On-line Measurement Of Flame Temperature,Emissivity And Pulsation Frequency Of Coal-fired Utility Boiler Based On Spectral Analysis

With the proposal of achieving carbon neutralization and carbon neutralization,the electric power system needs to accelerate the transformation of energy structure and the replacement of clean energy,but a large number of unstable wind power and photoelectric grid connection brings great pressure of peak regulation.The current energy structure of our country determines that coal power units are the mainstay of each power grid structure.However,the abnormal operation of coal-fired units will lead to the increase of pollution emission,the decrease of boiler efficiency,and even the occurrence of heat pipe explosion and equipment oxide peel off and other operation failures.The operation safety of coal-fired boilers is the primary concern of thermal power plants.The furnace flame temperature,emissivity and pulsation frequency are important parameters to reflect the combustion stability of coal-fired boilers.Therefore,their accurate measurement can provide an important basis for understanding the real-time combustion state of the flame and the stability of the combustion process.Based on the above background,this thesis carries out the following research work,mainly including:（1）The wavelet threshold denoising method based on empirical mode decomposition is studied to de-noise complex flame signals.The specific research is as follows:Firstly,the empirical mode decomposition algorithm is used to reconstruct flame signals,and the flame signals are decomposed into different IMF components and residual quantities.The error amplitude between reconstructed flame signals and original signals is less than 10^-15;Although the wavelet threshold denoising algorithm has the advantages of easy implementation,easy calculation and good effect,it has poor effect when dealing with non-stationary flame signal.Therefore,the empirical mode decomposition and wavelet threshold denoising method are combined,and the collected flame data is used to verify the wavelet threshold denoising method based on empirical mode decomposition.The method shows a good denoising effect,and the effective flame signal is obtained,which provides an important basis for the subsequent experimental research.（2）The flame pulsation frequency of coal-fired power station is studied,and the flame spectral data of pulverized coal collected from the burner layer and the burnout wind layer of the coal-fired power station are analyzed:Firstly,the flicker frequency experiment of incandescent lamp with different AC frequency was carried out,and the spectral information of incandescent lamp with five different frequencies was collected.The flicker frequency of incandescent lamp was calculated by power spectral density method,HHT method and extreme value method respectively.The results show that the extreme value method is more suitable for calculating the flame pulsation frequency of coal-fired power station.Then,the flame pulsation frequency of the burner layer and the burnout air layer of the coal-fired power station is obtained by using the extreme value method.The flame pulsation frequency of the burner layer and the burnout air layer of the pulverized coal power station is 24.3 HZ and 19.93 HZ respectively.Finally,the change of the flame pulsation frequency with time within 1 min is calculated.（3）The relationship between flame temperature,emissivity and parameters under different working conditions of coal-fired power station is studied,and calculation and analysis are carried out from different angles:Firstly,different emissivity temperature measurement models are used to calculate the flame temperature and emissivity.The calculation results show that,with the increase of the load,the temperature and emissivity increase at the same time,and the change trend is consistent.When the boiler load increases,the calculation accuracy of the three models shows a good consistency.After that,the change relationship between temperature and primary air volume,O₂ and NO_x in flue gas in a period of time is analyzed when the load is stable.When the load is stable,the change of temperature is stable.When the primary air volume,load,O₂and NO_x in the flue gas fluctuate greatly over a period of time,the temperature will also fluctuate,positively correlated with changes,and there is a small delay.