OCR Text |
Show b~amc possible to further reduce the natural gas support fuel from 8.6 MMBtulhr to 4 MMBtulhr. To further investigate whether this minimum support fuel could provide reliable flame stability under constantly changing LFG compositions, additional tests were arried out by increasing the fraction of inert gas in the surrogate LPG. Increasing the inert gas causes the flammability limits to become narrower because it reduces the flammaDle gases availablea>. The test results indicated that the flame quality did not deteriorate with methane as low as 23 percent in the LFG. Unfortunately, it was not possible to produce a self-supporting LFG flame. Due to a tight project schedule, no further attempts were made to continue improving burner performance. Similu tests using No. 2 oil as support fuel were also conducted with burner Configuration C. The test results suggested that the No. 2 oil support flame should not be less than 9 MMBtu/hr. Table 4 summarizes the screening results of key operating conditions for the prototype burner testing. Configuration C proved to be the most promising burner configuration in achieving both excellent flame stability and acceptable flame characteristics. NOx emissions for this burner configuration are presented in Figures 6 and 7 for natural gas and No. 2 fuel oil as support fuel, respectively. The operating conditions for data presented in these figures were not fully optimized because of a tight testing schedule. The data presented are based on using about 25 percent FGR. As expected, the impact of boiler O2 on NOs emissions is relatively mild. For instance, using minimum natural gas support, NOs emissions increase was less than 6 ppm per each one percent increase in O2• In general, NOs emissions are less than 25 ppm (@ 3 % O2, dry) using natural gas as support fuel. The cWa also showed that NOs emissions tend to decrease as the amount of LFG increases when firing with No. 2 fuel oil. With the same amount of support fuel, NOs emissions increased from 24 ppm (@ 3 % 02, dry) at a total burner firing duty of SS MMBtuJhr to 36 ppm (@ 3 % O2, dry) when the total firing duty was reduced to 2S -15- |