A new approach to improving heater efficiency
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The document describes improvements to heater efficiency using a split flow approach. In a typical implementation, the process stream is split, with the main flow heated through the radiant section and a split flow heated in the convection section before being recombined. Case studies at Citgo and Valero refineries achieved significant efficiency gains through split flow designs, reducing pressure drops, heat fluxes, and costs compared to conventional approaches.
A new approach to improving heater efficiency
- 1. A new approach to improving heater efficiency Ashutosh Garg, Furnace Improvements www.heatflux.com
- 2. Typical Fired Heater Fluid------ Convection section Radiant section www.heatflux.com
- 3. Conventional Approach to Efficiency Improvement www.heatflux.com Additional Heat Transfer Surface in Convection Section
- 4. Split flow Fired Heater www.heatflux.com
- 5. Typical Reformer Heater Process heated in radiant section Parallel passes, high volume, low pressure drop Convection-Waste Heat Recovery ( HC reboiler or steam generation service) www.heatflux.com
- 6. Split Flow Reformer Heater Process fluid split into two streams Main flow is heated through radiant section Split flow is heated in the convection section. Fluid mixed together at the radiant outlet www.heatflux.com
- 7. Case Studies Citgo Corpus Christi No. 4 Platformer Heater Valero Texas City No. 2 Platformer Heater and NHT heaters (Reboilers) www.heatflux.com
- 8. Citgo, Corpus Christi No. 4 Platformer Heater Objective: Improve Efficiency Stack temperature was 1100 F No steam generation No air preheater www.heatflux.com
- 9. Current Heater Operation www.heatflux.com Parameter Units Operating Value Total Heater Duty MMBtu/hr 158.10 Radiant Heat Duty MMBtu/hr 120.19 Convection Heat Duty MMBtu/hr 37.91 Firing Rate MMBtu/hr 229.20 Efficiency % 68.98
- 10. Flow Scheme - Before Revamp #4 Platformer Heater www.heatflux.com
- 11. Existing #4 Platformer Heater www.heatflux.com
- 12. Proposed Conventional Design High Pressure Drop www.heatflux.com
- 13. Conventional Design with Series Flow www.heatflux.com
- 14. Comparison of Pressure Drop at 22,000 BPD www.heatflux.com Pressure Drop, psi Original Design Series flow Design Cell 1 3.1 4.5 Cell 2 3.3 4.6 Cell 3 1.2 2.5 Cell 4 1.1 2.3 Total 8.7 13.9
- 15. Disadvantages Higher pressure drops Large Size piping Large Convection Sections Higher costs www.heatflux.com
- 16. FIS Split Flow* Scheme * Split flow - US Patent www.heatflux.com
- 17. FIS Split flow * design - Proposed * Patented. www.heatflux.com
- 18. Comparison (Cell 1) Parameters at 22,000 BPD www.heatflux.com Parameter Original Design Split flow Design Pressure Drop, psi 3.1 2.1 Firebox temperature, F 1,615 1,551 Radiant flux, Btu/hr ft2 19,823 15,047 Radiant tube metal temp, F 1,151 1,120 Firing rate, MMBtu/hr 116.35 82.65
- 19. #4 Platformer Heater Data Comparison www.heatflux.com Item Units Before Revamp After Revamp Capacity BPD 18,500 24,000 Heat Duty MM Btu/hr 158.0 194.5 Heat Release MM Btu/hr 234 225 Efficiency % 67.50 86.60 Stack Temp. °F 1,092 478 Fuel MSCFH 244 242.8 Fuel Savings $/annum 5.8 Million* *Based on $6.0 / MM Btu
- 20. #4 Platformer Heater Before and After Revamp www.heatflux.com
- 21. Case Study-2
- 22. Platformer Heaters - Existing Common Convection section with H-18/H-19 and H-23 Process heating-all Radiant Steam Generation in Convection Common Stack Natural Draft www.heatflux.com
- 23. Platformer Heaters (H-20/21/22) www.heatflux.com Parameter Units Original Design Total Heater Duty MMBtu/hr 155.98 Radiant Heat Duty MMBtu/hr 74.09 Convection Heat Duty MMBtu/hr 81.89 Radiant Fuel Efficiency % 54.2
- 24. Plan View of heater www.heatflux.com
- 25. Convection Section Steam Generator Bank Steam Superheater Bank BFW Preheater Bank Steam Generation: 73,669 lbs/hr@464 psig 14 tubes per row Eighteen rows Two future rows www.heatflux.com
- 26. H-18- Hydrotreater Charge Heater Duty-11.97 MMBtu/hr All Radiant Single pass 5 burners 24 tubes P9 metallurgy 8“ NPS tubes 16” spacing Efficiency -55% www.heatflux.com
- 27. H-19 Hydrotreater Stripper Reboiler Duty-18.45 MMBtu/hr All Radiant Four passes 5 burners 56 tubes CS 4” NPS tubes 8” spacing Efficiency -54% www.heatflux.com
- 28. H-23 Depropanizer Reboiler Duty- 15.15 MMBtu/hr All Radiant Two pass 6 burners 52 tubes CS 4” NPS tubes 8” spacing Duty- 56% www.heatflux.com
- 29. Field Survey High draft in all the radiant cells Burners flame spread out Very high fuel gas pressures Bowed tubes in H-21/H-22 Stack dampers are fully open High excess Oxygen in all the cells Burner registers practically closed www.heatflux.com
- 30. Operating Data Simulation Results Convection section was in bad state Fins are burnt out / fouled Steam superheater temperature is 40 F lower than design Thermal Efficiency is 78-81% compared to 88% design. Stack temperature is higher by almost 275 F. Stack temperature ~ 675 F www.heatflux.com
- 31. Conventional Scheme Waste heat recovery( with new convection section retubed in kind ) It would not have solved any of the problems linked to over firing of the heaters www.heatflux.com Description Units Design Stack temperature °F 404 BFW flow rate Lb/hr 94,000 SSH flow rate Lb/hr 92,120 SSH temperature °F 623 Steam pressure psig 472
- 32. Split Flow Scheme H-20/H-21/H-22 Limit radiant heat flux to 15,000 Btu/hr ft2 Shift the balance duty to convection section H-18/H-19/H-23 Limit heat flux to 8,000-9,000 Btu/hr ft2 Limit the firing to design rate Limit the volumetric heat release to 10000 Btu/ft3 Shift the balance duty to convection section www.heatflux.com
- 33. Valero Proposed Revamp – Split Flow Scheme www.heatflux.com
- 34. Split Flow for H-20/H-21 H-20- 3 Bare Rows H-21- 2 Finned Rows www.heatflux.com
- 35. H-18/H-19/ H-23 Revamping Options H-18/H-19/H-23 Heaters All Radiant Heaters Design Efficiency- Low -51-53% Operating Efficiency- 42-52% High Draft Very tight design www.heatflux.com
- 36. H-18/H-19/H-23 Revamping Options Do nothing High firing rates, firing limitation Existing burners may not handle Add convection sections on each heater Good option Expensive Add heat transfer surface in main convection Two rows Economical www.heatflux.com
- 37. Valero Proposed Revamp – Split Flow Scheme www.heatflux.com
- 38. H-18/H-19/H-23 Split Flow H-18- 8 tubes H-19-12 tubes H-23- 8 tubes Total- 2 rows of tubes www.heatflux.com
- 39. Split flow Convection Section Heat Recovery Sequence H-20 H-21 H-18 / H-19 / H-23 Steam Superheating Steam Generation BFW Preheating Total no. of rows – 20 Convection section dimensions unchanged www.heatflux.com
- 40. Proposed Split Flow Revamp Advantages Lower Pressure drop in all heaters Reduce Heat Flux – 15,000 Btu /hr ft2 Lower Firing Rate – 203 MMBtu /hr Lower Volumetric Heat Release More efficient system - 88% No civil works www.heatflux.com
- 41. Split flow – Control Scheme Balancing of heat transfer and pressure drop by: Variable resistance (butterfly control valve) Split stream outlet temperature control by adjusting convection section flow www.heatflux.com
- 42. Advantages of FIS Split flow scheme Lower pressure drop (process) Lower firing rate Lower fire box temperatures Lower radiant heat fluxes Lower tube metal temperatures Lesser turnaround time Lower installation cost www.heatflux.com
- 43. Thank you very much Questions and comments are welcome www.heatflux.com
Editor's Notes
- #2: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #3: Reliance Refinery, Jaam Nagar India February 24, 2007 What is this Novel Approach? Typically in a fired heater, the feed is preheated in the convection section and further heated in the radiant section.
- #4: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #5: Reliance Refinery, Jaam Nagar India February 24, 2007
- #6: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #7: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #8: Flint Hills - Corpus Christi, TX 12/01/11
- #9: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #10: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #11: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #12: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #13: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #14: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #15: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #16: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #17: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #18: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #19: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #20: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #21: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #22: Valero, Texas City Refinery,TX 12/01/11
- #23: Valero, Texas City Refinery,TX 12/01/11
- #24: Valero, Texas City Refinery,TX 12/01/11
- #25: Valero, Texas City Refinery,TX 12/01/11
- #26: Valero, Texas City Refinery,TX 12/01/11
- #27: Valero, Texas City Refinery,TX 12/01/11
- #28: Valero, Texas City Refinery,TX 12/01/11
- #29: Valero, Texas City Refinery,TX 12/01/11
- #30: Valero, Texas City Refinery,TX 12/01/11
- #31: Valero, Texas City Refinery,TX 12/01/11
- #32: Valero, Texas City Refinery,TX 12/01/11
- #33: Valero, Texas City Refinery,TX 12/01/11
- #34: Valero, Texas City Refinery,TX 12/01/11
- #35: Valero, Texas City Refinery,TX 12/01/11
- #36: Valero, Texas City Refinery,TX 12/01/11
- #37: Valero, Texas City Refinery,TX 12/01/11
- #38: Valero, Texas City Refinery,TX 12/01/11
- #39: Valero, Texas City Refinery,TX 12/01/11
- #40: Valero, Texas City Refinery,TX 12/01/11
- #41: Valero, Texas City Refinery,TX 12/01/11
- #42: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #43: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters
- #44: Premcor Refinining Energy Managers Conference February 9, 2005 Furnace Improvements, Low cost solutions for fired heaters