Investigation Into Fuel Tracking And Ignition Characteristics With Flame Monitors

Flame monitor is the important equipment to detect combustion conditions in real time in the boiler of the power plant. It is the essential of the furnace safeguard supervisory system. This research is based on the flame of fuel obtained from a self-made flame monitor. According to the characteristics of the fuel flame and the structure of an experiment system, the flame flicker frequency is calculated based on power spectrum density, empirical mode decomposition and extreme value method respectively. A new method to judge ignition behaviors of coals is put forward based on the flame monitor and the drop tube furnace. At last, the ignition behavior is analysed and evaluated from ignition temperature, max ignition point and ignition index.The full content of this research and innovation is as follows:1. The flame flicker frequency is one of the most important parameters to optimize the control of the boiler in site in power plant. The accuracy of this parameter will contribute to the accuracy control of boiler shutdown control. The flame flicker frequency is calculated based on power spectrum density, empirical mode decomposition and extreme value method respectively. These methods have greater flexibility than the calculation of flame flicker frequency in hardware circuit.2. Different features are extracted from the time and frequency domains from the flame signal. Comparing the data of biomass and coal on a laboratory-scale combustion test rig in four bands, the features with larger difference among the biomass and coals are as the inputs of fuzzy logic inference system. The system combined the typical features together and infered the type of fuel being burnt. Based on the same principle, the single coals and blended coals are tracing from the data obtained in the drop tube furnace. The single coal are inferred from the DC components of four observing windows, while the blended coals from the DC components of two observing windows and flame flicker frequency of three observing windows.3. The ignition behavior obtained from TGA analysis has larger difference with actual combustion conditions of the boiler, which can not reflect the real igniton behavior of coals. A new method of judging the ignition behaviors of pulverized coals and coal blends in a drop-tube furnace using a flame monitoring system is put forward. Characteristic parameters including oscillation frequency, fluctuation ratio and combustion dynamic energy were determined from the flame monitoring system and the structure of the drop tube furnace. The ignition behaviors of the coais are established respectively by combining the parameters results along the ignition section of the drop tube furnace. Results demonstrate that the parameters are suitable for distinguishing ignition behaviors from homogeneous, hetero-homogeneous to heterogeneous. The behaviors of 22 single coal and 2 kinds of blended coal are judged and the influence factors are also discussed.4. The ignition behavior is analysed and evalued from ignition temperature, max ignition point and ignition index. Ignition temperature has connection with the ignition behavior. The max ignition point reflects the ignition speed of max amplitude point. Integrate ignition index can direct compare the ignition behavior of coals according to three characteristic features.