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Show - 8 - Comparison of the measured NOx levels in the flue gas and the equilibrium NOx calculated based on the flue gas conditions confirmed the observed phenomena. For cases wi th gas injection velocities of 225 mis, the measured NOx emissions were up to 40% above the flue gas equilibrium values for the 20/12 and 12/1 2 configuration whilst for the 20/20 configuration the NOx levels were up to 30% below the flue gas equilibrium values at 225 m/s. At gas injection velocities of 75 and 125 rn/s the measured NOx levels for the 20/12 and 12/12 burners varied from 60 to 100% of the equilibrium value . For the 20/20 configuration NOx levels varying from 30 to 80% of the equilibrium value were measured. From these equilibrium considerations it can be concluded that the proximity of the flue NOx values to equilibrium is controlled predominantly by burner configurations and input condi tions. Furthermore, the flue NO levels are weakly affected by the post flame region below 1550°C due to the rela tively 10r 9 NO formation time scales at these temperatures (> 10 s) [3,7 ]. Other NOx reduction strategies Various other NOx reduction strategies were studied [2, 3J. Water in jec tion resulted in 25 to 75% NOx reduction and efficiency reductions of up to 10%. Fuel cracking did not show the expected effect on NOx level, because the amount of fuel cracked was not sufficient to significantly increase the flame emissivity . Thermal input reductions show a significant decreas e in l Ox e mis sions and an increase in efficiency, but this technique 1.S considered impractical due to production losses. rozzle type affects mixing and NOx; different nozzles res ultec in NOx levels va r ying from 1300-2100 ppm, with annular gas injec tio~ nozzles having the best NOx and efficiency performance. Spl:. ... fla m e no z z 1 e s showed hi g her NOx em iss ion s due tot he hi g h e::- 1. r. fla me temperatures as a result of reduced heat l osses fro. th e closely positioned gas jets. CONCLUSIONS A full scale glass melting furnace was successfull y simulat d a the semi-industrial scale. A wide variet y of operat1.ona..l. parameters were studied. Some paramete rs, such as air preheat a nd excess air, gave predictable trends, but quant itative inform 1.0 I was generated which is applicable to full-scal e glass furnaces . K number of other parameters gave promising results . In part culal, factors affecting mixing could be optimized to give low NOx and high efficiency. Full scale applicat1.on of t hes t chniques should be possible with acceptable fu r nace mod ' fical1.ons In addition to a wide variety of flames studied by npul /outpu analysis, detailed in-flame meas uremen s and a theoretica l analysis were used to interpret the data. The comb1.natio. of measurements and theory provide a r liable expla ation 0 .... t:' observed trends in NOx and furnace efficiency . These tools shou c |
