Piecewise loading bed for reversible adsorption of VOCs on silica gels

Publication date: Available online 21 June 2019Source: Journal of the Taiwan Institute of Chemical EngineersAuthor(s): Hong Sui, Zeli Wang, Lin He, Zhenwei Han, Xingang LiAbstractThe vacuum swing adsorption (VSA) with silica gel (SG) is proved to be a promising method for the recovery of volatile organic compounds (VOCs). The adsorption mechanisms of o-xylene on silica gels with different pore size have been revealed through the mathematic modeling of adsorption isotherms. The analysis of adsorption kinetics indicates that SG with micropore shows a steep concentration front and a long breakthrough time due to the strong adsorption force field, negligible transfer resistance and compressive effect of favorable isotherm. However, the reversible capillary condensation and mass transfer resistance cause a dispersed front and a short breakthrough time for mesoporous SG. The fast desorption rate makes mesoporous SG more energy-efficient compared with SG with micropore. Accordingly, to further improve the front slope and utilization of mesoporous SG in the adsorption process, a small amount of SG with micropore was loaded in the end of the fixed bed. The breakthrough time of the piecewise loading bed increased by 55.8% at the same loading volume with single mesoporous SG. The energy consumption was observed to exhibit an obviously decrease from 1.819 kWh/m3 to 1.295 kWh/m3, which proved that the piecewise loading method could recover VOCs in a more energy-saving way.
Source: Journal of the Taiwan Institute of Chemical Engineers - Category: Chemistry Source Type: research