Numerical simulation of vacuum pressure swing adsorption for biogas upgrading

Vacuum pressure swing adsorption(VPSA)is a technology for gas separation. There are some problems when it is applied to the process of biogas purification, among which is the concentration peak at the outlet of the column. To solve this problem, we use the linear driving force(LDF)model and Langmuir isothermal equilibrium to build a model and analyze the effect of CO₂ concentration in buffer tank on the purity of outlet of adsorption step. The results indicate that CO₂ enters the buffer tank in the second pressure equalization-depressurization and then the column in the first pressure equalization-pressurization, finally the concentration peak appears at the outlet of the column, and affects the CH₄ concentration. The simulation shows that in order to control the CO₂ concentration in buffer tank and improve the purity of the product, the adsorption time should be shorten as the adsorption pressure decreases.