Study On The Pulsating Rheological Pressure Swing Adsorption Separation Of CH₄/CO₂ By Experiments And Simulation

With the progress of society and the development of science and technolo gy,the application of high-carbon energy has been gradually restricted due to the characteristics of heavy pollution and environmental harm,while natural gas has been widely used due to its cleanness,efficiency,safety and reliability.The newly developed natural gas contains a large amount of CO₂ impurities and is difficult to remove,which will cause adverse effects on subsequent processing and use.The current widely used processes for removing carbon dioxide from natural gas include:amine alcohol method,pressure swing adsorption method,cryogenic separation method,membrane separation method,etc.Among them,the PSA method is widely used due to its advantages of low energy consumption,simple,convenient process and small pollution,but there are still problems such as flow dead zone and uneven adsorption in the PSA process.In this paper,using the pulsating flow can improve the flow effect,reduce the flow dead zone,and to a certain extent,the breakthrough block adsorption gas boundary layer,improve the efficiency of adsorption,combined with the commonly used pressure swing adsorption?PSA?process,pulse rheological pressure swing adsorption technology is put forward,can effectively improve the adsorption quantity of pressure swing adsorption?PSA?and separation factor,improve the absorption effect.In the experimental part,the effect difference of CH₄/CO₂ adsorption separation between dc and pulsating flow was analyzed by comparing single column CH₄/CO₂ transmission curve.The effects of different pulsation frequency,gas flow rate,adsorption pressure,sorbent type and other conditions on the pulsation separation effect of CH₄/CO₂ were studied.The experimental results show that the CH₄/CO₂ separation effect is improved first and then worse with the increase of pulsation frequency.With the increase of gas flow and adsorption pressure,the pulsation frequency corresponding to the optimal adsorption effect increases.Different adsorbents have different adsorption effects on pulsating flow,but the adsorption effects of the three adsorbents under pulsating conditions and the improvement effect of pulsating on their adsorption have the same trend,for the first improvement and then worse,the adsorption effect and the effect affected by pulsating adsorption are:13X zeolite>5A zeolite>coconut shell activated carbon.In the simulation part,the fluid dynamics software Fluent was used to simulate the adsorption process of dc and pulsating flow by combining the porous media model with the d-a model custom UDF adsorption program,and the CH₄/CO₂ penetration curves measured at different positions were compared and analyzed.The simulation results show that the pulsating adsorption process can improve the adsorption effect by improving the overall fl ow and making the gas distribution more uniform.On the other hand,in the first half of the adsorption column,the phenomenon of poor adsorption effect may occur due to excessive pulsating impact force.Therefore,the pulsating frequency of pulsating adsorption should be appropriate to the length-to-diameter ratio of the adsorption column.Otherwise,the adsorption effect will not be improved,but CH₄/CO₂ gas may be penetrated in advance.The experimental results are in good agreement with the simulation results in the first half,but the latter half of the pulsating adsorption experiment has a longer delay than the simulated one,indicating that the pulsating flow has a more obvious improvement effect on the dead zone and gas boundary layer.