本文選題：SCR + 硫酸氫銨/硫酸銨��； 參考：《浙江大學》2017年碩士論文

【摘要】：氮氧化物(NOx)是燃煤鍋爐的主要大氣污染物之一,對環(huán)境以及人體健康有多重危害。選擇性催化還原法(SCR)是脫除燃煤煙氣中NOx的主要方法。隨著煙氣溫度的下降,未反應完全的還原劑NH3易與煙氣中的SO3反應生成硫酸氫銨。液態(tài)硫酸氫銨具有極強的粘性以及腐蝕性,凝結在空氣預熱器表面并不斷捕捉飛灰,導致空氣預熱器的積灰、堵塞和腐蝕。當前燃煤機組的超低污染物排放技術不斷推廣,其中增加一層SCR催化劑是進一步脫除NOx的主要途徑,不僅增加S03濃度,且隨著機組運行時間的增加,催化劑老化失活,氨逃逸濃度也會上升,進一步增加硫酸氫銨的生成量,加劇空氣預熱器的積灰堵塞現(xiàn)象。因此本文研究脫硝煙氣中硫酸氫銨的生成機理,為空氣預熱器設計和運行提供理論依據(jù)。本文先從化學熱力學的角度計算NH3和S03反應過程中吉布斯自由能的變化,并判斷反應進行的方向。研究表明,由于S03易與H20反應生成H2SO4,煙氣中S03更多地以H2SO4形式反應生成硫酸氫銨,且SO3和NH3反應更易生成硫酸銨。在硫酸氫銨沉積溫度的實驗研究中發(fā)現(xiàn),NH3和SO3對沉積溫度有相同的影響。在實驗的濃度積Φ[NH3]·Φ[SO3]范圍內(nèi)(20～11000μL2·L-2),硫酸氫銨的沉積溫度與反應物濃度積的對數(shù)呈線性正相關關系,沉積溫度的變化范圍在225-251℃之間。在相同濃度積的情況下,摩爾比(NH3/S03)偏離1:1時,硫酸氫銨的沉積溫度略有上升。隨著煙溫的越低,硫酸氫銨/硫酸銨生成率不斷增加。S03和NH3濃度的增加導致硫酸氫銨的生成率上升;NH3濃度的增加導致硫酸銨的生成率增加,而SO3濃度增加則導致硫酸銨生成率的下降。根據(jù)分析結果推斷硫酸氫銨的生成進度由反應平衡控制,不考慮硫酸氫銨狀態(tài),反應平衡常數(shù)K1在各溫度下數(shù)據(jù)集中性都較好,隨著溫度的下降,lgK1在120-200℃和200-260℃兩個溫度區(qū)間基本呈線性增加,且高溫段增加速度更快。根據(jù)硫酸氫銨完全凝結假設的反應平衡常數(shù)集中性較好,lgK11在120-220℃之間隨著溫度的下降呈線性增加趨勢。K1和K11均有較強的實際應用價值。據(jù)分析推斷硫酸銨由硫酸氫銨和NH3反應生成。
[Abstract]:Nitric oxide (no _ x) is one of the main atmospheric pollutants in coal-fired boilers, which is harmful to the environment and human health. Selective catalytic reduction is the main method to remove NOx from coal-fired flue gas. With the decrease of flue gas temperature, NH3, which is not a complete reductant, can easily react with SO3 in flue gas to form ammonium bicarbonate. Liquid ammonium hydrogen sulfate is very viscous and corrosive, which condenses on the surface of air preheater and continuously captures fly ash, resulting in ash accumulation, blockage and corrosion of air preheater. At present, the ultra-low pollutant emission technology of coal-fired units is popularized, and the addition of a layer of SCR catalyst is the main way to further remove NOx. It not only increases the concentration of S03, but also deactivates the catalyst with the increase of unit operating time. The concentration of ammonia escape will also increase, further increase the amount of ammonium hydrogen sulfate, and aggravate the fouling and blocking phenomenon of air preheater. Therefore, the formation mechanism of ammonium hydrogen sulfate in denitrification flue gas is studied in this paper, which provides a theoretical basis for the design and operation of air preheater. In this paper, the change of Gibbs free energy in the reaction of NH3 and S03 is calculated from the point of view of chemical thermodynamics, and the direction of reaction is judged. The results show that because S03 reacts with H20 to produce H2SO4, S03 reacts more in the form of H2SO4 to produce ammonium hydrogen sulfate, and SO3 and NH3 react more easily to produce ammonium sulfate. It is found that NH _ 3 and SO3 have the same effect on the deposition temperature of ammonium hydrogen sulfate. In the range of 桅 [NH3] 桅 [SO3], the deposition temperature of ammonium hydrogen sulfate has a linear positive correlation with the logarithm of reactant concentration product, and the range of deposition temperature is from 225 鈩，

本文編號：1907829