HZ-PAN and AgZ-PAN Desorption Characterization

Abstract

While previous research focused on adsorption of Kr and Xe on HZ-PAN and AgZ-PAN, recent focus has shifted to desorption. Preliminary testing was completed last year, providing valuable information to guide further research.Previous isotherm studies indicated that thermal swing operations, along with a sweep gas, are required for effective desorption of captured species from both AgZ-PAN and HZ-PAN. This series of tests focused on characterizing the bulk gases removed from each sorbent and relative separation of Kr and Xe from each other and from the bulk air. Stepwise thermal desorption resulted in 99-100% separation of Xe from Kr, and 77-83% separation of Kr from air while concentrating Xe seven to tenfold and Kr three to fivefold from initial feed stream compositions. Previous isothermal studies of both sorbents have shown that sorbent capacity is proportional to feed gas concentration. Therefore, it is anticipated that additional HZ-PAN columns operated in series will further concentrate and purify the final Kr stream with higher efficiency. It is expected that Xe will be released to atmosphere after desorption. However, it could also be purified further with more AgZ-PAN columns in series. Further testing should be done to determine maximum purity achievable for both Kr and Xe. Additionally, renewed focus on increasing Xe capacity on AgZ-PAN and Kr capacity on HZ-PAN is recommended.