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Water Sorption on Coal: Effects of Oxygen Containing Function Groups and Pore Structure
Shimin Liu
Department of Energy and Mineral Engineering, G3 Center and Energy Institute, The Pennsylvania State University, University Park, PA 16802, USA
Corresponding Author
ORCiD: https://orcid.org/0000-0001-9612-0047
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Coal-water interactions has profound influences on gas extraction from coal and coal utilization. Experimental measurements on three coals using X-ray photoelectron spectroscopy (XPS), low-temperature nitrogen adsorption and dynamic water vapor sorption (DVS) were conducted. A mechanism-based isotherm model was proposed to estimate the water vapor uptake at various relative humidities, which was well validated with the DVS results. The validated isotherm model of sorption is further used to derive the isosteric heat of water vapor sorption. The pore specific surface area of coal is not the determining parameter that controls water vapor sorption at least during the primary adsorption stage. Oxygen containing degree dominates the primary adsorption, and togethering with the cumulative pore volume determine the secondary adsorption. Higher temperature has limited effects on primary adsorption process. The isosteric heat of water adsorption decreases as water vapor uptake increases, which was found to be close to the latent heat of bulk water condensation at higher relative humidity. The results confirmed that the primary adsorption is controlled by the stronger bonding energy while the interaction energy between water molecules during secondary adsorption stage is relatively weak. However, the thermodynamics of coal-water interactions are complicated since internal bonding interactions within the coal are disrupted at the same time as new bonding interactions take place with the water molecules. Coal has a shrinkage/swelling colloidal structure with moisture loss/gain and it exhibits collapse behavior with some collapses irreversible as a function of relative humidity, which plays a significant role in determining moisture retention.
Keywords
water vapor, isotherm, surface oxidation, pore collapse, isosteric heat of adsorption
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CURRENT STATUS: Under Revision
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Posted 17 Dec, 2020
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Editorial decision: Minor Revision
On 11 Jan, 2021
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Received 05 Jan, 2021
Review #1 received
Received 21 Dec, 2020
Reviewer #2 agreed
On 09 Dec, 2020
Reviewers invited
Invitations sent on 08 Dec, 2020
Reviewer #1 agreed
On 08 Dec, 2020
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On 02 Dec, 2020
Editor invited
On 02 Dec, 2020
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On 29 Nov, 2020
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This preprint is under consideration at International Journal of Coal Science & Technology. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research
Water Sorption on Coal: Effects of Oxygen Containing Function Groups and Pore Structure
Shimin Liu
Department of Energy and Mineral Engineering, G3 Center and Energy Institute, The Pennsylvania State University, University Park, PA 16802, USA
Corresponding Author
ORCiD: https://orcid.org/0000-0001-9612-0047
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Under Revision
Version 1
Posted 17 Dec, 2020
No community comments so far
Editorial decision: Minor Revision
On 11 Jan, 2021
Review #2 received
Received 05 Jan, 2021
Review #1 received
Received 21 Dec, 2020
Reviewer #2 agreed
On 09 Dec, 2020
Reviewers invited
Invitations sent on 08 Dec, 2020
Reviewer #1 agreed
On 08 Dec, 2020
Editor assigned
On 02 Dec, 2020
Submission checks complete
On 02 Dec, 2020
Editor invited
On 02 Dec, 2020
First submitted
On 29 Nov, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Energy Engineering
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Coal-water interactions has profound influences on gas extraction from coal and coal utilization. Experimental measurements on three coals using X-ray photoelectron spectroscopy (XPS), low-temperature nitrogen adsorption and dynamic water vapor sorption (DVS) were conducted. A mechanism-based isotherm model was proposed to estimate the water vapor uptake at various relative humidities, which was well validated with the DVS results. The validated isotherm model of sorption is further used to derive the isosteric heat of water vapor sorption. The pore specific surface area of coal is not the determining parameter that controls water vapor sorption at least during the primary adsorption stage. Oxygen containing degree dominates the primary adsorption, and togethering with the cumulative pore volume determine the secondary adsorption. Higher temperature has limited effects on primary adsorption process. The isosteric heat of water adsorption decreases as water vapor uptake increases, which was found to be close to the latent heat of bulk water condensation at higher relative humidity. The results confirmed that the primary adsorption is controlled by the stronger bonding energy while the interaction energy between water molecules during secondary adsorption stage is relatively weak. However, the thermodynamics of coal-water interactions are complicated since internal bonding interactions within the coal are disrupted at the same time as new bonding interactions take place with the water molecules. Coal has a shrinkage/swelling colloidal structure with moisture loss/gain and it exhibits collapse behavior with some collapses irreversible as a function of relative humidity, which plays a significant role in determining moisture retention.
Figure 1
Figure 3
Figure 4
Figure 4
Figure 5
Figure 7
Figure 7
Figure 8
Figure 10
Figure 11
Figure 11
Figure 12
Due to technical limitations, full-text HTML conversion of this manuscript could not be completed. However, the manuscript can be downloaded and accessed as a PDF.