Abstract
Transport in porous media with chemical and thermal effects is a common phenomenon; it is also a complicated scientific problem with applications in the field of mining engineering. In situ pyrolysis for coal gas generation is just such a problem, involving material and structural changes in the coal and surrounding rocks, with massive thermal and chemical effects. The transport properties of the coal are substantially changed, which in turn affect the thermal and chemico-mechanical reactions. A series of laboratory experiments on pore structure and permeability changes during gas coal pyrolysis were carried; the experimental procedure and results are described and analyzed in this study. The pore volume and permeability of tested specimens experienced modest changes during the heating process from 20 to 300°C, but when heated from 300 to 400°C, large pores in the specimens greatly increased and the overall porosity reached 23% at 400°C, which is larger than the percolation threshold value of the rock mass with pores and cracks. The permeability of the specimens increased exponentially with temperature, evidencing the massive structural changes that took place in the specimens during the pyrolysis process. In the high temperature range from 400 to 600°C, fewer changes in the specific surface area of microscopic and small pores in the coal took place, but the pore volume and porosity increased linearly with temperature.
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References
Balek V., de Koranyi A.: Diagnostics of structural alterations in coal porosity changes with pyrolysis temperature. Fuel 69(12), 1502–1506 (1990)
Butterfield I.M., Thomas K.M.: Some aspects of changes in the macromolecular structure of coals in relation to thermoplastic properties. Fuel 74(12), 1780–1785 (1995)
Charland J.P., MacPhee J.A., Giroux L. et al.: Application of TG-FTIR to the determination of oxygen content of coals. Fuel Process. Technol 81, 211–221 (2003)
Chen P., Xiuyi T.: The research on the adsorption of nitrogen in low temperature and micro-pore properties in coal. J. Chin. Coal Soc. 26(5), 552–556 (2001)
Dana E., Skoczylas F.: Gas relative permeability and pore structure of sandstones. Int. J. Rock Mech. Min. Sci. 36, 613–625 (1999)
Feng Z.-C., Zhao Y.-S., Wen Z.-M.: Percolation mechanism of fractured coal rocks as dual-continue. Chin. J. Rock Mech. Eng. 24(2), 236–240 (2005)
Feng Z.C., Zhao Y.S., Lv Z.X.: Study on percolation law of 2D porous and fractured double-medium. ACTA Phys. Sinica 56(5), 2796–2801 (2007)
Liang W., Zhao Y., Xu S.: Dissolution and seepage coupling effect on transport and mechanical properties of glauberite salt rock. Transp. Porous Med. 74(2), 185–199 (2008)
Shi B.M.: The micro structure analysis of the spontaneous combustion coal in oxidization and inhibition at low temperature. J. Chin. Coal Soc. 25(3), 294–298 (2000)
Tarasevich Y.I.: Porous structure and adsorption properties of natural porous coal. Colloids Surf. A Physicochem. Eng. Aspects 176, 267–272 (2001)
Tomeczek J., Gil S.: Volatiles release and porosity evolution high pressure coal pyrolysis. Fuel 82, 285–292 (2003)
Washburn E.W.: The dynamics of capillary flow. Phys. Rev. 17(3), 273–283 (1921)
Xiang Y., Wang Y., Zhang J., Dong Z., Li B., Xiang Y.H.: Study on structural properties and their affecting factors during gasification of chars. J. Fuel Chem. Technol. 30(2), 108–112 (2002)
Zhang H.: Genetical type of pores in coal reservoir and its research significance. J. Chin. Coal Soc. 26(1), 40–43 (2001)
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Yangsheng, Z., Fang, Q., Zhijun, W. et al. Experimental Investigation on Correlation Between Permeability Variation and Pore Structure During Coal Pyrolysis. Transp Porous Med 82, 401–412 (2010). https://doi.org/10.1007/s11242-009-9436-8
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DOI: https://doi.org/10.1007/s11242-009-9436-8