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Show where k = Fent = me = mj = L = = Pe = = correlation factor entrainment mass flow rate jet mass flow rate (may include diluent) distance traveled by fuel before intersecting main burner combustion products jet orifice diameter density of entrained flow density of jet flow For purposes of our work, the term, (pJPj) 112 , was assumed to remain constant. The other assumption was that the main burner flow diverged 10 degrees. Any interactions between jets were also ignored (i.e., jets entraining nearby jets). When the data in Figure 9 are plotted as a function of the entrainment factor, a clear trend is shown in Figure 11. Figure 11 shows that the higher the entrainment factor the lower the NOx emissions. Thus the best way to reduce NOx emissions in the second stage (the primary burner is already very low in NOx emissions) is to use the fuel jets to entrain furnace gases. Figure 12 takes into account the difference in furnace temperature by dividing NOx emissions by the absolute furnace temperature and plotting it as a function of the entrainment factor. When this is done the data corresponding to different boiler capacities fall on the same curve. 4. SUMMARY OF RESULTS After evaluating competing NOx reduction strategies and reviewing the available low NOx products on the market, Alzeta selected fuel staging as the best approach for meeting the stated technical and cost targets. Technical targets were sub-9 ppm NOx and sub-50 ppm CO when operating at 3% stack O2. Recognizing that fuel staging alone may not be sufficient in all applications to achieve sub-9 ppm NOx emissions, alternate NOx reduction strategies were also investigated. In order of preference, the strategies investigated were: 12 |
