Study on Different Dry Methods Affected to Porous Structure of Lignite and Re- adsorption Characteristic

The low temperature nitrogen adsorption method and the scanning electron microscope was applied to study the porous structure and surface features 0 f the coal sample before and after the nitrogen gas drying,air dry and thermal press dry and the study of the re-adsorption was conducted on the coal samples after drie d.The results showed that the specific surface area, pore volume and pore average diameter of the coal sample after the nitrogen air dry and air dry were increased.The specific surface area,pore volume and pore average diameter of the coal sample after thermal press dry were increased.the scanning electron microscope showed that the particle surface of the coal sample after the air dry and nitrogen dry was more uneven,the cracks became larger and the pores were increased. after the thermal pre ss dry,the surface of the coal samples became flat and smooth,the cracks were squeezed together and the pores were reduced. The re-adsorption experiment results sh owed that after 25 h re-adsorption of the coal sample dried,the re-adsorption curve was flat in tendency,the moisture content after the re-adsorption of the coal sample after the nitrogen dry and air dry was about 13% ,the moisture content of the coal sample after the thermal press dry was 9% and the moisture re-adsorption rate of the t hermal press dry coal sample was lower.