Multi-Column Experimental Test Bed for Xe/Kr Separation

Abstract

Previous research studies have shown that INL-developed engineered form sorbents are capable of capturing both xenon and krypton from various composite gas streams. The existing experimental test bed provided the capability of single column testing for capacity evaluations over a broad temperature range. To advance research capabilities, the employment of an additional column to study selective capture of target species to provide a defined final gas composition for waste storage was warranted. The second column addition also allows for compositional analyses of the final gas products to provide for final storage determinations.The INL krypton capture system was modified by adding an additional adsorption column to create a multi-column test bed. The purpose of this modification was to allow for the investigation of the separation of xenon from krypton supplied as a mixed gas feed. An extra (upstream) column was placed in a Stirling Ultra-low Temperature Cooler, capable of controlling temperatures between 190 and 253K and the column was filled with AgZ-PAN sorbent to capture the xenon from the feed gas. The effluent from this column would then be routed to the column in the cryostat filled with HZ-PAN to capture the krypton. Additional piping and valves were incorporated into the system to allow for a variety of flow path configurations.A limited scope of testing was performed to evaluate the performance of this updated test bed and to determine xenon and krypton separation, adsorption selectivity, desorption, and final concentrations in the desorbed gas streams. Sampling and analysis methods used in these tests included on-line GC-TCD analysis of the AgZ-PAN column outlet gas for xenon and krypton, as has been used in prior tests, and the addition of GC-MS evaluation of evacuated sample bombs. The sample bombs were analyzed after each test completion to measure xenon and krypton desorption from the columns as they were heated to above room temperature, with no purge gas flow.Two separation tests were performed utilizing a feed gas consisting of 1000 ppmv xenon and 150 ppmv krypton with the balance made up of air. The AgZ-PAN column temperature was held at 295 or 253K while the HZ-PAN column was held at 191K for both tests. The effluent from the AgZ-PAN column was monitored for xenon and krypton via GC-TCD during the tests. No xenon was detected exiting the AgZ-PAN column during the adsorption phase of either test.During the desorption phase of each test, gas samples from each column were taken via evacuated sample bombs and were analyzed by GC-MS analysis. No purge gas flowed during the sample bomb collection; the sample collection relied only on the evacuated bombs that drew gas from the sorbent beds when the connecting valve was opened.Results of these evaluations verified that the system operated as designed and demonstrated that AgZ-PAN exhibits excellent selectivity for xenon over krypton in air at or near room temperature, and that krypton with only small amounts of xenon was captured in the HZ-PAN column ...

Investigating the Effects of Ag, Cu, and Pd Functionalized Chabazite on the Adsorption Affinities of Noble Gases Xe, Kr, and Ar

“…Xe in particular has been proposed as an anesthetic, , and all three noble gases are used in specialized types of lighting. In addition to these practical uses, the atmospheric detection of Xe is used for monitoring undeclared nuclear tests for the purpose of verification of the Comprehensive Nuclear Test Ban Treaty. , Adsorbents such as metal–organic frameworks (MOFs) are also being considered for the collection of Kr from spent nuclear fuel. − However, finding an efficient and cost-effective method for the capture and separation of noble gases (especially Kr and Xe) from air has proven to be technologically challenging. Generally, the commercial separation of these gases from air involves a cryogenic distillation process that is both energy intensive and expensive.…”

Multi-Column Xe/Kr Separation with AgZ-PAN and HZ-PAN

“…The results of initial testing of the two column system with AgZ-PAN and HZ-PAN indicate that an excellent separation of Xe from Kr could be attained using the newly installed multi-column system. [1] Building upon these initial results, a series of additional multi-column testing was planned to be performed in FY-16. The purpose of this testing was to scale up the sorbent beds, test a different composition of feed gas and attempt to improve the accuracy of the analysis of the individual capture columns' compositions.…”