SCR煙氣脫硝過程中硫酸（氫）銨細(xì)顆粒生成及分解特性研究
發(fā)布時間：2018-09-11 19:23
【摘要】：選擇性催化還原(SCR)法脫除煙氣中氮氧化物是當(dāng)前煙氣脫硝的主要工藝。煙氣脫硝本身會形成PM2.5,主要成分為硫酸氫銨(ABS)及少量硫酸銨,但已有研究僅側(cè)重于硫酸銨鹽宏觀現(xiàn)象的考察,其形成與SCR脫硝的內(nèi)在關(guān)聯(lián)并未進(jìn)行深入探討。本文利用傅立葉原位紅外、TG、DTG、TG-FTIR聯(lián)用等測試手段研究了商用V2O5-WO3/TiO2催化劑表面SO2催化氧化、ABS生成及降解機理、硫酸銨鹽分解機制,為控制SCR脫硝過程中硫酸銨鹽生成及PM2.5排放提供試驗基礎(chǔ)。主要試驗結(jié)論如下：SO2在催化劑表面氧化過程：吸附在催化劑表面的V2O5活性位上,占據(jù)O原子并以SO32-形式存在,與催化劑表面的V5+-OH發(fā)生反應(yīng)生成金屬硫酸鹽(VOSO4)中間產(chǎn)物；O2重新氧化SO2/SO3催化氧化過程中由于被SO2奪取O原子造成的V2O5物種上的氧缺位,促進(jìn)金屬硫酸鹽(VOSO4)向SO3及V2O5的轉(zhuǎn)化。SO2與NO、NH3存在的競爭吸附阻礙SO2的吸附及氧化行為；O2的存在促進(jìn)SO2的吸附行為。SCR脫硝中V2O5-WO3/TiO2催化劑表面ABS生成的主要途徑：①由吸附活化態(tài)的NH3,主要為催化劑表面V=O基團上Lewis酸吸附配位結(jié)合的NH3,在O2環(huán)境中與SO2反應(yīng)生成；②由SO2與催化劑表面V2O5反應(yīng)生成的吸附態(tài)金屬硫酸鹽VOSO4與氣態(tài)NH3反應(yīng)生成；且兩種ABS生成行為均伴隨SCR脫硝反應(yīng)同時進(jìn)行,其反應(yīng)行為與NH3/NO的大小緊密相關(guān)。在SCR脫硝中,ABS形成溫度在250℃左右,生成的ABS在400℃左右發(fā)生分解,生成硫酸類物質(zhì)吸附在催化劑表面。NO通過與ABS中NH4+直接反應(yīng)降低ABS降解的溫度,促進(jìn)其在催化劑表面的分解,NO的脫除與ABS的生成是相互抑制關(guān)系;NH3與ABS在與NO的反應(yīng)方面存在競爭性行為,兩種反應(yīng)行為共存,互相抑制,NH3與NO的脫硝反應(yīng)的競爭抑制ABS的有效降解；催化劑上的ABS在SCR反應(yīng)溫度窗口內(nèi)存在揮發(fā)現(xiàn)象,ABS的負(fù)載量影響其揮發(fā)及分解行為,ABS負(fù)載量越小,越難揮發(fā),越難分解,降解溫度窗口相應(yīng)升高。純ABS通過一步分解反應(yīng)生成H2O,NH3和SO2；負(fù)載于催化劑上的ABS分為兩個分解階段：①ABS的脫氨過程；②脫氨生成的H2SO4在催化劑表面的SO2釋放行為；負(fù)載在催化劑上的ABS有明顯的分步分解現(xiàn)象：脫氨與SO2釋放在不同的溫度區(qū)間發(fā)生,催化劑促進(jìn)脫氨行為,但延緩SO2的釋放,推遲ABS完全分解的溫度窗口。純硫酸銨固體的熱分解分為三個階段,負(fù)載在催化劑上的硫酸銨分解分為四個階段,硫酸銨經(jīng)脫NH3反應(yīng)后生成ABS,催化劑的存在導(dǎo)致脫氨與SO2的釋放行為相區(qū)隔,促進(jìn)脫氨反應(yīng)提前發(fā)生,延緩SO2的釋放行為,抬高硫酸銨完全分解的溫度。
[Abstract]:Selective catalytic reduction (SCR) is the main process of flue gas denitrification. The main components of flue gas denitrification are ammonium hydrogen sulfate (ABS) and a small amount of ammonium sulfate. However, the study has only focused on the macroscopic phenomenon of ammonium sulfate, and the internal relationship between the formation of ammonium sulfate and the denitrification of SCR has not been deeply discussed. In this paper, the formation and degradation mechanism of SO2 on commercial V2O5-WO3/TiO2 catalyst surface and the decomposition mechanism of ammonium sulfate have been studied by means of FTIR in situ FTIR and TG-FTIR. It provides experimental basis for controlling ammonium sulfate formation and PM2.5 emission during SCR denitrification. The main results are as follows: the oxidation process of so _ 2 on the catalyst surface is as follows: adsorbed on the active site of V2O5 on the surface of the catalyst, O atom is occupied and exists in the form of SO32-, which reacts with V _ 5-OH on the surface of the catalyst to form the intermediate product of metal sulfate (VOSO4). Oxygen vacancies in V2O5 species due to O atom capture by SO2 during O 2 reoxidation of SO2/SO3, the competitive adsorption of VOSO4 to SO3 and V2O5. The competitive adsorption of so 2 with NO,NH3 hinders the adsorption and oxidation of SO2. The main pathway of the formation of ABS on the surface of V2O5-WO3/TiO2 catalyst in V2O5-WO3/TiO2 denitrification is: 1. The main way of ABS formation on the surface of V2O5-WO3/TiO2 catalyst is that the adsorption and coordination of Lewis acid on the surface of the catalyst is mainly composed of the adsorbed and activated NH3, on the surface of the catalyst, and the NH3, reacts with SO2 in O2 environment. (2) the adsorptive metal sulfate VOSO4 formed by the reaction of SO2 with the surface V2O5 of the catalyst reacted with the gaseous NH3, and the two kinds of ABS formation were accompanied by the SCR denitrification reaction, and the reaction behavior was closely related to the size of NH3/NO. In the denitrification of SCR, the formation temperature of ABS is about 250 鈩，
本文編號：2237643
[Abstract]:Selective catalytic reduction (SCR) is the main process of flue gas denitrification. The main components of flue gas denitrification are ammonium hydrogen sulfate (ABS) and a small amount of ammonium sulfate. However, the study has only focused on the macroscopic phenomenon of ammonium sulfate, and the internal relationship between the formation of ammonium sulfate and the denitrification of SCR has not been deeply discussed. In this paper, the formation and degradation mechanism of SO2 on commercial V2O5-WO3/TiO2 catalyst surface and the decomposition mechanism of ammonium sulfate have been studied by means of FTIR in situ FTIR and TG-FTIR. It provides experimental basis for controlling ammonium sulfate formation and PM2.5 emission during SCR denitrification. The main results are as follows: the oxidation process of so _ 2 on the catalyst surface is as follows: adsorbed on the active site of V2O5 on the surface of the catalyst, O atom is occupied and exists in the form of SO32-, which reacts with V _ 5-OH on the surface of the catalyst to form the intermediate product of metal sulfate (VOSO4). Oxygen vacancies in V2O5 species due to O atom capture by SO2 during O 2 reoxidation of SO2/SO3, the competitive adsorption of VOSO4 to SO3 and V2O5. The competitive adsorption of so 2 with NO,NH3 hinders the adsorption and oxidation of SO2. The main pathway of the formation of ABS on the surface of V2O5-WO3/TiO2 catalyst in V2O5-WO3/TiO2 denitrification is: 1. The main way of ABS formation on the surface of V2O5-WO3/TiO2 catalyst is that the adsorption and coordination of Lewis acid on the surface of the catalyst is mainly composed of the adsorbed and activated NH3, on the surface of the catalyst, and the NH3, reacts with SO2 in O2 environment. (2) the adsorptive metal sulfate VOSO4 formed by the reaction of SO2 with the surface V2O5 of the catalyst reacted with the gaseous NH3, and the two kinds of ABS formation were accompanied by the SCR denitrification reaction, and the reaction behavior was closely related to the size of NH3/NO. In the denitrification of SCR, the formation temperature of ABS is about 250 鈩，
本文編號：2237643
本文鏈接：http://sikaile.net/kejilunwen/huanjinggongchenglunwen/2237643.html
最近更新
教材專著
