973878 - Contactless Distant Desorption Monitoring Using Chipless Printable Sensing Tag

Thermal desorption methods have been widely used to regenerate spent adsorbents. In the thermal desorption process design, desorption time is a key parameter that directly impacts energy consumption, and thus, the cost of the air treatment process. Prediction of the desorption time can be challenging as the amount of adsorbate load in the adsorbent bed may vary depending on the properties of the polluted gas stream, such as the number of compounds and their concentration. In this study, a contactless distant RF sensor is presented for real-time monitoring of the desorption process. The main sensing element of the proposed desorption monitoring platform is a chipless flexible microwave split-ring resonator, ‘tag’, which is electromagnetically coupled to a readout circuit, ‘reader’.
A styrene-divinylbenzene resin was loaded with heptane (nonpolar) and n-propyl alcohol (polar) at different concentrations to evaluate the use of the sensor for desorption monitoring. After verifying the sensor's temperature stability, the desorption was carried out at 170 ºC. The sensor response was compared to effluent adsorbate concentration measured by flame ionization detector, and thereby, adsorbent dielectric properties were related to adsorbate load on the resin. A linear correlation (R2=0.96) between the adsorbate load and the measured frequency shift was observed. The proposed chipless microwave resonator sensor demonstrates the capability of real-time distant monitoring and detection, making it a suitable candidate for harsh environments and high-temperature sensing applications.