NOx Reduction Using Selective Catalytic Reduction … · Experienced People – Advanced Thinking 1...

Experienced People – Advanced Thinking

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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



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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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Typical Make-up of NOx

Fired Heaters90% NO – 10% NO2

Gas Turbines90% NO – 10% NO270% NO – 30% NO2



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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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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.



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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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• 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



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Types of NH3

• Aqueous (11%, 19%, 25%, 29%)

• Anhydrous

• Urea (CO(NH2)2)



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Aqueous SystemDiscussion 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.



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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.



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Typical components


• CFD / CFM

• Catalyst



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• CFD/CFM

• Catalyst

• SCR housing, support system and seal plate system



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• Process and Mechanical Engineering

• CFD/CFM

• Catalyst


• AIG/Manifold



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• CFD/CFM

• Catalyst


• AIG/Manifold

• Static Mixers / Perforated Plates (if necessary)

• AFCU skid



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• CFD/CFM

• Catalyst


• AIG/Manifold


• AFCU skid

• Duct sections (if necessary)

• Isolation/Control Dampers

• Fans



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• CFD/CFM

• Catalyst


• AIG/Manifold


• AFCU skid

• Duct sections (if necessary)

• Isolation/Control Dampers

• Fans

• Furnace/Boiler Equipment Modifications



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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



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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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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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• Low temperature catalyst300°F – 450°F

• Medium temperature catalyst450°F – 850°F

• High temperature catalyst850°F – 1000°F



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• How long does catalyst last?



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• How long does catalyst last?

Depends



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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



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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



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Design Aspects of an SNCR

Selective Non Catalytic Reduction (SNCR)

Brief Discussion of SNCR Technology


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• 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



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Positive Aspects

• Lower Capital Costs

• Lower Operating Costs

• Lower Maintenance Costs

• Smaller foot print



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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



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QUESTIONS

AND

ANSWERS

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NOx Reduction Using Selective Catalytic Reduction … · Experienced People – Advanced Thinking 1...

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