Concurrent measurement of temperature and soot concentration of pulverized coal flames

• To develop a prototype optical instrumentation system capable of measuring the distributions and fluctuations of temperature and soot concentration of pulverised coal flames. • To evaluate the performance of the system on a 0.5MWth combustion test facility at Innogy plc over a range of combustion conditions. • To establish quantitative relationships between the flame temperature and soot concentration measured and the corresponding combustion input data, thermal output and emission levels. Accurate and reliable measurement of the temperature and soot concentration of a pulverised coal flame and their fluctuations provides important information for the in-depth understanding of combustion and pollutants formation processes, carbon-in-ash levels, deposition and corrosion problems. Such measurement would also provide useful data for the validation of mathematical models in relation to flames, furnaces and emissions. As a result of this project, a prototype instrumentation system for the concurrent measurement of flame temperature and soot concentration has been developed. The system operates on the principle of multi-wavelength pyrometry combined with digital imaging and image processing techniques. A monochromatic imaging system is used to visualise the flame field in the furnace. The flame light incipient on the optical sensor installed on the furnace wall is split into separate beams passing through narrow band-pass filters of different wavelengths before reaching the imaging device. The resulting digital images are processed to determine temperature distribution of the flame field. The soot concentration of the flame is represented using a parameter called KL factor, which is derived from the temperature measured. The operability and effectiveness of the system have been evaluated on an industrial-scale combustion test facility operated by Innogy plc. During the earlier stage of the project, extensive analytical and design work was directed to developing a prototype instrumentation system under a laboratory environment. A novel optical transmission and filtering system was designed to split the flame light into three identical beams and form instantaneous images on a single CCD camera. Dedicated computing algorithms were developed for the determination of the temperature and KL factor. Following the successful evaluation of the system on the laboratory combustion rig, the system was scaled up and then tested on the combustion test facility at Innogy plc. Results obtained have demonstrated that the system is capable of measuring two-dimensional distributions and fluctuations of flame temperature and soot concentration. The accuracy of the system was verified using a tungsten lamp as a standard reference source. The relative …