IFRF 2012 Inclined Firing System

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.