Exergy Analysis of Air Separation with Pressure Swing Adsorption

Based on energy saving of pressure swing adsorption (PSA) device,a strict mathematical model was established by using the theory of engineering thermodynamics and adsorption thermodynamics.Through exergy analysis of air separation system with a small twin towers and PSA,It was concluded the influence law of adsorption pressure and back pressure on the exergy efficiency of PSA device.Through calculation,it is found that increasing back pressure or reduce adsorption pressure properly can improve the exergy efficiency;exergy loss occurs mainly in three processes,namely cooling process after the compressor,adsorption process inside the column,and exhaust gas valve losses in the blowdown step,the proportion of total energy input is 20.32%,33.57% and 19.10% respectively.In contrast,exergy losses less in the process of pressure release inside the column,pressure equalization,blowback and decompression in the valve used in pressure equalization.Referring to the research achievements,from the point of improving exergy efficiency,in the premise of ensuring product purity,recovery rate and adsorption capacity of molecular sieve,designers should reduce the adsorption pressure and increase the blowback pressure,so as to design more energy-saving PSA device.