Abstract
Gasification of coal, municipal waste, or other organic materials is a potential hydrogen source that entails complex thermal decomposition and transport processes. This study provides a multiscale analysis of these processes for sub-bituminous (Usibelli, Healy, Alaska) and lignite (Center, North Dakota) coals and provides data useful for process design. The chemistry, mineralogy, and pore structures of pyrolyzed coal and their evolution with thermal decomposition are discussed. Samples pyrolyzed at 200–1000 °C were analyzed by small-angle neutron scattering; ultra-small, small-, and wide-angle X-ray scattering; and other complementary techniques. Scanning electron microscopy showed new pores in the high-temperature-pyrolyzed material. Upon heating, the coals became progressively denser, and the concentration of hydrogen decreased. Changes in pore volume fell into three temperature ranges: an initial, low-temperature range that, for the Usibelli coal, involved an increase in overall porosity; a mid-temperature range associated with pore volume loss; and a high-temperature range associated with significant porosity increase and char formation. This transformation was paralleled by changes in fractal dimension and correlation length. The higher the pyrolysis temperature the greater the small-pore-volume fraction and overall surface area became. Pyrolysis increased the lateral size of coal crystallites, decreased the amorphous fraction, and increased the aromatics fraction and overall coal rank. Comparisons of neutron and X-ray scattering data and subsequent water uptake studies showed that pre-dried coals can re-hydrate relatively rapidly upon exposure to air, which can significantly affect the porosity calculated from small-angle-scattering data. Fits to the cumulative porosity curves provide a method for modeling the physical and chemical transformation of hydrogen-containing feedstock during gasification.
| Original language | English |
|---|---|
| Article number | 107853 |
| Journal | Journal of Analytical and Applied Pyrolysis |
| Volume | 197 |
| DOIs | |
| State | Published - Aug 2026 |
Funding
This material is based upon work supported by the U.S. Department of Energy, Hydrocarbons and Geothermal Energy Office. The authors thank David Lyons, Diane Madden, and Jai-Woh Kim for their support and input as well as William Rogers and Mehrdad Shahnam of the National Energy Technology Laboratory for useful technical discussions on gasification. The authors thank Chilkoot Ward of the Usibelli Coal Mine and Brent Sheets of the University of Alaska, Fairbanks for providing the Usibelli sub-bituminous coal samples and Mike Heger of BNI, Inc. for providing the Center lignite samples. Data analysis and writing by LMA were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Neutron-scattering research at the High Flux Isotope Reactor, Oak Ridge National Laboratory, was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05–00OR22725 with the U.S. Department of Energy. This research used resources of the Advanced Photon Source; a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357. We acknowledge the support of the National Institute of Standards and Technology, Center for Neutron Research, US Department of Commerce in providing the research neutron facilities used in this work. Access to NBG30 SANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249 . Certain commercial equipment, instruments, materials, and software are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology or the Department of Energy nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. The authors have no pertinent commercial of other relationships that are known to them to create a conflict of interest. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-planThis material is based upon work supported by the U.S. Department of Energy, Hydrocarbons and Geothermal Energy Office. The authors thank David Lyons, Diane Madden, and Jai-Woh Kim for their support and input as well as William Rogers and Mehrdad Shahnam of the National Energy Technology Laboratory for useful technical discussions on gasification. The authors thank Chilkoot Ward of the Usibelli Coal Mine and Brent Sheets of the University of Alaska, Fairbanks for providing the Usibelli sub-bituminous coal samples and Mike Heger of BNI, Inc. for providing the Center lignite samples. Data analysis and writing by LMA were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Neutron-scattering research at the High Flux Isotope Reactor, Oak Ridge National Laboratory, was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05–00OR22725 with the U.S. Department of Energy. This research used resources of the Advanced Photon Source; a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357. We acknowledge the support of the National Institute of Standards and Technology, Center for Neutron Research, US Department of Commerce in providing the research neutron facilities used in this work. Access to NBG30 SANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. Certain commercial equipment, instruments, materials, and software are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology or the Department of Energy nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. The authors have no pertinent commercial of other relationships that are known to them to create a conflict of interest. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan
Keywords
- Coal
- Neutron
- Porosity
- Pyrolysis
- Small-angle scattering
- X-ray
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