乙炔近红外吸收光谱理论及检测技术研究

发布时间：2017-12-27 07:29

本文关键词：乙炔近红外吸收光谱理论及检测技术研究　出处：《安徽大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着化工工业的迅速发展,乙炔已经成为化工生产过程中有机合成最重要的原材料。但因其易燃的特性,与空气混合形成爆炸性混合物,这严重威胁化工生产的安全。因此,准确检测乙炔气体浓度对保障工业生产安全具有重要的意义。伴随激光光谱技术的发展,可调谐半导体激光吸收光谱技术(TDLAS)因其高灵敏度、高分辨率、快速响应和无损探测的优点已经广泛应用于气体检测领域。直接吸收光谱(DAS)作为一种直接的光谱方法,通过检测分子与激光相互作用时的光强变化量,并结合郎伯-比尔定律与非线性最小二乘法拟合算法,即可反演出分子的浓度信息。吸收光谱所依赖的HITRAN数据库中的光谱参数均为理论计算结果,在实际应用中需要对其进行测量校正,以提高浓度反演的精确度。本文选用工作在近红外波段的半导体激光器作为光源,对乙炔在1.5μm处泛频v1+v3吸收带谱线参数进行了深入研究,并对部分线强大于10-20cm/molecule强吸收谱线参数进行了校正,实验结果与HITRAN12数据库对比,线强和加宽系数的相对误差小于2%;实验中,发现6526cm-1和6532 cm-1波段范围内,存在大量未被报道且吸收强度相对较弱的新谱线,本文通过结合长程吸收池技术和多光谱拟合算法,首次系统地研究了该光谱范围内的弱谱线参数。最终,我们计算了部分已知谱线与22条新谱线线强,并对新谱线的中心位置进行了归属,结果显示已知弱吸收谱线线强的相对误差基本小于10%,本文报道的乙炔新谱线参数将有利于HITRAN数据库的升级。此外,本文结合长程吸收池技术,搭建了一套痕量乙炔气体检测系统。根据乙炔1.5 μm处v1+v3吸收带谱线参数测量结果,以位于6578.5761 cm-1处的R9e(线强为1.34×10-20 cm/molecule)吸收谱线为目标测量谱线,通过选择激光器不同的波长扫描模式,利用直接吸收光谱技术(DAS)展开了乙炔浓度的测量研究。在72.44 m的吸收光程下,利用激光器的波长快速扫描功能,该系统实现了信噪比为1 dB时1.8 ppm的探测灵敏度;当使用激光器的波长慢速扫描时,根据艾伦偏差分析(Allan Variance),在1 s的积分时间内实现了 43.6 ppb的探测极限,当积分时间增加至133 s时,该系统的可探测限约为9.6 ppb。为了抑制信号噪声,论文中首次将Savitzky-Golay(SG)二阶微分算法应用于光谱信号处理中,模拟了该微分算法在不同滤波参数情况下对不同信噪比的模拟光谱信号的降噪效果,模拟与实验研究表明该微分算法具有很好的滤波效果。进一步用该二阶微分算法处理实验吸收光谱信号,结果显示SG二阶微分信号的幅值与气体浓度之间具有良好的线性关系,未来可以将其应用于工业气体检测、大气环境监测及医学气体检测等领域。
[Abstract]:With the rapid development of chemical industry, acetylene has become the most important raw material for organic synthesis in the process of chemical production. But because of its flammable characteristics, it is mixed with air to form an explosive mixture, which seriously threatens the safety of chemical production. Therefore, it is of great significance to detect the concentration of acetylene to ensure the safety of industrial production. With the development of laser spectroscopy, tunable diode laser absorption spectroscopy (TDLAS) has been widely applied in gas detection for its advantages of high sensitivity, high resolution, fast response and nondestructive detection. As a direct spectral method, direct absorption spectroscopy (DAS) can detect molecular concentration information by detecting the amount of light intensity interaction between molecules and laser, and combining the fitting algorithm of Bill's law and nonlinear least square algorithm. The spectral parameters in the HITRAN database which are dependent on the absorption spectrum are all theoretical calculation results. In practice, we need to measure and correct them, so as to improve the accuracy of concentration inversion. The work of semiconductor laser in the near infrared region as the light source of acetylene at 1.5 m v1+v3 overtone absorption band spectrum parameters is studied, and the portion of the line more than 10-20cm/molecule strong absorption spectrum parameters are corrected, and the experimental results of HITRAN12 database comparison, relative error and strong line broadening the coefficient is less than 2%; in the experiment, 6526cm-1 and 6532 cm-1 wavelength range, there are a lot of has not been reported and the absorption intensity is relatively weak in this new line, through a combination of long path absorption cell technology and multi spectral fitting algorithm, the first systematic study of the spectral line parameters of weak spectral range. Finally, we calculate the known spectral lines and 22 new spectral line intensities, and the center position of the new lines were assigned. The results showed that the relative error of known weak absorption spectral line intensities of less than 10%, the new acetylene line parameters will help HITRAN database upgrade. In addition, in this paper, a set of trace acetylene gas detection system has been set up with the technology of long range absorption pool. According to the acetylene 1.5 m v1+v3 absorption band spectra line parameters in 6578.5761 cm-1 R9e (line 1.34 * 10-20 cm/molecule) absorption spectrum as the target spectrum measurement, by selecting different laser wavelength scanning mode, using direct absorption spectroscopy (DAS) launched a study on measurement of acetylene concentration. In the optical path of 72.44 m, the laser wavelength scanning function, the system realizes the SNR detection sensitivity of 1.8 ppm 1 dB; when using the laser wavelength scanning slow, according to Alan (Allan Variance), deviation analysis in the integration time of 1 s is achieved in the detection limit of 43.6 ppb when the integration time is increased to 133 s, but the detection limit of the system is about 9.6 ppb. In order to suppress the noise signal, the first Savitzky-Golay (SG) two order differential algorithm is applied to spectral signal processing, simulation of the noise reduction effect of the simulated spectrum signal of the differential algorithm for different signal-to-noise ratio in different filtering parameters under the condition of the simulation and experimental research show that the differential algorithm has a good filtering effect. Further the two order differential algorithm experimental absorption spectrum showed a good linear relationship between the amplitude and the gas concentration SG two order differential signal, the future can be applied to industrial gas detection, environmental monitoring and medical gas detection etc..
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ221.242;O657.33

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