Research On Real-time Monitoring System Of Methane Based On TDLAS

Tunable Diode Laser Absorption Spectroscopy(TDLAS),which refers to the absorption characteristics of lasers using gases under specific temperature and pressure conditions and obtains important information such as gas concentration,temperature and pressure by the change of light intensity before and after absorption.The TDLAS technology has the advantages of high sensitivity,fast reaction time,no contact,no sampling.Based on the theoretical research on TDLAS harmonic detection technology,this paper independently constructed a system that can detect methane concentration in real time.The main contents are as follows:Through theoretical analysis and measurement requirements,design the overall architecture of the inspection platform,and adopt devices that meet the requirements of this platform,including tunable semiconductor lasers,photodetectors,etc.,while considering the existing conditions of the laboratory,independently designing and modifying some of the required devices,such as Gas absorption cell module,adder module,frequency multiplier module,etc.In the process of building the hardware part of the system,it is gradually debugged through a large number of experiments and theoretical analysis,observe its working conditions,and explore the best working conditions of the system.The final completion of the entire hardware platform provides an important hardware foundation for real-time detection systems.The system uses an integrated lock-in amplifier,a small phase-locked module,and a Fast Fourier Transformation(FFT)method under fixed bias to extract a second harmonic signal containing methane concentration information and establish about harmonic amplitude and methane concentration function.On the basis of building a good hardware platform.Using the C language to write the digital signal processing(DSP)program in the integrated development environment(Code Composer Studio)and complete a set of methane concentration real-time detection platform.The platform has a high linearity(0.97 or more)in the 1%to 10%methane concentration range and is capable of displaying the current methane concentration in real time.