氨法SCR脱硝过程中硫酸铵盐生成特性研究

论文总字数：26763字

摘 要

SCR脱硝工艺是目前工业上应用最为广泛的脱硝技术。但是，SCR在去除NO_x的同时，V₂O₅-WO₃/TiO₂作为SCR的商用催化剂，其中的活性成分V₂O₅会将SO₂氧化成SO₃，SO₃会与烟气中的NH₃和H₂O发生反应，生成大量的硫酸铵盐等颗粒物。这些颗粒物一部分会随着烟气排入大气环境，增加了PM_2.5的排放量,另一部分会沉积在催化剂和空预器的表面，造成催化剂受损和通道的堵塞，甚至会造成中毒失活以及空预器堵塞、腐蚀。

本文利用ELPI、PM_2.5/PM₁₀采样器、烟气分析仪、场发射扫描电镜-能谱分析、XRD分析、傅立叶原位红外技术等测试手段，对SCR脱硝反应器出口烟气中硫酸铵盐的排放特性、气相主体中硫酸铵盐的形成特性、催化剂表面硫酸铵盐的形成特性等进行了探究，得出了以下结论：（1）SCR脱硝反应会生成大量的颗粒物，其主要成分为 (NH₄)₂SO₄和NH₄HSO₄；（2）温度、SO₃浓度、烟气停留时间、H₂O含量等都会对硫酸铵盐的生成产生影响，硫酸铵盐的浓度随着SO₃浓度、烟气停留时间的增加而上升，随着温度的升高而下降，H₂O含量的影响很小；（3）硫酸铵盐会对飞灰的特性产生影响，使飞灰的粒径分布的峰值向着粒径增大的方向移动，粘附性迅速增加，比电阻则会有所下降；（4）在SCR脱硝过程中SO₂与NH₃在V₂O₅-WO₃/TiO₂催化剂表面存在竞争吸附，且 SO₂与NH₃共存时在催化剂表面会生成硫酸铵盐，硫酸铵盐中的NH₄ 来源于Lewis酸位的吸附态的NH₃。

关键词：选择性催化还原 硫酸铵盐 形成特性 气相主体 催化剂

Abstract

Selective catalytic reduction (SCR) De-NO_x is currently the most widely used in the industry. However, while SCR removes NO_x, V₂O₅-WO₃/TiO₂ acts as a commercial catalyst for SCR, in which active ingredient V₂O₅ oxidizes SO₂ to SO₃, and SO₃ reacts with NH₃ and H₂O in the flue gas, generating a large amount of particles of ammonium sulfate( (NH₄)₂SO₄) and ammonium hydrogen sulfate(NH₄HSO₄). Part of these particles will be released into the atmosphere with the flue gas, increasing the PM_2.5 emissions,, and the other part will be deposited on the surface of the catalyst and air preheater, causing damage to the catalyst and blockage of the channels, and even causing poisoning inactivation. And the air preheater is clogged and corroded. However, the existing research mainly focuses on the change of the physical properties of the export particles from the macro perspective, and has not conducted an in-depth study on the formation characteristics of ammonium sulfate in the SCR reaction.

The study uses the ELPI, PM_2.5/PM₁₀ sampler, flue gas analyzer, HRSEM/EDX,XRD and In situ FTIR spectroscopy to the emission characteristics of export ammonium sulfate in smoke from SCR denitrification reactors, the formation characteristics of the ammonium sulfate salt in the gas phase body, and the formation characteristics of the ammonium sulfate salt on the catalyst surface were investigated, and the following conclusions were drawn:(1) Selective catalytic reduction (SCR) De-NO_x produces a large amount of particles, whose main components are (NH₄)₂SO₄ and NH₄HSO₄;(2) Temperature, SO₃ concentration, flue gas residence time, H₂O content will affect the formation of ammonium sulfates, and the content of ammonium sulfates rises with the increase of SO₃ concentration and flue gas residence time, and decreases with increasing temperature. The effect of H₂O content is very small;(3) Ammonium sulfate affects the properties of fly ash and moves the particle size distribution of fly ash toward the direction of particle size increase.Adhesion increases rapidly and specific resistance decreases with increasing ammonium sulfate ; (4) There is competitive adsorption between SO₂ and NH₃ on the surface of catalysts, and ammonium sulfate is formed on the surface of catalysts when SO₂ and NH₃ coexist. NH4 in ammonium sulfate is derived from the adsorbed NH3 of Lewis acid sites.

KEY WORDS: petroleum, bioremediation, degrading strain, degradation rate,

目 录

摘要 I

Abstract II

第一章 绪论 3

1.1 研究背景及意义 3

1.2 SCR烟气脱硝技术 3

1.2.1 SCR布置方式 4

1.3 SCR脱硝过程中硫酸盐生成的研究进展 4

1.3.1 SO₂氧化机理的研究进展 5

1.3.2 硫酸铵盐生成机理研究进展 5

1.3.3 硫酸铵盐生成的影响因素 6

1.4 本文研究内容和方法 7

1.5 本章小结 7

第二章 试验系统与方法 8

2.1 引言 8

2.2 烟气模拟系统 8

2.2.1 SO₃发生装置 9

2.3 实验试剂 9

2.4 分析测试仪器 10

2.4.1 烟气分析仪 10

2.4.2 PM_2.5/PM₁₀采样器 10

2.4.3 电称低压冲击器 10

2.4.4 傅立叶原位红外光谱仪 11

2.4.5 XRD分析 11

2.5 本章小结 12

第三章 SCR脱硝反应器气相主体硫酸铵盐的形成特性 13

3.1 引言 13

3.2 SCR出口硫酸铵盐的排放特性研究 13

3.2.1 SCR出口颗粒物的浓度和粒径分布 13

3.2.2 颗粒物的形貌和元素组成 14

3.2.3 SCR出口颗粒物的物相组成 14

3.3 SCR反应器中硫酸铵盐的形成特性研究 15

3.3.1 温度 15

3.3.2 停留时间 16

3.3.3 H₂O含量 16

3.3.4 SO₃浓度 17

3.4 硫酸铵盐对于飞灰特性的影响 18

3.4.1 飞灰粒径分布 18

3.4.2 飞灰的粘附性 18

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