Design Of Interference System For Portable Fourier Transform Infrared Gas Analyzer

Fourier infrared gas analyzer is widely used in the detection of flue gas.It is an important equipment for industrial environmental monitoring.With the development of modern industry and society,the demand for Fourier infrared gas analyzer is developing towards portability,miniaturization and on-line.The interference system is the main function and structure of the Fourier infrared gas analyzer.Therefore,the main research direction of the portable Fourier infrared gas analyzer is to focus on the miniaturization of the interference system on the basis of ensuring the performance.In this paper,a set of double swing arm corner cube interferometer is designed.The numerical simulation and optical simulation of the designed system are carried out,and the relationship between the deviation and separation of laser in the interference system and the position of some key components is clarified.A portable FTIR gas analyzer was built by using the designed interference system,and the multi-component gas was measured.The linear error,repeatability and stability experiments of SO₂ and NO_x components in flue gas emission are carried out.The research work of this paper mainly includes the following aspects:1.This paper focuses on two classical portable interferometers:rotary interferometer and pendulum sweep interferometer.The two driving methods of moving mirror greatly reduce the volume of the interferometer and enhance the portability of the instrument,but the optical path difference is limited to the effective rotation angle and has nonlinear problems.Based on the pendulum sweep interferometer,a double swing arm corner cube interferometer is designed.Compared with rotary interferometer,it reduces optical elements,has simple optical path structure and high stability.Compared with the pendulum sweep interferometer,the double swing arm structure can obtain twice the optical path difference of the traditional pendulum sweep interferometer under the same moving distance.It has the advantages of good vibration resistance,good stability and small volume.2.The structure of double swing arm interferometer and the optical path characteristics of corner cube are analyzed and simulated.Aiming at the deviation and separation of the outgoing laser in the swing process of the interferometer,the outgoing laser equation is established by using the geometric optics method,and the numerical analysis is carried out.The relationship between the deviation and separation of laser and the position of some key devices in the interference system is clarified.The numerical analysis results are verified by optical simulation and experiment,which provides data support and theoretical basis for the design of pendulum sweep interferometer.3.A portable FTIR gas analyzer using double swing arm corner cube inter-ferometer is built for experiment.The experimental results show that the value error is within the standard allowable error range,and the repeatability and stability meet the requirements.The designed portable interference system can be applied to portable FTIR gas analyzer.