Aging effects of off-gas streams on the aged Ag0Z
The data of iodine adsorption on the aged adsorbents are placed in Figure 3 which show iodine loading capacity on the Ag0Z aged in dry air (d.p. < -70oC) and humid air (d.p. -15 oC) at 150 oC for up to 6 months (1 week ~ 6 months). Iodine loading capacity of the Ag0Z decreases after being aged in dry air and humid air. The aged Ag0Z samples in dry air for 1 week indicates that iodine loading capacity decreases to 10.5 wt.% from 12.3 wt.% (unaged Ag0Z), and further decreases to 8.0 wt.% after being aged for 1 month. Iodine loading capacity of Ag0Z aged in dry air for 1, 2, and 4 months shows similar drops which indicate no further degradation occurs during aging process over 1 month. A modest drop is observed after being aged for 6 months, but it could merely be owing to an experimental deviation caused by material nonuniformity. For the humid air aged Ag0Z, iodine loading capacity decreases to roughly 6 wt.% which is dropping more rapidly than dry air. No further significant drops are observed after 1 month. Compared to the dry air aged Ag0Z, these results suggest that the degradation rate increases as water is included in the air stream.
The decrease of maximum iodine loading capacity on both dry air aged and humid air aged Ag0Z as a function of aging time are consistent with previous studies5, 6 which show that dry air stream leads to a roughly 40% iodine capacity loss over 6 months and humid air stream leads to a roughly 50% iodine capacity loss over 6 months. However, the results of the aged Ag0Z in humid air show less iodine capacity loss than previous studies5, 6. It is because a higher dew point of humid air (+15 oC) was used in previous studies than a dew point of humid air (d.p. -15 oC) used in this study. It is appropriate to expect that the lower concentration of water vapor used in this study would result in a less deactivation which is consistent with the following discussion on Figure 7. To summarize, in terms of iodine adsorption capacity loss on both dry air and humid air aged Ag0Z, the aging effect of the humid air (d.p. -15oC) is higher than that of dry air.