Study On Pressure Swing Adsorption Performance To Low Concentration Gas Of Activated Carbon Materials

Coal-bed methane is a sort of clean energy which owns enormous economic values.China ranks in the top three in the world on the resources which reaches 4trillion cubic meters.However,because of the exhausted methane is mixed into quantity of air,it becomes hard to be in use.It must be concentrated and purified before it can meet the transportation and use requirements.The low-concentration coalbed methane contains a large amount of nitrogen,which owns the same nature with methane.Therefore,the denitrification technology of low-concentration coalbed methane is a key factor restricting its large-scale activity.Pressure swing adsorption technology is executable in the separation and purification of coal-seam methane because of its high reliability,flexible operation,low energy consumption and low economic cost.In this paper,activated carbon?AC?is taken as the main research object.The breakthrough characteristics and selective adsorption performance of adsorbents for CH₄/N₂ are experimentally studied.And its adsorption performance based on a simulated single-column pressure swing device for low concentration gas mixture is investigated.On this basis,the optimal separation and purification conditions for different concentrations of gas were proposed,and the activated carbon adsorbent suitable for industrialization was selected.A series of coal-based activated carbons with different iodine values were selected for structural characterization and breakthrough performance test.The results indicate that AC-1000 owns a better microstructure with the specific surface area of1234 m²/g.At the same time,AC-1000 showed the best CH₄/N₂ selective adsorption performance,which is consistent with their structural characterization experimental results.The above-mentioned preferred coal-based activated carbon sample AC-1000was modified by the alkali treatment method to prepare four modified activated carbons under different conditions of heating rate and heating time.And a variety of nutshell-based activated carbons were prepared using waste peanut shells as raw materials.The structural characterization of the above modified and prepared activated carbon materials was carried out,and they were selected for breakthrough performance measurement.The structural characterization results show that:MAC-B?heating rate 5?/min,heating time 90min?and PAC-E?temperature 700?,heating rate 5?/min and heating time 90 min?have better micro surface with their specific surface area reaching to 988 m²/g?379 m²/g?The breakthrough performance measurement results indicate that the methane/nitrogen selective adsorption performance of AC-1000 is the best,whereas the performance of MAC-B does not very well,probably because the concentration of KOH solution is too high during the modification process.The selective adsorption performance of PAC-E is the worst,which may be related to insufficient activation temperature or unsuitable properties of raw materials.Operate high-pressure adsorption isotherm test on the above activated carbon adsorbent and calculate their adsorption selection parameters.Design a single-column pressure swing adsorption device and select a typical activated carbon adsorbent,then perform a single-column pressure swing adsorption performance test.By changing a series of experimental parameters,the best experimental conditions for single adsorption are obtained,and the methane concentration in the product gas and recovery rate is calculated.The results show that AC-1000 has the highest CH₄/N₂adsorption selection parameter value(S_CH4/N2 17.88)and the best PSA separation and purification effect,which indicates that AC-1000 has the best methane/nitrogen selective adsorption performance.With AC-1000 as the adsorbent,after a single adsorption separation operation,the methane concentration in the simulated gas can be increased by 76%compared with that before the experiment,and the methane recovery rate is stable above 50%.Therefore,the pressure swing adsorption separation method has very good industrial application prospects.The paper has 23 pictures,15 tables,and 64 references.