OCR Text |
Show 4 the condition of constant gas turbine exhaust quantity, flame temerature gets lower and easy to generate CO at approx. T.D.R 1:4 when the burner load decreased. This tendency is more conspicuous at the gas nozzle angle of 90° than 80°. As we can decrease CO by discharging exhaust gas at low burner load, we have made a standard gas nozzle with the angle of 90° and 6 holes. 3-3 Burner Specifications The burner specifications which are decided by the elementary experiment is summarized in table 2. When composition of the gas turbine exhaust is made under 4,000 Nm3/H (wet) of gas quantity and 500° and 15% (dry) of 02' we have obtained stable firing from 2,300 kW to 850 kW of firing rate. Then, remaining 02 became lower than 3% (dry) at the maximum combustion, and the NOx emission was lower than 50 ppm. 4. Applied Experiment Result and Discussion The firing is stably done under the condition for the experimented gas turbine exhaust with temperature 350° - 600° and 14% - 17% (dry) of 02' at wide firing rate of 2,800 kW - 350 kW. At the maximum firing rate of 2,800 kW, remaining 02 is until 3% (dry) or below. However, the flame lifts off with gas turbine exhaust of 500°C and 13% (dry) of °2 , and we can say that the firing range is more than 14% (dry) of 02 at 500°C. The Burner exhaust pressur difference is 86 mmH20. 4-1 NOx Emission In Fig. 9 and 10, NOx emission for each firing rate in case of various gas turbine exhaust conditions is shown. Wi th regard to any exhaust gas condition, maximum NOx emission is obtained when firing rate is 2,100 kW or 1,400 kW. In this condition, when the firing rate decreases flame temperature becomes lower and NOx emission decreases. But NOx emission increases as remaining 02 increases with a decrease of firing rate. Its thought that NOx emission is maximum at 2,100 - 1,400 kW of the firing rate by effect of flame temperature and remaining 02. When the exhaust gas temperature or 02 concentration increases, NOx emission increases. We found that influence on NOx emission by 100°C rise of the exhaust gas is almost the same as that by 1% increase of the exhaust gas 02. NOx emission as most likely gas turbine exhaust condition at present, at 500°C and 15% of 02' is less than 50 ppm (02 = 0%) and is the same level as at 350° and 16 - 17% of 02. In Fig. 11, shows influence of H20 content of exhaust gas on NOx emission. The gas turbine is normally added with steam or water for NOx reduction. The quantity is shown as ratio of water or stearn quantity = W (kg) to gas turbine fuel gas weight = Fe (kg); W/Ft. Normally, operation is done with WIFe = 0.8 and NOx of gas turbine exhaust gas is about 100 ppm (02 = 0%). Maximum input figure is W/Ft = 1.3. When additive H20 quantity is W/Ft = 0.8, the NOx emission of the supplimentary burner decrease 17 - 24% as compared with W/Ft =0. With W/Ft = 1.3, the NOx emission decreases 25 - 32~. However, inversely CO tends to increase even in the low firing rate. |