论文总字数：25149字

摘 要

近年来，随着人们环保意识的加强，国家对污染物的排放也有了严格要求。SCR烟气脱硝技术作为主流的脱硝方法，拥有较高的脱硝效率。同时，其系统运行可靠，内部反应不会产生副产物，且系统装置结构简单。SCR技术因此受到了广泛关注，并得到大力发展。计算流体力学（CFD）软件的出现与发展对此起到了积极的作用。使用CFD软件对SCR脱硝系统进行仿真数据模拟，能够较为真实的还原SCR系统的真实工况，为脱硝系统的设计及其改进方案提供有效的参数。

本文以某300MW机组脱硝系统的省煤器与SCR反应器之间连接的异径烟道为研究对象，采用工程流体力学的研究方法，使用FLUENT软件对SCR反应器异径烟道的烟气流场进行分析模拟。主要研究内容如下：通过对不同扩充方式的异径烟道的流场进行数值模拟，分析当异径烟道采用不同的扩充方式时模型内部流场的均匀性，结果表明变截面烟道能够在一定程度上使流场分布更均匀，但变截面烟道会使流场产生回流以及低速区，降低流场的均匀性。通过分析导流板对异径烟道流场的影响，结果表明导流板能够大大改善扩充烟道的回流问题，减少低速区，使流场更加均匀。同时，进行导流板布置方案的模拟分析，设计导流板布设方案。其中，单次扩充烟道的标准速度偏差降至6.02%，总压差为51.14Pa；二次扩充烟道的标准速度偏差降至12.71%，总压差为43.80Pa。

关键词：烟气脱硝；SCR；异径烟道；流场；数值模拟

Gas Distribution Optimization of Variable Cross-section Flue in SCR Denitration System

Abstract

In recent years, people attach importance to environmental protection, and our country has more regulations on the emission standard of pollutants. SCR flue gas denitrification technology, as the main denitrification method, has a high denitrification efficiency. At the same time, its system operation is reliable, internal reaction will not produce by-products, and the system structure is simple. Therefore, SCR technology has received extensive attention and been developed vigorously. The appearance of computational fluid Dynamics (CFD) software plays an important role in the development of SCR technology. It can restore the real condition of SCR system and provide effective plans for its improvement scheme to perform simulation data for the SCR system.

In this paper, the reducing flue gas field connected between the coal economizer and SCR reactor of a 300MW unit denitrification system is taken as the research object. The research method of engineering fluid mechanics is adopted, and the FLUENT software is used to analyze and simulate the reducing flue gas field of SCR reactor. Main research content is as follows: based on the different expansion ways of reducing flue of a numerical simulation of the flow field analysis when reducing flue adopt different ways of expanding model of internal flow field uniformity, the results show that the variable section flue can make the flow field more uniform to some extent, but the variable section flue will make backflow and low speed zone, reducing the uniformity of the flow field. By analyzing the influence of the guide plate on the flow field of the reducing flue, the results show that the guide plate can greatly improve the backflow problem of the extended flue, reduce the low speed zone, and make the flow field more uniform. At the same time, the simulation analysis of the layout scheme of the guide plate is carried out, and the layout scheme of the guide plate is designed. Among them, the standard velocity deviation of single expansion flue is reduced to 6.02%, and the total pressure difference is 51.14Pa. The standard velocity deviation of the secondary expansion flue was reduced to 12.71% and the total pressure difference was 43.80Pa.

Key words: Flue gas denitration; SCR; Variable cross-section flue; Flow field; Numerical simulation

目 录

摘 要 I

Abstract II

目 录 IV

第一章 绪论 1

1.1 研究背景及意义 1

1.2 国内外研究现状 2

1.2.1 SCR脱硝技术综述 2

1.2.2 数值模拟在SCR中的应用 2

1.3 主要研究内容 8

第二章 SCR反应器异径烟道流场的数值模拟方法 9

2.1 引言 9

2.2 流场的数值模拟方法 9

2.3 SCR系统异径烟道模型 11

2.4 CFD数值模拟的求解过程 12

2.5 本章小结 12

第三章 SCR脱硝反应器异径烟道流场分析 14

3.1 引言 14

3.2 变截面异径烟道的扩充方式对烟道流场的影响 14

3.2.1 无扩充异径烟道模型流场分析 15

3.2.2 原扩充烟道模型流场分析 16

3.2.3 单次扩充烟道模型流场分析 18

3.2.4 二次扩充烟道模型流场分析 19

3.3 最佳导流板布置方案 21

3.3.1单次扩充烟道的导流板布设 21

3.3.2二次扩充烟道的导流板布设 27

3.4 本章小结 35

第四章 总结与展望 37

4.1 总结 37

4.2 展望 37

致谢 38

参考文献 39

第一章 绪论

1.1 研究背景及意义

21世纪以来，中国的经济发展呈现快速趋势，随着进一步的工业化、城镇化发展，主要的污染物排放也呈现出迅速增长的形势。2007年以后，国家加大节能减排政策的力度，污染物的防治工作迅速推进，资源循环利用逐步实行，各种治理技术加快应用，主要污染物排放快速增长的势头得到了一定的缓解。

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