| 题名 | 基于傅里叶变换的差分吸收光谱法测量氨气和二氧化硫浓度的实验研究 |
| 作者 | 郁敏捷 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 董作人 |
| 关键词 | 光谱学 差分吸收光谱 傅里叶变换 经验模态分解 氨气 二氧化硫 |
| 其他题名 | Study on Measuring Concentration of Ammonia and Sulphur Dioxide by Differential Optical Absorption Spectrometry Based on Fast Fourier Transform |
| 中文摘要 | 火力发电厂排放的烟气严重污染了空气，其中气体污染物主要为二氧化硫和氮氧化物，造成人类生存环境的恶化。国家为控制排放，出台了一系列法规，对烟气也采取了脱硫脱硝措施，在此过程中又会产生氨逃逸问题，为有效治理烟气排放，必须对烟气进行实时准确的监测。目前国内大多使用的烟气监测技术来自于国外，因此发展具有自主知识产权的烟气监测技术具有重要意义。本文在此背景下，开展了对 NH3和SO2浓度在线检测方法的研究，主要研究工作如下： 1. 分析了各种气体检测方法的优缺点，选用差分吸收光谱（DOAS）技术作为本课题的测量方法，结合NH3和SO2吸收光谱的准周期性，在DOAS基础上采用傅里叶变换处理光谱数据并反演气体浓度，针对吸收曲线以及实际中出现的高斯白噪声的特点，提出采用经验模态分解（EMD）法对光谱数据进行降噪处理； 2. 根据DOAS技术特点以及被测气体的吸收波段，采用氘灯作为光源，设计并搭建了紫外差分吸收光谱技术测量系统，选用紫外波段的光谱仪探测气体吸收光谱，并对光谱仪的特性进行了测量； 3. 针对NH3和SO2气体吸收谱线在196～214nm波段区域存在谱线重叠的问题，在采用傅里叶变换的差分吸收光谱法测量气体浓度基础上，采用分波段方法，解决NH3和SO2特征频谱相互串扰对测量的影响； 4. 研究了SO2在196～214nm波段非线性吸收现象，并采用非线性修正方法，解决了在SO2高浓度情况下出现的非线性吸收对NH3气体测量的影响，最终实现对NH3和SO2气体浓度的同时准确测量。测量结果显示，NH3各个浓度测量误差均在±0.15ppm以内，相对误差不超过±1.5%，最低可探测浓度为1.5ppm；SO2各个浓度测量误差均在±2ppm以内，相对误差不超过±1%，最低可探测浓度为16ppm。 5. 模拟了谱线漂移对测量结果的影响，结果显示，由于傅里叶变换的平移性，特征频谱的强度对谱线漂移不敏感，免去了光谱仪谱线校准过程。 |
| 英文摘要 | The flue gas emissions such as sulfur dioxide and nitrogen oxides from the thermal power plant seriously pollute the air, causing the deterioration of human living environment. In order to reduce emissions, the related departments have formulated a series of laws and regulations. The flue gas desulfurization and denitrification technology has been applied, but it brings ammonia escape problems. It is necessary to monitor the flue gas real-timely and accurately for effective governance of flue gas. At present, the flue gas monitoring technologies used in domestic are from abroad. So it is of great significance to develop the flue gas monitoring technology with independent intellectual property rights. In this context, this paper conducted a study of concentration of NH3 and SO2 detection method based on DOAS, the major work in this dissertation is outlined as follows: 1. The advantages and disadvantages of various gas detection methods are analyzed, and the differential optical absorption spectroscopy (DOAS) technology is chosen as measurement method in this subject. Considering the quasi periodicity of absorption spectra of NH3 and SO2, we use Fourier transform to process the spectrum data based on DOAS, and then retrieve the concentration of gases. In view of the characteristics of the absorption curve and white noise, empirical mode decomposition (EMD) noise reduction method is proposed to improve the signal to noise ratio. 2. Considering the characteristic of DOAS technique as well as the measured gas absorption bands, the deuterium lamp is chosen as light source, the measurement system of UV-DOAS is designed and built. The ultraviolet spectrometer is used to detect the absorption spectrum of gases, and its response parameters are measured. 3. For the absorption of NH3 and SO2 have serious overlapping from 196nm to 214nm, based on differential optical absorption spectrometry combined with fast Fourier transform, we propose a method that detecting these two gases simultaneously at two wave bands. The crosstalk effects between the characteristic spectrum of NH3 and SO2 are solved. 4. We correct the interference of SO2 to NH3 which is caused by the nonlinearity of the absorption of SO2 within 196～214nm wave band, so the real concentration of NH3 are obtained. The measurement errors of NH3 are within ±0.15ppm, the relative errors are less than ±1.5%, and the detectable concentration limit is 1.5ppm. For SO2, the measurement errors are within ±2ppm, the relative errors are less than ±1%, and the detectable concentration limit is 16ppm. 5. The line drift effects on measurement results has been simulated, it proved that the intensity of the characteristic spectrum is not sensitive to line drift due to the shifting properties of Fourier transform. So the time-consuming preprocess of spectra calibration is not required in this DOAS technology. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16921]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 郁敏捷. 基于傅里叶变换的差分吸收光谱法测量氨气和二氧化硫浓度的实验研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
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