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Show producing than a pure oxygen process. More, if we take into account an other advantage of the 100% 02 combustion, it means smaller fume volume, it comes that the NOx production could be 40 times graeter than preheating air, when expressing the NOx in mg per kY transfered to the melt. Ye also could remind here as it appears in table 1, that the pure oxygen process is fuel saving. Table 2 Air 600°C Air 1100 0C ~here P E ~t NO* R Comparison between preheated air and pure oxygen combustion in a glass melting furnace. P (kY) 1860 1200 1120 E .40 .62 .69 ~t (k~) 744 744 743 Burner power Combustion efficiency NO (ppm) 634 2150 227 Heat tranfered to the melt Vfumes (Nm 3 /Nm 3 de GN) 11.8 11.8 3.09 NO mass (mg) per kYh transfered to the melt ( PCI : 10.1 kYh/Nm3 ) Ratio NO*/NO*(100% 02) NO* R (mg/k~) 3740 8184 211 18 38 1 This table gives the more favourable comparison for the oxygen process. However we have to keep in mind that the model does not account for atmospheric air likeage and we all know that it could be a important source of NOx formation. This point will be studied in future work. This last comment must attenuate the huge difference showed in table 1, but does probably not affect the conclusion. These preliminary computed results, completed by experimental measurements on pilot and scale 1 furnaces, show that pure oxygen processes could become very attractive regarding the air pollution problem, especially for NOx emissions. Every body knows that future regulations are in preparation and that the BAT concept (Best Available technology) will be probably one of the driving tool to achieve low industrial atmospheric pollution. It means that, if proof is made of the interest of oxygen, a new BAT could be pure oxygen process and a new unit of emission could be the pollutant mass per kYh transfered to the charge. Obviously, this unit appears to be more relevant to -the actual and very sensitive problem of air pollution. V Conclusion The previous section pointed out the real interest of 100% 02 processes. But using pure 02, makes worried industrial partners most of the time for reasons such as reliability ( high wall temperature for instance ). That is why the process has to be very well controled. The second reason is that to get back all the advantages of the 100% 02 combustion, all the process parameters have to be perfectly mastered. For instance, NOx formation is very sensitive to atmospheric air leakage, combustion chamber pressure, or burner design. The |
