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Show IFRF Doc N o K 70/y/113 IJmuiden, April 1997 -5 AFRC Spring meeting 1997 Pure Coal Bunker Pure Coal Bunker Loss in weight feeder Coal Transport line Compressed Air Coal Transport line Figure 2.3. Fuel setup for firing blends 3. RESULTS 3.1 Internally Fuel Staged Burner Baseline flue gas emissions for typeH (unstaged) and type I (staged) flames with El Cerejon coal at swirl numbers (So') of 1.4, 1.0 and 0.5 are given below. Type II flames were created with the coal gun in the throat of the quarl and the type I flames by axially inserting the coal gun 95 cm into the quarl. o2% NOx [ppm @ 3 % 02] CO ppm co2 % Type LI [So' 1.4] avg 3.04 avg 869 avg 4 avg 16 Typell [So' 1.0] avg 3.07 avg 793 avg 4 avg 16 Type II [So' 0.5] 3.07 742 4 16 Type I [So' 1.0] 2.91 403 5 16 Type I [So' 0.5] 2.95 383 12 16 The results are consistent with previous findings [12] in that N O x levels decrease by ~ 17 % when the swirl number is reduced for both flame types. 3.1.1 El Cerejon as primary fuel and Natural Gas as reburn fuel Effect of primary stoichiometry on N O x The data shown in Figure 3.1 shows the effect of the secondary and tertiary air velocity as well as the velocity and injection direction of the reburn fuel. The maximum reduction in N O x is shown to occur at a primary stoichiometry of-0.65 with the reburn fuel injected at low velocity and in an axial direction. In general, NOx levels were lower than those of the baseline type I flame with a swirl number of 1, and can only be related to the interaction of C H radicals (from the reburn fuel) with primary N O from the primary fuel. This interaction has been shown to be effective in the first step of the reburning mechanism as a means of reducing N O x. One observation that can be made is that there is insufficient residence time for the reburning |