脱气时间对中煤级煤低温氮吸附实验的影响OA北大核心CSTPCD

The low-temperature nitrogen adsorption method is widely employed for the characterization of pores with diameters ranging from 0.35 nm to 300 nm in coal samples.Experi-mental data obtained from this method provides valuable insights into the pore structure charac-teristics of coal.Various parameters,such as particle size,degassing temperature,and degassing time,play crucial roles in determining the outcomes of low-temperature nitrogen adsorption ex-periments.In this study,a series of experiments was conducted to investigate the effect of degas-sing time on the results of low-temperature nitrogen adsorption experiments,with a focus on var-ying only the degassing time while keeping other factors constant.2 h,3 h,4 h,5 h,6 h,9 h,12 h,24 h were selected as degassing time for the experiment.Three kinds of middle-grade coal rock samples sourced from gas coal at Jining No.3 well and Zhangbei mine,as well as coking coal from Linhuan mine were used as raw meterials in the experiment.The evolution of the pore structure of these middle-grade coal samples under different degassing times was examined to de-termine the optimal degassing time.Analysis of the adsorption curve,"hysteresis loop"of ad-sorption-desorption curve,stage pore volume curve,average pore size and other parameters of coal samples reveal significant variations in pore structure as a function of degassing time.Exper-imental results show that coal samples exhibit primarily H3 adsorption-desorption curve after de-gassing for 2 h or 3 h,indicating a relatively simple pore structure.The average pore size of coal samples peak at 3 h of degassing and reach its minimum after 5 h.Notably,a degassing time of 3 h minimizes the influence of moisture and volatiles on the coal pore structure,leading to a more accurate representation of the sample's pore characteristics.Consequently,it is recommended that the optimal degassing time for middle-grade coal samples from Jining No.3 well,Linhuan mine and Zhangbei mine is 3 h.