Optimizing Control Of Boiler Super-heater Steam Temperature Based On Inducing Radiant Energy Signal

The boiler main steam temperature control system in large-scale coal-fired power plant plays a key role in improving the economic efficiency and ensuring the safety of the unit operation. The main steam temperature can be seen as the controlled object of multicapacity distribution parameters, in which the over high temperature of flue gas is the main reason for overheating of the superheated steam. The dynamic test of steam temperature and the analysis on power plant operation show that the superheated steam temperature delays little under the flue gas disturbances, while delays great under the disturbances caused by the spray water quantity. This characteristic will make the control of the overheating steam delayed, and induce it difficult to maintain the main steam temperature steady in operation by using the usual regulate method. Many domestic and foreign researchers introduced the intelligent control technology into the control of the boiler steam temperature, including predict control technology, adaptive technology, fuzzy control technology, neural network technology, genetic algorithm and so on, with a view to resolve the problems encountered in PID control system. However, it is difficult to satisfy the main steam temperature control, whether the traditional PID control system or the control strategy blended with advanced intelligence technology. That's because these systems still use the heat signal to reflect the variety of fuel into the boiler, since the heat signal essentially belongs to the boiler steam side parameters, the characteristics of the heat transfer resistance, delay and lag still restrict the respond speed of the heat signal.It can make the lag weak by detecting the furnace combustion situation and temperature distribution to adjust spray water quantity in advance, so as to control main steam temperature effectively. The technology to monitor burning temperature distribution by flame radiation image, can detect furnace temperature distribution in real-time. Import furnace side signal to the main steam temperature control circuit, then adjust spray water quantity in advance, so as to control the superheating steam temperature effectively. The subject adopts the solution based on visual furnace combustion 3D temperature pattern, to get real-time furnace combustion information and temperature distribution, so as to extract furnace combustion radiation energy signal. Based on dynamic test on variable work conditions, the relation between the radiation energy signal and unit's main operating parameters is analyzed to explore the change regulation of radiation energy signal during the thermal process. Through studying the heat absorption capacity of each heat transfer surface, the change rule between the heat release in furnace and the heat absorbing by heat transfer surface, as well as the static relation between radiation energy and heat transfer both in furnace and flue are explored.Contraposing lag problem in the traditional PID control system of the main steam temperature, and combining with the result of variable work condition tests and the analysis of heat transfer law, the paper put forward a new control tragedy which combined with the steady heat signals of boiler and furnace side radiation energy signal with rapid response. Make the radiation energy signals plus steam flow correction circuit signals as the original leading steam temperature control signals, and to form the new leading control signals of main control circuit by multiplied with the heat signal. Under the guidance of the qualitative analysis conclusion, the model identification and numerical simulation are realized by Matlab toolbox about experimental data which is gathered under certain conditions. Furthermore, two different main steam temperature control strategies depending on whether the furnace radiation energy signals imported or not are analyzed and compared, and a preferable simulation control effect is acquired.The main steam temperature optimization and control strategy based on radiation energy signals by importing it to the main steam control circuit have been carried out. The main steam temperature adjustment quality, with in-situ expriments in two 300MW boiler, is improved and the change range is from±10°C to±3°C by adjusting their weights.