Enhancement effect on adsorbent utilization rate based on Twin–Bed tandem adsorption

Abstract

The actual adsorption loading of the adsorbent is usually less than the equilibrium capacity in the abatement of volatile organic compounds (VOCs) with industrial fixed-bed adsorption. In this study, the twin-bed tandem adsorption (TBTA) cycle was proposed. Adequate time was ensured for the upstream bed to adsorb and reach saturation via the take-up and protection of the downstream bed, thus utilizing the full capacity of the adsorbent. A mathematical model and an extended bed depth service time (BDST) model were developed to describe the characteristics of the TBTA. Then, fixed-bed adsorption experiments were performed to validate the accuracy of the aforementioned two models. Results of the parametric analysis showed that the best enhancement effect could be achieved at low packing height, low feed concentration and high superficial velocity conditions. By defining the unit energy consumption (UEC) as the fan power consumption for the recovery of contaminants per unit amount, suggestions for adsorption parameters were provided. Tracking the UEC at each concentration point on the breakthrough curve, the relative concentration of 70% to 80% was found to be the cost-efficient switch point for TBTA. This study demonstrated the operational dynamics of the TBTA and parametric effects on adsorption performance. Our findings can help to improve the adsorbent utilization rate in fixed-bed systems.