Assessment of Hybrid Membrane – Low Temperature Process for Post-Combustion Capture

X. P. Zhang, T. GundersenNorwegian University of Science and Technology, Trondheim, Norway

R. Anantharaman, D. BerstadSINTEF Energy Research, Trondheim, Norway

Presentation Outline

►Background►Gas membrane separation process evaluation►Hybrid Membrane – Low Temperature process►Results and discussion►Conclusion

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Challenges of CCS► Energy: Energy penalty (Electricity, steam……)► Economy: Cost increase (Investment, operational cost…)► Environment: Additional impact (MEA degradation…)

► Industries: Understand the status of energy/mass efficiency, economic performance and environmental impacts;

► Researchers: Provide information to develop new or retrofit old CCS technologies, new material synthesis, process design……

► Decision-makers: Provide a roadmap for the commercialization of CCS

Integration & assessment of CCS ChainMotivation

CO2 capture technologies

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J. D. Figueroa, T. Fout, S. Plasynski, H. McIlvried and R. D. Srivastava, Int J Greenh Gas Control, 2008, 2, 9-20.

2010 2015 2020

Post-combustion capture

MEA-based systemEconamine FG+KS-1Cansolv process

……Chilled ammonia

1.Ready for Demonstration

MembraneCarbonate-based sorbentsIonic liquidsEnzyme-based systems……

2. Emerging technologies

DOE & NETL

MEA-based capture system

CO2 capture ratio: ~90%, CO2 purity > 95%, Lean solvent: MEA 28.3%(wt)Absorption temp.: 35-50oC., Stripper temp.: 100-120oC

Energy demands:Q1 (Sensible) + Q2 (Reaction) + Q3 (Stripping) + W1 (Blower) + W2 (Pumps)Advanced solvent methods aim to reduce all or parts of these energies

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Two-stage gas membrane capture process

Energy demands:Q1 (Sensible) + Q2 (Reaction) + Q3 (Stripping) + W1 (Compressors) + W2 (Pumps)

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Chemical solvent based and Membrane systemsLimitations of chemical solvent based system► Degradation: results in high material costs and high disposal costs;► Additional environmental pollution caused, emissions of NH3, MEA; ► High energy consumption, extraction of LP steam from turbine; ► Auxiliary retrofitting measures or costs in power plants

Hussain, A.; Hagg, M. B. Journal of Membrane Science 2010, 359, (1-2), 140-148. Zhao, L.; Riensche, E.; Blum, L.; Stolten, D. Journal of Membrane Science 2010, 359, (1-2), 160-172.

Some viewpoints on membranes

► Less environmental impact, and small footprint; ► Lower energy requirement (no steam load, but significant shaftwork requirement); ► Ease of scale up, both for grassroot power plants and retrofitting of existing ones► Suitable when high purity gas streams are not vital

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Tech. DataMembrane model

with PRO/II®

Techno-Economic assessment models

Cost Models 22

( +0.2 )CC(US $ / ton CO )=fluegas CO

VOM TPIm x CR

VOM: Annual variable operating & maintenance costTPI: Total plant investmentCR: Capture ratio

Membrane Models

Flow structure

InputOperational parameters:PressureTemperatureFlow rateGas Composition

Membrane parameters:Membrane areaSelectivityPermeance

OutputCapture ratioCO2 purityGas volumesGas compositions

Parameter optimization

Fick’s lawHagen-Poiselle eq.

Parametric study - membrane process

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Capture ratio 90%, CO2 purity 90% (mol); CR 90% and XCO2 90%(mol)1-stage with Turboexpander; Excluding CO2 compression; PPermeate 0.05 bar, CO2/N2Selectivity: 150 – 250, CO2 permeance value: 1 - 5 Nm3/m2•bar•hr.

Increasing selectivity will decrease energy consumption and increase area, thus permeance & selectivity should be optimized due to an inverse relationship

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0.4

0.8

1.2

1.6

2.0

2.4

2.8

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

150 170 190 210 230 250 270

E1E2E3E4E5A1A2A3A4A5

CO2/N2 Selectivity

Mem

bran

earea (10

6m

2 )

Specific energy

consum

ption (M

Je/ t C

O2)

Specific equivalent enery consumed with MEA

A B

Per-1

Per-5

Inverse relationship of Area～Power

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N2

CO2

W1 W2

W3

Total power= W1 + W2 – W3

P1 P2

P1 P0

Trade-off between energy consumption and area

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Two-stage gas membrane capture process

Influence of parameters on capture cost

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Energy

Area

Cost

2-stage capture, CO2 purity: 95% (mol); capture ratio: 90%

CO2/N2 selectivity: 70~90

Influence of capture ratio

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Optimal capture ratio range: 65～70% (50 $ /m2 membrane) 75～80% (100 $ /m2 membrane

Motivation for Hybrid Membrane –Low Temperature Process► Polymeric membranes function ideally as a bulk separation medium► With CO2/N2 selectivities of 50-100 single stage membrane process is not

feasible to attain required CO2 purity (95%) and degree of separation (90%)► Driving force is partial pressure difference across the membrane and hence

significant compression work required for separation Increases exponentially with purity and degree of separation

► Low temperature processes have been the standard for CO2 purification in oxy-combustion cases Efficient process to attain high purity CO2 when feed stream has CO2 concentration

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Process Block Diagram15

Membrane – LT interface

USC Coal Fired Power Plant16

European Benchmarking Task Force – Reference case ► Power plant: Net electricity 754 MWe (without capture)► Flue gas flowrate: 596.4 Nm3/s (781.8 kg/s)► Flue gas composition: CO2 13.73%, N2 72.86%, O2 3.65%, H2O 9.73% (mol)

Membrane section PFD17

Low Temperature section PFD18

Energy requirement - Membrane19

CO2/N2 selectivity: 70, CO2 permeance: 5 Nm3/m2·bar·hr

Energy Requirement – LT process20

Hybrid processOverall performance

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Hybrid processOverall performance

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Comparing performance of processes23

Comparing performance of processes24

CO2/N2 selectivity: 80CO2 permeance: 5 Nm3/m2.bar.hr

Membrane properties

8% improvement over 2-satge Membrane process

Comparing performance of processes25

CO2/N2 selectivity: 200CO2 permeance: 1 Nm3/m2.bar.hr

Membrane properties

Energy penalty nearly the same as MEA case

Conclusions

► Membrane method has weak advantages over MEA process for CO2 capture due to relatively lower capture cost. However, membrane processes have larger energy consumption

► Membrane – Low Temperature hybrid process have lower energy penalty than 2-stage membrane process for high CO2 capture ratios. 8% lower energy penalty at 90% capture

► 2-stage membrane process perform better than the hybrid process at capture ratios below ~80%.

► MEA capture process performs better than the hybrid and membrane processes at 90% capture ratio.

► New membranes optimized for these processes are expected reduce cost and energy consumption.

► Further work: Develop cost models for the low temperature process to optimize overall process design.

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Acknowledgements

This publication has been produced with support from the BIGCCS Centre, performed under the Norwegian research program Centres for Environment-friendly Energy Research (FME). The authors acknowledge the following partners for their contributions: Aker Solutions, ConocoPhillips, Gassco, Shell, Statoil, TOTAL, GDF SUEZ and the Research Council of Norway (193816/S60).