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Pore Connectivity of Different Ranks of Coals and Their Variations Under the Coupled Effects of Water and Heat

Abstract

In this paper, a series of experiments were conducted to reveal differences in pore connectivity between different ranks of coal, as well as their variations under the coupled effects of water and heat. The results demonstrated that the pore connectivity of coal undergoes three stages of evolution: Stage I, in which pore size is \({>}36\,{\upmu }\hbox {m}\); Stage II, in which pore size ranges from 0.07 to \(36\,{\upmu }\hbox {m}\); and Stage III, in which pore size is \({<}0.07\,{\upmu }\hbox {m}\). The highest pore connectivity occurs in Stage I, and the lowest pore connectivity occurs in Stage III. This trend is likely observed because the coupled effects of water and heat promote the flow of fluids in coal, thereby reducing the capillary forces between the fluids and the walls of pores and increasing coal pores and microscopic cracks. The coupled effects of water and heat produce two different types of pores: first, distensible pores form when hydrothermal processes cause original coal pores to expand; second, corrosive pores are generated when mineral crystals embedded in the coal body are eroded by hydrothermal processes and form new pore spaces. The results of these experiments have significant implications for increasing the efficiency of methane gas drainage.

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Correspondence to Guanhua Ni.

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Cheng, W., Ni, G., Li, Q. et al. Pore Connectivity of Different Ranks of Coals and Their Variations Under the Coupled Effects of Water and Heat. Arab J Sci Eng 42, 3839–3847 (2017). https://doi.org/10.1007/s13369-017-2506-2

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Keywords

  • Pore connectivity
  • Different rank coals
  • Coupling action of water and heat
  • Gas drainage
  • Water blocking effect