SCR烟气脱硝过程中硫酸（氢）铵细颗粒生成及分解特性研究
发布时间：2018-09-11 19:23
【摘要】：选择性催化还原(SCR)法脱除烟气中氮氧化物是当前烟气脱硝的主要工艺。烟气脱硝本身会形成PM2.5,主要成分为硫酸氢铵(ABS)及少量硫酸铵,但已有研究仅侧重于硫酸铵盐宏观现象的考察,其形成与SCR脱硝的内在关联并未进行深入探讨。本文利用傅立叶原位红外、TG、DTG、TG-FTIR联用等测试手段研究了商用V2O5-WO3/TiO2催化剂表面SO2催化氧化、ABS生成及降解机理、硫酸铵盐分解机制,为控制SCR脱硝过程中硫酸铵盐生成及PM2.5排放提供试验基础。主要试验结论如下：SO2在催化剂表面氧化过程：吸附在催化剂表面的V2O5活性位上,占据O原子并以SO32-形式存在,与催化剂表面的V5+-OH发生反应生成金属硫酸盐(VOSO4)中间产物；O2重新氧化SO2/SO3催化氧化过程中由于被SO2夺取O原子造成的V2O5物种上的氧缺位,促进金属硫酸盐(VOSO4)向SO3及V2O5的转化。SO2与NO、NH3存在的竞争吸附阻碍SO2的吸附及氧化行为；O2的存在促进SO2的吸附行为。SCR脱硝中V2O5-WO3/TiO2催化剂表面ABS生成的主要途径：①由吸附活化态的NH3,主要为催化剂表面V=O基团上Lewis酸吸附配位结合的NH3,在O2环境中与SO2反应生成；②由SO2与催化剂表面V2O5反应生成的吸附态金属硫酸盐VOSO4与气态NH3反应生成；且两种ABS生成行为均伴随SCR脱硝反应同时进行,其反应行为与NH3/NO的大小紧密相关。在SCR脱硝中,ABS形成温度在250℃左右,生成的ABS在400℃左右发生分解,生成硫酸类物质吸附在催化剂表面。NO通过与ABS中NH4+直接反应降低ABS降解的温度,促进其在催化剂表面的分解,NO的脱除与ABS的生成是相互抑制关系;NH3与ABS在与NO的反应方面存在竞争性行为,两种反应行为共存,互相抑制,NH3与NO的脱硝反应的竞争抑制ABS的有效降解；催化剂上的ABS在SCR反应温度窗口内存在挥发现象,ABS的负载量影响其挥发及分解行为,ABS负载量越小,越难挥发,越难分解,降解温度窗口相应升高。纯ABS通过一步分解反应生成H2O,NH3和SO2；负载于催化剂上的ABS分为两个分解阶段：①ABS的脱氨过程；②脱氨生成的H2SO4在催化剂表面的SO2释放行为；负载在催化剂上的ABS有明显的分步分解现象：脱氨与SO2释放在不同的温度区间发生,催化剂促进脱氨行为,但延缓SO2的释放,推迟ABS完全分解的温度窗口。纯硫酸铵固体的热分解分为三个阶段,负载在催化剂上的硫酸铵分解分为四个阶段,硫酸铵经脱NH3反应后生成ABS,催化剂的存在导致脱氨与SO2的释放行为相区隔,促进脱氨反应提前发生,延缓SO2的释放行为,抬高硫酸铵完全分解的温度。
[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，
本文编号：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，
本文编号：2237643
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