燃煤煙氣SCR脫硝對(duì)細(xì)顆粒物排放特性影響的試驗(yàn)研究
發(fā)布時(shí)間：2018-10-18 16:12
【摘要】：當(dāng)前我國(guó)正面臨嚴(yán)重的細(xì)顆粒物(PM2.5)污染,其中燃煤電廠是我國(guó)PM25的主要排放源。SCR脫硝對(duì)于PM25的生成和脫除以及化學(xué)組成都有可能產(chǎn)生影響,并引起燃煤電廠排放特征的改變,在我國(guó)燃煤電廠大規(guī)模安裝SCR脫硝裝置的背景下,研究脫硝對(duì)燃煤電廠PM2.5排放的影響具有重要意義。本文利用自主設(shè)計(jì)搭建的SCR脫硝模擬試驗(yàn)裝置,基于V2O5-WO3/TiO2商用催化劑,采用電稱低壓沖擊器(ELPI)、PM10/PM2.5采樣器、X射線衍射(XRD)、場(chǎng)發(fā)射掃描電鏡-能譜分析(FSEM-EDX)等分析測(cè)試儀器,首先考察了SCR脫硝系統(tǒng)對(duì)細(xì)顆粒排放濃度及粒度分布的影響,并對(duì)SCR煙氣脫硝中形成的細(xì)顆粒形貌、元素及物相組成進(jìn)行了測(cè)試分析。結(jié)果表明,SCR脫硝過(guò)程中會(huì)形成大量顆粒物,其數(shù)量濃度約1x106個(gè)/cm3,質(zhì)量濃度約數(shù)十mg/m3,從數(shù)濃度角度,形成的顆粒物主要屬于亞微米級(jí)微粒,但從質(zhì)量濃度角度,則以微米級(jí)及大于10微米的顆粒物為主。顆粒物的主要成分為硫酸氫銨以及少量硫酸銨。在此基礎(chǔ)上,通過(guò)調(diào)節(jié)脫硝操作參數(shù)和模擬煙氣中氣體組分含量,試驗(yàn)考察了SCR脫硝工藝參數(shù)和煙氣組分對(duì)SCR脫硝過(guò)程中細(xì)顆粒形成的影響,分析了細(xì)顆粒物形成與SCR脫硝中SO2氧化的關(guān)系。結(jié)果表明,細(xì)顆粒生成量隨反應(yīng)溫度的升高和NH3/NO摩爾比的增加而增加,在脫硝效率較高時(shí),顆粒物形成量也趨于增多；煙氣中H20和Oz濃度的增加均會(huì)導(dǎo)致細(xì)顆粒物形成量的增加；細(xì)顆粒物數(shù)濃度的變化趨勢(shì)與SO2氧化為SO3的變化趨勢(shì)呈現(xiàn)出良好的相關(guān)一致性。細(xì)顆粒物產(chǎn)生及物性發(fā)生變化的主要原因可歸結(jié)于：一是在SCR脫硝反應(yīng)器中S03與NH3、H20反應(yīng)生成硫酸銨、硫酸氫銨細(xì)顆粒,該反應(yīng)為與SCR脫硝同時(shí)進(jìn)行的可逆過(guò)程,一部分以可凝結(jié)細(xì)顆粒形式帶出SCR脫硝系統(tǒng),其余在催化劑表面沉積,導(dǎo)致催化劑失活；二是SO3與逃逸的NH3、H20在SCR脫硝裝置后續(xù)系統(tǒng)(如空預(yù)器)等裝置時(shí)發(fā)生反應(yīng)形成硫酸銨、硫酸氫銨細(xì)顆粒；三是煙氣中游離堿土金屬氧化物(如CaO等)通過(guò)與SO3的反應(yīng)改變顆粒物的物性。最后,在自行設(shè)計(jì)搭建的燃煤熱態(tài)SCR脫硝試驗(yàn)裝置中,利用商用蜂窩狀釩鎢鈦催化劑,試驗(yàn)考察了SCR脫硝反應(yīng)前后細(xì)顆粒物的物性變化。結(jié)果表明：在實(shí)際燃煤煙氣環(huán)境下,SCR脫硝反應(yīng)同樣會(huì)加重細(xì)顆粒物的排放,細(xì)顆粒物的生成量隨著氨氮摩爾比和SO2濃度的增加而提高；同時(shí)研究還發(fā)現(xiàn),SCR脫硝過(guò)程中形成的亞微米級(jí)細(xì)顆粒難以被后續(xù)電除塵及濕法脫硫工藝有效捕集,從而導(dǎo)致WFGD系統(tǒng)出口細(xì)顆粒物濃度的增加。
[Abstract]:At present, China is facing serious fine particulate matter (PM2.5) pollution, of which coal-fired power plant is the main emission source of PM25 in China. SCR denitrification may have an impact on the formation and removal of PM25 and chemical composition, and cause the change of emission characteristics of coal-fired power plant. Under the background of large-scale installation of SCR denitrification unit in coal-fired power plants in China, it is of great significance to study the effect of denitrification on PM2.5 emissions from coal-fired power plants. In this paper, the SCR denitrification simulation test device is designed and built. Based on the commercial catalyst of V2O5-WO3/TiO2, the (ELPI), PM10/PM2.5 sampler of low pressure impactor, the scanning electron microscopy (FSEM-EDX) of X-ray diffraction (XRD), field emission and energy dispersive analysis (FSEM-EDX) are used in this paper. The effects of SCR denitrification system on the concentration and particle size distribution of fine particles were investigated, and the morphology, element and phase composition of fine particles formed in SCR flue gas denitrification were analyzed. The results showed that a large number of particles were formed in the process of denitrification with SCR. The mass concentration of 1x106 / cm3, was about tens of mg/m3,. From the angle of number and concentration, the particles formed mainly belonged to submicron particles, but from the angle of mass concentration. Micron and more than 10 micron particles are the main. The main components of particulate matter are ammonium hydrogen sulfate and a small amount of ammonium sulfate. On this basis, the effects of SCR denitrification process parameters and flue gas components on the formation of fine particles in the denitrification process of SCR were investigated by adjusting the operation parameters of denitrification and simulating the gas component content in flue gas. The relationship between the formation of fine particles and SO2 oxidation in SCR denitrification was analyzed. The results showed that the yield of fine particles increased with the increase of reaction temperature and the molar ratio of NH3/NO. When the denitrification efficiency was high, the amount of particles formed tended to increase. The increase of H20 and Oz concentration in flue gas would lead to the increase of fine particulate matter formation, and there was a good correlation between the change trend of fine particle number concentration and the trend of SO2 oxidation to SO3. The main reasons for the formation of fine particles and the change of physical properties can be attributed to the following: first, in SCR denitrification reactor, S03 reacts with NH3,H20 to form ammonium sulfate and ammonium hydrogen sulfate fine particles, which is a reversible process in parallel with SCR denitrification. A portion of the SCR denitrification system was carried out in the form of condensable fine particles, while the rest was deposited on the surface of the catalyst, which resulted in the deactivation of the catalyst. Second, the SO3 reacted with the escaping NH3,H20 in the SCR denitration unit follow-up system (such as an air preheater) to form ammonium sulfate. Third, free alkaline earth metal oxides (such as CaO) in flue gas changed the physical properties of particles by reacting with SO3. Finally, the physical properties of fine particles before and after SCR denitrification were investigated using commercial honeycomb vanadium tungsten titanium catalyst in a self-designed SCR denitrification test facility. The results showed that the denitrification reaction of SCR would also increase the emission of fine particles in the actual coal-fired flue gas environment, and the amount of fine particles would increase with the increase of the molar ratio of ammonia to nitrogen and the concentration of SO2. At the same time, it is found that the submicron fine particles formed in the process of SCR denitrification are difficult to be effectively captured by the subsequent electrodedusting and wet desulphurization process, resulting in the increase of the concentration of fine particles at the outlet of the WFGD system.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X773
本文編號(hào)：2279660
[Abstract]:At present, China is facing serious fine particulate matter (PM2.5) pollution, of which coal-fired power plant is the main emission source of PM25 in China. SCR denitrification may have an impact on the formation and removal of PM25 and chemical composition, and cause the change of emission characteristics of coal-fired power plant. Under the background of large-scale installation of SCR denitrification unit in coal-fired power plants in China, it is of great significance to study the effect of denitrification on PM2.5 emissions from coal-fired power plants. In this paper, the SCR denitrification simulation test device is designed and built. Based on the commercial catalyst of V2O5-WO3/TiO2, the (ELPI), PM10/PM2.5 sampler of low pressure impactor, the scanning electron microscopy (FSEM-EDX) of X-ray diffraction (XRD), field emission and energy dispersive analysis (FSEM-EDX) are used in this paper. The effects of SCR denitrification system on the concentration and particle size distribution of fine particles were investigated, and the morphology, element and phase composition of fine particles formed in SCR flue gas denitrification were analyzed. The results showed that a large number of particles were formed in the process of denitrification with SCR. The mass concentration of 1x106 / cm3, was about tens of mg/m3,. From the angle of number and concentration, the particles formed mainly belonged to submicron particles, but from the angle of mass concentration. Micron and more than 10 micron particles are the main. The main components of particulate matter are ammonium hydrogen sulfate and a small amount of ammonium sulfate. On this basis, the effects of SCR denitrification process parameters and flue gas components on the formation of fine particles in the denitrification process of SCR were investigated by adjusting the operation parameters of denitrification and simulating the gas component content in flue gas. The relationship between the formation of fine particles and SO2 oxidation in SCR denitrification was analyzed. The results showed that the yield of fine particles increased with the increase of reaction temperature and the molar ratio of NH3/NO. When the denitrification efficiency was high, the amount of particles formed tended to increase. The increase of H20 and Oz concentration in flue gas would lead to the increase of fine particulate matter formation, and there was a good correlation between the change trend of fine particle number concentration and the trend of SO2 oxidation to SO3. The main reasons for the formation of fine particles and the change of physical properties can be attributed to the following: first, in SCR denitrification reactor, S03 reacts with NH3,H20 to form ammonium sulfate and ammonium hydrogen sulfate fine particles, which is a reversible process in parallel with SCR denitrification. A portion of the SCR denitrification system was carried out in the form of condensable fine particles, while the rest was deposited on the surface of the catalyst, which resulted in the deactivation of the catalyst. Second, the SO3 reacted with the escaping NH3,H20 in the SCR denitration unit follow-up system (such as an air preheater) to form ammonium sulfate. Third, free alkaline earth metal oxides (such as CaO) in flue gas changed the physical properties of particles by reacting with SO3. Finally, the physical properties of fine particles before and after SCR denitrification were investigated using commercial honeycomb vanadium tungsten titanium catalyst in a self-designed SCR denitrification test facility. The results showed that the denitrification reaction of SCR would also increase the emission of fine particles in the actual coal-fired flue gas environment, and the amount of fine particles would increase with the increase of the molar ratio of ammonia to nitrogen and the concentration of SO2. At the same time, it is found that the submicron fine particles formed in the process of SCR denitrification are difficult to be effectively captured by the subsequent electrodedusting and wet desulphurization process, resulting in the increase of the concentration of fine particles at the outlet of the WFGD system.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X773
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