本文選題：ABS + 揮發(fā)特性�。� 參考：《華北電力大學(xué)》2017年碩士論文

【摘要】：以NH3或尿素為還原劑的選擇性催化還原法(SCR)是目前火電廠應(yīng)用最為廣泛的脫硝技術(shù),該方法技術(shù)成熟、脫硝效率高、運行可靠且便于維護(hù)和操作。在煙氣脫硝的過程中,SCR催化劑在催化還原NOX的同時,也使煙氣中部分SO2(0.5%-2.0%)氧化成SO3,進(jìn)而與SCR脫硝過程中的逃逸氨生成硫酸氫銨(ABS),液態(tài)的ABS具有粘性,易于在催化劑表面及SCR反應(yīng)器的下游設(shè)備和管道上沉積,吸附煙氣中的大量飛灰,引起催化劑活性降低、空預(yù)器阻力增大,傳熱元件傳熱效率下降等,嚴(yán)重時導(dǎo)致停機(jī)。因此,研究ABS的揮發(fā)特性與調(diào)控方法非常有必要。本文利用自行設(shè)計的揮發(fā)試驗臺,研究ABS的揮發(fā)特性及揮發(fā)后的冷凝規(guī)律,得出:隨溫度升高,ABS揮發(fā)速率增大,溫度達(dá)400℃時,揮發(fā)速率出現(xiàn)陡增;接觸面積增大,ABS的揮發(fā)速率明顯升高;ABS顆粒越細(xì),其揮發(fā)速率越快;隨著飛灰中摻雜ABS量的增加,揮發(fā)速率呈下降趨勢;利用離子色譜法對冷凝產(chǎn)物進(jìn)行分析,得出當(dāng)揮發(fā)溫度低于300℃時,冷凝管中冷凝產(chǎn)物可能為NH4HSO4和少量的H2SO4,高于350℃時,冷凝產(chǎn)物可能是H2SO4和少量的硫酸銨(AS)。熱重分析表明,ABS起始揮發(fā)溫度為206℃左右,297-390℃為快速揮發(fā)階段,在378℃時實現(xiàn)最快揮發(fā)速率;ABS的分解過程為:先發(fā)生脫氨反應(yīng),隨后硫酸進(jìn)一步分解為SO3和H2O;熱重數(shù)據(jù)和等速升溫動力學(xué)分析表明:ABS的揮發(fā)過程分為三個溫度段,各段均符合反Jander揮發(fā)動力學(xué)模型,為三維擴(kuò)散。高溫條件下,ABS和AS對碳鋼的腐蝕速率均隨溫度升高而降低,200℃以上變化不大;低于200℃時,ABS對碳鋼的腐蝕速率比AS快;ABS濃度越高,腐蝕速率越快;利用SEM/EDS和XRD分析,確定腐蝕產(chǎn)物可能為鐵的氧化物和(NH4)Fe(SO4)2等;機(jī)理為碳鋼先發(fā)生酸性腐蝕和氧腐蝕,生成的Fe2+發(fā)生系列次生反應(yīng),生成鐵的氧化物和(NH4)Fe(SO4)2等。結(jié)合實驗研究結(jié)果表明,采用空預(yù)器控溫的手段,應(yīng)使煙氣溫度在350℃左右,以保證在實現(xiàn)一定的ABS揮發(fā)效果的同時,避免后續(xù)腐蝕問題。DSI法可以實現(xiàn)較好的SO3脫除效率,對ABS的控制效果好且運行費用較低。本論文研究對企業(yè)控制或減輕ABS的不良影響提供了理論基礎(chǔ)。
[Abstract]:Selective catalytic reduction method with NH3 or urea as reductant is the most widely used denitrification technology in thermal power plants at present. The technology is mature, the denitrification efficiency is high, the operation is reliable and easy to maintain and operate. In the process of flue gas denitrification, the catalyst catalyzes the reduction of NOX, at the same time, it also oxidizes part of so _ 2 in flue gas to so _ 3, and then forms ammonium bisulfate with the escaping ammonia in the process of SCR denitrification. The liquid ABS is viscous. It is easy to deposit on the surface of catalyst and on the downstream equipment and pipeline of SCR reactor, and adsorb a large amount of fly ash in flue gas, which results in the decrease of catalyst activity, the increase of air preheater resistance and the decrease of heat transfer efficiency of heat transfer elements. Therefore, it is necessary to study the volatilization characteristics and control methods of ABS. In this paper, the volatilization characteristics and condensation law of ABS after volatilization are studied by using the self-designed volatilization test rig. It is concluded that the volatilization rate of ABS increases with the increase of temperature, and the volatilization rate increases steeply when the temperature reaches 400 鈩，

本文編號：1869766