發(fā)布時間：2017-12-28 14:27

  本文關(guān)鍵詞：氯化鎂調(diào)質(zhì)煙氣促進(jìn)汞催化氧化的試驗與機(jī)理研究　出處：《山東大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 汞 SCR催化劑 氯化鎂 氧化 活性氯

【摘要】：汞具有劇毒性、高揮發(fā)性和生物富集性,是一種全球性污染元素。燃煤汞排放被認(rèn)為是大氣中汞污染的主要來源,對環(huán)境造成的污染問題越來越受到世界各國的廣泛關(guān)注。煙氣中的汞主要有3種形態(tài)：單質(zhì)汞(Hg0)、氧化態(tài)汞(Hg2+)和顆粒態(tài)汞(Hgp),Hg2+易溶于水,絕大部分可通過濕法脫硫設(shè)備得到脫除,Hgp易于被除塵設(shè)備所捕獲,單質(zhì)汞由于具有極大的化學(xué)穩(wěn)定性和較差的水溶性而不易被現(xiàn)有污染物控制設(shè)備所脫除。利用SCR催化劑對汞的催化氧化作用,結(jié)合濕法脫硫設(shè)備聯(lián)合脫汞投資及運(yùn)行成本低、適合現(xiàn)有電廠的改造,是一種經(jīng)濟(jì)可行且極具競爭力的燃煤電廠汞污染控制方法。利用常規(guī)污染物控制設(shè)備聯(lián)合脫汞的關(guān)鍵在于提高SCR催化劑對單質(zhì)汞的氧化效率。由于SCR催化劑對單質(zhì)汞的氧化效率受煙氣中氯含量的制約,煤中氯含量高,煙氣中HCl含量就越高,SCR催化劑對汞的氧化效率越高,因而對于低氯煤,SCR催化劑對汞的氧化受到限制。脫硫廢水中富含氯化鎂,氯化鎂在高溫下可分解產(chǎn)生氯化氫(HCl)氣體,本文提出將脫硫廢水中的主要成分氯化鎂噴射在SCR脫硝裝置的前置煙道中,利用高溫?zé)煔獯龠M(jìn)氯化鎂分解,產(chǎn)生氯化氫,從而促進(jìn)SCR催化劑對單質(zhì)汞的氧化。首先,研究了商業(yè)釩鈦基SCR催化劑對單質(zhì)汞的氧化性能,進(jìn)而對SCR催化劑氧化單質(zhì)汞的機(jī)理進(jìn)行了探討。試驗結(jié)果表明,HCl可以明顯提高SCR催化劑對單質(zhì)汞的氧化作用,汞的氧化效率隨著溫度的升高而升高,350℃時氧化效率可達(dá)到80%左右,繼續(xù)升高溫度,氧化效率變化不大,可見催化劑對脫汞和脫硝的溫度窗口相一致。O2可以顯著提高SCR催化劑對單質(zhì)汞的吸附能力,HCl和Hg0都可以吸附在催化劑表面,但HCl的吸附弱于單質(zhì)汞的吸附,SCR催化劑催化Hg0氧化的反應(yīng)機(jī)理主要是Eley-Rideal機(jī)理,即催化劑表面吸附態(tài)的Hg與氣相中的HCl或弱吸附態(tài)的HCl反應(yīng),實現(xiàn)汞的氧化。其次,在固定床試驗臺上研究了商業(yè)SCR催化劑添加氯化鎂對單質(zhì)汞形態(tài)轉(zhuǎn)化的影響,主要考察氯化鎂添加量、溫度以及氣氛對汞形態(tài)轉(zhuǎn)化的影響。試驗結(jié)果表明,氯化鎂在高溫下分解產(chǎn)生HCl和活性氯,可以促進(jìn)單質(zhì)汞的均相氧化。用氯化鎂調(diào)質(zhì)SCR催化劑可以大幅度提高其對單質(zhì)汞的氧化效率,在350℃,基本煙氣條件下,氯化鎂添加量從0wt%到1wt%范圍內(nèi),汞的氧化效率隨添加量增加從22.3%迅速提高至83.4%。溫度升高有利于單質(zhì)汞向氧化態(tài)汞轉(zhuǎn)化,其中在350℃達(dá)到峰值,是汞催化氧化的最佳溫度。O2和NO可以促進(jìn)添加氯化鎂后催化劑對單質(zhì)汞的氧化,SO2和H2O抑制單質(zhì)汞的氧化,添加氯化鎂后對催化劑的脫硝效率沒有明顯的影響。機(jī)理試驗表明氯化鎂分解產(chǎn)生HCl和活性氯,在催化劑的作用下可以達(dá)到對汞的高效氧化。最后,量子化學(xué)密度泛函理論是計算晶體結(jié)構(gòu)和表面反應(yīng)機(jī)理的精確方法,本文利用密度泛函理論結(jié)合周期性平板模型研究氯化鎂產(chǎn)生的活性氯促進(jìn)SCR催化劑氧化單質(zhì)汞的機(jī)理。模擬結(jié)果表明,Cl在V2O5(001)表面為化學(xué)吸附,Cl與V2O5表面的O有強(qiáng)烈的成鍵作用,對V2O5起到改性的作用,增加了催化劑表面的活性位。Hg0在吸附Cl后的V2O5(001)表面可以穩(wěn)定地生成HgCl,一部分HgCl吸附在催化劑表面,一部分HgCl從催化劑表面脫附,兩種情況都有利于單質(zhì)汞的氧化。
[Abstract]:Mercury is a global pollution element, which is highly toxic, highly volatile and bioenriched. Mercury emission from coal burning is considered to be the main source of mercury pollution in the atmosphere, and the pollution problem caused by the environment has attracted more and more attention from all over the world. Mercury in flue gas mainly has 3 forms: elemental mercury (Hg0), oxidized mercury (Hg2+) and particulate mercury (Hgp), Hg2+ soluble in water, most can be removed by wet desulfurization equipment, Hgp can easily be captured by the elemental mercury removal equipment, because of its great chemical stability and the poor water solubility and not easy to be the removal of existing pollutant control equipment. Using SCR catalyst to catalyze the oxidation of mercury, combined with the combined mercury removal from wet desulphurization equipment and low cost of operation, is suitable for the transformation of existing power plants. It is an economically viable and competitive way of mercury pollution control in coal-fired power plants. The key of combined dehhl removal by conventional pollutant control equipment is to improve the oxidation efficiency of SCR catalyst for Hg. Because the oxidation efficiency of SCR catalyst to elemental mercury is restricted by chlorine content in flue gas, the content of chlorine in coal is high, the content of HCl in flue gas is higher, and the oxidation efficiency of SCR catalyst to Hg is higher. Therefore, for SCR of low chlorine coal, the oxidation of Hg is limited. Rich in magnesium chloride desulfurization wastewater, magnesium chloride can be decomposed to produce hydrogen chloride at high temperature (HCl) gas, this paper put forward the main components of magnesium chloride injection in SCR desulfurization wastewater in flue pre denitrification device, promote the decomposition of magnesium chloride by high temperature flue gas, hydrogen chloride is produced, so as to promote the oxidation of elemental mercury catalyst SCR the. First, the oxidation performance of commercial vanadium and titanium based SCR catalyst for the oxidation of Hg was studied, and the mechanism of SCR catalyst for the oxidation of Hg was discussed. The test results show that HCl can significantly improve the oxidation effect of SCR catalyst on elemental mercury, mercury oxidation efficiency increases with the increase of temperature at 350 DEG C, the oxidation efficiency can reach about 80%, with increasing of temperature, the oxidation efficiency changed little, visible catalyst on the temperature window for mercury removal and denitrification are consistent. O2 can significantly improve the adsorption ability of SCR catalyst for the mercury, HCl and Hg0 can be adsorbed on the catalyst surface, but the adsorption of HCl on the weak adsorption of elemental mercury, the reaction mechanism of Hg0 catalytic oxidation of SCR catalyst is the main mechanism of Eley-Rideal, Hg and HCl reaction gas adsorption state phase HCl or weak adsorption state, realize the oxidation of mercury. Secondly, the influence of commercial SCR catalyst added with magnesium chloride on the transformation of elemental mercury was studied on a fixed bed test bench. The effects of magnesium chloride addition, temperature and atmosphere on mercury transformation were investigated. The results show that the decomposition of magnesium chloride at high temperature produces HCl and active chlorine, which can promote the homogeneous phase oxidation of the elemental mercury. The SCR catalyst with magnesium chloride quenched and tempered can significantly improve the oxidation efficiency of elemental mercury. At 350, the oxidation efficiency of mercury increased from 22.3% to 83.4% when the amount of magnesium chloride increased from 0wt% to 1wt%. The increase of temperature is beneficial to the conversion of the elemental mercury to the oxidized mercury, which reaches the peak at 350, which is the best temperature for the catalytic oxidation of mercury. O2 and NO can promote the oxidation of elemental mercury after adding magnesium chloride, and SO2 and H2O inhibit the oxidation of elemental mercury. The addition of magnesium chloride has no obvious effect on the denitration efficiency of the catalysts. The mechanism test shows that magnesium chloride is decomposed to produce HCl and active chlorine, and the high efficient oxidation of mercury can be achieved under the action of the catalyst. Finally, quantum chemical density functional theory is an accurate method to calculate crystal structure and surface reaction mechanism. In this paper, the theory of density functional theory combined with periodic slab model is used to study the active chlorine produced by magnesium chloride to promote the mechanism of SCR catalyst to oxidize elemental mercury. The simulation results show that Cl is chemisorbed on the surface of V2O5 (001), and Cl has strong bonding effect with O on the surface of V2O5, which plays a modified role in V2O5 and increases the active site on the catalyst surface. Hg0 can stably generate HgCl on the V2O5 (001) surface after Cl adsorption. A part of HgCl adsorbed on the surface of the catalyst. A part of HgCl is adsorbed on the catalyst surface. The two conditions are beneficial to the oxidation of elemental mercury.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ132.2;X773

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 李永華,王五一,楊林生,李海蓉;汞的環(huán)境生物地球化學(xué)研究進(jìn)展[J];地理科學(xué)進(jìn)展;2004年06期

2 徐麗梅玫;李彩亭;夏扎旦·阿不力克木;高招;;利用現(xiàn)有設(shè)備和技術(shù)控制燃煤煙氣汞污染研究進(jìn)展[J];環(huán)境工程;2010年03期

3 趙永椿;張軍營;劉晶;DíAZ-SOMOANO Mercedes;ABAD-VALLE Patricia;MARTíNEZ-TARAZONA M Rosa;鄭楚光;;燃煤飛灰吸附脫汞能力的實驗研究[J];中國科學(xué):技術(shù)科學(xué);2010年04期

4 沈伯雄;陳建宏;蔡記;何川;李卓;;KI改性黏土脫除煙氣中單質(zhì)汞的研究[J];環(huán)境科學(xué);2014年08期

5 董勇;喻敏;王鵬;張夢澤;睢輝;崔琳;張立強(qiáng);徐夕仁;馬春元;;CaCl_2添加對熱解煤中汞析出規(guī)律影響的實驗研究[J];燃料化學(xué)學(xué)報;2014年01期

6 黃治軍;段鈺鋒;王運(yùn)軍;孟素麗;焦永剛;;改性氫氧化鈣吸附脫除模擬煙氣中汞的試驗研究[J];中國電機(jī)工程學(xué)報;2009年17期

7 孟素麗;段鈺鋒;黃治軍;王運(yùn)軍;楊立國;;煙氣成分對燃煤飛灰汞吸附的影響[J];中國電機(jī)工程學(xué)報;2009年20期

8 趙鵬飛;郭欣;鄭楚光;;活性炭及氯改性活性炭吸附單質(zhì)汞的機(jī)制研究[J];中國電機(jī)工程學(xué)報;2010年23期

9 王錚;薛建明;許月陽;王宏亮;劉s，

本文編號：1346391