Large scale gas leakage monitoring with tunable diode laser absorption spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detecting and industrial control due to its high sensitivity, selectivity, and rapidity of response. An open path TDLAS system is developed for monitoring large scale methane leakage around the oil refinery. The tunable distributed feedback (DFB) diode laser emits at 1.65 fun. In order to enhance the sensitivity, a system combining long open path and second harmonic detection technique is developed. The test results show that the time resolution is less than 0.1 second and the detection limit is lower than 3.6 ppmv. This system is adapted for monitoring a large scale methane concentration changing trend instead of measuring its absolute concentration.     

1.3-2.0μm光参量振荡的实验研究

本文首先阐述光参量振荡器的调谐原理及其温度调谐的计算.接着讨论研制光参量振荡器的若干技术问题.最后给出信号单谐光参量振荡的实验结果.波长谐范围为1.3—2.0μm.当波长调谐到1.9μm且工作重复率为10PPS时,输出能量为0.37mJ/脉冲.     

A high sensitivity spectrometer with tunable diode laser for ambient methane monitoring

Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. In the measurement of these trace gases, harmonic detection combined with a multi-pass white cell could remarkably enhance the detection sensitivity. In this paper, a portable TDLAS system built specifically for long time monitoring methane in the atmosphere is introduced. The detection limit is below 100 ppb that is enough for the monitoring of ambient methane, and the long time monitoring results obtained in Beijing are given, which is well coincident with that of the Fourier transform infrared (FTIR) spectroscopy.     

氢和甲烷混合气体的受激喇曼散射

使用调Q Nd~(3+):YAG激光的二次谐波(532nm)作为泵浦源,探讨了氢和甲烷混合气体的受激喇曼散射效应。利用光学光谱分析仪(OSA)监测,在不同比例的混合气体中,观测到氢和甲烷各自的SRS谱线以及两种气体的联合谱线,[m,n,=0,|±1,±2,…];观察到斯托克斯和反斯托克斯的谱线频移。实验表明两种气体的混合使得氢和甲烷的受激喇曼散射过程发生了竞争和耦合。     

基于TDLAS技术的HCl气体在线探测温度补偿方法研究

HCl是非常重要的化工原料,而且具有很强的腐蚀性和毒性,对其实现在线监测不但对工业生产工艺的优化会起到重要作用,也能有效的为环境污染提供必要的参照和数据。可调谐半导体激光吸收光谱技术(tunable diode laser absorption spectroscopy, TDLAS)具有高灵敏、高选择性、快速响应等特点,该技术利用了半导体激光器的可调谐和窄线宽特性,通过选择待测气体的某条吸收线可排除其他气体的干扰可实现待测气体浓度的快速在线检测。介绍基于TDLAS的HCl气体检测的系统及实验,重点研究了温度对HCl测量的影响及其温度补偿方法,得出了一个经验公式。最后的实验结果验证了经验公式的合理性,进一步提高了TDLAS传感器在工业高温环境下测量气体浓度的准确性和可行性。     

可调谐半导体激光吸收光谱法监测燃烧过程中CO浓度的变化

可调谐半导体激光吸收光谱技术(tunable diode laser absorption spectroscopy, TDLAS)是利用二极管激光器的波长调谐特性,获得被选定的待测气体特征吸收线的吸收光谱,从而对待测气体进行定性或定量分析。它具有高灵敏、高分辨以及快速检测等特点,已经广泛用于大气中多种痕量气体的检测以及泄漏气体的检测,也是在燃烧环境下对气体进行非侵入式实时测量的理想方法。TDLAS技术与开放式的多次反射池相结合,并利用自平衡探测加波长调制的新型检测方法,测量了酒精喷灯燃烧过程中产生的CO浓度,从测量结果中发现酒精喷灯火焰中CO的浓度成一定的周期性,并且得到火焰中CO的平均浓度为49.4(10-6体积比)。实验结果表明利用开放式多次反射池,结合自平衡探测加波长调制探测的新方法,满足了酒精喷灯燃烧过程中CO检测的需要,此系统为发展基于TDLAS的燃烧在线诊断技术奠定了基础。