Biogas upgrading to natural gas pipeline quality using pressure swing adsorption for CO2 separation over UiO-66: Experimental and dynamic modelling assessment

Biogas upgrading (CO2 removal) is an important process to produce biomethane that meets the fuel quality standards or pipelines injection specifications. Assessment of microporous UiO-66 as a potential adsorbent for CO2 removal from biogas was performed to gauge the viability of the media for methane purification and CO2 removal in pressure swing adsorption under non-isothermal conditions. UiO-66 was synthesized and characterized using various analysis tools such as SEM, BET, FTIR, XRD, TGA, particle size distribution, and TPD. A dynamic model for the proposed PSA system was built to study the effects of some parameters i.e., outside temperature, length/diameter ratio, and CO2 feed concentration on the purity and recovery of the product gases. The developed model was validated by comparing the simulation and experimental data from CH4 and CO2 breakthrough curves under similar operating conditions and adsorption bed geometry. A central composite design method was employed to optimize and examine the interaction effects of the studied parameters on the PSA system. The results confirmed the high separation performance of the PSA system using UiO-66 adsorbent with bioCH4 purity of 98.2 % and recovery of 94.68 %. The RSM model showed that the studied parameters possessed significant effects on PSA performance. The optimized parameters for achieving maximum purity and recovery were operating temperature of 290 K, length/diameter ratio of 5.6 and CO2 concentration of 39 %. Under those optimized conditions, the PSA cycle over UiO-66 recorded a purity of 99.99 %, recovery of 99.99 %, and system productivity of 8.57 mol/kg.hr.