OCR Text |
Show industrial scale test furnace. They are a generic, FDI and FDI flat flame burners. The emphasis is put on the radiative heat flux characteristics and N O x emission. The effect of nitrogen content in the fuel and oxidant was also examined. From the knowledge gained in this study, an innovative FDI flat flame oxy-fuel burner has been developed which generates high radiative heat flux along with low N O x emission. 2. TEST BURNERS 2.1 Generic oxy-fuel burner Figure 1 shows a generic oxy-natural gas burner tested in the study. The burner consisted of an annular oxygen injector with a single-hole gas nozzle in the center. Velocity of natural gas and that of oxygen were maintained identical and relatively low to allow slow mixing between natural gas and oxygen, creating a long and lazy flame. Velocity of natural gas and oxygen, V, was varied for parametric study. 2.2 FDI oxy-fuel burner Figure 2 shows the FDI (Fuel Direct Injection) oxy-natural gas burner tested in the study. The FDI burner(15) has already been commercialized for ultra-low N O x emission for high temperature preheated air combustion. The oxy-natural gas version of the FDI burner has a natural gas nozzle in the center with two parallel oxygen nozzles located at the upper and lower positions of the natural gas nozzle. Natural gas and oxygen are directly and separately injected into the furnace at high velocity. Injected natural gas and oxygen entrain substantial amount of combustion products, creating an enhanced effect of self-induced E G R (exhaust gas recirculation). Since the self-induced E G R effect reduces peak flame temperature, N O x emission is reported to decrease drastically.(6) Velocity of natural gas and oxygen, V, and the P C D (pitch circle diameter) of the two oxygen nozzles, L, were varied, which showed great influence on N O x emission. 2.3 FDI flat flame oxy-fuel burner Figure 3 shows the FDI (Fuel Direct Injection) flat flame oxy-natural gas burner tested in the study. This burner was designed to generate high radiation with low N O x emission. The FDI flat flame burner has a natural gas nozzle in the center with two oxygen nozzles inclined toward the axis of the natural gas nozzle. Like the original FDI burner, injected natural gas and oxygen entrain substantial amount of combustion products, creating an enhanced effect of self-induced E G R (exhaust gas recirculation). The self-induced E GR effect reduces peak flame temperature leading to substantial reduction of N O x emission. Injected natural gas and oxygen collide at a point on the horizontal plane of the natural gas 2 |