SHIFT CONVERSION UNIT Program IN A GASIFICATION PLANT · PDF fileSHIFT CONVERSION UNIT IN A...

UCI Advanced Power & Energy Program

1Gasification Technologies Council - 2006 Annual Meeting Washington DC

Gasification Technologies CouncilAnnual Meeting 2006

Washington, DC October 1- 4, 2006

Ashok Rao Akshay Verma

Advanced Power And Energy ProgramNational Fuel Cell Research Center

University Of California, Irvine

Douglas H. CortezHensley Energy Consulting LLC

412 North Coast Highway Suite B346Laguna Beach, CA 92651

OPTIMIZATION OF THE OPTIMIZATION OF THE SHIFT CONVERSION UNIT SHIFT CONVERSION UNIT

IN A GASIFICATION PLANT IN A GASIFICATION PLANT



Presentation OutlinePresentation Outline

• Shift Unit Study Background– Role of Shift Unit Optimization in Coke IGCC Plant with Co-

production of Refinery Hydrogen

• Design Approach– Shift Unit Design Factors & Trade-offs

• Design Basis for Case Study– Refinery Coke to IGCC Power– Co-Production of Hydrogen

• Process Description• Results & Conclusions



Shift Unit Study BackgroundShift Unit Study Background

• With added Emphasis given to H2 Coproduction & CO2Capture / Sequestration, Optimization of Shift Unit Critical– To Lower Capital & Operating Costs– To Increase Overall Plant Efficiency

• Many Gasification Process Produces Raw Syngas with High CO / H2 Ratio, Example:– Shell– E-Gas

• Shifting this Gas Requires Large Amount of Additional Steam to:– Limit Temperature Rise across Shift Catalyst Bed– Avoid Carbon Deposition on Catalyst

• Large Steam Additions Increase Shift Unit Equipment Sizes, Cost & Decreases Plant Efficiency



Design ApproachDesign Approach

• Two-stage Sweet Shift with Syngas Bypass– Bypass Fraction of Syngas Around 1st Shift Reactor– Combine with Effluent from 1st Reactor (Thermal Diluent)– Feed Combined Stream to 2nd Reactor

• Benefits: – Overall Steam Consumption Reduced

• Detriments: – CO Concentration in Shift Effluent Increased– Syngas to be Processed in Shift & Pressure Swing Absorption

(PSA) Units Increased– Tail Gas Generated by PSA Increased– Size of Tail Gas Compressor Increased

• Trade-off Analysis is Required



Case Study Design BasisCase Study Design Basis

Plant Application Coke to IGCC Power & Refinery H2

Feedstock Delayed Petroleum Coke

Ambient Conditions ISO

Plant Make-up Water Fresh Water

Plant Heat Rejection Mechanical Draft Cooling Towers

NOx Limit 15 ppmVd (15%O2 Basis)

H2 Export to Refinery 80 MMSCFD (99% Purity)

Gasification Technology High Temperature 2-Stage Slurry Fed Entrained Bed

Gas Turbine Technology “F” Technology



Main Features of PlantMain Features of Plant

• Elevated Pressure Air Separation Unit– Integration with GT

• Slurry Fed 2-Stage Entrained Bed Gasifier– High Temperature Raw Syngas Coolers

• Gas Treating– COS Hydrolysis– Amine (MDEA) Acid Gas Removal

• Hydrogen Production & Recovery– High Temperature Sweet Shift– PSA H2 Purification

• Combined Cycle Power Generation– General Electric 7FB Type GT (Syngas Fuel)– Triple Pressure Reheat Steam Cycle



Overall Plant ConfigurationOverall Plant Configuration



Plant SimulationsPlant Simulations

• Gasifier– Thermodynamic Model– Specified Carbon Conversion– Approach to Equilibrium to Account for Reaction Extent

• Gas Turbine– Model Calibrated using GE Published Data for 7FB on Nat

Gas– Model “Operated” on Syngas in Off-Design Mode– Reduced Firing Temperature

• Shift Reactors– Performance / Catalyst Volume Provided by Sud-Chemie

for 2 Cases– Kinetic Model used to Interpolate / Extrapolate Remaining

Cases• PSA

– Performance / Cost Estimates Provided by UOP for 2 Cases– Interpolate / Extrapolate Remaining Cases



Shift / PSA UnitsShift / PSA Units



Humid Syngas CharacteristicsHumid Syngas Characteristics(Stream 2)(Stream 2)

CO / H2 Ratio, mole / mole 1.91

Temperature, °F 550

H2O Content, mole % 16.72

H2S + COS Content, ppmV <110

Flow Rate, Moles/h 60,760

Pressure, psia 443



Advantages of HTS CatalystAdvantages of HTS Catalyst

• Fe based Catalyst with Cr & Cu Promoter• More Robust Catalyst than LTS• Better Tolerance to Sulfur

– Avoids Deep S Removal (ZnO Bed)– Some Catalysts Suppliers

• Sud-Chemie• Katalco• Haldor Topsoe



Shift Unit CharacteristicsShift Unit Characteristics

Basis: 80 MMSCFD H2 Export

Shift Reactor 1 Bypass, % 0 25 50 75

Feed Gas Flow Rate (Stream 4), moles/h 15,820 16,286 17,393 20,307

Steam Required, lb/h 428,810 332,730 235,410 137,400

HP Boiler Duty, MM Btu/h 80.04 64.16 46.24 22.79

IP Boiler Duty, MM Btu/h 64.73 73.04 81.89 91.52

LP Boiler Duty, MM Btu/h 212.69 121.45 36.77 32.95

Relative Reactor 1 Volume 1 0.78 0.56 0.33

Relative Reactor 2 Volume 1 0.92 0.86 0.71



Impact on PSAImpact on PSA

Basis: 80 MMSCFD H2 Export

Shift Reactor 1 Bypass, % 0 25 50 75

PSA Feed Gas Flow Rate (Stream 15), moles/h

19,690 20,000 20,720 22,590

CO Conc. in Feed Gas, mole % 2.1 3.5 6.7 14.2

H2 Conc. in Feed Gas, mole % 51.4 50.7 49.1 45.6

Tail Gas Compression, kW 17,188 17,706 18,922 22,091



Performance ComparisonPerformance ComparisonIncremental Over No Bypass CaseIncremental Over No Bypass Case

Basis: Constant Coke Feed Rate of 6,127 ST/D (as received basis)

& 80 MMSCFD H2 Export

Shift Reactor 1 Bypass, % 25 50 75Increase in Steam Turbine Power, kW 2,393 5,405 12,115

Increase in In-plant Power Consumption, kW 1,121 2,524 6,984

Increase in Net Plant Power, kW 1,272 2,882 5,131



Relative EconomicsRelative EconomicsIncremental Over No Bypass CaseIncremental Over No Bypass Case

Shift Reactor 1 Bypass, % 25 50 75

Increase in Installed Plant Cost, 1000$ 4,235 7,237 8,953

Increase in Net Plant Power, kW 1,272 2,882 5,131

(∆ Installed Cost)/(∆ Net Power), $/kW 3,330 2,511 1,745

Decrease in Operating Cost (Catalyst), 1000$/yr

90 174 280

Basis: Constant Coke Feed Rate of 6,127 ST/D (as received basis)

& 80 MMSCFD H2 Export



Basis for Plant EconomicsBasis for Plant Economics

• Plant Installed Costs based on – Icarus Cost Data & Licensor Quotations– Installed Costs Overnight $2006 Costs– Excludes Contractor Profit, Risk Fees & Contingency

• Simplified Economics based on Utility Cost of Service– WACC of 8% (Typical Investor Owned Utility)– Incremental Maintenance Costs of 1.5% of Capex– Incremental Property Taxes & Insurance at 1% of Capex– No Added Fuel Costs or H2 Revenues (Fixed by Design)

• Cost of Electricity (COE) Methodology– General Inflation of 2.5% / year, Excluding Property Taxes (no

Escalation)– Simplified DCF Model Used to Compute Nominal COE

Deflated to $2006



Cost of Incremental PowerCost of Incremental PowerTypical Utility COE, $2006Typical Utility COE, $2006

Shift Reactor 1 Bypass, % 25% 50% 75%

$/MWh $/MWh $/MWh

Weighted Ave Cost of Capital 42.2 31.9 22.1

Incremental Fuel Cost, Hydrogen Revenues 0 0 0

Savings in Annual Catalyst Cost (9.0) (7.7) (6.9)

Incremental Property Taxes, Insurance 4.2 3.2 2.2

Incremental Annual Fixed Maintenance 6.3 4.8 3.3

Cost of Incremental Electricity, $/MWh (2006) 43.8 32.2 20.7



Results & ConclusionsResults & Conclusions

• Economics Favor Increasing Shift Reactor 1 Bypass• Upper Limit Constrained by Minimum Steam Required to

– Avoid Carbon Deposition on Catalyst, Reduction of Catalyst to FeC– Limitations on Shift Reactor 2 Exit Temperature

• Feed Gas CO to H2 Ratio has Major Impact on Results • Optimum Shift Unit Design Dependent on Fuel Type, Gasification

Technology, other Technology Choices• Future Study: Sour Shift Optimization

– Applicable to Certain Gasifiers & CO2 Capture Plants designed for “Near Zero” Carbon Emission Plants

– Tradeoff between CO Slip & Percentage of CO2 Captured in AGR• Future Study: PSA Tail Gas used as Boiler Fuel

– Tail Gas Compression Penalty is Minimized– Trade-off of Steam Value & Environmental Issues



Sources of Information Sources of Information & Acknowledgements& Acknowledgements

• Process Design – Proprietary Simulation Software (A. Rao)– Adjusted for Unit Performance from Published Data

• Shift Catalyst – Quotes from Sud-Chemie• PSA – Quotes from UOP• Cost Estimates - Icarus Software & Published Reports,

adjusted for Escalation using Industry Indexes• Economic Analysis & Peer Review – Hensley Energy

Consulting• Special Thanks for Support from:

– University of California, Irvine – UOP– Sud-Chemie– Hensley Energy Consulting



Questions and Comments?Questions and Comments?

For more information, please contact:

Ashok Rao

Ashok RaoAdvanced Power & Energy ProgramUniversity of California, Irvine CA [email protected]

Douglas H. Cortez

Managing Director Hensley Energy Consulting LLC412 North Coast Highway Suite 346Laguna Beach, CA [email protected]

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