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Show 4197299444 CORP. HQ 489 P13 MAR 17 '94 12:12 into formation of additional NOx. The amount of additional NOx depends on many factors such as the temperature of gases entering the reburning zone, heating value or percentages of H2 and CO in flue gases, the zone 2 temperature and method of mixing the completion air and the flue gases. Effects of the first two factors can be incorporated in one parameter, identified as calculated adiabatic flame temperature. In Figure 9 change in NOx across zone 3, the reburn zone, are plotted as a function of calculated adiabatic flame temperature for two different air fuel ratios in the rich zone. It is apparent that the NOx values remain fairly low for the process conditions in which the adiabatic flame temperature is below 2800-F, especially for the original air fuel ratio of les5 than 6 to 1. The test results indicate that it is indeed possible to reduce the NOx levels to as low as 5 ppm in zone 1 while using combustion air preheat levels of 704·C (1300·F) and an air-fuel ratio af 5:1. NOx measurements in zone 3, where the flue gases are reburned, show concentrations of 15 ppm to 20 ppm NOx while maintaining zero values of H2 and CO. I P'IGURE 7: NO AND TEMPERATURE VS DISTANCE FROM BURNER O.5MM Btu/hr. 5.6 : 1 Air to Gas, 1283() F Preheat 50 r----~-.---------------------___, 3000 o Tem() c NO 40 jo-----------------------------i 2500 , --~-........ -.",,-------__ "' ....... _.I._- ___ ------""' .. ,..,..---- 30 ~-------~~-------------------~-~ 2000 ~ e ~ l ~ ---,.r...--~---- S ~ ~ 20 ~-------------~----------~-----~ 1500 ~ ------~ ....... ----- 10 r---------------------~-----------~ 1000 ____. " ........I .·.· .. ·.·-,._-----_.. _--'""·, ... _~·_VO· .. -------_ _ _ ,\ , \ ~.~~--------------------~ o ~------~------~-------~----~------~ sao , \ o 50 100 ISO 200 2S0 Inche$ from MlcroNOx burner |