
Post Combustion Technology
KTI Corporation
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Agenda
• Introduction
• Discussion of SCR Technology
• Brief Discussion of SNCR Technology
• Question and Answers
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Agenda:
• Design aspects of an SCR
• Typical components of SCR System
• Operating aspects of an SCR
• Benefits of an SCR System
• Drawbacks of an SCR System
Discussion of SCR Technology
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Design Aspects of an SCR
Selective Catalytic Reduction (SCR)
Specifically NOx but can be others
Discussion of SCR Technology
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Discussion of SCR Technology
Design Aspects of an SCR
What are we trying to accomplish?
Mix Ammonia into a NOx laden stream and causethem to react in the presence of a catalyst.
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Design Aspects of an SCR
Typical Make-up of NOx
Fired Heaters90% NO – 10% NO2
Gas Turbines90% NO – 10% NO270% NO – 30% NO2
Discussion of SCR Technology
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Design Aspects of an SCR
Basic Chemistry
4NH3 + 4NO + O2 4N2 + 6H2O
4NH3 + 6NO 5N2 + 6H2O
4NH3 + 2NO2 + O2 3N2 + 6H2O
8NH3 + 6NO2 7N2 + 12H2O
2NH3 + NO + NO2 2N2 & 3H2O
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Design Aspects of an SCR
In order for the SCR to work, we must do the following correctly:
• Distribute the flowrate evenly to the face of the catalyst.
• Mix the NH3 intimately in the effluent stream.Match the NH3 with NOx in the correct stoichiometric ratios.
• Distribute the temperature of the stream evenly to the face of the catalyst.
Discussion of SCR Technology
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Discussion of SCR Technology
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Design Aspects of an SCR
Typical Tolerance
NH3 to NOx Ratio 5% to 10% RMS
Temperature ± 20°F
Flow Rate ± 15% RMS
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Discussion of SCR TechnologyDesign Aspects of an SCR Typical Tolerance on NH3 to NOx Distribution vs.
Reduction
±3 to 5% RMS2 ppm95% Reduction
±5% RMS5 ppm90% Reduction
±10% RMS10 ppm80% Reduction
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Design Aspects of an SCR
• SCR Design Factors– Flue Gas Flow Rate– Flue Gas Temperature– Inlet NOx Concentration– Required NOx Reduction Efficiency or Outlet NOx Concentration– SO2, SO3 Levels– Particulate Loading Rate– Allowable Pressure Drop– Physical Site Constraints– Location Relative to Other Equipment in Flue Gas Stream– Poisons– NO to NO2 split
Discussion of SCR Technology
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Design Aspects of an SCR
Types of NH3
• Aqueous (11%, 19%, 25%, 29%)
• Anhydrous
• Urea (CO(NH2)2)
Discussion of SCR Technology
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Aqueous SystemDiscussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Anhydrous SystemDiscussion of SCR Technology
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Typical components of SCR System:
• Process and Detailed Engineering• CFD/CFM (Cold Flow Modeling)• Catalyst• SCR housing, support system and seal plate system• AIG/Manifold• Static Mixers / Perforated Plates (if necessary)• AFCU skid• Duct sections (if necessary)• Isolation/Control Dampers• Fans• Furnace/Boiler Equipment Modifications
The above items form the critical components of the SCR system to ensure proper operation of the entire system.
Discussion of SCR Technology
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Typical components
• Process and Detailed Engineering
• CFD / CFM (Cold Flow Modeling)
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Why is CFD/CFM so important?To make sure we get the three key issues correct:
• Distribute the flowrate evenly to the face of the catalyst.
• Mix the NH3 intimately in the effluent stream.Match the NOx in the correct stoichiometric ratios.
• Distribute the temperature of the stream evenly to the face of the catalyst.
Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Typical components
• Process and Detailed Engineering
• CFD / CFM
• Catalyst
Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Typical components of SCR System:
• Process and Detailed Engineering
• CFD/CFM
• Catalyst
• SCR housing, support system and seal plate system
Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Typical components of SCR System:
• Process and Mechanical Engineering
• CFD/CFM
• Catalyst
• SCR housing, support system and seal plate system
• AIG/Manifold
Discussion of SCR Technology
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Discussion of SCR Technology
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Typical components of SCR System:
• Process and Mechanical Engineering
• CFD/CFM
• Catalyst
• SCR housing, support system and seal plate system
• AIG/Manifold
• Static Mixers / Perforated Plates (if necessary)
• AFCU skid
Discussion of SCR Technology
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Typical components of SCR System:
• Process and Mechanical Engineering
• CFD/CFM
• Catalyst
• SCR housing, support system and seal plate system
• AIG/Manifold
• Static Mixers / Perforated Plates (if necessary)
• AFCU skid
• Duct sections (if necessary)
• Isolation/Control Dampers
• Fans
Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Typical components of SCR System:
• Process and Detailed Engineering
• CFD/CFM
• Catalyst
• SCR housing, support system and seal plate system
• AIG/Manifold
• Static Mixers / Perforated Plates (if necessary)
• AFCU skid
• Duct sections (if necessary)
• Isolation/Control Dampers
• Fans
• Furnace/Boiler Equipment Modifications
Discussion of SCR Technology
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Discussion of SCR Technology
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Additions Components of SCR System:
• Construction• Storage tank• Pump skid• Control system/PLC/DCS• Foundations• Auxiliary equipment (ESP, Bag house
scrubbers, etc.)• Emission Analyzers• Interconnecting piping
Discussion of SCR Technology
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Discussion of SCR Technology
Ammonium Sulfate2NH3 + H2O + SO3 (NH4)2SO4
Dry Powder particulate emission
Ammonium BisulfateNH3 + H2O + SO3 (NH4)HSO4
Sticky and corrosive
Operating Aspects of an SCR
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Discussion of SCR Technology
Catalyst Volume
Lower Thermal EFT
Ammonium Bisulfate amount
Operating Temperature
CatalystVolume
Ammonium Bisulfateamount
SO2 to SO3
Catalyst VolumeAmmonium Bisulfateamount
NH3 SlipOperating Aspects of an SCR
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Operating Aspects of an SCR
• Low temperature catalyst300°F – 450°F
• Medium temperature catalyst450°F – 850°F
• High temperature catalyst850°F – 1000°F
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Operating Aspects of an SCR
• How long does catalyst last?
Discussion of SCR Technology
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Operating Aspects of an SCR
• How long does catalyst last?
Depends
Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Discussion of SCR Technology
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Benefits of a SCR System
• Lowest proven emission level possible
• Well established technology (client’s facility is not a laboratory)
• Flexible design that can accommodate known future expansion
• Address NOx formation from some processes that can not be addressed with any other technologies
Discussion of SCR Technology
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Drawbacks of a SCR System
• Typically higher capital cost
• Operating cost from NH3
• Operating cost from Catalyst
• Plot space
• Potential of pluggage
Discussion of SCR Technology
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Design Aspects of an SNCR
Selective Non Catalytic Reduction (SNCR)
Brief Discussion of SNCR Technology
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Brief Discussion of SNCR Technology
• Also known as Thermal DeNox
• Same basic technology as SCR
• Inject NH3 or UREA into a NOx laden stream and allow enough time to react
• Amount of Reduction 40 – 75%
• Operating temperature 1500°F-2200°F
• Residence time 0.75 – 1.5 seconds
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Typical components of SNCR System
• NH3 AFCU (Vaporization) Skid
• NH3 or UREA Storage Tank
• NH3 or UREA Pump Skid
• NH3 or UREA Injection
• Analyzers
Brief Discussion of SNCR Technology
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Positive Aspects
• Lower Capital Costs
• Lower Operating Costs
• Lower Maintenance Costs
• Smaller foot print
Brief Discussion of SNCR Technology
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Negative Aspects
• Limited amount of NOx Reduction
• Difficult to find the operating window in terms of temperature and residence time
• Lower Maintenance Costs
Brief Discussion of SNCR Technology
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QUESTIONS
AND
ANSWERS