OCR Text |
Show The modification allows flame radiation monitoring directly through the N G injector while the flow of N G over the optical surface provides both cooling and cleaning. At the rear of the enclosure a fiber optic cable is attached to transport the collected flame radiation to a detection system. For the work presented here a PC spectrometer board that covers the UV-visible wavelength range of 250-800 n m was used with a spectral resolution of 3 n m for a 100 u.m fiber optic. The advantage of using the spectrometer system over simpler conventional detection systems, e.g., photodiode or photomultiplier, is that the spectrometer provides information on spectral features over a large wavelength range. These spectral features can be process dependent, thus the spectrometer allows the user to identify which features provide important information applicable for monitoring and/or process control. Using the configuration shown in FIG. 3, an example spectra obtained from Air Liquide's combustion facility in Countryside, IL is shown in Fig. 4. In this example, the oxy-fuel (fuel=natural gas (NG)) burner operated at 1.7 MMBtu/hr and was mounted in a fully instrumented 4 m J pilot furnace. The pilot furnace is rated for 2.0 MMBtu/hr and temperatures up to 2900 °F. From the raw spectrum shown in Fig. 4 the major peaks 4000 tt 3500 c * 3000 £ 2500 290 1.7 MMBtu/hr A L G L A SS Background "NO FLAME" Na 390 490 590 Wavelength (nm) 690 790 Figure 4. Typical oxy-fiiel flame emission spectrum collected through the N G injector for a 1.7 MMBtu/hr flame. 5 |