Condition Monitoring Of Heating Surface And Performance Analysis On Boiler

With the rapid development of the power industry and the increasing demand for energy saving and environmental protection,China's generating units have reached the stage of large capacity and high-parameter.Meanwhile,thermal deviation and over-temperature tube burst of the high-temperature heating surface on coal-fired boilers have become increasingly prominent,threatening safety and economy of unit operation seriously.The study of condition monitoring of heating surface and performance analysis on boiler aims to reveal the coupling relationship among the three-dimensional flue gas field,wall temperature distribution and combustion products in the furnace,providing operation instruction for utility boiler.In this paper,based on a 660 MW tangentially fired boiler,not only the coupled modeling of coal combustion and heat transfer for heating surface was introduced,but also the characteristics of the three-dimensional flue gas field and wall temperature distribution were surveyed.In addition,both the analysis of combustion performance and wall temperature safety on diverse conditions and combustion optimization considering gas temperature deviation were performed.Firstly,based on FLUENT and MATLAB platform,the coupled model of combustion and wall temperature calculation was established,and the joint solution of gas-solid two-phase flow,pulverized coal combustion,radiation,NOx generation and heat transfer among flue gas,wall and steam were achieved.The simulation results were compared with the experimental values to verify the reliability of the model.The simulation results show that the temperature the bottom of platen heating surface is relatively high because of a large amount of radiation energy from high-temperature flame.Furthermore,affected by the residual rotation,there are different degrees of thermal deviation along the furnace width and height direction on the horizontal flue,resulting significantly higher wall temperature on partial left surface.Secondly,based on the coupling model,the comprehensive effect of the out-of-burnout wind-sweep angle on combustion product generation characteristics,flue gas speed and temperature deviation,and wall high-temperature zone were analyzed.The simulated law is consistent with the on-site hot-state test.It's indicated that concentration of CO and NO reduce at the upper swing of the SOFA,leading to better combustion performance.However,the residual rotation at the furnace exit and the temperature of the flue gas both increase at upper SOFA angle,resulting in higher proportion of the high-temperature area of the final reheater and superheater.Therefore,it is necessary to take gas temperature deviation into account while optimizing boiler combustion.Finally,the comprehensive optimization of boiler combustion considering gas temperature deviation was studied by introducing the prior knowledge of simulation and experiment into the data driving model.It can be concluded that the priori support vector machine model describes the combustion characteristics better.Then,the range of SOFA angle was adjusted to calculate the Pareto front line with the highest furnace efficiency and the lowest NOx underdifferent gas temperature deviation,providing instructions for utility boiler's economical and environmentally friendly operation with consideration of security.