| OCR Text |
Show -8- Figure 10 plots NOx versus LOI for the OFA tests. This figure illustrates the tradeoffs made when using OFA. At loads of 155 MWand 115 MW, increases in OFA resulted in reduced NOx emissions and a corresponding increase in LOI levels. At minimum load, LOI levels increased with increasing NOx emissions. This occurs because LOI levels at 75 MW decreased with increasing OFA, as discussed previously. These data can be used to estimate ash carbon levels for a given NOx emissions level for the coal used during the test program. For example, if it was desired to maintain NOx emissions at 0.5 Ib/MMBtu, the corresponding full load LOI levels would be about 380/0. This correlation will be useful in assessing cost tradeoffs in using either increased OFA or urea flow to achieve NOx compliance. SNCR TEST RESULTS Parametric testing of the SNCR system installed on Salem Harbor Unit 3 included evaluation of the following process parameters: • I njector Location • Reagent Flow Rate/Distribution • Dilution Water Flow Rate • Atomization Pressure At the completion of the parametric testing, SNCR system operation was characterized at each of the load points tested. Both pre- and post-LNB/OFA retrofit tests were performed. Throughout this paper, SNCR performance is plotted as a function of Normalized Stoichiometric Ratio (NSR). The NSR is defined as follows: NSR = moles N injected moles initial NOx NSR is used so that the effect of urea flow, taken at different operating conditions, can be compared on a normalized (Le., non-dimensional) basis. Data are presented for a low-sulfur South American coal, which was the coal burned during the post-retrofit SNCR testing. |
