An Improved Three-Dimensional Microscope Image Analysis Method for Studying Solvent Swelling of Single Coal Particles

Gao, Hong; He, Jicheng; Cai, Jiuju; Ishigaki, Masahiro; Nomura, Masakatsu

doi:10.1021/ef8006454

Cited by 6 publications

(8 citation statements)

References 25 publications

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“…Solvent kinetics are not easily followed with the standard swelling approach but can be adequately followed using either dilatometry, 30,39 coal mass gain (with solvent vapor) as a swelling proxy, 26,40 single particle time-lapse videography, 9 or microscopy observations of particles swelling. 28,29,41 The kinetic evaluations are complicated by the dual nature of the process: dissolution and swelling 25 as well as by metastable states that are often observed in coal particle or coal piece swelling experiments. 7,9,28,42 Unfortunately, little work in this area has utilized Illinois coal.…”

Section: Coal As a Strained System And Its Preferential Alignmentmentioning

confidence: 99%

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

2015

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There has been copious research exploring the interactions between coal and various solvents either for coal structural investigations using coal swelling or industrial consideration exploring extraction yields. Here the literature is reviewed for Illinois no. 6 coal. This is the most well studied coal in existence and so offers an opportunity to reveal a wealth of information with a wide variety of solvents and extractions. This coal swells extensively (raw) in a good solvent such as pyridine (Q-factors of 2.2) and lesser degrees in benzene (Q-factor of 1.1). However if first extracted the extent of swelling can be greater. The swelling process is typically slow, sometimes taking days with anisotropic swelling being evident on the first exposure but absent from subsequent exposures. Overshoot phenomena, similar to polymer swelling, is also observed for some particles. These behaviors are related to the complex interactions of solvent diffusion and coal "relaxation" that is related to the nature of the solvent and its interactions with coal. Extraction yields are similarly varied with values ~30 wt.% (daf basis) with pyridine although greater values are obtained with two-stage, higher temperature, and exhaustive extractions. With CS 2 /NMP/H 2 O a yield as high as 70% wt.% (daf basis) have been reported at 600 K. Using light cycle oil has yields between 20 and 70 wt.% depending on consitions at 633 K. The swelling evidence supports a cross-linked structure and solvent extraction supports a considerable amount of extractable material. These statements are not necessarily in conflict.

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Section: Coal As a Strained System And Its Preferential Alignmentmentioning

confidence: 99%

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

2015

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“…The kinetic parameters obtained by coal swelling studies would facilitate better design and optimization of coal‐slurry preheater in direct coal liquefaction process. A semi‐empirical equation for solvent sorption process in glassy polymers has often been used to analyze the swelling kinetics of coal in solvent . On the other hand, the coal swelling process is assumed as a pseudopolymolecular or pseudoelementary reaction for the dissociation of the noncovalent bonds during coal swelling in solvent .…”

Section: Introductionmentioning

confidence: 99%

“…The isothermal swelling kinetics of coal in pyridine or other strong polar solvents under ambient temperature and pressure have been extensively studied because of the significant swelling of coal in these solvents. However, there is no significant swelling of coal in coal liquefaction process derived recycle solvent (REC) and pure tetralin (THN) found at ambient temperature and pressure because REC and THN are nonpolar solvent and there is no specific interactions between coal and solvent. Therefore, the kinetics of coal swelling in REC and THN would be explored at elevated temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Swelling behavior of coal in solvent at elevated temperature and pressure and non‐isothermal kinetic analysis

Chen

Zhao

Cao

et al. 2016

Asia-Pacific J Chem Eng

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The swelling ratio of a packed coal bed in a coal liquefaction process derived recycle solvent (REC) and pure tetralin (THN) at elevated temperature and pressure is obtained by a so‐called linear variable differential transformer (LVDT) deformation transducer apparatus. Effects of heating rate and coal rank on the swelling behavior are investigated. A kinetic model based on a pseudopolymolecular reaction is used to model the swelling data up to the maximum swelling ratio. With the increase of the temperature, the thermal motion of solvent molecule and coal macromolecules is enhanced, and the interactions increase between coal macromolecules and solvent molecule. As the temperature is further increased, the swelling ratio of the packed coal bed reduces for the softening and decomposition of coal. For faster heating rates, the maximum swelling ratio shifts to higher temperature and the apparent activation energy and pre‐exponential factor slightly increase with the increase of heating rates. A comparison of coal rank illustrates that the maximum swelling ratio of bituminous coal in REC and THN is more and shows at higher temperature than lignite. The apparent activation energy for coals swelling in REC and THN at elevated temperature and pressure is between 20 and 55 kJ/mol. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

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“…Coal matrix swelling in solvents like pyridine has been widely studied [113][114][115][116]. A large body of research with regard to coal particle size change has been conducted using multiple methods [114,117], among which, camera observation is a simple and sufficient method as described in Van Niekerk's work [118,119]. Other researchers, such as Murata [116], Gao et al [114,117,120] [21].…”

Section: Introductionmentioning

confidence: 99%

“…A large body of research with regard to coal particle size change has been conducted using multiple methods [114,117], among which, camera observation is a simple and sufficient method as described in Van Niekerk's work [118,119]. Other researchers, such as Murata [116], Gao et al [114,117,120] [21]. Furthermore, the oxidative products in each experiment were different with mostly alkanoic acid and alkanedioic acids produced in lignite oxidation and benzene carboxylic acids from anthracite oxidation [17,20,21].…”

Section: Introductionmentioning

confidence: 99%

Oxidant stimulation of coal seams to increase coal seam permeability

Jing¹

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Low permeability renders a significant fraction of coal seam gas (CSG) resources subeconomic. An effective permeability enhancement strategy is thereby crucial in monetising low permeability CSG resources. Though employed in a number of coal basins, conventional low permeability stimulation treatments have not been ubiquitously successful. The natural cleat system of coal is the primary conduit for gas flow and low permeability is in many cases attributed to low cleat porosity and connectivity. Cleat demineralisation by acid has been addressed previously with mixed results. This thesis explores the possibility that coal cleats could be etched and the cleat aperture could be widened by use of oxidants. It could have high potential to increase the cleat porosity and connectivity, thus enhancing the coal permeability in the near well bore region where high permeability is critical. Two coal samples, from the Bowen (coal B) and Surat (coal S) basins in Queensland, Australia were selected. A screening method was designed based on time-lapse photography to assess the extent of coal particle size change immersed in potential oxidants, including sodium hypochlorite (NaClO), potassium permanganate (KMnO4), hydrogen peroxide (H2O2), and potassium persulfate (K2S2O8). Results show coal solubilisation and the propensity to swell in all the oxidants as well as coal breakage in specific oxidants (NaClO and KMnO4). Both coals react vigorously with NaClO and KMnO4, where massive coal solubilisation occurs, but react only slightly with K2S2O8 and H2O2. Given the solid products of the KMnO4 reaction (MnO2), NaClO is selected as the most promising oxidant stimulant. After NaClO treatment, the total accessible pore volume of both coals increases. Pore size distributions indicate that oxidation can enlarge the pores, particularly for coal S, which was confirmed by scanning electron microscopy (SEM). A microfluidic cleat flow cell (CFC) was used to inject NaClO into artificial channels scribed on polished coal samples, and measured an increase in the widths of the channels after NaClO treatment. The channel aperture increase indicates that coal solubilisation/etching is a more dominant mechanism than coal swelling when coal is confined in coal cleats. The channel aperture of coal S increases more than coal B.

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An Improved Three-Dimensional Microscope Image Analysis Method for Studying Solvent Swelling of Single Coal Particles

Cited by 6 publications

References 25 publications

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

Swelling behavior of coal in solvent at elevated temperature and pressure and non‐isothermal kinetic analysis

Oxidant stimulation of coal seams to increase coal seam permeability

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