Kinetics of the aging process
Figure 3 shows the effects of dry air and humid air on the performance of Ag0Z at 150 oC for up to 6 months. Especially, the aged Ag0Z in dry air and humid air (d.p. -15 oC) showed a significant decrease of iodine loading capacities. For instance, the aged Ag0Z in dry air and humid air for 1 month had a capacity loss for iodine by 34.7% and 49.4%, respectively. To obtain insight of the kinetics of aging on Ag0Z, aging experiments under different conditions including time (1 day to 1 month), temperatures (100oC to 200 oC), and water vapor concentrations (d.p. -40 oC to +15oC) were performed.
Iodine loading data of each aged Ag0Z sample was obtained and compared with the data of deactivation from the chemical analyses because the iodine capacity loss should be consistent with the amount of Ag which was oxidized. Figure 7 shows the kinetic data of iodine loading capacities on the Ag0Z aged in different gas streams including dry air and humid air (d.p. -40oC, -15 oC, and +15oC) at different temperatures (100oC, 150 oC, and 200oC) for from 1 day to 1 month. The kinetic data shown in Figure 7 indicated that iodine loading capacities on the aged Ag0Z decreased with increasing aging temperatures and time when exposed to off-gas streams, which mean that dry air and humid air have a negative impact on the iodine loading capacity of Ag0Z. For example, iodine loading capacities on Ag0Z aged in dry air (Figure (A)) decreased by 15.5%, 34.8%, and 36.4% at 100 oC, 150oC, and 200 oC after 1 month, respectively. Iodine loading capacities on Ag0Z aged in humid air (d.p. -15 oC, Figure (B)) decreased by 42.4%, 44.8%, and 58.2% at 100 oC, 150oC, and 200 oC after 3 days, respectively. Figure (C) indicates the effect of water vapor concentration on iodine loading capacity of Ag0Z; iodine loading capacities were decreased by 34.8% (d.p. -40oC), 44.8% (d.p. -15 oC), and 56.3% (d.p. +15 oC) at 150 oC after 3 days. Results in Figure 7 (B) and (C) show that the effect of humid air increases with increasing temperatures and water vapor concentrations. The aging processes for short periods of time are sensitive to time, so some aging experiments were repeated to make sure of reliabilities of the results, and marked with standard error bars in Figure 7.