Characterization Of Pore Structure And Full Aperture Splicing Of Coal With Different Coal Ranks

In order to characterize the full pore structure characteristics of different rank coal,8 groups of different rank coal samples were taken as the research objects,mercury injection porosimetry(MIP),low temperature liquid nitrogen adsorption(LTN₂A),carbon dioxide adsorption(LPCDA)experiments and low field nuclear magnetic resonance(NMR)tests were carried out.Combined with 29 groups of MIP,LTN₂A and LPCDA data provided by the tutor's research group,the compression effect of coal matrix block was corrected,and different gases were compared and analyzed.The optimal pore size obtained by different test methods was selected to characterize the full pore size of different rank coal samples,and the pore size of NMR T₂ value was converted based on the pore size distribution after joint characterization.The results show that the compressibility of coal matrix of different rank ranges from 0.18×10^-10to 2.28×10^-10 N/m²,affected by the second and third jump of coalification,the overall performance is a three-stage change trend of first decrease,then increase and then decrease with the increase of coal rank.Moisture content,volatile matter yield and inertinite content have a promoting effect on the compressibility of coal matrix,while ash yield,fixed carbon content and vitrinite content are on the contrary;different adsorption models have a positive effect on the pore size of the same sample.The non local density functional theory(NLDFT)model is the most accurate one.The corrected high pressure mercury injection data and low temperature liquid nitrogen adsorption data are well connected at the pore size of about 100 nm.There are different forms of pore size at the critical pore size for carbon dioxide adsorption method and low temperature liquid nitrogen adsorption method due to the different adsorption models The pore structure of micropore(<10nm)was characterized by carbon dioxide adsorption data(<2nm)and partial low temperature liquid nitrogen adsorption data(2-10nm),the pore structure of transition pore(10-100nm)was characterized by partial low temperature liquid nitrogen adsorption data(10-100nm),and the pore structure of mesopore(100-1000nm)and macropore(1000-10000nm)was characterized by corrected high pressure The results show that the pore size distribution obtained by the combined characterization is in good agreement with the corresponding pore size distribution obtained by NMR.