skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Density Distributions and CO2 Sorption in a Confined Coal Sample for Carbon Sequestration

Abstract

A confined core of a Pittsburgh #8 coal obtained from a mine near Waynesburg, Pennsylvania, has been investigated using computerized tomography. The 3-D density distribution of the coal was calculated for the stressed and confined core with, and without CO2 sorption. We used a dual energy technique to quantify volumetric variations in bulk density and effective atomic number. CO2 sorption of coal was then investigated at predetermined injection pressures. The density changes in the coal matrix were calculated and correlated with the CO2 adsorbed for a multitude of regions of interest (ROI) chosen in slices perpendicular to the bedding plane. The results show that even in small core samples, coal heterogeneity is high. Large variation of density was observed in small regions of interest compared to the average density of slices. Also, the coal density distribution was changed significantly due to the CO2 uptake. This technique seems very useful in calculating density distribution for stressed and confined coal samples and the change in volumetric density distribution due to CO2 adsorption. Furthermore the kinetics of heterogeneous adsorption and swelling in coal can be determined.

Authors:
; ;
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
913364
Report Number(s):
DOE/NETL-IR-2007-119
TRN: US200802%%790
DOE Contract Number:
None cited
Resource Type:
Conference
Resource Relation:
Conference: 2007 AAPG Annual Convention and Exhibition, Long Beach, CA, Apr. 1-4, 2007
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; ADSORPTION; ATOMIC NUMBER; BULK DENSITY; CARBON SEQUESTRATION; COAL; COMPUTERIZED TOMOGRAPHY; DISTRIBUTION; KINETICS; SORPTION; SWELLING

Citation Formats

Jikich, S.A., McLendon, T.R., and Smith, D.H.. Density Distributions and CO2 Sorption in a Confined Coal Sample for Carbon Sequestration. United States: N. p., 2007. Web.
Jikich, S.A., McLendon, T.R., & Smith, D.H.. Density Distributions and CO2 Sorption in a Confined Coal Sample for Carbon Sequestration. United States.
Jikich, S.A., McLendon, T.R., and Smith, D.H.. Sun . "Density Distributions and CO2 Sorption in a Confined Coal Sample for Carbon Sequestration". United States. doi:.
@article{osti_913364,
title = {Density Distributions and CO2 Sorption in a Confined Coal Sample for Carbon Sequestration},
author = {Jikich, S.A. and McLendon, T.R. and Smith, D.H.},
abstractNote = {A confined core of a Pittsburgh #8 coal obtained from a mine near Waynesburg, Pennsylvania, has been investigated using computerized tomography. The 3-D density distribution of the coal was calculated for the stressed and confined core with, and without CO2 sorption. We used a dual energy technique to quantify volumetric variations in bulk density and effective atomic number. CO2 sorption of coal was then investigated at predetermined injection pressures. The density changes in the coal matrix were calculated and correlated with the CO2 adsorbed for a multitude of regions of interest (ROI) chosen in slices perpendicular to the bedding plane. The results show that even in small core samples, coal heterogeneity is high. Large variation of density was observed in small regions of interest compared to the average density of slices. Also, the coal density distribution was changed significantly due to the CO2 uptake. This technique seems very useful in calculating density distribution for stressed and confined coal samples and the change in volumetric density distribution due to CO2 adsorption. Furthermore the kinetics of heterogeneous adsorption and swelling in coal can be determined.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Measurements of sorption isotherms and transport properties of CO2 in coal cores are important for designing enhanced coalbed methane/CO2 sequestration field projects. Sorption isotherms measured in the lab can provide the upper limit on the amount of CO2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may significantly reduce the sorption capacities and/or transport rates. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from themore » important bituminous coal Pittsburgh #8 was kept under a constant, three-dimensional external stress; the sample was scanned by X-ray computer tomography (CT) before, then while it sorbed, CO2. Increases in sample density due to sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the computerized tomography showed that gas sorption advanced at different rates in different regions of the core, and that diffusion and sorption progressed slowly. The amounts of CO2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO2 source. Also, the calculated isotherms showed that less CO2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure due to CO2 sorption.« less
  • No abstract prepared.
  • Measurements of sorption isotherms and transport properties of carbon dioxide (CO 2) in coal cores are important for designing enhanced coalbed-methane/CO 2-sequestration field projects. Sorption isotherms measured in the laboratory can provide the upper limit on the amount of CO 2 that might be sorbed in these projects. Because sequestration sites will most likely be in unmineable coals, many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may reduce the sorption capacities and/or transport rates significantly. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. Amore » core from the important bituminous coal Pittsburgh #8 was kept under a constant, 3D effective stress; the sample was scanned by X-ray computer tomography (CT) before, then while, it sorbed CO2. Increases in sample density because of sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the CT showed that gas sorption advanced at different rates in different regions of the core. and that diffusion and sorption progressed slowly. The amounts of CO 2 sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh #8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO 2 source. Also, the calculated isotherms showed that less CO 2 was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure because of CO 2 sorption.« less
  • Measurements of sorption isotherms and transport properties of carbon dioxide (CO{sub 2}) in coal cores are important for designing enhanced coalbed-methane/CO{sub 2}-sequestration field projects. Many of the coals will be deep and under considerable lithostatic and hydrostatic pressures. These lithostatic pressures may reduce the sorption capacities and/or transport rates significantly. Consequently, we have studied apparent sorption and diffusion in a coal core under confining pressure. A core from the important bituminous coal Pittsburgh no. 8 was kept under a constant, 3D effective stress; the sample was scanned by X-ray computer tomography (CT) before, then while, it sorbed CO{sub 2}. Increasesmore » in sample density because of sorption were calculated from the CT images. Moreover, density distributions for small volume elements inside the core were calculated and analyzed. Qualitatively, the CT showed that gas sorption advanced at different rates in different regions of the core and that diffusion and sorption progressed slowly. The amounts of CO{sub 2} sorbed were plotted vs. position (at fixed times) and vs. time (for various locations in the sample). The resulting sorption isotherms were compared to isotherms obtained from powdered coal from the same Pittsburgh no. 8 extended sample. The results showed that for this single coal at specified times, the apparent sorption isotherms were dependent on position of the volume element in the core and the distance from the CO{sub 2} source. Also, the calculated isotherms showed that less CO{sub 2} was sorbed than by a powdered (and unconfined) sample of the coal. Changes in density distributions during the experiment were also observed. After desorption, the density distribution of calculated volume elements differed from the initial distribution, suggesting hysteresis and a possible rearrangement of coal structure because of CO{sub 2} sorption.« less
  • The CO2 storage capacity in coal seams is typically estimated from isotherm measurements obtained from manometric techniques. In the calculation of the isotherm, two major parameters must be estimated. First, the compressibility factor must be calculated from an equation of state to account for the non-ideality of CO2 at elevated pressures. Second, the volume change associated with the volume occupied by the sorbed CO2 must be estimated. These two parameters can dramatically affect the shape of the CO2-coal isotherm. Of the few papers that published CO2–coal isotherms at high pressures, a variety of curve shapes have been reported. This lackmore » of agreement reduces the confidence in the accuracy of CO2 storage capacities estimated from volumetric isotherm measurements. In this study, the direct interaction between CO2 and two Argonne premium coals [Pocahontas #3 (low volatile bituminous) and Beulah Zap (lignite)] was probed using Attenuated Total Reflectance – Fourier Transform Infrared (ATR-FTIR) spectroscopy at 328 K and pressures up to 8.0 MPa. Sorbed CO2 on Argonne coals was detected at 2335 cm-1 for Buelah Zap coal and 2332 cm-1 for Pocahontas #3 coal. The energy of adsorption (18.8 - 20.5 kJ/mol), estimated using the Langmuir equation, was consistent with physisorption. The spectral data indicated that only one type of site was available for sorption. No evidence could be found for specific interactions between CO2 and oxygen functional groups in the coals. The CO2-coal sorption isotherm was derived without estimating the CO2 compressibility and adsorbed layer density, both of which are needed in manometric techniques. The ATR-FTIR isotherms (units of net absorbance) and manometric isotherms (units mmol/g) compare well below the critical temperature providing some confidence in the values selected for the gas phase density and adsorbed layer density that were used to calculate absolute adsorption from the manometric data. In summary, we find that sorption of CO2 is energetically similar for the two coal types, is due only to London forces and quadrupole interactions, and occurs preferentially on a hydrocarbon site.« less