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Show Measurement and Interpretation - 15 - of Flames Issued from a Generic Multi-Fuel Bumer "'N 700 0 0~ 600 C") ~ (/) 500 0 ca ..c 0 ~400 "C 0 Particulates I C') E 300 0 NO" Z C> .s 200 (/) c .Q (/) tIO ~ E 0 0 W 0 0 1) 20 0 0 30 40 Combustion Air Staging Ratio (%) IFRF-~ 0 0 50 Fig. 4.1. NOx and Particulate Emissions for Different Levels of Combustion Air Staging. 4.2.2. Natural Gas Rebuming. In-furnace rebuming was tested in addition to emission reduction strategies based on modifications to the burner head. For this study "classical" rebuming was applied with all the reburning conditions maintaining both a primary zone and global stoichiometry at an excess oxygen of 100/0. Natural gas was used as the reburn fuel with ambient temperature air injected as the tertiary oxidant source. Natural gas and combustion air were added with injectors positioned on the furnace centerline with radial injection normal to the primary flow. The natural gas and air were introduced from the west and east sides of the furnace, respectively, using specially designed injectors. Rebum Fuel Fraction. Fig. 4.2 shows the results of natural gas reburning at three, 0, 10 and 20%, rebum fuel fractions. The reburn fuel fraction is defined here as the ratio of thermal input from the reburn fuel to the primary fuel source (i.e., 200/0 reburn fuel fraction for a 2.0 MW oil flame results in 400 kW thermal input from natural gas as the rebum fuel). The rebum fuel was injected at 2.40 m from the quarl outlet and the tertiary air at 1.80 m. A reburn fuel fraction of 20% resulted in an emissions reduction of 29%. |