论文总字数：25552字

摘 要

作为世界第一大能源消费国的中国，一直以来，以煤为主要能源。燃煤的最大问题是环境污染问题。作为常规能源的煤炭和清洁能源相比，不存在前期投资成本高以及能量密度小的问题，如果能清洁高效利用优势很大。

SCR脱硝系统，作为一个高效率的脱硝技术，国内外对SCR脱硝技术研究已经比较深入了，选择性还原脱硝技术主要原理是通过催化剂的催化，氨气和氮氧化物能在较低的温度下发生化学反应，生成氮气和水。研究SCR脱硝技术主要从两方面去研究：一是催化剂；二是喷氨设备和混合装置。其中，由于氮氧化物和氨气是在催化剂表面发生反应的，催化剂是SCR技术的工艺核心。而喷氨装置和混合装置，主要是保证到达催化剂表面的烟气和氨空混合气是否已经混合均匀，这对于提高脱硝效率至关重要。

商业SCR脱硝系统氨混合机构有喷氨格栅型、涡流型和静态混合器型三种。其中，喷氨格栅型可实现分区控制，具有灵活性及适应性强的特点，能根据烟气的速度分布，自主的调节各区的喷氨量，有利于提高氨混效果，从而提高脱硝效率。本文以喷氨格栅型氨混机构为研究对象，应用CFD软件建模和进行数值模拟，研究喷嘴数量、喷嘴管径（喷射速度）及喷射角度对烟道内氨混合效果的影响。

本文首先讨论喷嘴数量对于喷氨格栅氨混效果的影响，喷口数目从336增加至448，喷口后5m的出口截面的氨浓度分布相对标准偏差减小了4.54%，模拟结果表明，喷氨格栅的喷嘴数量越多，氨混效果越好，喷嘴数为448的方案一为最佳方案，在方案一的基础上，讨论喷嘴喷射角度对于氨混效果的影响，模拟了喷射角度为45°、30°的喷氨格栅结构，其中喷射角度为30°的方案四出口截面氨氮比相对标准差最小，为32.4%。再以模型四为改进对象，调整喷嘴直径大小，设计了喷嘴直径为15mm，25mm两种模拟方案，喷嘴直径为15mm的方案六最佳。

除此之外，本文以单组喷管结构为研究对象，讨论喷氨速度与烟气速度的关系对氨混效果的影响，证明了烟气速度不变，随喷氨速度增加，出口截面的氨氮比相对标准差会存在两个极小值点。本文还讨论了喷嘴在截面上的分布以及管路结构的扰流对于氨混效果的影响。

综上，本文最佳设计方案为：直径为15mm、喷射角度为30°、喷嘴数量为448个的分区控制式喷氨格栅。

关键词：SCR系统 喷氨格栅 喷氨优化 数值模拟

Research on Structure and Performance Optimization of Ammonia Injection Grid in SCR Denitration System

Abstract

As the world's largest energy consumer, China has always mainly used coal. The biggest problem with the use of coal is environmental pollution. Compared with clean energy, coal, which is a conventional energy source, does not have the problems of high initial investment cost and small energy density. If it can be clean and efficiently used, it has great advantages.SCR denitration system, as a high-efficiency denitration technology, domestic and foreign research on SCR denitration technology has been in-depth, the main principle of selective reduction denitration technology is through the catalyst catalysis, ammonia and nitrogen oxides can be at a lower temperature A chemical reaction occurs, producing nitrogen and water.

The research of SCR denitration technology mainly involves two aspects: one is catalyst; the other is ammonia injection equipment and mixing device. Among them, since nitrogen oxide and ammonia gas react on the surface of the catalyst, the catalyst is the core of the SCR technology. The ammonia spraying device and the mixing device mainly ensure that the flue gas and the ammonia-air mixture reaching the catalyst surface have been mixed evenly, which is very important for improving the denitration efficiency.

This article first discusses the effect of the number of nozzles on the ammonia mixing effect of the ammonia injection grid. The number of nozzles increased from 336 to 448. The relative standard deviation of the ammonia concentration distribution at the outlet section 5m behind the nozzle was reduced by 4.54%. The simulation results show that The greater the number of nozzles in the grid, the better the ammonia mixing effect. The first solution with 448 nozzles is the best solution. On the basis of the first solution, the effect of the nozzle spray angle on the ammonia mixing effect is discussed. The injection angle is simulated at 45 ° A 30 ° ammonia spray grid structure, in which the relative standard deviation of the ammonia-nitrogen ratio at the four-outlet section of the scheme with a spray angle of 30 ° is the smallest, at 32.4%. Then take the model 4 as the improvement object, adjust the nozzle diameter, design two simulation schemes with the nozzle diameter of 15mm and 25mm, and the scheme 6 with the nozzle diameter of 15mm is the best.

In addition, this article takes a single group of nozzle structure as a research object to discuss the influence of the relationship between ammonia injection speed and flue gas velocity on the effect of ammonia mixing. There are two minimum points for the relative standard deviation of the ammonia-nitrogen ratio. This article also discusses the distribution of nozzles on the cross section and the influence of the turbulence of the pipeline structure on the effect of ammonia mixing.

In summary, the best design scheme in this paper is: a zone-controlled ammonia injection grid with a diameter of 15 mm, an injection angle of 30 °, and a nozzle number of 448.

Key words: SCR system；ammonia injection grid；ammonia injected optimization；double variable section

目 录

摘要 III

ABSTRACT V

第一章 绪论 1

1.1 研究背景及意义 1

1.1.1现实意义 1

1.1.2 SCR研究背景 2

1.2 研究现状 3

1.2.1 SCR脱硝系统的应用 3

1.2.2 SCR脱硝系统催化剂的研究 3

1.2.3 SCR系统流场均匀性的研究现状 4

1.2.4 SCR系统喷氨格栅的研究现状 6

1.2.5 总体SCR系统优化的应用现状 7

1.3 本文的研究内容 8

第二章 数值计算理论 9

2.1 CFD软件简介 9

2.2 网格的划分 9

2.3 数值模型的选择 11

2.3.1 基本方程 11

2.3.2 湍流模型 12

2.3.3 组分运输方程 12

2.3.4 数值模拟的基本方案与步骤 13

2.4 本章小结 14

第三章 300MW机组SCR系统喷氨格栅模拟 15

3.1 喷氨格栅边界条件计算 15

3.1.1 烟气入口边界条件计算 15

3.1.2 氨空混合气入口边界条件 18

3.2 原模型的数值模拟 18

3.3 喷口数量的影响规律 21

3.4 喷嘴的喷射角度的影响规律 23

3.5 喷嘴尺寸的影响规律 25

3.5.1 喷嘴尺寸模拟 25

3.5.2 喷氨速度与烟气速度的关系对氨混效果的影响 27

3.6 喷氨格栅的管路结构及喷嘴分布的影响 30

3.6.1 喷嘴分布对于氨混效果的影响 30

3.6.2 管路结构的扰流对氨混效果的影响 31

3.7 本章小结 33

第四章 结论与展望 34

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