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99學年度第一學期專題討論

Sorption of methane and CO2 for enhanced coalbed methanerecovery and carbon dioxide sequestrationPrusty, B. K., 2008. Sorption of methane and CO2 for enhanced coalbed methane recovery and carbon dioxide sequestration. Journal of Natural Gas Chemistry, 17, 29-38.

Adviser： Loung-Yie Tsai

Presenter： Ling-Szu Wang

Date： 2010/12/30

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OutlineIntroductionObjectivesMethods of StudyResults and Discussion

Conclusions

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Introduction

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溫室效應示意圖

co2

N2O

CH4 O3

H2O

CFCs

Greenhouse gases causing global warming with their increasing concentration in the atmosphere are H2O, CO2, CH4, N2O, O3, and CFCs. (Mavor, M.J. et al., 2002; Orr, F. M., 2004.)

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Diagram of CBM recovery. (http://serc.carleton.edu/coalbed.htm)

Clean Energy： Coalbed Methane (CBM)

CBM

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Injection of CO2 in coal seams may help in enhancing the recovery of coalbed methane. (Gunter, W. D. et al., 1997)

CO2

CH4

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Objectives

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To investigate whether recovery of methane could be enhanced by injecting CO2 after partial desorption of methane by pressure depletion.

To assess the ability of coal to sequester CO2.

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Methods of Study

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Figure 1. Schematic of the experimental set up.

FV： fixed volume cylinderSC： sample container PT： pressure transducer GC： Gas Chromatograph

CO2

CH4

1. adsorption experiment

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Figure 1. Schematic of the experimental set up.

FV： fixed volume cylinderSC： sample container PT： pressure transducer GC： Gas Chromatograph

2. (ad/de)sorption and injection experiment

CO2

CH4

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Peng-Robinson equation (Peng, D. Y., and Robinson, D. B., 1976)

Vads = Volume of gas adsorbedR = Universal gas constant for real gasT = TemperatureP1 = Pressure of FV before opening the valveP2 = Pressure of FV after opening the valveVR = Volume of FVVv = Void volume in SCZ= Compressibility factor of the adsorbate gas at the

corresponding P and T

21 2

1 2 2

1 VR Rads

PVPV PVV

RT Z Z Z

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Results and Discussion

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Table 1. Overview of the coal samples.

Adsorption capacity of coals

Figure 2. CO2 and CH4 adsorption isotherm for the coal samples.

Coal Sample

Ash content (%)

Moisture content (%)

Seam 1

11.3 10.0

Seam 2

7.8 8.7

Seam 3

3.9 10.0

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CO2 injection and release of methane sample 1：

Desorption pressure (MPa)

Injection

CO2 injectionpressure (MPa)

CH4 partialpressure (MPa)

Sorbed CH4(ml/g)

3.4 pre-injection

- - 5.0

1st 3.4 1.4 2.1

2nd 3.4 0.6 1.0

Figure 3. Results of (ad/de)sorption and injection experiment on Seam 1.

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CO2 injection and release of methane sample 2：

Desorption pressure (MPa)

Injection

CO2 injectionpressure (MPa)

CH4 partialpressure (MPa)

Sorbed CH4(ml/g)

3.4 pre-injection

- - 7.2

1st 3.4 1.5 4.6

2nd 3.4 0.6 3.5

3rd 3.4 0.3 3.4Figure 4. Results of (ad/de)sorption and injection experiment on Seam 2.

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CO2 injection and release of methane sample 3：

Desorption pressure (MPa)

Injection

CO2 injectionpressure (MPa)

CH4 partialpressure (MPa)

Sorbed CH4(ml/g)

3.7 pre-injection

- - 7.8

1st 3.7 1.6 6.5

2nd 3.7 0.7 4.5

3rd 3.7 0.4 0.5

Figure 5. Results of (ad/de)sorption and injection experiment on Seam 3.

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Figure 6 . Methane released as percentage of gas-in-place after CO2 injections.

Enhanced methane recovery behavior of coals is not uniform and varied for different coals.

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CO2 sequestration capacity

Figure 7. Volume of CO2 adsorbed with different CO2 injections.

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Conclusions

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It is possible to enhance the recovery of methane by injecting CO2.

Enhanced methane recovery behavior of coals is not uniform and varied for different coals.

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It is possible to sequester a large quantity of CO2 in all the coals tested.

More studies need to be undertaken to understand the enhanced methane recovery process and preferential sorption behavior of various coals.

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Thanks For Your Attention.