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Show It is fired with 2 pairs of regenerative burners, one pair mounted on each 17' wall, with burners angled downwards to the bath surface at 15 degrees. Each burner is fitted with two propane injectors for a capacity of 13 M M Btu/h per burner pair hot. The nominal furnace operating temperature is 1700F and the specified NOx target was a generous 225 ppmv ( @ 3 % 02). Actually achieved NOx is 55 ppmv, with 51 ppmv CO. Our furnace OEM customer provided us with some interesting comparative data from 3 similar furnaces, one cold air, one low-NOx recuperative (with 750F preheated combustion air), and the subject LNI regenerative furnace (average. 1400F 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 F 1670 1650 1680 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: Combustion Ambient Recuperative Regenerative Energy consumption M M Btu/t 2.61 2.09 1.67 NOx (ppmv @ 3% 02 / Ib/MM Btu) 66/0.08 143/0.172 55/0.067 NOx (Ib/tAI melted) 0.2 0.36 0.11 The regenerative burner system produces the least amount of NOx per ton of molten aluminum". 19 |