Absorption Spectroscopic Analysis And On-line Monitoring Method Of Sulfur Dioxide And Nitrogen Oxide

As the process of modernization is becoming faster, the requirment forresources are increasing enormously. Based on the resource structure in China, coalburning to power generation is the main approach to get energy. However, theburning of coal will bring to us pollution problems, especially for gases, mailyincluding sulfer dioxide, nitric oxide and nitric dioxide. China has implemented alaw for controlling the emission of totoal pollutants. The effective realization of thelaw depends on the monitoring level of the pollutants. At present, the techniques andproducts for monitoring the pollutants in China are controlled by foreign contries.So there is great significance to the development of techniques for monitoringpollutants with our own intellectual property rights. In this thesis, under the abovecircumstances, we studied polluted gas monitoring techniques for SO₂, NO and NO₂measurement.The research on SO₂monitoring using spectropic technique was developed. Weselected the spectral rang270-310nm as the studied range based on the study of theabsorption spectrum of SO₂. We established an advanced DOAS technique tomonitor SO₂based on Beer-Lambert’s law and the characteristic spectral feature ofSO₂which is the combination of continuous and periodic oscillated spectrum. Wedesigned and setup the experimental equipments. The research results manifestedthe monitoring index of SO₂as follows: The detection limit of the system was0.1ppm×m when the SNR is2. The zero drift of the system was less than0.2ppm. Themeasurement erro and the drift of measurement range was no more than1%. Wedeveloped a prototype based on the above study and realized functions such asauto-detection, auto-data processing, auto-save and so on. The on-site applicationindicates that the SO₂analyzer is very appropriate to on-site measurement.The temperature influences on SO₂monitoring was invesgated. The studymanifested that temperature would influence the detection of SO₂in two aspects. Onone hand, temperature will affect the properties of absorption spectra. On the otherhand, the feature of the spectrometer will also be affected when temperature changes.The optical parameter in SO₂measurement is linear to the temperauture during30-130℃and the spectral parameter show quadratic function feature in the rangefrom15℃to40℃. After correlation, the accuracy of the system for monitoringSO₂is less than1%between24℃and42℃.The research on NO concentration measurement was developed. Thecharateristic absorption wavelengths of NO overlape with the characteristic absorption range of SO₂. As a result, the most importance question for developingNO monitoring technique is to decomposit the overlapped absorption spectrabetween SO₂and NO. We discovered by the study that we can deduce theabsorption spectra of SO₂near226nm from the known concentration of SO₂at300nm. Then by substracting the co-spectrum of SO₂and NO with the deductedabsorption spectrum of SO₂, we got the absorption spectrum of NO. Based ontheoretical analysis, an experimental setup for measuring NO was built up. Thestudy manifests that the detection limit is less than0.8ppm×m with the zero driftless than1ppm. The measurement erro and measurement range drift are both lessthan1%. Furthermore, the NO measurment results showed that the fluctuation ofsystem is less than1%even until1000ppm SO₂interferance. We developed a NOanalyzer and the software realizing functions such as auto-detection, auto-dataprocessing, auto-save and so on. The on-site application indicates that the NOanalyzer is very appropriate to on-site measurement.Moreover, we also developed NO₂monitoring technique. The absorptioncharacter of NO₂is similar to SO₂that the absorption cross section can be devidedinto continuous spectrum and periodic oscillation spectrum. Thus, we can achieveconcentration measurement of NO₂using improved DOAS technique. Experimentalsetup was established. The study manifests High linear calibration curve of NO₂wasacquired by measuring a searies of concentration of NO₂.The detection limit andzero drift of the measuring system are both less than1ppm. The measurment rangedrift and erro are both within1%. The research results manifested the monitoringindex of SO₂as follows: the detection limit and zero drift of the system are less than1ppm; the measurement range drift and erro are both within1%.