天然气高压输送管道微量泄漏TDLAS检测技术理论研究

Theoretical probe on the TDLAS detection technology for minor leakage of natural gas transmission pipeline

天然气输送管网规模随着城镇化进程加快而急剧扩大,高压管道气体微量泄漏的威胁日益严重,传统检测方法不能实现连续地精确检测。利用可调谐半导体激光吸收光谱(TDLAS)检测技术可以实现对微量泄漏的甲烷等气体进行快速、精确地检测。介绍了TDLAS技术的检测原理和压力管道的泄漏物理模型。选择CH4在1 653.7 nm处的吸收谱线为研究对象,结合已有的数据与参数,分析了光谱吸收率和可探测浓度下限随温度、压强的变化特征,以及激光扫描步长对测量精度的影响。结果表明,TDLAS技术应用于高压管道微量泄漏的实时检测是可行的。测量得到的气体浓度符合检测标准,可作为相关检测的基准值谱。

This paper would like to introduce the theoretical principle of TDLAS detection technology, which may include the basic regularity,the physical denotation of the parameters,the way to choose the absorption line and the calculation of the gas concentration. As is well known,with the acceleration of the urbanization process,the scale of natural gas transmission pipe network has been expanding and extending quickly. And,in turn,it has brought about greater potential threat of the micro leakage of high pressure pipeline gas. Facing the serious problem,traditional potential risk detection methods would soon fail to work. Thus,the situation pushes us to search for a novel technology known as the tunable diode laser absorption spectroscopy（ TDLAS） technology to achieve the purpose of rapid and precise detection of the gas,such as methane and so on. And,then,the paper has also introduced the physical leakage model of high pressure pipeline gas,in which the discussion tends to deal with the leakage flow rate and its detection principle. However,what we have chosenprimarily is the absorption spectrum of CH4 at 1 653. 7 nm. Our analysis goes on with the change of the spectral absorption rate at different temperatures and pressure conditions in combination with the currently existing basic data and parameters. For instance,we have made a detailed analysis of the effects of the different temperatures and pressures on the minimum detectable concentration.At the same time,our discussion turns to the influence of the laser scanning step size on the measurement accuracy. The results of our analysis and discussion demonstrate that it proves available and feasible to apply the TDLAS technology to the real-time detection of the minor leakage of high pressure pipelines. The measurement of the gas concentrations in the high pressure pipeline has to be,as a matter of fact,in line with the detection standard in reference to the spectrum of the correlation detection. Thus,it can be concluded that the the TDLAS technology can help to lay a foundation to the next step of the conventional measurement of comparative analysis. At the same time,it can provide reference for the practical application of the technology in the future,so as to make the TDLAS technology more popular in the routine testing and measurement,as well as in the routine inspection in the infrastructure engineering practice.