Superheater Tube Wall Temperature Analysis Of Power Station Boiler Based On MechanismModeling And Operation Data Identification

Nowadays, with China’s energy production and consumption transformation, coal-fired power units often need peaking operations to cooperate with new energy power units, which brings more challenges to the safety and reliability of unit operation. Located at the furnace outlet in large coal-fired power plants, superheater works in long-term high temperature and high pressure environment and is the heat-exchange part with the highest metal wall temperature in the boiler unit, which is prone to overheating and even tube explosion. Because the furnace tube wall temperature cannot be directly measured in ultra high temperature flue gas environment at the furnace outlet, it is necessary to conduct a research on analysis methods of wall temperature of the utility boiler high temperature superheater based on boiler structure mechanism and operation data.In this paper, theoretical researches were carried out on the causes of thermal deviation at the furnace exit of the power station boiler from both working medium side and flue gas side. Based on the analysis of power plant operation data, this thesis focuses on the non-uniform thermal load distribution at the flue gas side and established parametric modes of the flue gas thermal load distribution at the furnace outlet along the width direction for online calculation of the furnace tube wall temperature of the utility boiler superheater.Adopted the prediction method of thermal load distribution model based on support vector machine. And on the basis of the pretreatment of power plant operation data, extracted the input feature vector influencing thermal load distribution to set up data sample set for the experiment. In the process of training support vector machine, improved the prediction accuracy by using cross validation method in order to realize the identification of the flue gas thermal load distribution model at the furnace exit under operating conditions.Based on the thermodynamic calculation mechanism, divided heat transfer regions of boiler high temperature superheater, established piecewise models of the superheater furnace tube and calculated the working medium temperature and metal wall temperature through solving the heat transfer and the working medium flow of by iteration. In the calculation of wall temperature, the flue gas thermal load distribution model and the flue gas uneven coefficient were introduced to solve the problem of uneven heating at the flue gas side. By comparing and analyzing the calculated results with actual measurement data, the validity of thermal load distribution model and the accuracy of multi-classification support vector machine prediction were verified.With furnace tube wall temperature calculation as the core, developed an online calculation system of furnace tube wall temperature of power station boiler based on mechanism modeling and operation data identification. The system adopted a SOA-based architecture contains background model building and front-end display modules, obtains the boiler furnace tube wall temperature distribution through online calculation and monitors the condition of superheater and over-temperature alert, which provids guidance for engineering and technical personnel on safe operation of power plant boiler.