| OCR Text |
Show N O , Emissions Test Results Initial testing of the 6 MMBtu/hr VIStA Burner, focused on characterizing the baseline first stage emissions, turndown, and combustion stability, has been completed. During this testing, second stage emissions were also determined but no attempt was made to optimize the second stage operation. Figure 6 shows the first stage N O emissions versus first stage stoichiometry for a range of thermal inputs. In general, N O levels were approximately 5 ppmv with a first stage stoichiometry of 0.6 and were relatively flat at approximately 2 ppmv below a 0.55 stoichiometry. 40 35 30 E Q. B 25 <2 20 w 15 10 x 4.3 MMBtu/hr + 3.2 x 6.00 -•-4.95 -o-5.13 -*-4.2 -•-3.14 -•-2.45 •- _ • * • •x '-"* ^ , -/S"P» r L 0.40 0.45 0.50 055 0.60 0 65 0.70 First Stage Stoichiometry 0.75 0.80 0.85 0 90 Wfitcfc Figure 6. First Stage N O Levels at Various Thermal Inputs At first stage stoichiometrics of between 0.5 and 0.6, the overall N O x emissions were between 25 to 40 ppmv (at 3 % 02) as shown in Figure 7. Although higher than the design goal, the results are encouraging based on the fact that second stage optimization has not been conducted during this first round of testing. The second stage carbon monoxide emissions shown in Figure 8 ranged from 2 to 25 ppmv, well below the design goal of 50 ppmv. Visual observations of the second stage flame indicated that mixing between the secondary air and first stage exit gases were circumferentially very uniform, but more rapid than desired. To reduce the intensity of the second stage mixing in future designs, the secondary air flow will be directed away from the first stage exit nozzle and a swirl component added. This should improve second stage flue gas recirculation, resulting in lower peak secondary zone flame temperatures and associated N O x levels. This was verified by making temporary modifications to introduce the secondary air further downstream of the nozzle, resulting in N O x levels of less than 15 ppmv. However, C O levels were excessive due to non-uniform mixing. 8 |
