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Show ~ ~ Information about the nitrogen contents of the coal (%Nc), char (%NCh) and volatile matter (%NVM) are also presented in Table 2. The %Nc and %NCh values were measured and the %NVM value was calculated. Most of the coals have similar absolute values for all the nitrogen contents. For example, %Nc is 1.7% for four of the coals. The exceptions are Peak Downs with high nitrogen values and Coal Valley and Rhein Braun coals with relatively low values. If the distribution of the nitrogen is viewed, it can be seen that the nitrogen preferentially exists in the volatile fraction. The ratio of %NVM/%Nch varied from 1.2 to 1.7 with the exception of Rhein Braun coal with a value of 0.7. As with the other analyses, although trends can be identified, the results are not predictable from simple proximate and ultimate analyses. In the trials, data was gained on NOx emissions for both the externally and aerodynamically air staged burners (EASB, AASB) [1, 2, 4, 20-22]. In order to understand the data, it is best to begin by considering the unstaged flames. In the unstaged flames the coals are mixed rapidly with enough air for complete combustion (in this study A = 1.15). Under these conditions the maximum generation of NOx occurs. This mixing is rapid and combustion occurs under fuel lean conditions for all coals. Under these conditions, the effect of coal quality is easily identified. Table 3, listed below, contains the data from the unstaged flames. (All NOx data in this report is quoted at 0% 02 . ) As can be seen, the data from the two burners is somewhat different with the AASB having higher unstaged NOx values Table 3: Unstaged NOx Emissions "'- Coal NOe/ VMIPfR %NVM EASB PfP" 07001/ Peak Downs 450 34 2.4 Heinrich Roberts 390 44 2.2 Elk Creek 700 62 1.8 Scotts Branch 825 64 2.0 AASB ~ ' ~ Hugo 520 39 2.2 oJ Heinrich Roberts 790 44 2.2 ;~ Scotts Branch 940 " Coal Valley 940 Rhein Braun 960 64 83 91 ,, 1.7 1.0 0.8 7 |
