Research On Laser Spectral Measurement Method Of Carbon Dioxide Concentration In Flue

Global warming is one of the greatest challenges human facing today,because of that the production activities,e.g.consumption of fossil fuels and woods,induced greenhouse gas?CO₂,etc.?concentration increases rapidly since the first industrial revolution.According to the Fifth Assessment Report?Climate Change 2013?of the Intergovernmental Panel on Climate Change?IPCC?,the concentration of the most important greenhouse gas,CO₂,in 2011 has increased by about 40%when compared to that in 1750.Among all the sources of CO₂ emissions,the stationary emission sources?factories?are the major contribution of the greenhouse effect.In order to improve the accuracy of data,IPCC recommends the direct measurement techniques for stationary emission sources as the highest level of GHG emissions inventory statistics.In this paper,the author bulided the technique for accurately measuring the CO₂ concentration of the stationary emission sources based on the non-saturated absorption molecular vibrational spectra and thermodynamic theory.The experimental apparatus adopts a Herriott-type multiple reflection optical absorption cell.The experimental results show that the theoretical method of this paper can accurately measure the CO₂ concentration of the given gases.The measurement uncertainty is comparable with the balance weighing method.The specific works are:1.The theoretical model for measuring the concentration of stationary emission sources is established.According to the basic principle of molecular absorption,the relationships between the light intensity,gas temperature,gas pressure and gas concentration are established.Also,the influences of various non-ideal factors on concentration measurement are considered.This article gives relative measurement method of CO₂concertration.In addition,according to the principle of uncertainties,the influence laws of the concentration measurement uncertainty are studied.2.A multi-reflection absorption spectrometer based on the Herriott-type was established.The working temperature of the measurement system was controlled to be?293±0.1?K and the operating wavelength range was?0.4¹2??m.In order to find out the operating laser wavelength,the author tested the effect laws of the temperature and current of the laser on its wavelength.The important baseline treatment methods in direct absorption spectroscopy were also analyzed.The author chosed the suitable experimental parameters and achieved a high signal-to-noise ratio of 2900:1.3.The spectra of the?30012???00001?R20e transition(6362.5 cm^-1)and the?30012???00001?R16e transition(6359.99 cm^-1)were recorded at 293 K and?0¹3?kPa.The nominal carbon dioxide gas mixtures of 15%,35%,50%,and 75%?nitrogen as buffer gas?were used as sample gases.The experimental measurement results are in good agreement with the results obtained by the balance weighing method.The maximum relative measurement uncertainty?k=2?is 0.7%?R20e line?and 1.17%?R16e line?.