Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

A new approach to improving heater efficiency

2,546 views

Published on

Published in: Technology, Business

A new approach to improving heater efficiency

  1. 1. A new approach to improving heater efficiency <ul><ul><li>Ashutosh Garg, Furnace Improvements </li></ul></ul>www.heatflux.com
  2. 2. Typical Fired Heater Fluid------  Convection section  Radiant section www.heatflux.com
  3. 3. Conventional Approach to Efficiency Improvement www.heatflux.com Additional Heat Transfer Surface in Convection Section
  4. 4. Split flow Fired Heater www.heatflux.com
  5. 5. Typical Reformer Heater <ul><li>Process heated in radiant section </li></ul><ul><li>Parallel passes, high volume, low pressure drop </li></ul><ul><li>Convection-Waste Heat Recovery ( HC reboiler or steam generation service) </li></ul>www.heatflux.com
  6. 6. Split Flow Reformer Heater <ul><li>Process fluid split into two streams </li></ul><ul><li>Main flow is heated through radiant section </li></ul><ul><li>Split flow is heated in the convection section. </li></ul><ul><li>Fluid mixed together at the radiant outlet </li></ul>www.heatflux.com
  7. 7. Case Studies <ul><li>Citgo Corpus Christi No. 4 Platformer Heater </li></ul><ul><li>Valero Texas City No. 2 Platformer Heater and NHT heaters (Reboilers) </li></ul>www.heatflux.com
  8. 8. Citgo, Corpus Christi No. 4 Platformer Heater <ul><li>Objective: </li></ul><ul><li>Improve Efficiency </li></ul><ul><ul><li>Stack temperature was 1100 F </li></ul></ul><ul><li>No steam generation </li></ul><ul><li>No air preheater </li></ul>www.heatflux.com
  9. 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. 10. Flow Scheme - Before Revamp #4 Platformer Heater www.heatflux.com
  11. 11. Existing #4 Platformer Heater www.heatflux.com
  12. 12. Proposed Conventional Design High Pressure Drop www.heatflux.com
  13. 13. Conventional Design with Series Flow www.heatflux.com
  14. 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. 15. Disadvantages <ul><li>Higher pressure drops </li></ul><ul><li>Large Size piping </li></ul><ul><li>Large Convection Sections </li></ul><ul><li>Higher costs </li></ul>www.heatflux.com
  16. 16. FIS Split Flow* Scheme * Split flow - US Patent www.heatflux.com
  17. 17. FIS Split flow * design - Proposed * Patented. www.heatflux.com
  18. 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. 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. 20. #4 Platformer Heater Before and After Revamp www.heatflux.com
  21. 21. Case Study-2
  22. 22. Platformer Heaters - Existing <ul><li>Common Convection section with H-18/H-19 and H-23 </li></ul><ul><li>Process heating-all Radiant </li></ul><ul><li>Steam Generation in Convection </li></ul><ul><li>Common Stack </li></ul><ul><li>Natural Draft </li></ul>www.heatflux.com
  23. 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. 24. Plan View of heater www.heatflux.com
  25. 25. Convection Section <ul><li>Steam Generator Bank </li></ul><ul><li>Steam Superheater Bank </li></ul><ul><li>BFW Preheater Bank </li></ul><ul><li>Steam Generation: 73,669 lbs/hr@464 psig </li></ul><ul><li>14 tubes per row </li></ul><ul><li>Eighteen rows </li></ul><ul><li>Two future rows </li></ul>www.heatflux.com
  26. 26. H-18- Hydrotreater Charge Heater <ul><li>Duty-11.97 MMBtu/hr </li></ul><ul><li>All Radiant </li></ul><ul><li>Single pass </li></ul><ul><li>5 burners </li></ul><ul><li>24 tubes </li></ul><ul><li>P9 metallurgy </li></ul><ul><li>8“ NPS tubes </li></ul><ul><li>16” spacing </li></ul><ul><li>Efficiency -55% </li></ul>www.heatflux.com
  27. 27. H-19 Hydrotreater Stripper Reboiler <ul><li>Duty-18.45 MMBtu/hr </li></ul><ul><li>All Radiant </li></ul><ul><li>Four passes </li></ul><ul><li>5 burners </li></ul><ul><li>56 tubes </li></ul><ul><li>CS </li></ul><ul><li>4” NPS tubes </li></ul><ul><li>8” spacing </li></ul><ul><li>Efficiency -54% </li></ul>www.heatflux.com
  28. 28. H-23 Depropanizer Reboiler <ul><li>Duty- 15.15 MMBtu/hr </li></ul><ul><li>All Radiant </li></ul><ul><li>Two pass </li></ul><ul><li>6 burners </li></ul><ul><li>52 tubes </li></ul><ul><li>CS </li></ul><ul><li>4” NPS tubes </li></ul><ul><li>8” spacing </li></ul><ul><li>Duty- 56% </li></ul>www.heatflux.com
  29. 29. Field Survey <ul><li>High draft in all the radiant cells </li></ul><ul><li>Burners flame spread out </li></ul><ul><li>Very high fuel gas pressures </li></ul><ul><li>Bowed tubes in H-21/H-22 </li></ul><ul><li>Stack dampers are fully open </li></ul><ul><li>High excess Oxygen in all the cells </li></ul><ul><li>Burner registers practically closed </li></ul>www.heatflux.com
  30. 30. Operating Data Simulation Results <ul><ul><li>Convection section was in bad state </li></ul></ul><ul><ul><li>Fins are burnt out / fouled </li></ul></ul><ul><ul><li>Steam superheater temperature is 40 F lower than design </li></ul></ul><ul><ul><li>Thermal Efficiency is 78-81% compared to 88% design. </li></ul></ul><ul><ul><li>Stack temperature is higher by almost 275 F. </li></ul></ul><ul><ul><li>Stack temperature ~ 675 F </li></ul></ul>www.heatflux.com
  31. 31. Conventional Scheme <ul><li>Waste heat recovery( with new convection section retubed in kind ) </li></ul><ul><li>It would not have solved any of the problems linked to over firing of the heaters </li></ul>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. 32. Split Flow Scheme <ul><li>H-20/H-21/H-22 </li></ul><ul><ul><li>Limit radiant heat flux to 15,000 Btu/hr ft2 </li></ul></ul><ul><ul><li>Shift the balance duty to convection section </li></ul></ul><ul><li>H-18/H-19/H-23 </li></ul><ul><ul><li>Limit heat flux to 8,000-9,000 Btu/hr ft2 </li></ul></ul><ul><ul><li>Limit the firing to design rate </li></ul></ul><ul><ul><li>Limit the volumetric heat release to 10000 Btu/ft3 </li></ul></ul><ul><ul><li>Shift the balance duty to convection section </li></ul></ul>www.heatflux.com
  33. 33. Valero Proposed Revamp – Split Flow Scheme www.heatflux.com
  34. 34. Split Flow for H-20/H-21 <ul><li>H-20- 3 Bare Rows </li></ul><ul><li>H-21- 2 Finned Rows </li></ul>www.heatflux.com
  35. 35. H-18/H-19/ H-23 Revamping Options <ul><li>H-18/H-19/H-23 Heaters </li></ul><ul><ul><li>All Radiant Heaters </li></ul></ul><ul><ul><li>Design Efficiency- Low -51-53% </li></ul></ul><ul><ul><li>Operating Efficiency- 42-52% </li></ul></ul><ul><ul><li>High Draft </li></ul></ul><ul><ul><li>Very tight design </li></ul></ul>www.heatflux.com
  36. 36. H-18/H-19/H-23 Revamping Options <ul><li>Do nothing </li></ul><ul><ul><li>High firing rates, firing limitation </li></ul></ul><ul><ul><li>Existing burners may not handle </li></ul></ul><ul><li>Add convection sections on each heater </li></ul><ul><ul><li>Good option </li></ul></ul><ul><ul><li>Expensive </li></ul></ul><ul><li>Add heat transfer surface in main convection </li></ul><ul><ul><li>Two rows </li></ul></ul><ul><ul><li>Economical </li></ul></ul>www.heatflux.com
  37. 37. Valero Proposed Revamp – Split Flow Scheme www.heatflux.com
  38. 38. H-18/H-19/H-23 Split Flow <ul><li>H-18- 8 tubes </li></ul><ul><li>H-19-12 tubes </li></ul><ul><li>H-23- 8 tubes </li></ul><ul><li>Total- 2 rows of tubes </li></ul>www.heatflux.com
  39. 39. Split flow Convection Section <ul><li>Heat Recovery Sequence </li></ul><ul><ul><li>H-20 </li></ul></ul><ul><ul><li>H-21 </li></ul></ul><ul><ul><li>H-18 / H-19 / H-23 </li></ul></ul><ul><ul><li>Steam Superheating </li></ul></ul><ul><ul><li>Steam Generation </li></ul></ul><ul><ul><li>BFW Preheating </li></ul></ul><ul><li>Total no. of rows – 20 </li></ul><ul><li>Convection section dimensions unchanged </li></ul>www.heatflux.com
  40. 40. Proposed Split Flow Revamp <ul><ul><li>Advantages </li></ul></ul><ul><ul><li>Lower Pressure drop in all heaters </li></ul></ul><ul><ul><li>Reduce Heat Flux – 15,000 Btu /hr ft2 </li></ul></ul><ul><ul><li>Lower Firing Rate – 203 MMBtu /hr </li></ul></ul><ul><ul><li>Lower Volumetric Heat Release </li></ul></ul><ul><ul><li>More efficient system - 88% </li></ul></ul><ul><ul><li>No civil works </li></ul></ul>www.heatflux.com
  41. 41. Split flow – Control Scheme <ul><li>Balancing of heat transfer and pressure drop by: </li></ul><ul><ul><li>Variable resistance (butterfly control valve) </li></ul></ul><ul><li>Split stream outlet temperature control by adjusting convection section flow </li></ul>www.heatflux.com
  42. 42. Advantages of FIS Split flow scheme <ul><li>Lower pressure drop (process) </li></ul><ul><li>Lower firing rate </li></ul><ul><li>Lower fire box temperatures </li></ul><ul><li>Lower radiant heat fluxes </li></ul><ul><li>Lower tube metal temperatures </li></ul><ul><li>Lesser turnaround time </li></ul><ul><li>Lower installation cost </li></ul>www.heatflux.com
  43. 43. Thank you very much <ul><li>Questions and comments are welcome </li></ul>www.heatflux.com

×