The document summarizes a study to improve a furnace design by reducing flame impingement on tubes and lowering tube temperatures. It recommends bringing burners closer to the center and inclining them by 5 degrees. CFD modeling shows benefits of the proposed modifications, including: 1) Eliminating a recirculation region that diverted flow towards tubes. 2) Increased flame length from 20 to 24 feet with temperatures confined to the center. 3) Eliminated flame impingement on tubes.

1. Study Objectives
• Identify ways to eliminate flame impingement on
the tubes and reduce tube metal temperature in
radiant section
• FIS has recommended the following modifications:
– Bring Burners Closer to the Center by about 1-2 ft..
– Incline burners by 5 towards the center
• Carry out CFD Modeling of the Burners and
Combustion Chamber to demonstrate the benefits
of the proposed modifications
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04/09/12 Furnace 1

2. Existing Burner Arrangement Elevation
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EXISTING FLOOR & PLENUM ARRANGEMENT
04/09/12 Furnace Improvements

3. Velocity Vectors at 45 deg
Base Case vs. Proposed Case
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4. Temperature Contours at 45 deg
Base Case vs. Proposed Case
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Base Case Proposed
Case

5. Temperature Contours at 5ft
Base Case vs. Proposed Case
At 5 ft. At 5 ft.
Base Case Proposed
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Case

6. Temperature Contours at 10ft
Base Case vs. Proposed Case
At 10 ft. At 10 ft.
Base Case Proposed
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Case

7. CO mass fraction contours (PPM) at
10ft Base Case vs. Proposed Case
At 10 ft. At 10 ft.
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8. CO mass fraction contours (PPM) at
15ft Base Case vs. Proposed Case
At 15 ft. At 15 ft.
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9. Path lines colored by temperature
(o F)- Base Case vs. Proposed Case
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Base Case Proposed

10. Iso surface of CO mass fraction 2000 PPM colored
by flame height (ft.)- Base Case vs. Proposed Case
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Base Case Proposed
Case

11. Summary
• Base case has the recirculation region at center of
heater, there by diverting the flow towards the
radiant tubes.
• Proposed Case has no recirculation zone between
opposite burners there by no bending of flame is
observed
• Due to above reason flame length is increased for 20
ft(for base case) to 24 ft. for Proposed Case
• High temperatures are confined to center of heater
• Flame impingement is eliminated
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