economic comparison between membrane and adsorption processes for separation of co2 and ch4 mixture

in this work, the economic comparison between a pressure swing adsorption (psa) process and a membrane unit for removal of carbon dioxide from a carbon dioxide/methane mixture was studied. the adsorption process for the adsorbent of zeolite 13x and the membrane unit for membrane of 6fda tapdo was studied. first, the calculation of tac for membrane unit with the five prices of membrane including 20$/m², 50$/m², 100/m²,150$/m² and 200$/m² was done and the best pressure for every price of membrane with minimum of tac was selected. then, the psa process was investigated for the adsorbent of zeolite 13x in the two pressure of 10 bar and 15 bar. all the simulations of psa (includes 4 beds and 8 steps) were done in the aspen adsorption v8.8 and the membrane process was simulated in the matlab. for pressure of 15 bar and membrane price of 100$/m² , the results showed that the tac for psa unit is 12% less than the tac for membrane unit in spite of that the mole fraction of co₂ in the product for psa unit is 0.0001 and for membrane unit is 0.017. the cost of membrane unit and adsorption unit is mostly related to the compressor and electricity costs, and also the adsorbent cost is almost 2% of psa process tac while the membrane cost is more than 20% of membrane process tac.