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

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

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

Conventional Crude Fractionation

 Many changes have been made but areas of improvement exist

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

Areas of Improvement  Wasted Heat  Condenser duty  Distillate product cooling  Bottoms product  High heat demand  Reboiler duty  Pre-heated feed

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)

Heat Integrated Distillation

Heat-Integrated Distillation Column 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 (Bio)chemical Process Technology. 2005, Unpublished.  Rectifying section pressurized to increase bubble point and allow heat transfer

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 Unpublished.

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 Unpublished.

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

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.

Implementation Obstacles  No consensus on column mechanical design and internals  Concentric columns  Plate fins 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. 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.

Usage in Crude Fractionation

 Adjustment of pump andcompressor Top Product Vapor Compressor Flash SR Valve Bottom Product Reboiler Condenser Heat Higher pressure gives higher temperature driving force.

Usage in Crude Fractionation Top Product Vapor Compressor Flash Q furnace SR Valve Bottom Product Condenser Heat Steam  Replacement of reboiler by steam Higher pressure gives higher temperature driving force.

Usage in Crude Fractionation  Increased size of rectifying section Top Product Vapor Compressor Flash Q furnace SR Valve Bottom Product Condenser Heat Steam Higher pressure gives higher temperature driving force.

Usage in Crude Fractionation  A single column Compressor Flash occurring within column

Conventional Crude Fractionation

Product Specifications  Naphtha D86 95%: C  Kerosene D86 95%: C  Diesel D86 95%: C  Gas Oil D86 95%: C  Overflash: 0.04  Allows flexibility in column for different crudes and operating conditions.

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

Conventional Design Results ResultsConventional Naphtha Flow Rate38353 bbl/day Kerosene Flow Rate21542 bbl/day Diesel Flow Rate11048 bbl/day Gas Oil Flow Rate25395 bbl/day Residue Flow Rate23699 bbl/day Kerosene Stripping Steam81656 lb/day Diesel Stripping Steam72696 lb/day Gas Oil Stripping Steam23230 lb/day Residue Stripping Steam lb/day (5-95) Kerosene-Naphtha Gap16.7 C (5-95) Diesel-Kerosene Gap0 C (5-95) Gas Oil-Diesel Gap-2.9 C Condenser Duty33.9 MW Pump-around 1 Duty22.3 MW Pump-around 2 Duty26 MW Pump-around 3 Duty25.6 MW Hot Utility62.6 MW Cold Utility47.5 MW Pinch Temperature280 C

Conventional Vapor Flow Profile  Opportunity for better separation in stripping section

Temperature Profiles Comparison HIDC Rectifying Section at 2 atms  Availability of heat transfer

Temperature Profiles  Availability of heat transfer HIDC Rectifying Section at 2 atms

Results of HIDC as applied to crude fractionation

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

HIDC Product D86 Points

HIDC Flowrates

 The increase in residue is less profitable.

HIDC Hot Utility

Economic Analysis Basis  Costs  Hot Utility $0.085/kWh (2002)  Cold Utility Cooling Water (C) $0.135/m 3 (2002)  Total Cost Differential (E conv – E new )*Cost heat + (C conv -C new )*Cost water +W Operating cost mainly due to energy for heating and steam for stripping E – energy used in process (MW), U – utility required for heating, H i s – enthalpy of low pressure steam, W – work of compressor

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

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

Alternative Treatment of Residue R S Q furnace Crude Feed Atm Residue Q vacuum furnace Vacuum Column Vacuum Residue Vacuum Gas Oils Atmospheric Gas Oil

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.

HIDC Modified Gross Profit

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

New Design D86 Points

New Design Flowrates

New Design Hot Utility

New Design Economic Analysis  Less profitable than conventional method

New Technologies

While investigating HIDC we discovered two new technologies Technical details cannot be disclosed Impact and economics will be shown

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

Technology 1: Product Flowrates  The increase in flowrate of gasoil makes the distillation more profitable.

Technology 1: Hot Utility

Technology 1: Gross Profit Flowrate Basis

Technology 1: Economic Analysis

Technology 1: Gross Profit Flowrate Basis Vacuum Column Basis  Vacuum Column basis makes the bad worse & the good better.

Technology 2: Bottoms Products  As D86 points get heavier, light ends in the residue are being recovered as more desirable products.

Technology 2: Bottoms Products  As D86 points get heavier, light ends in the residue are being recovered as more desirable products.

Technology 2: Product Flowrates  The decrease in flowrate of gasoil is less profitable.

Technology 2: Hot Utility  The decrease in total energy required makes the distillation more profitable.

Technology 2: Gross Profit Flowrate Basis

Technology 2: Economic Analysis

Technology 2: Gross Profit Flowrate Basis Vacuum Column Basis  Vacuum basis is even more profitable

Summary  Five different fractionation systems  Conventional Modeled after normal systems  Retrofitted Heat-Integrated Distillation Column (8:1) Less Residue, Diesel, and Naphtha, More Gas Oil  New Heat-Integrated Distillation Column (Extra Trays) Less energy required, less gas oil, more residue  New Technology 1 More energy required, more gas oil, less residue  New Technology 2 Less energy required, less gas oil, more residue

Conclusions  We investigated the use of HIDC in the context of crude fractionation  We determined that this technology does not have potential at current prices  In the process of analyzing the above, we discovered two new promising technologies

Questions?

HIDC Flowrates

New Design Flowrates

Economics  With turbine, net profit $ million.  Payback time years.