Experimental Study On Pore Structure Of Low Rank Coal Affected To Gas Adsorption Thermodynamics Characteristics For ZhunNan

The prevention and control of coal mine gas and the development and utilization of coalbed methane are closely related to the microstructure characteristics of coal and the law of gas adsorption.It is beneficial to study the effect of the pore structure on the adsorption characteristics of low-rank coal.That 10 typical experimental coal samples from Zhunnan Coalfield,Xinjiang was selected,and combined with the characteristics of coal pore structurethe the gas adsorption characteristics from the perspective of thermodynamics was analysied.(1)The low-rank coal pore structure of Zhunnan are analysied by low temperature nitrogen adsorption experiment The results show that the porosity of the low-rank coal are more developed,the pore structure are complex,the specific surface area and the pore size and the proportion of the same pore size are different.The specific surface area are mainly micropore and transition hole.The pore size and pore volume of the same pore size are similar with the law of pore diameter change.(2)Based on the PCT-C80 adsorption calorimetry system,the gas adsorption heat data of the experimental low-rank coal are measured.The comparison of the four adsorption models showed that the D-A adsorption model are more suitable for describing the gas adsorption characteristics of the experimental low-rank coal.The Clausius-Clapeyron equation theory is used to calculate the equivalent adsorption heat value,the adsorption free energy equation of the standard equilibrium pressure constant is established to calculate the gas adsorption free energy and the Gibb-Helmholtz equation is used to calculate the adsorption entropy change.It is showed that there are difference between the calculated value and the experimental test value.With the temperaure imporve the coal gas equivalent adsorption heat and the adsorption heat of coal are reduced,the adsorption free energy increases and adsorption entropy decreases.From the thermodynamic point of view confirmed that the temperature is not conducive to coal gas adsorption.The gas adsorption thermodynamic parameters are suitable for expressing the gas adsorption characteristics of low-rank coal.(3)By analyzing the influence of pore structure feature on the gas adsorption thermodynamic characteristics,the relationship between the low-rank coal pore structure and the gas adsorption of coal is obtained.It is showed that with the specific surface area of the experimental coal sample and the specific surface area of the other pores increase,the gas adsorption heat increased,Free energy variable ?G,adsorption entropy change ?S linear increase in addition to the specific surface area of the transition hole.The microporous specific surface area plays a major role on the effect of Q,with the BJH pore volume and pore volume increases Q,?G,?S all increase.The effect of micropore volume on Q plays a major role.The research of this paper provides some experimental datas base and theoretical basis for the gas extraction of low-rank coal in Zhunnan Coalfield,Xinjiang.