AdjustmentCatalytic Combustion EquipmentThe Distribution Of Airflow Needs To Be Addressed From Three Aspects: Equipment Structural Modification, Optimization Of Airflow Control Components, And Adjustment Of Catalyst Loading, Based On Specific Issues Such As Airflow Deviation, Local Eddies, And Uneven Flow Velocity. The Following Are Specific Methods And Operational Points:
1、 Structural Renovation: Optimizing Airflow Channels
1. Design Of Intake Guide Device
Problem Scenario: The Right Angle Elbow And Variable Diameter Pipe Of The Intake Duct Cause The Airflow To Deviate To One Side (as Shown In Figure 1).
Resolvent:
Install Guide Vanes: Install Arc-shaped Guide Vanes (with A Spacing Of 100-200mm) Inside The Elbow Or Variable Diameter Pipe To Guide The Airflow To Spread Evenly (as Shown In Figure 2).
Using Tapered/expanding Pipes: Change The Abrupt Cross-section To A Tapered Pipe With A Length Of 2-3 Times The Pipe Diameter (expansion Angle ≤ 15 °) Or A Tapered Pipe To Reduce Eddy Currents (as Shown In Figure 3).
Example: If The Diameter Of The Intake Duct Suddenly Expands From 300mm To 600mm And Is Changed To A Gradually Expanding Pipe, The Uniformity Index (UI) Of The Airflow Can Be Increased From 0.6 To Above 0.85.
2. Current Grid And Rectifier Device
Applicable Scenario: The Upstream Airflow Velocity Gradient Of The Catalyst Bed Is Large (such As High Central Flow Velocity And Low Edge Flow Velocity).
Renovation Plan: Metal Orifice Plate Flow Equalization Grille: Install A Porous Plate With An Opening Rate Of 30%~50% (aperture 10-20mm, Hole Spacing 20-30mm) 1-2m Downstream Of The Air Inlet, And Balance The Airflow Through Resistance (as Shown In Figure 4).
Honeycomb Ceramic Rectifier: Filled With Honeycomb Ceramic Components (side Length 20-50mm), Forcing Airflow To Flow Along Parallel Channels To Eliminate Swirling Flow
Effect Verification: After Installation, Testing Showed That The Flow Rate Deviation Can Be Reduced From ± 30% To Within ± 15%.
3. Optimization Of Internal Flow Channels In The Reactor
Dead Volume Treatment: If There Is Unused Space At The Top Or Bottom Of The Reactor (dead Volume>10%), An Inclined Baffle Can Be Installed To Fill And Guide The Airflow Towards The Effective Area.
Diverter/collector Design: For Multi Bed Or Parallel Reactors, A Conical Splitter Is Installed At The Connection Between The Inlet Manifold And Branch Pipes To Ensure That The Flow Deviation Of Each Branch Is ≤ 5%.
2、 Airflow Control Components: Dynamically Adjust Flow Rate
1. Adjustable Air Door And Guide Valve
Installation Position: Install Manual/electric Dampers At The Branch Of The Intake Duct Or Upstream Of The Catalyst Bed.
Adjustment Method: After Conducting Multi-point Wind Speed Testing, Close The Air Damper In Areas With High Flow Velocity And Open The Valve In Areas With Low Flow Velocity Until The Flow Velocity Deviation At Each Measuring Point Is ≤ ± 10%.
Example: The Flow Velocity On The Left Side Of A Certain Device Is 25% Higher Than That On The Right Side. By Closing The Left Air Door 15 °, The Flow Velocity Difference Between The Two Sides Is Reduced To 5%.
2. Pressure Balancing Device
Differential Pressure Feedback Control: Install Differential Pressure Transmitters Before And After The Catalyst Bed, And Adjust The Opening Of The Intake Air Door In A Coordinated Manner To Ensure Consistent Pressure Loss In Each Area.
Application Scenario: Suitable For Handling Working Conditions With Large Fluctuations In Gas Volume, Such As Intermittent Production Waste Gas Treatment.
3、 Catalyst Loading And Support Structure Adjustment
1. Optimization Of Catalyst Module Arrangement
Problem Identification: Uneven Gaps Between Catalyst Modules Lead To "short Circuiting" Of Airflow (such As A Gap Width That Is 50% Larger Than The Average, Resulting In An Increase Of 2-3 Times In Airflow).
Solution: Use Standardized Catalyst Carriers (such As Honeycomb Ceramic Or Metal Mesh Plates Of The Same Specifications), And Fill The Modules With High-temperature Resistant Sealing Materials (such As Ceramic Fiber Ropes), With Gaps ≤ 2mm. For Granular Catalysts, Layer By Layer Vibration Is Used During Loading To Ensure Uniform Packing Density (error ≤ 3%) And Avoid Local Looseness Or Agglomeration.
2. Correction Of Flatness Of Supporting Structure
Inspection Method: Use A Level To Measure The Catalyst Support Mesh Plate, And Adjust It If The Flatness Error Is Greater Than 3mm/m.
Rectification Operation: Weld The Support Beam Or Add A Stainless Steel Plate Pad To Ensure That The Levelness Of The Support Surface Is ≤ 2mm/m. For The Corrugated Plate Support Structure, Ensure That The Heights Of The Peaks And Valleys Are Consistent To Avoid Airflow Deviation Along The Height Difference.
4、 Staged Debugging And Effectiveness Verification
1. Cold Commissioning (no Exhaust Gas Condition)
Step: Introduce Ambient Temperature Air (with Flow Rates Of 50%, 75%, And 100% Of The Design Value), And Use An Anemometer To Measure The Flow Velocity Of The Upstream And Downstream Sections Of The Catalyst Bed Point By Point. Adjust The Air Damper And Flow Guide Device According To The Test Results Until The Uniformity Index (UI) Of Flow Velocity Under Each Operating Condition Is ≥ 0.85.
Key Data: Record Pressure Loss Curves At Different Air Volumes To Ensure A Linear Relationship Between Pressure Difference And Air Volume (abnormal Nonlinearity May Indicate Airflow Obstruction).
2. Hot Commissioning (normal Operating Conditions)
Monitoring Focus:
Temperature Field: The Temperature Difference Between The Catalyst Bed And The Same Horizontal Plane Is ≤ 20 ℃, And The Axial Temperature Rise Gradient Is Consistent (such As A Temperature Rise Fluctuation Of ≤ 10% Per Meter Of Bed).
Processing Efficiency: When The Inlet Exhaust Gas Concentration Is Stable, The Outlet Concentration Fluctuates By ≤ 5% And Reaches The Designed Purification Efficiency (such As ≥ 95%).
Dynamic Adjustment: If The Temperature In A Certain Area Is Too High Under Hot Conditions, The Opening Of The Upstream Air Door In That Area Can Be Fine Tuned To Reduce The Airflow By 10% To 15% And Lower The Local Reaction Intensity.
5、 Typical Problem Solution Cases
Case 1: The Intake Elbow Causes The Airflow To Deviate To The Left
Phenomenon: The Flow Velocity On The Left Side Is 30% Higher Than That On The Right Side, And The Left Side Of The Catalyst Is Severely Worn.
Renovation: Install 3 Guide Vanes (angle 45 °, Spacing 150mm) Inside The Elbow, And Add A Flow Equalization Grille (opening Rate 40%) At The Outlet.
Effect: Flow Rate Deviation Reduced To ± 8%, And Catalyst Surface Wear Became Uniform After Six Months Of Equipment Operation.
Case 2: Short Circuit In The Center Of The Catalyst Bed
Phenomenon: The Flow Velocity In The Central Area Is 40% Higher Than That At The Edge, Resulting In An Excessively High Temperature At The Center (50 ℃ Higher Than At The Edge).
Transformation: The Center Spacing Of The Catalyst Module Has Been Reduced From 50mm To 20mm, And Flow Deflectors (with A Height Of 1/3 Of The Module Thickness) Have Been Added Between The Edge Modules.
Effect: The Flow Velocity Difference Between The Center And The Edge Is Reduced To 12%, And The Temperature Difference Is Reduced To 25 ℃.
6、 Precautions
Material Compatibility: The Modified Components Should Be Made Of High Temperature Resistant (≥ 300 ℃) And Corrosion-resistant (such As 316L Stainless Steel, Ceramics) Materials To Avoid Deformation Or Secondary Pollution At High Temperatures.
Pressure Loss Control: Adding A Diversion Device May Increase The System Pressure Loss By 10% To 20%, And It Is Necessary To Calculate The Fan Margin (reserved Pressure Head ≥ 200Pa).
Safe Operation: When Conducting Hot Work Inside The Equipment, Gas Replacement (oxygen Content<1%) Should Be Carried Out First, And The Concentration Of Combustible Gases (LEL<5%) Should Be Monitored.
Summarize
Adjusting The Airflow Distribution Should Follow The Principle Of "structural Optimization First, Dynamic Adjustment Then, And Finally Filling Correction". By Combining Cold And Hot State Debugging, The Quantification Of Airflow Uniformity Can Be Achieved (UI ≥ 0.85, Flow Velocity Deviation ≤± 15%). For Complex Working Conditions, CFD Simulation Can Be Used To Simulate The Transformation Effect In Advance, Reducing On-site Debugging Costs. Regular (quarterly) Retesting Of Airflow Distribution And Establishment Of Equipment Operation Records Can Effectively Prevent The Decrease In Processing Efficiency And Catalyst Failure Caused By Uneven Airflow.
