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IFRF- May 2012Inclined Burner Firing System Eliminates Flame ImpingementBy: Ashutosh Garg
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Inclined Burner Firing System
• Client facing flame impingement and high tube metal temperatures in radiant section
• FIS recommended inclined burner firing system to eliminate flame impingement
• Carry out CFD Modeling of the Burners and Radiant Section to demonstrate the benefit of inclined burner firing system
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Burners-Existing
• Forced draft gas fired ultra low burners
• 24 burners, 12 Numbers in each cell
• Normal firing rates- 4.9 MMkcal/hr
• Burner air pressure drop- 22.5 mmwc
• Burner to tube center clearance – 1500 mm
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Existing Burner Arrangement
EXISTING FLOOR & PLENUM ARRANGEMENT
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Inclined Firing System Burner Arrangement
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Heater Geometry for Base Case
Outlet
Radiant tubes
Reed wall
Fuel inlets Air inlets
• Fuel inlets are mentioned independently for primary and secondary tips (shown in the figure) i.e. fuel distributor is not modeled in the current case
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Inclined Firing System Modification
• In this modification burner was made 12’’ closer towards center i.e. the BCD was made 15 ft 3.75’’
• Burner is inclined 5 deg towards center
• Reed wall is removed in this model
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Burner Geometry
Recirculation hole Burner tiles
Staged tip with 3 holes
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Results of CFD Modeling
• Velocity Vectors• Temperature Contours-Elevation• Temperature Contours- Plan View• CO Contours – Plan View• Path lines by temperature• Iso surfaces at 2000 ppm ( flame boundaries)- top view and
elevation view-colored by temperature• Conclusion
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Velocity vectors (ft/s)Base Case
• Velocity vectors shows that it is moving away from center due to circulation at center
Circulation zone
50 ft
36 ft
19 ft
0 ftheight
in ft
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Velocity vectors (ft/s) at 45 ° Inclined Firing System
• Velocity vectors shows that flame is inclined towards center, this is due to no circulation formed at the center of heater
No Circulation zone
50 ft
36 ft
19 ft
0 ftheight
in ft
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Velocity vectors (ft/s) at 45 deg –Base case vs. Inclined Firing System
50 ft
36 ft
19 ft
0 ft
height in ft
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Temperature contours (°C) – Base Case
30° Angle 40° Angle 50° Angle 60° Angle
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Temperature Contours (°C) – Inclined Firing System
40° Angle 50° Angle30° Angle 60° Angle
• High temperature regions are concentration in the center of burner. No high temperature species is moving towards radiant tubes
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Temperature Contours (°F) at 45° Section- Base Case VS. Inclined Firing System
Base case Inclined Firing System
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Temperature contours at different section (°F)- Base Case
At 5 ft At 10 ft
At 15 ft At 20 ftwww.heatflux.com
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Temperature contours at different section (°F)- Inclined Firing System
At 5 ft from heater base At 10 ft
At 15 ft At 20 ft
Low temperature
regions
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Temperature contours(°F) at 5ftsection- Base Case VS. Inclined Firing System
1
At 5 ft
Base case
At 5 ft
Inclined Firing System
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Temperature contours(°F) at 10 ft section- Base Case VS. Inclined Firing System
Base case Inclined Firing System
At 10 ft At 10 ft
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CO mass fraction contours (PPM) at different sections – Base Case
1At 5 ft from heater base At 10 ft
At 15 ft At 20 ftwww.heatflux.com
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CO mass fraction contours (PPM) at different sections - Inclined Firing System
At 5 ft from heater basement At 10 ft
At 15 ft At 20 ft
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CO mass fraction contours (PPM) at 15 ft section- Base Case VS. Inclined Firing System
1
Base case
At 15 ft At 15 ft
Inclined Firing System
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Iso surfaces of 2000 PPM of CO colored by temperature (°F)- Base Case
• Top and front views shows that flame is interacting with radiant tubes
Top viewQuarter section
Flame on radiant tubes
Front view
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Iso surfaces of 2000 PPM of CO colored by temperature (°F)- Inclined Firing System
• Top view shows that flame is not interacting with radiant tubes• Front view shows how the flame is inclined towards center of heater
section
Top view
Quarter section
Front view
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Iso surface of CO mf 2000 PPM colored by temperatures (°F) Base Case VS. Inclined Firing System
Base Case Inclined Firing System
Top Viewwww.heatflux.com
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Summary
• Base case has the recirculation region at center of heater, there by diverting the flow towards the radiant tubes.
• Inclined Firing System- has no recirculation zone between opposite burners there by no bending of flame is observed
• High temperatures are confined to center of heater • FIS recommends inclined firing system revamp of
burners and floor revamp.
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We hope you will find our presentation helpful and informative.
