gtl presentation april18

Natural Gas to Liquid Fuels Using Ion-Transport Membrane Technology

Process Design & Profitability Analysis of

Doug Muth, Eve Rodriguez, Christopher Sales

Faculty Advisor: Dr. Stuart Churchill

Senior Design Project 2005

What is Gas-to-Liquids?

Conversion of natural gas to liquid fuels (e.g., diesel).

Gas-to-Liquids (GTL)

SYNGAS PRODUCTION

HYDROCRACKING

FISCHER-TROPSCH SYNTHESIS

Diesel

Natural Gas

Motivations for GTL• Transportation

– Natural gas reserves are often too far from gas pipelines.– Transporting liquid or electricity is more feasible.

• Environmental– US EPA regulations require reduction of sulfur content. – GTL naturally produces extra low-sulfur diesel.

• High Fuel Quality– High cetane numbers for GTL diesel.– Low aromatic and olefin content.

Design Basis

• GTL plant to be located in Ohio.

• Minimum DCFRR of 12% required.

• Evaluate ion-transport membrane technology for syngas production.

GTL Conversion Strategies• Direct Conversion of CH4 to Methanol

– Too difficult to control.– High activation energy required.– No suitable catalyst.

• Indirect Conversion Via Synthesis Gas– Syngas converted to long-chain hydrocarbons by the

Fischer-Tropsch (FT) reaction.– Syngas production methods:

1. Steam reforming of methane.2. Dry reforming of methane.3. Partial oxidation of methane.

Production of Synthesis Gas• Steam reforming of methane.

CH4 + H2O → CO + 3H2 (endothermic)

• Dry reforming of methane.CH4 + CO2 → 2CO + 2H2 (endothermic)

• Partial oxidation of methane.*

CH4 + ½ O2 → CO + 2H2 (exothermic)

*Optimal H2/CO ratio (2:1) for FT synthesis.

Partial Oxidation of Methane

Nearly pure O2 required for partial oxidation.

O2 Purification Methods

• Cryogenic distillation of air.– Hundreds of equilibrium stages required.– High energy costs of refrigeration.– Substantial capital cost (insulation, compressors, etc).

• New Alternative: Oxygen ion-transport membrane.– Potentially cheaper than cryogenic air separation plant.– Membrane not yet commercialized, cost not known.

Ion-Transport Membrane

• Membrane provides O2 for syngas production.

CH 4 + H O 2 CO + 3H 2

O 2-

2e -

Natural Gas Steam

Syngas Oxygen -Depleted

Air

Air Membrane

Reforming Catalyst

Reducing atmosphere Oxidizing

atmosphere

CH 4 + 1/2 O 2 CO + 2H 2

Oxygen Reduction Catalyst

Courtesy of Air Products, Inc.

Ion-Transport Membrane• Membrane material: non-porous mixed conducting metallic oxides.

– Perovskites– LaxA1-xCoFe1-yO3-z (La = Lanthanides, 0<x<1, A = Sr, Ba, or Ca, 0<y<1, z = number which renders the compound charge neutral)

• Conducts O2- through membrane vacancies.• O2 partial pressure gradient creates electrochemical driving force.

Courtesy of Air Products, Inc.

GTL Process OverviewGTL process divided into four main parts:

1. Convert CH4 to CO/H2 with membrane reactor.CH4 + 1/2O2 → CO + 2H2

2. Convert CO/H2 to synthetic hydrocarbons (Fischer-Tropsch).

nCO + 2nH2 → (-CH2-)n + H2O

3. Hydrocrack synthetic hydrocarbons to fuels (mainly diesel).

4. Separate hydrocracked product into standard oil fractions.

GTL Process OverviewNatural Gas

ITM Reactor(Syngas

Production)

Syngas

Fischer-TropschSynthesis

Hydrocracking

Synthetic wax

Hydrocracked wax

FractionationTower

HP Steam

Turbine andGenerator

H2

Heavy Gas Oil

Fuel Gas

NaphthaKerosene

Diesel

Excess Electricity

1.

2.

3.

4.

Air

Key Equipment Details

ITM Reactor Fischer-Tropsch Reactor

Hydrocracker Distillation

ITM Reactor Vessel

Function:• Convert methane into synthesis gas.

Design Details:• T = 1650oF, P = 300 psig• Horizontal “shell/tube” reactor.• 45,000 ft2 membrane area required.• 2900 membrane tubes (OD = 2 in, L = 30 ft).• Inconel Alloy for shell and tubes.• Shell packed with 39,300 lbs nickel/alumina catalyst.

CH4 + ½O2 → CO + 2H2

CH4 + H2O → CO + 3H2

Praxair ITM Reactor Model (2002)

Steam ReformingCatalyst Bed

ITM Membrane

Gottzmann et al. (US Patent)

Praxair ITM Reactor Model (2003)

ITM MembraneSteam ReformingCatalyst Bed

Syngas Methane & Steam

AirO2-depleted Air

Halvorson et al. (US Patent)

Entire ITM Section

Fischer-Tropsch Reactor

Function:• Produce long-chain hydrocarbons from synthesis gas.

Design Details:• T = 400oF, P = 400 psig• Slurry volume of 3400 ft3.• 276,000 lbs cobalt/ruthenium catalyst required.• Synthesis gas bubbled through bottom.• 13 ft diameter ensures proper gas superficial velocity.• Dynamic settler separates molten wax from catalyst

particles.• Stainless steel construction.

nCO + 2nH2 → (-CH2-)n + H2O

Fischer-Tropsch ProductsAnderson-Schulz-Flory Distribution

Diesel

M{n} = (1 - ) n-1

W{n} = n (1 - )2 n-1

For Co/Ru, = 0.94Mole Fraction M{n}

Weight Fraction W{n}

Entire Fischer-Tropsch Section

Hydrocracker Reactor

Function:• Cracks and isomerizes long-chains to shorter chains.

Design Details:• Molten wax trickles down from top. • Hydrogen-rich stream fed through bottom.• T = 725oF, P = 675 psig• Height = 27 ft, ID = 9 ft• 30,000 lbs catalyst bed (0.6% Pt on alumina).• H2/Wax = 0.105 kgH2 / kgwax

• WHSV = 2 kgwax / hour - kgcat.

• Stainless steel construction.

Modeling the HydrocrackerFrom Hydrocracking Kinetic Model

(developed by Pellegrini et al).

• Lumped hydrocarbon groups

• Hydrocracking reaction pathways

• Cracking and isomerization occur.

Modeling the HydrocrackerFrom Hydrocracking Kinetic Model

(developed by Pellegrini et al).

• MW drops along reactor length.

• Longer chains crack more quickly.

• Isomerization improves cold properties.

Entire Hydrocracker Section

Fractionation TowerFunction:• Separates HC effluent into standard oil fractions.

Design Details:• P = 10 psig, Tcondenser = 100oF, Tbottoms = 725oF• Feed preheated to 725oF and fed on bottom stage.• Steam injected on bottom stage (0.5 lb / bbl bottoms)• 16 Koch Flexitrays.• 6 ft tray diameter, 2 ft spacing 40 ft height• Diesel drawn off at tray 12.• Kerosene drawn off at tray 8.• Naphtha & Fuel Gas in overhead.• Heavy Gas Oil recycled to hydrocracker• Sidedraws eliminate need for multiple towers.

Entire Fractionation Tower Section

Auxiliary Units

Process Summary

Raw Materials ProductsNatural Gas 1.95 MM SCFH Diesel 2,700 bbl/day

Kerosene 1,800 bbl/dayNaphtha 200 bbl/dayHGO 90 bbl/dayElectricity 10,500 kW

US Proven Natural Gas Reserves (2003)• For a 15 year plant life, required puddle

size for plant is 0.263 trillion standard cubic feet (TSCF).

• 1.126 trillion SCF available in Ohio.• U.S. Total: 189 TSCF

Profitability Analysis• Membrane price unknown.• Determine maximum membrane cost that still allows profitability.• Criterion: minimum IRR of 12%

Unit ID Description Cost Method Cp, Purchase Cost Bare-Module Factor Total Bare-Module CostC1 Air Compressor Seider et al. $2,228,888.71 2.15 $4,792,110.73C2 Syngas Compressor Seider et al. $1,410,323.09 2.15 $3,032,194.64C3 H2 Rich Compressor Seider et al. $239,837.22 2.15 $515,650.02P1 FT Wax Pump Seider et al. $7,863.98 3.3 $25,951.13P2 FT Wax Pump 2 Seider et al. $7,863.98 3.3 $25,951.13HX1 Air Heat Exchanger Aspen B-JAC $65,000.00 3.17 $206,050.00HX4 Kettle HP Steam Generator Aspen B-JAC $98,500.00 3.17 $312,245.00HX6 Syngas Cooler Aspen B-JAC $21,960.00 3.17 $69,613.20RX1 ITM Syngas Reactor Vessel (without membrane) Seider et al. $417,187.88 4.16 $1,735,501.58RX2 Fischer-Tropsch Reactor Vessel Seider et al. $198,836.93 4.16 $827,161.63RX3 Hydrocracker Reactor Vessel Seider et al. $298,149.10 4.16 $1,240,300.26TB1 Steam Turbine Seider et al. $513,962.10 2.15 $1,105,018.52V1 Water Decanter Seider et al. $85,054.51 3.05 $259,416.26V2 Water Condenser Seider et al. $20,000.00 3.17 $63,400.00T1 Fractionation Tower Vessel Seider et al. $94,922.89 4.16 $394,879.22

Trays Seider et al. $38,745.41 1 $38,745.41Fired Preheater Seider et al. $229,100.83 2.19 $501,730.82

HX5 Overhead Condenser Seider et al. $45,479.00 3.17 $144,168.43Five Tower Pumps Seider et al. $36,193.26 3.3 $119,437.77

V3 Reflux Accumulator Seider et al. $10,000.00 4.16 $41,600.00G1 Electric Generator - $513,962.10 2.15 $1,105,018.52Membrane Ceramic Ion Transport Membrane Not commericalized Financial Variable N/A N/A

Nickel-Alumina Market Price $196,500.00 1 $196,500.00Cobalt Market Price $3,309,919.29 1 $3,309,919.29Platinum Market Price $2,518,778.30 1 $2,518,778.30

TOTAL $22.6 million

Variable Cost Summary

Natural gas price trumps other variable costs of operation.

Assumed Product Prices

• Diesel Fuel $1.82/gal*• Kerosene $1.24/gal• Naphtha $1.00/gal• HGO 70¢/gal• Electricity 6¢/kW-hr

*Assumed 15% higher than typical diesel due to low-sulfur and high cetane number.

Source: US DOE

Membrane Cost Tolerability

• Membrane costs that give IRR = 12%• NG cost cannot exceed $6/MSCF.

PROBLEM:Analysis assume no price correlationbetween liquid fuels and natural gas!

Energy Price Correlation

• Hydrocarbon prices historically show correlation.

Energy Price Correlation

• Regression Analysis– R = 0.85– Diesel changes 16¢/gal for every $1/MSCF change in NG.

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

0 1 2 3 4 5 6 7 8

Natural Gas Price ($/MSCF)

Die

sel P

rice

($/g

al)

ActualPredicted

New Membrane Cost Tolerability

• Shallower slope less dependence on NG price.• Maximum tolerable NG cost increases to $12.5/MSCF.

Without price correlation

With price correlation

Sample Cash Flow• Assume NG costs $5/MSCF• Assume $5 million membrane investment.• NPV @ 12% is $59 million.

April, 2005

YearPercentage of Design Capacity

Sales Capital Costs Working Capital Variable Costs Fixed Costs Depreciation Allowance

Depletion Allowance

Taxable Income Income Tax Costs

Net Earnings Annual Cash Flow

Cumulative Net Present Value

at 12.0%

2005 0.0% Design -$20,039,000 -$10,691,200 -$30,730,200 -$30,730,2002006 0.0% Construction -$20,039,000 -$10,691,200 -$30,730,200 -$58,167,9002007 45.0% $34,291,000 -$14,385,500 -$8,552,900 -$7,156,800 $0 $4,195,800 -$1,552,400 $2,643,400 $9,800,200 -$50,355,2002008 67.5% $51,436,400 -$21,578,300 -$8,552,900 -$11,450,900 $0 $9,854,300 -$3,646,100 $6,208,200 $17,659,100 -$37,785,8002009 90.0% $68,581,900 -$28,771,000 -$8,552,900 -$6,870,500 $0 $24,387,500 -$9,023,400 $15,364,100 $22,234,600 -$23,655,3002010 90.0% $68,581,900 -$28,771,000 -$8,552,900 -$4,122,300 $0 $27,135,700 -$10,040,200 $17,095,500 $21,217,800 -$11,615,8002011 90.0% $68,581,900 -$28,771,000 -$8,552,900 -$4,122,300 $0 $27,135,700 -$10,040,200 $17,095,500 $21,217,800 -$866,2002012 90.0% $68,581,900 -$28,771,000 -$8,552,900 -$2,061,200 $0 $29,196,800 -$10,802,800 $18,394,000 $20,455,200 $8,386,7002013 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $16,340,2002014 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $23,441,5002015 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $29,782,0002016 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $35,443,1002017 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $40,497,7002018 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $45,010,7002019 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $49,040,2002020 90.0% $68,581,900 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $19,692,500 $52,637,9002021 90.0% $68,581,900 $21,382,400 -$28,771,000 -$8,552,900 $0 $31,258,000 -$11,565,500 $19,692,500 $41,074,900 $59,338,100

Cash Flow SummaryGTL Membrane

Why not just burn it?• Alternative: Burn the natural gas across a gas turbine to create

electricity.• Using data from 2001 senior design project Combined-Cycle Power

Generation by Beaver, Matamoros, and Prokopec.– 290 MW possibility @ 57% total efficiency.– Total BM cost of plant: $150 million ($22.6 million + membrane)– Annual sales: $145 million ($68 million)– Total annual costs: $120 million ($38 million)– NPV @ 12% is -$118 million ($59 million)– IRR is only 2.7%

Not a competitive alternative!

Conclusions• Profitability is weakly dependent upon natural gas

cost.– ITM/GTL profitable at any NG price below $12.5/MSCF.– Current NG prices well-below this limit ($6/MSCF).

• Membrane price unlikely to be a prohibitive factor.– NG price of $5/MSCF $26 million max membrane cost

allowed ($572/ft2).– BM Cost of plant without membrane is approx. $22.6

million.

• Power plant unlikely to be competitive alternative.

Recommendations

• Confirm ITM O2 flux rate– Flux rate of 10 cm3/cm2-min assumed for design.– Current research report values from 0.1 to 20 cm3/cm2-min.– Required membrane area strongly dependent on O2 flux

rate.• Determine ITM stability and durability.• Investigate low-sulfur, high cetane diesel price.

Recommend ITM/GTL plant constructiononce membrane is commercialized.

Acknowledgements

• Professor Leonard Fabiano• Dr. Stuart Churchill

• Industrial Consultants– Gary Sawyer– Peter Schmeidler– Adam Brostow– William Retallick– David Kolesar– Henry Sandler– John Wismer

gtl presentation april18

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