Monitoring the residual capacity of activated carbon in an emission abatement system using a non-contact, high resolution microwave resonator sensor

The accumulation of non-desorbed species or heel buildup reduces the capacity and lifetime of adsorbents used in cyclic adsorption/desorption processes. This study investigates the changes in the physical, chemical, and dielectric properties of beaded activated carbon (BAC) and their relation to the adsorbent residual capacity (i.e., residual lifetime) during cyclic adsorption/desorption using a non-contact, high-resolution microwave resonator sensor. The resonant frequency of the sensor responds to changes in the dielectric properties of the medium surrounding the sensor. BAC samples with different degrees of capacity reduction as indicated by the apparent density, BET surface area, total pore and micropore volumes were tested. A linear correlation (R-2 = 0.93) between the apparent density of the BAC samples and the resonant frequency shift of the sensor was observed, irrespective of heel composition indicating that the effect of adsorbent porosity on dielectric property variation is more important than heel composition. The sensor's ability for fast and continuous measurement makes it an ideal candidate for real-time monitoring of adsorbent capacity status in cyclic adsorption/desorption processes.