OCR Text |
Show Figures 3-5 show that NO is the major nitrogenous species in the gas at SR1=1.1 for oil and 30% nitrotoluene doped toluene. For 100% nitrotoluene the hydrogen cyanide and ammonia concentrations are at low levels ((SR1=1.1), 1-5 ppm). To generate Figures 3-5 the measurements of NH3 and HeN were carried out without staged air at a distance of 1.39 m from the top of the furnace with a stoichiometric ratio SRI from 0.5 to 1.1. NO measurements were carried out at the distance 3.365 m and staged air at 1.39 m. The results show that for all fuels the second stage NO decreased with decreasing first stage stoichiometry. HeN and NH3 concentrations increased dramatically when the first stage stoichiometry was reduced below 1.0 for the oil, 0.7 for the 30NT and 0.8 for the 100% nitro-toluene, respectively. Under extremely fuel rich conditions (SRI <0.6) the results show an increase in HeN formation while NH3 remained constant. '..". o • o .1. ~~----------------------~ e 30HT • lOON .~--~~~-=~~~~~-J Total fixed nitrogen (TFN) measured at the exit of the fuel-rich zone as a function of stoichiometric ratio is presented for oil in Figure 3 and for the 30% nitrotoluene doped toluene and 100% nitrotoluene in Figure 6. All fuels investigated showed similar trends. TFN reached ·a minimum concentration at approximately .... 0.8 SRI 1.0 1.2 SRI=0.9, and then increased significantly as the primary zone became more fuel rich. Total fuel nitrogen conversionin second stage Exhaust NO emissions in a staged combustor result from conversion of TFN exiting the first stage (XNi) and any thermal NO production during burnout. Figure 7 shows minimum exhaust NO and associated TFN as a function of total fuel nitrogen content for the liquid fuels. In general, the minimum exhaust NO concentration occurred at SRI <0.8. Under these optimum staged conditions, NO emissions (and TFN) correlate well with total fuel nitrogen content, but the slope is significantly less compared to excess air conditions (Figure 7b). Figure 8 shows the percent of the TFN exiting the first 5 Figure 6.The effect of fuel type. 10000 E a. .e l1OOO 0 z E a) :) E 6000 C -zE• coo )( 2000 0 2 .. I fuel N coo e bp. SRI~ .7 3000 • bp. SRO-I E a. b) ~ 0 2000 z lOGO 0 0 2 .. 6 I fuel H 8 Figure 7. The effect of fuel nitrogen. 10 10 |