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Show Table I: N O x Testing Results Boiler A B C D E F Boiler (lb/hr stm) 90 120 85 100 100 100 Capacity (MBtu/hr) 108 145 100 115 115 115 Boiler Type field erected field erected package field erected field erected package Burner Equipment 2 burners 1 burner 1 burner (530°F air) 1 burner 2 burners 1 burner %Nin Fuel 0.45 0.35 0.49 0.34 0.45-0.53 0.45-0.53 N Ox Original 0.266 0.369 0.35 0.460 0.312 0.360 Results Low N Ox 0.202 0.277 0.32 0.360 0.270 0.360 N Ox Reduction 24% 25% 9% 22% 13% 0% Residual oil contains a significant amount of fuel bound nitrogen which can contribute more than 5 0 % of the total N O x emissions. L o w N O x residual oil techniques require the reduction of the conversion of fuel bound nitrogen to N O x in addition to thermal N O x . Figure 2 illustrates the great potential for fuel bound N O x generation and the typical effects of F B N on N O x emissions.1 Previous research has shown that rich-lean spray staging has great potential for reducing fuel N O x production from residual oil flames.2'3 The greatest limiting factor to rich-lean staging in residual oil spray flames is the generation of particulate matter. A s the oil droplet vaporizes in the furnace, a hollow cenosphere of carbonaceous material is formed whose diameter and mass are dependent upon the original oil droplet diameter and the quantity of coke forming carbon in the original fuel.4,5 Any successful low N O x atomizer must meet current particulate requirements. B y using the Coke Formation Index (CFI) relationship, the expectant coke particle diameter can be calculated from the original droplet diameter as shown in Figure 3. The oxidation of these particles is based on surface combustion of carbon and the expected burnout for various particle sizes at typical furnace oxygen and temperature conditions is shown in Figure 4. Finally, Figure 5 illustrates that the smaller droplets generate small coke particles which have sufficient residence time to oxidize completely. This figure also demonstrates that the dominant particulate emissions arise from the large original droplet sizes. This analysis demonstrates that attempts to produce fuel rich zones of combustion with large droplet diameters results in increased particulate emissions. RESULTS Boiler emissions testing initiates with an inspection of the existing boiler and burner equipment to determine if any repairs are required. A set of baseline emissions data are obtained to determine the "as found" emissions of the boiler. The original equipment is then optimized to reduce burner excess air levels and obtain the best N O x and C O performance. These optimized data are then used as the baseline for comparison with n e w low N O x atomizer caps. Several low N O x atomizer caps are then test fired to determine their performance. The most promising cap is then optimized |
