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Show IFRF Doc N o K 70/y/113 IJmuiden, April 1997 -8- A F R C Spring meeting 1997 competing effects between increasing volatile content which causes a progressively more reducing environment in the LRZ, and volatile-N which results in an effectively constant production of volatile-NOx. Introducing the Klein Kopje as rebum fuel with the Polish coal, also results in an increase in N O x compared to the condition where Polish coal is used as both primary and rebum fuel. The general observation, is that overall, emissions are lower for the staged conditions, and when the primary and rebum fuel is a high volatile content coal. Effect of primary stoichiometry on NOx In Figure 3.4, the effect of varying the primary stoichiometry on N O x is shown for the case with 3 0 % rebum fuel fraction. Varying the primary stoichiometry from 0.3 to 0.8 increases the N O x emission by approximately 20-50 ppmv dependent on the coals fired. Rff=30% : So' SA=1.1 : TA=0.56 800 600 3" 6 400 P -Q -°- ° -DQ--- 200 v <*<><* O - SJ. . Primary M D Klein Kopje O Klein Kopje A Polish V Polish O B Cerejon Rebum fuel Klein Kopje Poftsh Klein Kopje Polish Polish 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Primary stoichiometry (Xp) Figure 3.4 Effect of primary stoichiometry (A^,) on N O , 3.2 Fuel Staging with Municipal Sewage Sludge Fuel staging municipal sewage sludge with pulverised coal may give rise to operational difficulties in utility applications. The two main aspects are the relatively high fuel nitrogen content of the fuel making burner operation of extreme importance for reducing the potential for N O x formation, and extensive slagging and fouling which may occur due to the high ash content. Figure 3.5 shows the different injection methods for the unstaged type II (high NO^ and staged type I (low N O ^ flame. Type I flames were created by the injection of fuel through the centre of the burner or insertion of the fuel gun into the quarl. |
