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Pre-flash Crude Fractionation

Pre-flash Crude Fractionation. Jonathan Peters Miguel Bagajewicz. Outline. Conventional Distillation Pre-flash Fractionation Previous Work Mission Statement Optimization Results: Light Crude Results: Heavy Crude. Conventional Distillation. Inject steam in the bottom

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Pre-flash Crude Fractionation

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  1. Pre-flash Crude Fractionation Jonathan Peters Miguel Bagajewicz

  2. Outline • Conventional Distillation • Pre-flash Fractionation • Previous Work • Mission Statement • Optimization • Results: Light Crude • Results: Heavy Crude

  3. Conventional Distillation • Inject steam in the bottom • Feed is desalted and heated • 5 products

  4. D86 Points • ASTM standard - specifies product purity • Defined as a percentage of the product that boils at a specific temperature • Naphtha – 95% D86 182oC

  5. Light Crude - D86 Points

  6. Heavy Crude – D86 Point

  7. Gaps Minimum gap refers to the lowest temperature difference required to obtain the desired separation Gaps greater than the minimum are acceptable Boiling Point Temp.

  8. Light Crude - Gaps

  9. Light Crude - Gaps

  10. Heavy Crude - Gaps

  11. Side Column • 4 trays • No reboiler or condenser • Inject steam to control separation • Draw from column • Return to tray above draw return draw steam product

  12. Conventional Distillation Add side columns

  13. Conventional Distillation Add pumparounds to reduce heat utility

  14. Conventional Optimization Simulation PFD for conv. optimization

  15. Conventional Optimization Heat Demand-Supply Diagram Heat supply and demand are represented by areas. Supply can only cover demand on the left. Uncovered demand is satisfied by utilities (red area). Shift heat from condenser to PA1 to reduce Utility

  16. Conventional Optimization Heat Demand-Supply Diagram Shift heat from PA1 to PA2

  17. Conventional Optimization Heat Demand-Supply Diagram Shift heat from PA2 to PA3

  18. Conventional Optimization Heat Demand-Supply Diagram Some heat demand still remains

  19. Crude Unit Flow Diagram Heat Exchanger Network Crude Unit PFD with HEN

  20. Conventional Distillation Pinch Calculator Replace HEN with a “black box”

  21. Pre-flash Fractionation Pinch Calculator Add a preflash drum

  22. Previous Work Tray 1 Tray 15 34 Trays Total Heated to 163oC Send vapor to Tray 15

  23. Previous Work Pre-flash reduces vapor-liquid holdup

  24. Previous Work

  25. Previous Work Residue/feed ratio decreases with an increasing K value

  26. Previous Work • Concluded that pre-flash was only more energy efficient if gas oil yield was reduced • Steam cannot replace all carrier effect of light components

  27. Mission Statement • Previous work studied pre-flash fractionation with the addition of one flash drum • This work studies the effect of pre-flash fractionation with the addition of multiple flash drums in both light and heavy crude systems • Systematic optimization of pre-flash fractionation

  28. Pre-flash Optimization Set pre-flash temperature

  29. Pre-flash Optimization Vapors are sent to column

  30. Pre-flash Optimization Set pumparound duty

  31. Pre-flash Optimization Red - simulation did not converge, readjust

  32. Pre-flash Optimization Blue – simulation converged

  33. Results • Light Crude • Heavy Crude

  34. New Design • In the process of investigating this, a new design was proposed • Technical details of this new design cannot be made public at this time • We will only disclose the impact of the new design in terms of new flow rates of products and the economics

  35. Light Crude - Flow Rates For the light crude, the new design increases gas oil yield from pre-flash design, but not from conventional

  36. Light Crude – Min. Heat Utility New design reduces min. heat utility

  37. Light Crude – Steam Usage New design steam usage is about the same as conv.

  38. Heavy Crude – Flow Rates New design increases gas oil yield over the conventional case

  39. Heavy Crude – Min. Heat Utility New design reduces min. heat utility

  40. Heavy Crude – Steam Usage New design steam usage is about the same as conv.

  41. Economics Light Crude Heavy Crude New design increases profit from conv. for heavy crude

  42. Conclusion • Multiple pre-flashing does not reduce the minimum heat utility • Gas Oil flow rate is reduced and Residue is increased • The new design shows noticeable energy improvement and gas oil recovery from conventional distillation for heavy crudes • Further studies are warranted

  43. References 1. Bagajewicz M. and S. Ji. Rigorous Targeting Procedure for the Design of Crude Fractionation Units with Pre-Flashing or Pre-Fractionation. Industrial and Engineering Chemistry Research, 41, 12, pp. 3003-3011 (2002). 2. Bagajewicz M. and S. Ji. Rigorous Procedure for the Design of Conventional Atmospheric Crude Fractionation Units Part I: Targeting. Industrial and Engineering Chemistry Research. Vol. 40, No 2, pp. 617-626 (2001).

  44. Acknowledgements Stephanie English Jesse Sandlin Ernest West Chris Wilson Su Zhu Dan Dobesh

  45. Questions?

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