Response of Porosity and Permeability of Powder Structural Coal on Freeze

This paper, taking strong brittle deformation of powder structural coal as an example, we use the methods of mercury intrusion porosimetry, low temperature liquid nitrogen and steady-state to test the original, frozen samples for 7 days and 30 days. Results show that the method of freezing damages to pore volume, pore structure of samples, and makes smaller pores transfer to the larger pores because of cracked effect. The damage extent was different in various pore sizes and different freezing time. In the sample of frozen 30 days, due to the confined effect of the peripheral square barrel, the development of the damage was restricted; for nanoscale pore, pore volume fell in turn with the frozen time. The longer the freezing time, cracked effect will fully exert its effect, and additional confined effect, the increasing amount of pore that is still within 100 nm after cracking is limited, resulting in the loss of this phase pore. After freezing, the permeability of the sample was improved. Due to the confined effect, compared to the original, the increase of seepage-flow pores of frozen sample for 30 days is less than frozen sample for 7 days.