OCR Text |
Show (5) under the 4l condition, in each flame there are all stages of gas burning (including emission generation) taking place independently of the same processes in the neighbor flame; (6) both flames are formed at the same excess 02=2.3% (this moderate number is based on the test results obtained on the operating boilers equipped with the Vanflame-2 burner); (7) since the C F G flame is a regular turbulent high temperature gas flame, it means that: (a) approximately 9 5 % of N O x consists of N O and only - 5 % is NO2, (b) practically all of the N O x reduction (~ 20%) achieved with EFGR induction in the Variflame-2 burner, only takes place in this flame; (8) based on well-known supporting literature data and our own experimental materials, it can be conditionally considered, that: (a) the comparatively cold stage gas injector diffusion flame has generated N O x consisting of 6 7 % N O and 3 3 % N O 2 (it is the worse case for N O x suppression, if N O portion gets increased N O x reduction will be risen), (b) though the major part of EFGR flow comes into the secondary air stream, there is a very small influence of EFGR on N O x reduction - no more than 1 % per 1% FGR; (9) as per stable test data at all above mentioned customer sites, the following critical test results have been taking into consideration: (a) there is no gas flame impingement at the furnace walls, (b) a burning out intensity of C O is much less than other ICP, that is why a conservative conclusion of the burning out completion percentage can be made, based on C O data only; (c) the optimal value of the ratio between C F G and injector gas flow rates is of 0.15:0.85, (d) at the boilers firing natural gas with ambient air, values of the EFGR relative flow rate and temperature are 6% and ~ 2,000 °F, respectively. The results of the approximate calculations performed for the Variflame-2 burner application with 84.8 M M B T U / h r heat input, firing natural gas with a mixture of ambient air and the mentioned 6 % internal F G R flow (that increases the mixture temperature from 80 to 189°F) in the furnace with BZFER = 168xl03 BTU/(sf x hr) at full load with 2.3% excess O2, are presented in Fig.2 to 9. The above conditions in the furnace have been providing an average flue gas temperature of -2,590 °F and accordingly a residence time value of - 0.49 s. It can be seen from the mentioned Figures that: 1. Though the ambient air temperature is only 80 °F and excess O2 concentration is comparatively low (<3%), the quasi pre-mixed flow of the C F G jets and the primary swirled air forms a high temperature flame ( T max > 3,020 °F without EFGR, Fig.2), providing actual completion of incomplete combustion products burning out of 9 9 % and 99.9% at a relative distance from the burner exit of < 2.5 and <4 burner diameters, respectively (Fig.3), and correspondingly generating a high level of N O concentration (~ 100 ppm, Fig.2) and a typical moderate C O concentration ( <100 ppm, Fig.3). 2. Fig.2 shows a N O leap increasing in the C F G flame at a temperature zone of 29Q0 to 3020 °F ( the average value is ~ 2,960 °F) located at a relative distance of 2 to 3 3 |