Research On Logic Strategy For Air Distribution Control Of Power Plant Boiler Burner

China is a country with abundant coal resources.However,due to its large population and low per capita occupation,China’s use of coal resources is not reasonable enough,causing serious environmental pollution and resource waste.Thermal power generation consumes a large amount of coal,and boilers are one of the three major equipments of thermal power plants,which has an important status and significance.At present,the combustion control level of power station boilers in China is relatively low.Operators manually adjust the air distribution related settings.There are problems with operational lag and inaccuracy.It is of great significance to explore the automatic control of boiler air distribution.This article takes a 350 MW supercritical coal-fired boiler as the research object,establishes a mathematical model and a physical model and performs related calculations,and finally sets up a model of air distribution control strategy.The significance of this study is to reduce the workload of operators and improve the real-time and accuracy of air distribution control.First of all,according to the actual size of the furnace,a mathematical and physical model is constructed and simplified.The combustion parameters of the boiler at several typical loads ranging from BMCR to 50% THA are known(Inlet air temperature and volume,furnace coal consumption,furnace outlet temperature,excess air coefficient,boiler combustion efficiency,etc.).The above conditions are brought into the program to calculate the flue gas heat exchange in the furnace and the furnace blackness,which can be used as the wall thermal boundary conditions in the furnace combustion simulation.Secondly,according to the research object and the reaction process,a suitable calculation model and parameters are selected for numerical simulation of furnace combustion.The boundary conditions under 6 typical loads were determined based on the known data of boiler operation.The remaining load-related conditions were replaced by linear interpolation.This article assumes that the wind speed of the secondary wind is constant,and the opening degree of the combustion-supporting and separate over fire air(SOFA)dampers is variable,and this is used as the main research variable.In the simulation of low load conditions,there are three types of air distribution modes for the combustion air:positive pagoda,waist reduction,and inverted pagoda.The best air distribution mode is selected based on the combustion characteristics,NO concentration and wall temperature characteristics of the main combustion zone.Then,based on the optimal air distribution mode of the combustion air under typical load and the opening state and opening degree of the SOFA damper,the secondary opening degree of the secondary damper is increased and decreased as a whole,and the law of the mean change in the average oxygen output at the outlet is calculated.The calculation results show that at a lower load(less than 280MW),increasing / decreasing the opening of the combustion air damper by 5% as a whole can adjust the furnace outlet oxygen within a range of ± 2%;when the load is higher than 280 MW,the effect of reducing the opening of the combustion air damper on the outlet oxygen amount is not obvious,it is adjusted in conjunction with the SOFA wind.Finally,based on the calculated data,a boiler air distribution control program is written and a GUI is built.The program automatically rounds after reading the boiler load,ignores small amplitude load changes,and adjusts the dampers of all levels to the preset opening degree;after the combustion is stable,read the value of the oxygen content at the furnace outlet.If the oxygen amount is within a reasonable range,keep the state unchanged,otherwise adjust according to the logic described above;If the program receives abnormal data input,it requests manual operation if it cannot be resolved automatically.At present,the boiler air distribution process of each power station is manual operation.The program set up in this article can provide a brief idea for the automation of the adjustment process.