可调谐半导体激光光谱仪对高温下CO的测量研究

发布时间：2017-12-31 22:36

  本文关键词：可调谐半导体激光光谱仪对高温下CO的测量研究　出处：《上海大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 可调谐半导体激光器 波长调制技术 高温 一氧化碳

【摘要】：人类工业的快速发展带来了能源枯竭以及空气污染等严重问题,其中由化石燃料燃烧产生的CO气体不仅能够与人体血红蛋白结合造成机体缺氧而中毒,排放到大气中也会对OH自由基产生消耗,极大降低了大气的自净化能力。对工业燃烧炉内CO浓度和温度的测量能够实时监测燃料的燃烧效率,同时也能抑制尾气中CO的浓度。与传统的气体测量方法相比,可调谐半导体激光光谱技术具有选择性好、抗干扰能力强、灵敏度低、快速、实时在线检测的优势,能够对气体组分浓度、温度、压强、气体流速进行测量,在工业领域得到了广泛的应用。结合波长调制技术可以有效去除由于TDLAS光电器件产生的白噪声,极大优化了测量检测线,拓宽了该技术在痕量气体浓度检测领域的应用。本文以波长调制可调谐半导体激光吸收光谱技术为理论指导,自主搭建了一套用于高温条件下CO测量的实验装置,主要取得了以下成果:1)通过对高斯、洛伦兹、福吉特吸收线型函数进行机理分析,得到了在常压条件下,使用洛伦兹线型函数对实际吸收线型进行模拟最为合理。2)使用傅里叶变化对洛伦兹线型函数的n阶导数进行理论推导,给出了同时考虑波长调制和功率调制下洛伦兹线型函数的二次谐波信号表达式,为后续的最小二乘法拟合待测信号提供了理论依据。3)结合HITRAN数据库,对化石燃料产生的尾气吸收峰位置进行模拟,最终确定选取干扰小、强度大且适用于DFB激光器的R14线(1563.6nm)作为CO的待测吸收线。4)自主搭建一套同时包含激光调制系统、标气配制系统、高温系统、信号探测解调系统以及信号采集储存系统的实验装置,该装置基于波长调制可调谐半导体激光光谱技术,使用DFB激光器作为可调谐半导体激光器,以高频正弦信号作为调制信号,使用锁相放大器对测量信号进行解调,得到最终的二次谐波作为定量的标准。5)实验采取标定定量法,通过建立水汽背景库扣除CO吸收峰附近的水汽干扰信号,并以CO标准吸收库作为标定对待测组分中CO的浓度进行标定定量。6)最终的测量结果包括水汽、CO浓度和温度值,其中CO测量的线性动态范围为0~10%,检测限在100ppm量级;温度测量范围为300~1000°C;水汽、CO浓度以及温度的测量误差分别在5%、5%、10%以内。7)本套实验装置基于波长调制可调谐半导体激光光谱技术,具有抗干扰、低检测限、实时在线的特点,且适用于高温等恶劣工作条件下,在煤发电、钢铁冶炼等领域具有极大的应用潜力。
[Abstract]:The rapid development of human industry has brought serious problems such as energy depletion and air pollution. The CO gas produced by fossil fuel combustion can not only combine with human hemoglobin but also lead to hypoxia and poisoning. Emissions into the atmosphere will also produce consumption of OH free radicals, greatly reducing the self-purification capacity of the atmosphere. The measurement of CO concentration and temperature in industrial combustion furnace can monitor the combustion efficiency of fuel in real time. Compared with the traditional gas measurement method, the tunable semiconductor laser spectrum technology has good selectivity, strong anti-jamming ability, low sensitivity and fast. The advantage of real-time on-line detection is to measure the concentration, temperature, pressure and velocity of gas components. Combined with wavelength modulation technology, white noise generated by TDLAS optoelectronic devices can be effectively removed, and the measurement line can be greatly optimized. The application of this technology in the field of trace gas concentration detection is broadened. The wavelength modulated tunable semiconductor laser absorption spectroscopy is used as the theoretical guide in this paper. A set of experimental equipment for CO measurement under high temperature was built independently. The following results were obtained: 1) the mechanism of the absorption line function of Gao Si, Lorenz and Fugit was analyzed by means of the absorption line function of Gao Si, Lorentz and Fugit. It is obtained that under normal pressure, it is most reasonable to use Lorentz linear function to simulate the actual absorption line. 2) Fourier variation is used to deduce the n-order derivative of Lorentz linear function. The second harmonic signal expression of Lorentz linear function considering both wavelength modulation and power modulation is given. It provides a theoretical basis for the following least square method to fit the signal to be tested. 3) combined with the HITRAN database, the location of the tail gas absorption peak produced by fossil fuel is simulated, and the selection is determined with small interference. R14 line (1563.6nm), which is high intensity and suitable for DFB laser, is used as the absorption line of CO. (4) A set of simultaneous laser modulation system, standard gas preparation system and high temperature system are built independently. Signal detection and demodulation system and signal acquisition and storage system experimental device, this device is based on wavelength modulation tunable semiconductor laser spectrum technology, using DFB laser as tunable semiconductor laser. The high frequency sinusoidal signal is used as the modulation signal and the phase-locked amplifier is used to demodulate the measured signal. The final second harmonic is obtained as the quantitative standard. 5) the calibration method is adopted in the experiment. The water vapor interference signal near the CO absorption peak is deducted by establishing the water vapor background pool. The CO standard absorption library is used as calibration method to calibrate the concentration of CO in the measured components. 6) the final measurement results include the concentration of CO in water vapor and the temperature value. The linear dynamic range of CO measurement is 0 ~ 10 ppm and the detection limit is 100 ppm. The temperature measurement range is 300 鈩，

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