high pressure distributed ethanol reforming · • study steam reforming of ethanol at high...

Argonne National Laboratory

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High Pressure Distributed Ethanol Reforming2005 DOE Hydrogen, Fuel Cells & Infrastructure Technologies Program ReviewArlington, VA, May 23-26, 2005

S.H.D. Lee, S. Ahmed, D. Applegate, R. Ahluwalia

The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Project ID# PDP7

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Pioneering Science andTechnology EEREHydrogen, Fuel Cells & Infrastructure

Technologies Program

Overview

Timeline• Project start: October, 2004• Project end: September, 2007

Barriers addressed• Efficiency• Cost

Partners• Pacific Northwest National

Laboratory

Budget• Total project funding: $225K• DOE share: 100%• FY05 funding: $225K

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Objectives• Study steam reforming of ethanol at high pressure

- Evaluate high pressure reforming options- Study reforming equilibria and kinetics at elevated pressures- Evaluate membrane reactors

Relevance• Ethanol is a bio-derived renewable liquid fuel• Ethanol has a high volumetric energy density• Ethanol (liquid) is easy to transport

Decision Factors• Liquid fuels can be steam reformed at high pressure,

avoiding/reducing cost of post-reformer compression• Higher pressures assist membrane purification/separation • Pressurized systems require high capital cost

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Approach• Study thermodynamic equilibria

- Effects of temperature, pressure, and steam-to-C ratio• Evaluate system options with respect to efficiency and cost

- Compare high pressure reforming, compressing reformate, compressing high purity hydrogen

- Evaluate purification options with high pressure reformate• Establish reforming kinetics through experiments and models

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Hydrogen compression represents a significant power loss

18.519.8

21.3

23.5

31.5

27.5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10Initial Pressure of Hydrogen, atm

Com

pres

sion

Los

s / L

HV

(%)

5-Stage Intercooled Compressor Compressor Efficiency: 70%Mechanical Efficiency: 97%

Electric Motor Efficiency: 90%FinalPressure: 6000 psi

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At 70 atm (1050 psi), CO2 can be condensed out at -130°C

0

10

20

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-140 -120 -100 -80 -60 -40 -20 0Temperature, o C

% C

O2 C

onde

nsed

0

1

2

3

4

5

6

7

8

9

10

Hea

t Loa

d (%

LH

V)

70 atm

20 atm

70 atm

20 atm

The energy needed to cool to -130°C represents 5% of the fuel’s (ethanol) lower heating value.

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Reforming at high pressure favors more methane, less hydrogen yields at thermodynamic equilibrium

• Tendency to form carbonaceous deposits (coke) increases at higher pressures

• Coking tendency can be reduced with excess steam and/or higher temperature

0

1

2

3

4

5

6

0 1000 2000 3000 4000 5000Pressure, psia

Prod

uct Y

ield

mol

/(mol

-EtO

H)

H2

CO2

CH4

CO

S/C = 6, T = 700°C

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000Pressure, psia

CO

x Sel

ectiv

ity% COx

S/C = 6, T = 700°C

COx Selectivity, % =Mols of CO+CO2 Produced

G-Atoms of C in Feed•100

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Higher temperature and excess steam favor equilibrium hydrogen yields

0

1

2

3

4

5

6

600 700 800 900 1000Temperature, °C

Prod

uct Y

ield

, mol

/(mol

-EtO

H)

H2

CO2

CO CH4

S/C = 6, P = 2000 psia

0

1

1

2

2

3

3

1 2 3 4 5 6S/C Ratio

Prod

uct Y

ield

, mol

/(mol

-EtO

H)

H2

CO2

CO

CH4

T = 700°C, P = 2000 psia

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Simulated process efficiencies approach 70% at a steam-to-carbon ratio of 5• C2H5OH + xH2O(l) CO2, CO, H2, H2O(g), CH4, CnHm, …• Chemcad simulated process based on

- steam-reformer at equilibrium- hydrogen separation with membrane

- 90% hydrogen recovery- combustion of raffinate to generate heat - heat exchange to reformer feeds- exhaust at 200°C

• Efficiency decreases with increasing S/C

50

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5 6 7 8 9 10Steam-to-C Ratio

Effic

ienc

y%

of L

HV

Ideal Reaction

Simulated Process

equilibrium

EquilibriumReactor

MembraneSeparator Burner

HeatExchanger

AirHydrogen

Ethanol+Water

Exhaust

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Experiments will help define suitable operating conditions

• Effects of temperature, pressure, space velocity• Kinetic parameters, reaction pathways

P

Vaporizer

T

T

T

T

Gas ChromatographEthanol-Water

Mixture

To VentBack-pressure

Regulator

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Ethanol tends to decompose to carbon oxides, methane, and hydrogen in the preheating zone above the catalyst

Pressure, psig 15

Temperature, °C 525

H2O/C in Feed 6

C2H5OH Conversion, % 9.7

H2 (mol/mol EtOH) 0.206

CO (mol/mol EtOH) 0.015

CO2 (mol/mol EtOH) 0.054

CH4 (mol/mol EtOH) 0.0097

10% of the ethanol decomposed at 1 atm and 525°C

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Preliminary experiments are confirming anticipated trends

Hydrogen concentrations in reformate gas increases with temperature and decreases with pressure.

Pressure, psig 15 1000 1000

Temperature, °C 530 530 700

H2O/C in Feed 6 6 6

H2 (%-dry) 71.2 45.2 53.1

CO (%-dry) 6.3 8.5 9.4

CO2 (%-dry) 18.4 16.6 17.7

CH4 (%-dry) 4.1 29.7 19.8

Gas composition analysis methods and equipment for condensible components are being readied

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Hydrogen Safety

• The most significant hazard of these experiments is the combination of high temperature and high pressure reactor processing combustible gases

• The hazard has been addressed by- Appropriate design (size and materials of construction) of

experimental apparatus- Locating apparatus within a vacuum-frame hood

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Interactions and collaborations

• Catalysts developed by Sud Chemie- PNNL offered alternative formulation

• Membrane developers expected to provide samples for testing- Synkera

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Accomplishments

• Thermodynamic equilibrium analysis has been done• Simple process models are being evaluated

- System models will explore efficient and cost-effective pathways• An experimental apparatus has been designed and fabricated

to evaluate reaction data- Apparatus has been safety approved- Experiments have been initiated to establish kinetic parameters

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Future Work

• System modeling will identify suitable processes- Compare separation options (operation/process, and location),

such as for example,- high pressure reforming followed by hydrogen separation vs.- compressing hydrogen purified after low pressure reforming

- Assess CO2 sequestration options• High temperature membranes will be evaluated• Membrane reactor will be designed and tested

Publications/Presentations• Abstract submitted to 2005 Fuel Cell Seminar

high pressure distributed ethanol reforming · • study steam reforming of ethanol at high...

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