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Show Direct Charged Aluminum Melter, Norway The furnace is a rectangular, tilting, 30 ton capacity, 10 ton/h melt rate, unit charged with 7 0 % extrusion scrap, 30 % ingot, having dimensions of 7.6 m wide, 5.2 m deep, and 2.4 m high, and is shown in Figure 14. Figure 14 It is fired with 2 pairs of regenerative burners, one pair mounted on each 5.2 m wall, with burners angled downwards to the bath surface at 15°. Each burner is fitted with two propane injectors for a capacity of 3.8 M W (13 x 106 Btu/h) per burner pair hot. The nominal furnace operating temperature is 1200 K and the specified N O x target was a generous 225 ppm. Actually achieved N O x is 55 ppm, with 51 ppm CO. Our furnace O E M customer provided us with some interesting comparative data from 3 similar furnaces, one cold air, one low-NOx recuperative (with 670 K preheated combustion air), and the subject LNI regenerative furnace (average. 1030 K preheated combustion air), which is quoted below (units converted) [Ref. 4]: "A summary of average values measured under about the same conditions, is stated below: Combustion Ambient Recuperative Regenerative T flue gas K 1183 1172 1189 NOx (ppmv @ 3%02) 66 143 55 CO (ppmv @ 3%02) 401 401 51 From this table it can be concluded that furnaces equipped with regenerative air burners produce the lowest levels of NOx and that ambient air burners produce about the same level. However, the energy efficiency of the ambient air burners is low. To compensate for this, the NOx emission is related to the energy necessary to melt one ton of aluminum. The results can be seen in the table below: |