American Flame Research Committee

Page 13

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Title Low Emission Burner Techniques
Creator Martin, Dr. Richard T.; Deller, Jim Ph.D.
Publisher Digitized by J. Willard Marriott Library, University of Utah
Date 1996
Spatial Coverage presented at Baltimore, Maryland
Abstract The reduction of NOx emissions from fired equipment has been driven by environmental regulations for over a quarter of a century. During that time period, various techniques have been developed to achieve the sometimes mandatory reductions. These techniques include the use of a variety of "low NOx" burner designs, staged combustion techniques, flue gas recirculation, and post treatment of the combustion products. Most, if not all of the burner designs and staged combustion techniques reduce the temperature of combustion which, in turn, decreases the thermal NOx. Flue gas recirculation adds mass to the combustion zone which suppresses the combustion temperature which reduces NOx emissions. The effect of steam injection into the combustion zone either mixed with the fuel or the combustion air on NOx reduction is well documented. The purpose of this paper is to discuss the use of certain "low combustion temperature fuels" to reduce thermal NOx formation. These fuels are usually by-products of plant processes that can, in addition to reducing the generated thermal NOx, provide greater operating flexibility by reducing the impact of excess air on NOx generation. Correlations are presented that characterize the reduction in thermal NOx emissions that result from the use of the low combustion temperature fuels. Additional correlations and detailed discussion are presented that provide insight on the effect of excess air in combination with these fuels.
Type Text
Format application/pdf
Language eng
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ARK ark:/87278/s6vx0k3z
Setname uu_afrc
ID 11770
Reference URL https://collections.lib.utah.edu/ark:/87278/s6vx0k3z

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Title Page 13
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OCR Text effect of LHV off gas increases with the increase in excess air levels. In these circumstances, the quantity of fuel entering the flame is greater and the mixing of the fuel and air less rapid on a proportional basis. Increasing the excess air levels will therefore increase the combustion intensity and the propensity for NOx formation. In this case the introduction of LHV off gas is the sole NOx controlling technique and demonstrates greater effect as the excess air is increased. IX. Discussion Further manipulation of the results for which the reduction in NOx emissions achieved by the use of LHV off gas fuel are simply interpreted as a reduction in NOx emissions by a flame temperature controlling technique, while not intended to be used for prediction purposes, provides some interesting observations. If the horizontal axis of Figure 14 were replaced by a generic scale of fraction of base line NOx remaining after implementation of the primary NOx controlling technique, for example, the use of flue gas recirculation or steam injection, then the relative effects of varying excess air levels on the reduced NOx emissions may be calculated; Figure 15. Given the relationship demonstrated in Figure 15, it may also be conceivable to relate the relative effect of varying flame stoichiometry on NOx emissions to reduction in adiabatic or measured flame temperature from a baseline case, Figure 16. The validity of these correlations in this latter form; however, are questionable, particularly due to the varying effectiveness of introducing inert species to the flame by different methods as discussed in section VI (flex - inspirated RFG) where reductions in theoretical adiabatic flame temperature due to inspirated furnace gases were assumed to be a less effective than when achieved by the inclusion of inert gaseous components in the fuel gas; and for variations in burner design or heat release where flame structural differences greatly effect the NOx emissions but will not effect the theoretical adiabatic flame temperature. 13
Setname uu_afrc
ID 11755
Reference URL https://collections.lib.utah.edu/ark:/87278/s6vx0k3z/11755