(393g) Zeolite Characterization Testing
AIChE Annual Meeting
2007 Annual Meeting
Nuclear Engineering Division
Advances in Processes for Metals Separation and Purification
Wednesday, November 7, 2007 - 2:35pm to 3:00pm
Zeolite or molecular sieve is used in tritium processing operations to remove moisture and other contaminants from the process gas streams and tritium from streams released to the environment.. Zeolites are synthetically produced. The zeolites are chosen based on their cage or pore size to match them to the material to be absorbed. The isotherms for absorption are characterized for each type of zeolite and known absorbent. However, the zeolite is not discriminating enough and can absorb off-gas products from plastics and other substances used in the glove box environment (Krytox, etc.)
In tritium processing, water produced from the process environment (glove box air infiltration and hydrogen present react in the presence of a hot catalytic metal to form water), must be removed from the process stream. The formation of water and subsequent trapping on molecular sieve is used to scavenge tritium from a gas stream prior to release to the environment.
The molecular sieve beds are regenerated upon filling to restore their capacity. The regeneration of the molecular sieves can release the trapped compounds into the zeolite bed regeneration system. The moist gas from the zeolite bed is passed through a magnesium bed to crack the waters. But in doing so, can crack other substances. The cracking of these materials, zeolite acting as a catalyst, or the zeolite can create free radical species of chlorine, fluorine, sulfite, phosphates, etc. These radials can contribute to system piping corrosion. A program to test the zeolite is intended to eliminate it as a source of corrosion inducing products.