OCR Text |
Show conditions of the FD I burners tested in the study. Along with the velocity of gas and oxygen, the peD (pitch circle diameter) between the two oxygen nozzles was widely varied, which reportedly has a large influence on NOx emission for high temperature preheated air combustion. Test facility Figure 3 shows the experimental furnace used in the study. The furnace was refractory lined with its inner dimension of 1500 x 1500 x 3600 mm. A test oxy-fuel burner was mounted in the center of the furnace front wall. An auxiliary air-fuel burner was mounted above the oxy-fuel burner to heat up the furnace before the oxy-fuel flame was started. The furnace was equipped with six refractory-lined water-cooled heat sinks to simulate the furnace load. The furnace had inspection holes in the center of the load simulators. The inspection holes were used to mount water-cooled IFRF ellipsoidal radiometers to measure total hemispherical radiative heat flux into the furnace load. For safety reasons the furnace was equipped with a UV flame detector (Yamatake-Honeywell), which was cooled by injecting a known flow rate of CO2 gas instead of fresh air normally used. Use of CO2 gas prevented unnecessary N2 from entering into the furnace. Likewise, the furnace pressure was maintained positive at around +10 Pa to prevent the ambient air from leaking into the furnace. The experiment fired typical natural gas supplied in Japan. Table 3 shows the composition of the natural gas. Since it is produced from LNG (liquefied natur al gas), the natural gas contains virtually no molecule nitrogen. Vaporized liquefied, and thus pure, oxygen was used as the oxidant. The oxygen had no molecule nitrogen either. The exhaust gas was sampled at the exit of the furnace and analyzed aft.er removing the water vapor with a gas cooling unit. The dry exhaust gas was analyzed by Shimadzu URA-I07 (CO, CO2), MAG-6000A (02) and CLM- 107 (NO). The exhaust gas temperature was measured by a suction pyrometer with a type-R thermocouple (PtIPt-13%) developed by IFRF. Total radiative flux was measured by an ellipsoidal radiometer developed by IFRF as shown in Fig. 4. Total radiative flux was measured at six |