USE OF HEAT INTEGRATED DISTILLATION TECHNOLOGY IN CRUDE FRACTIONATION

1. USE OF HEAT INTEGRATED DISTILLATION TECHNOLOGY IN CRUDE FRACTIONATION The University of Oklahoma Department of Chemical, Biological, and Materials Engineering April 29, 2008 Su Zhu, Stephanie N. English, Miguel J. Bagajewicz

2. Overview • Conventional Crude Fractionation • Overview • Areas of opportunity • Heat-Integrated Distillation Columns • Overview • Application to Crude Units • Specifications used • Results • New Technology

3. Crude Distillation • Capacity ~ 100,000 bbl/day • Separation for further processing. • Consumes 2% of crude processed.

4. Conventional Crude Fractionation

5. Conventional Crude Fractionation • Many changes have been made but areas of improvement exist

6. Conventional Crude Fractionation We treat the system as if we can build an energy integration heat exchanger network that achieves minimum utility corresponding to minimum temperature differences

7. Areas of Improvement • Wasted Heat • Condenser duty • Distillate product cooling • Bottoms product • High heat demand • Reboiler duty • Pre-heated feed

8. Previous Improvements Attempted • Operational Changes • Adjusting reflux ratio • Minimizing air to furnace • Lowering steam use • Architecture/Process Changes • Heat recovery equipment • Plant-wide energy planning • New column designs (VRC, HIDC)

9. Heat Integrated Distillation

10. Heat-Integrated Distillation Column • Rectifying section pressurized to increase bubble point and allow heat transfer Heat Heat Hugill, J.A.; van Dorst, E.M. Design of a Heat-Integrated Distillation Column Based on a Plate-fin Heat Exchanger. (Bio)chemical Process Technology. 2005, Unpublished.

11. Advantages • Energy savings of 25 – 50% • Increasing compression ratio reduces energy required. Iwaskabe, K.; Nakaiwa, M.; Huang, K.; Nakanishi, T.; Ohmori, T.; Endo, A.; Yamamoto, T. Recent Advances in the Internally Heat-Integrated Distillation Columns (HIDiC). Unpublished.

12. Advantages • Reduction in size as compression ratio increases. Iwaskabe, K.; Nakaiwa, M.; Huang, K.; Nakanishi, T.; Ohmori, T.; Endo, A.; Yamamoto, T. Recent Advances in the Internally Heat-Integrated Distillation Columns (HIDiC). Unpublished.

13. Implementation Obstacles • Lack of energy incentives • Energy in abundance • Too expensive • Common conventional distillation • Relatively simple design • Easy to control

14. Implementation Obstacles • Vapor loads are insufficient for heat/mass transfer in the top and bottom of the column. Hugill, J.A.; van Dorst, E.M. Design of a Heat-Integrated Distillation Column Based on a Plate-fin Heat Exchanger. (Bio)chemical Process Technology. 2005, Unpublished.

15. Implementation Obstacles • No consensus on column mechanical design and internals • Concentric columns • Plate fins Olujic, Z.; Fakhri, F.; de Rijke, A.; de Graauw, J.; Jansens, P. Internal Heat Interation-The Key to an Energy-Conserving Distillation Column. J. Chem. Technol. Biotechnol. 2003, 78, 241. Hugill, J.A.; van Dorst, E.M. Design of a Heat-Integrated Distillation Column Based on a Plate-fin Heat Exchanger. (Bio)chemical Process Technology. 2005, Unpublished.

16. Usage in Crude Fractionation

17. Usage in Crude Fractionation • Adjustment of pump andcompressor Vapor Compressor Condenser Heat Heat S R Top Product Higher pressure gives higher temperature driving force. Reboiler Bottom Product Flash Valve

18. Usage in Crude Fractionation • Replacement of reboiler by steam Vapor Compressor Condenser Heat Heat S R Top Product Higher pressure gives higher temperature driving force. Steam Bottom Product Flash Qfurnace Valve

19. Usage in Crude Fractionation • Increased size of rectifying section Vapor Compressor Condenser Heat Heat S R Top Product Higher pressure gives higher temperature driving force. Steam Bottom Product Flash Qfurnace Valve

20. Usage in Crude Fractionation • A single column Compressor Flash occurring within column

21. Conventional Crude Fractionation

22. Product Specifications • Naphtha D86 95%: 182 0C • Kerosene D86 95%: 271 0C • Diesel D86 95%: 327 0C • Gas Oil D86 95%: 377-410 0C • Overflash: 0.04 • Allows flexibility in column for different crudes and operating conditions.

23. Product Gaps • Due to variable composition, products are specified by D86 points and gaps.

24. Conventional Design Results

25. Conventional Vapor Flow Profile • Opportunity for better separation in stripping section

26. Temperature Profiles Comparison • Availability of heat transfer HIDC Rectifying Section at 2 atms

27. Temperature Profiles • Availability of heat transfer HIDC Rectifying Section at 2 atms

28. Results of HIDC as applied to crude fractionation

29. HIDC Applied to Crude Fractionation • Compression ratio of 2 • Heat transfer from tray 28 to 33 Compressor Flash occurring within column

30. HIDC Product D86 Points

31. HIDC Product D86 Points

32. HIDC Flowrates

33. HIDC Flowrates • The increase in residue is less profitable.

34. HIDC Hot Utility

35. Economic Analysis Basis • Costs • Hot Utility • $0.085/kWh (2002) • Cold Utility • Cooling Water (C) • $0.135/m3 (2002) • Total Cost Differential • (Econv– Enew)*Costheat + (Cconv -Cnew)*Costwater+W Operating cost mainly due to energy for heating and steam for stripping E – energy used in process (MW), U – utility required for heating, His – enthalpy of low pressure steam, W – work of compressor

36. Economic Analysis Basis • Costs • Profit • Naphtha-$110/bbl • Kerosene-$95/bbl • Diesel-$109.9/bbl • GasOil-$75.9/bbl • Residue-$67.9/bbl • Crude Feed-$98/bbl • Total Profit Differential

37. HIDC Gross Profit • Integrating heat, gross loss >-$2.7 million/year • Less profitable than conventional method.

38. Alternative Treatment of Residue Vacuum Column R Atmospheric Gas Oil Crude Feed Vacuum Gas Oils S Qfurnace Atm Residue Vacuum Residue Qvacuum furnace

39. Modified Economic Analysis Basis • Costs • Profit • Naphtha - $110/bbl • Kerosene - $95/bbl • Diesel - $109.9/bbl • GasOil: No price differential (except in duty required) • Residue: Not price differential • Crude Feed-$98/bbl • Total Profit Differential Accounted in duty costs Comparison based on energy changes from heating residue, instead of changes in flowrate of residue and gasoil.

40. HIDC Modified Gross Profit

41. New Design HIDC • 50 trays instead of 34 • Compression ratio of 2 • Heat transfer from tray 28 to 49 S Compressor Flash occurring within column Bottom Product

42. New Design D86 Points

43. New Design D86 Points

44. New Design Flowrates

45. New Design Flowrates

46. New Design Hot Utility

47. New Design Economic Analysis • Less profitable than conventional method

48. New Technologies

49. New Technologies • While investigating HIDC we discovered • two new technologies • Technical details cannot be disclosed • Impact and economics will be shown

50. Technology 1: Bottoms Composition • As D86 points get heavier, light ends in the residue are being recovered as more desirable products.