| OCR Text |
Show Tge .results under these conditions, which might be considered to be a type of burner failure, indicate that significant emissions begin to appear near stoichiometric operation and that they increase dramatically between -10 and -25% excess air. Note that in the figures some of the data for -25% excess air has a scale change of one to three orders of magnitude due to the jump in emission and that benzene replaces toluene as the dominant emission (with benzene/toluene ratios reaching order 100: 1). Also note that for each species increasing the hydrogen content of the fuel (balanced with propane) causes an increase in VOC emission. Variability in the emission levels was investigated in the region where they fust to begin to appear in significant quantities (0 and -10% excess air) for RFG3 fuel. The results (listed in Fig. 12 Table VI) are depicted in Fig. 12. These data are from tests conducted on different days as part Table V1 of different testing sequences. For species above the detection limit (benzene and toluene), variations of a factor of three were observed. For species at the detection limit, the results are more erratic with o-xylene showing variations of an order of magnitude « 0.5 to 5 ppbv). 3 Failure Modes In order to further investigate the idea that the level of emissions observed in field data might result from a lack of control or failure of the burner to operate properly, two additional tests were conducted. In the first, one of the fuel tips was plugged, resulting in an unbalanced flame in one of the three merged flame jets. In the second, this same tip was unplugged and redirected so that its fuel (116 of the total) was directed radially outward from the burner. As can be imagined, both failure mode tests resulted in a distorted flame structure that might be presumed to form toxics. Table vn shows the results for these tests, conducted. with 25% excess· air and RFG6 fuel. Although detectable emissions of benzene, toluene, and the xylenes resulted from these failures, none was present in excess of 3 ppbv. CONCLUSIONS Various compositions of blended fuel gas, assumed to be representative of that used in refineries, were burned in an industrial-style, but well-controlled, research burner. Variations in flame - 10- Table VII |
