论文总字数：26844字

摘 要

随着人类生活的不断发展，越来越多的人认识到保护环境的重要性，在人们对能源开发利用的过程中，会产生许多对人体健康有危害的污染物，例如NO_x对人体肺部有较大的刺激作用，会导致人体患上呼吸系统相关的疾病。而NO_x大部分来源于发电厂，因此需要对燃煤电厂中现有的脱硝技术进行改进，减少发电过程中的NO_x排放，目前SCR脱硝技术是比较完善的脱硝技术之一。在对SCR反应器的优化中，借助计算流体力学（CFD）数值模拟方法的仿真优化应用日益广泛，实践证明其对于工程应用具有较好的指导意义。已有的SCR脱硝反应器系统中，常采用2种反应器入口结构，平顶结构与斜顶结构，不同的入口结构对气流组织的要求有所不同，亦会影响实际的脱硝过程，因此研究不同的顶部结构与对应导流板安装的匹配特性及两者对反应器入口流场的影响对于SCR反应器的设计具有重要的指导意义。

本文以某300MW燃煤机组的单台SCR反应器为研究对象，通过对数值模拟结果的分析，研究SCR脱硝反应器的斜顶和平顶结构，以及相应的导流板设计对催化剂入口截面速度均匀性和系统阻力损失的影响。通过对模拟结果的计算分析得到，反应器的斜顶结构优于平顶结构。反应器内未布置任何导流板时阻力损失是最小的，布置相应的导流板能有效的促进流场的均匀性但需要付出一定的阻力损失代价。在平顶结构中，在竖直烟道与水平烟道的转弯处均匀布置3块圆弧直形导流板，在反应器上方布置8块圆弧直形导流板的设计方案较为合理，该方案下通过计算得到的系统压降为73.03Pa，第一催化剂入口的速度相对标准偏差为9.77%，平均速度矢量偏角为6.81°，较为有效的改善了反应器内的烟气流场。在斜顶结构中，反应器入口与水平烟道连接处布置三块与水平方向呈35°夹角的直形导流板，整流格栅厚度为250mm，安装在反应器入口拐角处，斜顶角度调整为13.42°时对流场的优化效果最佳，该方案下首层催化剂入口的速度相对标准偏差为6.18%，速度矢量平均偏角为7.95°，系统压降为98.52Pa，满足优化要求。

关键词：氮氧化物 选择性催化还原（SCR） 导流板 数值模拟

The Top Structure Contrast and Optimization of the Entrance Flue for SCR Denitration Reactor

Abstract

With the continuous development of human life, more and more people realize the importance of protecting the environment. In the process of people's development and utilization of energy, many pollutants that are harmful to human health will be produced such as NO_x. The Ministry has a large stimulating effect, which will cause the human body to suffer from respiratory-related diseases. And most of the NO_x comes from power plants. It is necessary to improve the existing denitration technology in coal-fired power plants to reduce NO_x emissions during power generatio. At present, SCR denitration technology is one of the more perfect denitration technologies. In the optimization of SCR reactors, simulation optimization with the help of computational fluid dynamics（CFD）numerical simulation methods is increasingly used. Practice has proved that it has good guiding significance for engineering applications. In the existing SCR denitration reactor system, two kinds of reactor inlet structures are often used. The flat roof structure and the inclined roof structure. Different inlet structures have different requirements on the airflow organization, which will also affect the actual denitrification process. It is significant for guiding the design of the SCR reactor to discuss the matching characteristics of different top structures and corresponding deflector installations and their influence on the inlet flow field of the reactor.

In this paper, the single SCR reactor of a 300MW coal-fired unit is taken as the research object. Through the analysis of the numerical simulation results, the inclined roof and flat roof structure of the SCR denitration reactor are studied. The corresponding deflector design has a uniform catalyst inlet cross-sectional velocity. The impact of loss of resistance and system resistance. Through calculation and analysis of the simulation results, it is obtained that the inclined roof structure of the reactor is superior to the flat roof structure. The resistance loss is minimal when no deflectors are arranged in the reactor. Arranging the corresponding deflectors can effectively promote the uniformity of the flow field. But it needs to pay a certain amount of resistance loss. In the flat roof structure, it is more reasonable to arrange 3 circular arc straight deflectors evenly at the turning point of the vertical flue and horizontal flue, and to arrange 8 circular arc straight deflectors above the reactor. The calculated system pressure drop under this scheme is 73.03Pa, the relative standard deviation of the first catalyst inlet velocity is 9.77%, and the average velocity vector deviation is 6.81 °, which effectively improves the flue gas field in the reactor. In the inclined roof structure, three straight deflectors at an angle of 35 ° to the horizontal direction are arranged at the junction of the reactor inlet and the horizontal flue. The thickness of the rectifying grid is 250mm. It is installed at the corner of the reactor inlet. The optimization effect is the best when the angle is adjusted to 13.42 °. Under this scheme, the relative standard deviation of the first layer catalyst inlet speed is 6.18%, the average deviation of the velocity vector is 7.95 °, and the system pressure drop is 98.52Pa. This design meets the optimization requirements.

Keywords: Nitrogen oxides; Selective Catalytic Reduction; Deflector; Numerical simulation

目 录

摘 要 I

Abstract II

第一章 绪 论 1

1.1 研究背景及意义 1

1.2 SCR脱硝技术及数值模拟研究现状 2

第二章 研究思路与方法 5

2.1 主要研究内容 5

2.2 模型建立及设计参数 5

2.2.1 模型设计 5

2.2.2 设计参数及设计要求 6

第三章 平顶SCR脱硝反应器烟道内流场分析 7

3.1 反应器结构建模 7

3.1.1 平顶反应器结构 7

3.1.2 结构建模与设计方案 7

3.2 未安装导流板的流场分布 8

3.3 加装导流板后的流场分布 9

3.3.1 初步设计分析 9

3.3.2 最优设计分析 14

3.4 章节总结 15

第四章 斜顶SCR脱硝反应器烟道内流场分析 17

4.1 反应器结构建模 17

4.1.1 斜顶反应器结构 17

4.1.2 结构建模与设计方案 17

4.2 未安装导流板的流场分布 18

4.3 安装导流板后的流场分布 19

4.3.1 导流板形状及数量对流场分布的影响 19

4.3.2 导流板布置偏角对流场分布的影响 23

4.4 整流格栅和斜顶角度对流场分布的影响 26

4.4.1 整流格栅厚度对流场的影响分析 26

4.4.2 整流格栅位置和斜顶角度的优化 29

4.5 章节总结 30

第五章 结论与展望 33

5.1 全文总结 33

5.2 展望 33

参考文献 35

致 谢 38

第一章 绪 论

1.1 研究背景及意义

目前我国国内蕴藏着许多的资源，随着人类社会的不断进步，对能源的需求日益增多，人类不断开发各类能源以保证社会经济的持续发展，但是在许多能源开发利用的过程中，伴随有很多对人体健康不利的物质生成，产生的NO_x对人体肺部有较大的刺激作用，会导致人体患上呼吸系统相关的疾病，对儿童甚至可能会损害肺部发育。此外，NO_x是产生光化学烟雾的主要组成物质，它具有刺激性气味，能降低大气的可见度，对植物造成相当大程度的损害。

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