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Show -6- each test run, the Teflon line and glassware were washed and the rinse added to the impinger sample solution. The impinger solutions were analyzed for ammonia using a calibrated specific ion electrode. RESULTS The tests were conducted using a sample of a commercially available titanialvanadia SCR catalyst. The catalyst was formulated for natural gas applications and had a pitch of 3.4 mm with a wall thickness of nominally 0.5 mm. All tests were performed using natural gas products containing 30/0 O2 (dry) and a total NOx level (NO + N02) of nominally 100 ppm. The NO/NOx ratio was varied over the range of 0 to 0.75. The test program addressed three issues associated with the effects of N02 on SCR performance: 1) the effect on catalyst activity, 2) the effect on NH:/NOx stoichiometry, and 3) the preferential removal of either NO or N02 from the mixture. Figure 3 shows the overall effect of N02 on SeR performance for a space velocity of 36,000 hr1 (stp). In this figure, NOx removal is shown as a function of the NH3/(NO + 1.33 N02) ratio, for varying mixtures of NO/NOx• The inlet ammonia has been normalized by NO + 1.33 N02, rather than NOx, to better reflect the actual overall stoichiometry. As can be seen in Figure 3, the NOx removal is increased by having N02 present. Further maximum NOx removals occur when the flue gas contains an equal molar amount of NO and N02 (Le., NO/NOx = 0.5), rather than NO or N02 alone. Similar behavior is seen at other space velocities, although the magnitude of the effect decreases as the space velocity decreases. The effect on NH3 slip is shown in Figure 4 for a NO/NOx ratio of 0.5 and space velocity of 36,000 hr-1. In Figure 4, NOx removal and NH3 slip have been plotted as a function of the NH3/NOX ratio. Since the stoichiometric NH3 requirement is higher for the NO/NOx mixture, a given NH3/NOx ratio in Figure 4 represents a lower stoichiometry for the N02"NOx mixture than for NO alone. Again, the effect is clearly seen; for a given amount |