Research On Simultaneous Detection Of Ammonia And Hydrogen Concentration Based On TDLAS Technology

Synthetic ammonia is an important raw material for industrial and agricultural production.Every year,production worldwide requires large amounts of industrial synthetic ammonia.Synthetic ammonia is usually formed by mixing nitrogen and hydrogen with a catalyst under high temperature and high pressure conditions.Ammonia and hydrogen leaks can cause huge damage.Therefore,it is of great significance to detect the leakage concentration of ammonia and hydrogen in the industrial ammonia production environment.According to the environmental characteristics of industrial ammonia production,the existing gas concentration detection technologies and methods that simultaneously detect multiple gas concentrations are analyzed.Considering signal processing,it is noteasy to construct a complex optical path in an industrial production environment.According to the absorption spectrum characteristics of hydrogen and ammonia,combined with TDLAS technology and frequency division multiplexing detection method,the concentration of ammonia and hydrogen can be detected simultaneously.A visualization tool based on the HAPI database interface HAPI was developed to remotely acquire the spectral data of ammonia and hydrogen to analyze the characteristics of the gas absorption pipeline.According to the characteristics of the peak of the second harmonic signal,the peak method is used to calculate the gas concentration.Designed to measure ammonia and hydrogen systems simultaneously in an industrial ammonia production environment.SIMULINK tool is used to simulate and analyze the wavelength modulation,frequency division multiplexing,gas absorptionprocess and harmonic detection of the system to verify the feasibility of the system.Provide a basis for the model.Finally,the factors that affect the accuracy of the system measurement results are analyzed.Aiming at the modulation noise,a three-level convolution noise reduction algorithm is proposed,and an experimental platform is established.Take ammonia gas as an example for experimental verification.The results show that the application of the noise algorithm can increase the noise removal rate of the high-frequency modulation signal of the ammonia absorption line to 88.2%,and improve the signal-to-noise ratio of the ammonia absorption line.The signal-to-noise ratio increased from 21.09 to90.16;according to measurements,the average deviation was 0.0743% and the relativestandard deviation was 1.4%.Its inversion accuracy and stability are superior to db6 wavelet noise reduction and non-noise reduction processing.This method can effectively remove modulation noise and provide a certain reference for improving the accuracy of laser detection of gas concentration in industrial production.In view of the measurement error caused by temperature changes,this paper simulates and analyzes the influence of the coupling variables of concentration and temperature on the absorption spectrum characteristics of ammonia on the HITEMP-TDLAS platform.Using polynomial regression and global linear fitting of shared parameters,a temperature-concentration coupled variable ammonia spectrum was obtained.Correlate the absorbance and verify the prediction model.Within the range of concentration 1% ? 15% and measurement temperature 263 k ? 333 k,the relative error range of the inversion results is within ± 0.25%.It can be seen that the application of this technology can effectively correct measurement errors caused by temperature changes in the production environment.