Basic Research On Column Separation Of Low Concentration Gas Purification

The coal resources and coal bed gas resources?Methane?in China are both abundant.In the process of coal mine gas mining,a considerable amount of the extract gas concentration is so low that limits its application.It also has a great influence on environmental protection and the effective use of resources.A large number of experiments and practical studies were conducted,and a variety of methods for gas separation and purification have been invented,such as cryogenic method,membrane separation method and adsorption method.However,the methods currently used are still lacking in the conditions of use and the difficulty of operation.Column separation method is used in this article to separate and purify the methane of low concentration.Two stationary phase adsorbents?Carbon Molecular Sieves and 5A Molecular Sieve?were comparatively analyzed through experimental methods.The adsorption and separation of methane of low concentration was conducted with a packed column.Gas chromatography was used to analyze the separation of low concentration methane from three angles of different volumes of quantitative loop,different temperatures of packed column and different concentrations of gas.The research results will provide theoretical guidance for obtaining higher concentration of gas.Firstly,through the research on basic characterization,specific surface area and adsorption property of 5A molecular sieve and carbon molecular sieves,a stationary phase adsorbent suitable for column separation method was selected.In this paper,x-ray powder diffraction?XRD?,scanning electron microscopy?SEM?,specific surface area and pore size distribution analysis,high pressure adsorption isotherm testing and static high pressure selective adsorption performance testing.In addition,a self-constructed micro reaction equipment of adsorption and desorption were used to perform atmospheric pressure adsorption property test on the two adsorbents.The studies above have shown that the 5A molecular sieve exhibit high crystallinity,relatively complete crystal form and regular,uniform size grains,and the adsorption and desorption rate of nitrogen on the 5A molecular sieve is better than that of methane,so it is more suitable for the column separation method.In the meantime,the 5A molecular sieve is cheap and more economical.Secondly,by using helium as a carrier gas and changing the condition parameter in column separation?such as volume of quantitative loop,temperature of packed column and concentration of gas?,the separation of low concentration mixture gas in packed column filled by 5A molecular sieve was tested and the mechanism of process was analyzed.The experimental results show that in the case of only changing the volume of the quantitative loop,the other conditions remain unchanged,as the volume increases,the separation limits of nitrogen and methane tend to be insignificant until the peak of methane is completely covered by the peak of nitrogen,and a maximum amount of gas that the gas concentration can be doubled for a single separation can be obtained under this condition.Also,by changing the temperature,the optimum purification separation condition can be obtained.Furthermore,the chromatograms of CH₄/He and He/N₂ also were recorded.The curve that fitted from the two chromatograms is little different from the actual measured curve of CH₄/N₂.Finally,using the principle of gas chromatography adsorption and separation analysis,a methane adsorption and concentration system for gas extraction with extremely low concentration was designed,which provided a way for industrial concentration and purification of low-concentration gas in mines.