發(fā)布時間：2019-03-08 08:06

【摘要】：隨著環(huán)境污染問題受到的社會關注度越來越高,國家對于環(huán)境保護也日趨重視。發(fā)電廠在生產過程中會產生大量的氮氧化物,是目前大氣污染的主要成分之一,加大對氮氧化物的治理力度,安裝脫硝裝置成為必然的發(fā)展方向。在脫硝過程中,氨氣被廣泛的作為一種光催化還原劑使用,但未反應的NH3從脫硝系統(tǒng)中排除,難免的造成二次污染。由此可見,對于逃逸氨的在線測量,隨工況運行精確制定NH3的噴入量,顯得尤為重要。目前,基于光譜理論的可調諧激光吸收光譜(TDLAS)技術在痕量氣體測量時具有非接觸性、無需預處理,響應迅速,測量精確的優(yōu)勢,成為了當前工業(yè)污染痕量氣體監(jiān)測的代表性測量方法之一。本文主要研究的目的是利用可調諧吸收光譜技術(TDLAS)實現對發(fā)電廠逃逸氨的在線測量,并重點對測量時出現的關鍵性問題進行了研究。本文首先介紹了光譜學原理、譜線強度及吸收光譜線性函數,重點研究了可調諧激光吸收光譜技術的測量原理、基本技術方法。其次對逃逸氨的監(jiān)測方法進行了全面的對比分析,調研了國內外應用廣泛的、成熟度高的監(jiān)測設備進行了考察分析,并對測量方法進行了確定。經對比、分析,選用了在線測量取樣法的直插式TDLAS技術的監(jiān)測裝置作為測量工具,相對于其他方法,此種方法具有反應快、背景信號小、抗干擾能力強、精度高等優(yōu)勢。結合所在電廠煙道的實際工況,提出了具體的設計搭建方式,并對設計的光路部分和機械部分進行了介紹。之后,在確定了TDLAS測量逃逸氨的中心頻率后,對在線監(jiān)測設備進行了零氣實驗和標定實驗,從而利用具體實驗驗證設備的可靠性和準確性。在驗證后,利用最小二乘法推導氣體的反演算法,以滿足系統(tǒng)的需要。最后,用實驗來分析了溫度對氨氣濃度測量的影響。并為驗證實際現場中因溫度變化而導致的對逃逸氨測量影響的情況。溫度的影響需要要對濃度反演進行溫度校正,本文提出了溫度補償經驗公式。通過實驗驗證,溫度補償公式可大幅提高測量系統(tǒng)的精確度。經過驗證,該補充公式能夠有效提升測量精度,進一步提高了TDLAS技術的準確性和可靠性。
[Abstract]:With the increasing social concern about environmental pollution, the state pays more and more attention to environmental protection. A large number of nitrogen oxides will be produced in the production process of power plants, which is one of the main components of air pollution at present. It is an inevitable development direction to strengthen the control of nitrogen oxides and install denitrification devices. In the process of denitrification, ammonia is widely used as a photocatalytic reducing agent, but the unreacted NH3 is excluded from the denitrification system, which inevitably results in secondary pollution. It can be seen that for the on-line measurement of ammonia escape, it is particularly important to accurately determine the injection amount of NH3 with the operating conditions. At present, the tunable laser absorption spectroscopy (TDLAS) technique based on spectral theory has the advantages of non-contact, no pretreatment, rapid response and accurate measurement in the measurement of trace gases. It has become one of the representative measurement methods for monitoring trace gases in industrial pollution. The main purpose of this paper is to realize the on-line measurement of fugitive ammonia in power plant by means of tunable absorption spectroscopy (TDLAS), and focus on the key problems in the measurement. In this paper, the principle of spectroscopy, the intensity of spectral line and the linear function of absorption spectrum are introduced, and the measurement principle and basic technique of tunable laser absorption spectroscopy are mainly studied. Secondly, the monitoring methods of ammonia escape are compared and analyzed comprehensively, and the widely used and mature monitoring equipments at home and abroad are investigated and analyzed, and the measuring methods are determined. Through comparison and analysis, the direct-insertion TDLAS monitoring device of on-line sampling method is selected as the measuring tool. Compared with other methods, this method has the advantages of quick response, small background signal, strong anti-jamming ability and high precision. Combined with the actual working conditions of the flue in the power plant, the concrete design and construction methods are put forward, and the optical and mechanical parts of the design are introduced. Then, after determining the center frequency of TDLAS measurement of ammonia escape, zero-gas experiment and calibration experiment of on-line monitoring equipment are carried out, and the reliability and accuracy of the equipment are verified by specific experiments. After verification, the least square method is used to derive the gas inversion algorithm to meet the needs of the system. Finally, the effect of temperature on the measurement of ammonia concentration was analyzed by experiments. In order to verify the effect of temperature change on the measurement of escape ammonia in the field. Temperature effect requires temperature correction for concentration inversion. An empirical formula for temperature compensation is presented in this paper. The experimental results show that the temperature compensation formula can greatly improve the accuracy of the measurement system. It is proved that the supplementary formula can effectively improve the accuracy of measurement and further improve the accuracy and reliability of TDLAS technology.
【學位授予單位】：華北電力大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP274;O433

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本文編號：2436603