發(fā)布時(shí)間：2018-09-17 07:48

【摘要】：汞是一種有毒的重金屬元素,若過量排放,不僅會(huì)對(duì)工農(nóng)業(yè)生產(chǎn)造成重大影響,還會(huì)威脅到人們的身體健康。我國汞污染較嚴(yán)重,并且?guī)啄昵熬鸵杨C布條款控制汞的排放,所以現(xiàn)在對(duì)汞尤其是氣態(tài)汞進(jìn)行有效的監(jiān)測變得越來越重要。近些年,隨著光電技術(shù)的發(fā)展,很多化學(xué)監(jiān)測方法逐漸被簡單、高效、造價(jià)低廉的光學(xué)監(jiān)測方法所取代,而在光學(xué)監(jiān)測技術(shù)中,光譜學(xué)監(jiān)測方法已成為主流方向。本課題主要針對(duì)元素汞,對(duì)象包括大氣中和工廠排放廢氣中的氣態(tài)汞。進(jìn)行氣態(tài)汞的監(jiān)測,不僅有助于脫汞效率的提高,還對(duì)環(huán)境污染監(jiān)測及改善有重要意義。本文提出利用可調(diào)諧多模二極管激光器倍頻技術(shù)和和頻技術(shù)產(chǎn)生中心波長253.7 nm的紫外激光的方法,結(jié)合關(guān)聯(lián)光譜技術(shù),經(jīng)自動(dòng)峰值檢測及廣義線性擬合的算法得出樣品氣室中的汞濃度,從而實(shí)現(xiàn)汞的連續(xù)監(jiān)測。汞的吸收譜線很窄,對(duì)253.7 nm波長的光有強(qiáng)吸收。在倍頻實(shí)驗(yàn)中,可調(diào)諧多模綠光二極管激光的中心波長為505 nm。通過電流和溫度的控制,并在加外腔的情況下可將其波長調(diào)至507.3 nm,由BBO晶體的倍頻效應(yīng)得到253.7 nm的紫外光。經(jīng)計(jì)算得到,合成紫外光強(qiáng)度為16.6 nW,且在1 m路徑,4 s積分時(shí)間下,汞濃度測量靈敏度達(dá)到0.07μg/m~3,且汞濃度測量線性動(dòng)態(tài)范圍大約是0~45μg/m~3。最后對(duì)該系統(tǒng)的氣體選擇性和實(shí)用性進(jìn)行了測試并完成了汞濃度的連續(xù)監(jiān)測。在和頻實(shí)驗(yàn)中,應(yīng)用中心波長在687 nm的可調(diào)諧多模紅光二極管激光器和中心波長在401 nm的可調(diào)諧多模藍(lán)光二極管激光器,經(jīng)BBO晶體產(chǎn)生和頻效應(yīng)進(jìn)而獲得253.7 nm的紫外光,并分別在紅光和藍(lán)光激光器上施加掃描信號(hào),進(jìn)行雙路掃描。經(jīng)計(jì)算得到,合成紫外光強(qiáng)為1.0 nW,在1 m路徑,10 s積分時(shí)間下,汞濃度測量靈敏度達(dá)到0.13μg/m~3。汞濃度測量線性動(dòng)態(tài)范圍大約是0~36μg/m~3,并給出了線性范圍與非線性范圍相應(yīng)的解析式。通過改變兩激光器溫度我們對(duì)系統(tǒng)穩(wěn)定性進(jìn)行評(píng)估并完成汞的揮發(fā)與擴(kuò)散的連續(xù)監(jiān)測。
[Abstract]:Mercury is a toxic heavy metal element, if excessive emissions, not only will have a significant impact on industrial and agricultural production, but also threaten the health of people. Mercury pollution is serious in our country, and some years ago, some provisions have been issued to control mercury emissions, so it is becoming more and more important to monitor mercury effectively, especially gaseous mercury. In recent years, with the development of optoelectronic technology, many chemical monitoring methods have been replaced by simple, efficient and low-cost optical monitoring methods. In optical monitoring technology, spectroscopic monitoring methods have become the mainstream direction. This paper focuses on elemental mercury, including gaseous mercury in atmospheric and factory exhaust gases. Monitoring of gaseous mercury not only contributes to the improvement of mercury removal efficiency, but also plays an important role in monitoring and improving environmental pollution. This paper presents a method of generating ultraviolet laser with center wavelength of 253.7 nm using tunable multimode diode laser frequency doubling and sum-frequency technology, combined with correlation spectroscopy. The mercury concentration in the sample chamber is obtained by the automatic peak detection and generalized linear fitting algorithm, and the continuous monitoring of mercury can be realized. The absorption line of mercury is very narrow and has a strong absorption at 253.7 nm wavelength. In the frequency doubling experiment, the center wavelength of tunable multimode green diode laser is 505 nm.. The wavelength can be adjusted to 507.3 nm, under the control of current and temperature, and the wavelength can be adjusted to 507.3 nm, under the condition of adding external cavity. 253.7 nm ultraviolet light can be obtained from the frequency doubling effect of BBO crystal. The calculated results show that the UV intensity is 16.6 nW, and the sensitivity of mercury concentration measurement is 0.07 渭 g / m ~ (-3) at 1 m path / 4 s integral time, and the linear dynamic range of mercury concentration measurement is about 0 ~ 45 渭 g / m ~ (-3). Finally, the gas selectivity and practicability of the system were tested and the mercury concentration was continuously monitored. In sum-frequency experiments, tunable multi-mode red diode lasers with central wavelength of 687 nm and tunable multi-mode blue diode lasers with central wavelength of 401 nm are used to obtain 253.7 nm ultraviolet light through sum-frequency effect generated by BBO crystal. Scanning signals are applied to red and blue lasers, respectively, and double-channel scanning is carried out. The calculated results show that the sensitivity of mercury concentration measurement is 0.13 渭 g / m ~ (-3) at 1 m path / 10 s integral time when the UV intensity is 1.0 nW,. The linear dynamic range of mercury concentration measurement is about 0 ~ 36 渭 g / m ~ (3), and the analytical formulas of linear range and nonlinear range are given. By changing the temperature of the two lasers, we evaluate the stability of the system and complete the continuous monitoring of the volatilization and diffusion of mercury.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN249;TN23

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