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Show i ......... No!. Gos/02 No!. Gas/Air o A • G 0.03 0 B • H 6 C v 0 o E • f' CJ) 0.02 o· z ii: ..... 0.0' - ~ I .... Q .... ,-- -- .... 70 'U E Q. 60 Q. ~ 50 'U N o 40 .~" 10 ~:;~ --- - 0.00 ......-..- y-~.." " ".~.: .. ..:. .::...~....:-..1-.........~-L.........~--'--~.....J 0 o 20 .0 60 80 1 00 N2 , 7. vol. (wet) Fig. 8. NOx emissions for a variety of burner arrangements in which both the fuel and oxidant emanated from the front face of the furnace. Both natural gas/oxygen and natural gas/air cases are shown. No!. Gos/02 o A 0.03 0 B ~. 0.02 z ii: 0.01 6 C v 0 Not. Gas/AIr • E • r 40 60 N2 , 7. vo l. (wet) I I I o I 80 70 60 50 40 30 20 10 o 100 'U E Q. Q. ~ 'U ON ~ ." @ a- .C.D ~ . 0 z Fig. 9. NOx emissions as a function of furnace nitrogen content for a variety of burner configurations in which the fuel and oxid,-,nt were injected from opposite ends of the furnace. Both natural gas/oxygen and natural gas/air cases are shown. 55%, the NOx is lower than 5.10-3 g/MJ (10 ppmd air equiv. @ 3% O2 dry). The dependence of NOx emissions on furnace nitrogen content is linear up to nitrogen concentrations of 55 %. Interestingly, the NOx levels for all of the co-frring burner arrangements are similar for a given furnace nitrogen content, including the natural gas/air cases. In general, the CO emissions were low, typically less than 35 ppmd. However, for a few of the co-frring burner arrangements, CO excursions (detected at the furnace flue) up to approximately 200 ppmd occurred in a periodic manner. Hence, the location of the fuel and oxidant injection points relative to the furnace flue location, and, in general, the mixing pattern within the furnace must be designed properly for commercial installations. Opposed-Firing Burner Arrangement A series of tests were conducted for burner arrangements in which the fuel and oxidant were introduced into the furnace from opposite ends of the furnace. The operational conditions of these tests were quite similar to those of the co-frring burner arrangements. The furnace wall temperature was held constant at 1371 K (2008°F), the oxygen concentration at the flue was typically between 2-3 % vol. wet and, again, the frring rate was 185 kW . The power emissions index, PINox, is plotted as a function of burner arrangement (opposed-frring) and furnace nitrogen content in Fig. 9. Natural gas and oxygen were the reactants for four of the cases, while natural gas and air were the reactants for two of the cases. In general, the NOx emission characteristics for the natural gas/oxygen combinations were similar. NOx emissions below 8.10-3 g/MJ ( -15 ppmd air equiv. @ 3 % O2 dry) were observed for furnace nitrogen concentrations below 55 % . Relatively low NOx readings were obtained for 12 |
