叠式流化床流动数值模拟

论文总字数：27176字

摘 要

由于随着化石燃料的不断消耗，CO2排放量逐年提高，温室效应也逐渐加重。因此有必要实现对CO2的捕集，从而减轻温室效应。钙基循环制氢技术能实现煤制富氢合成气的CO2分离和捕集，是一种理想的CO2捕集技术路线。以叠式流化床为钙循环煤气化系统的气化炉，可制备高浓度的氢气，该叠式流化床将鼓泡流化床和快速提升管相结合，论文对其内部气固两相流动过程进行CFD模拟研究，可对叠式流化床进行结构优化，进一步为该技术的开发奠定研究基础。

本文以叠式流化床的冷态试验台为研究对象，建立了叠式流化床气固两相流动双欧拉模型、k-ε标准湍流模型，选择了Syamlal-O’Brien曳力模型，利用ANASY组件对叠式流化床的冷态试验台进行了网格划分和数值模拟，研究了不同工况下鼓泡流化床的流化过程、快速提升管的流场分布和叠式流化床的整体压力分布，并将模拟结果与实际实验结果进行了对比，以与实验结果相互补充与验证。最终得出实验结果与模拟结果所呈现的规律大致相同，但由于模拟之初所做出的简化，两者之间仍存在一些差异，对装置结构做了一定的优化。

关键词：叠式流化床；欧拉双流体模型；数值模拟；Fluent；流动特性

Abstract

Due to the continuous consumptions of fossil fuels, the CO2 emissions have increased year by year, and the greenhouse effects have gradually become more and more serious. Therefore, it is necessary to develop a variety of technologies of CO2 capture and to alleviate the greenhouse emissions. Calcium-looping hydrogen production technology is one of the most effective methods. This method can not only capture the CO2 in the process of coal gasification, but can also produce high purity of hydrogen syngas. In order to realize this process, a compact fluidized bed is used as the gasifier of the calcium-looping technology. The compact fluidized bed is composed of a fluidized bed riser and a bubbling fluidized bed. The superficial gas velocity of the upper riser can be changed by changing the flow area of the lower bubbling fluidized bed. The fluid dynamics of the compact fluidized bed is studied in this work in order to understand the gasifier design and to develop the technology by changing the lower.

Limited by various kinds of the factors of the experiments, numerical simulation becomes a relatively good way to analyze the internal process of the compact fluidized bed. In this paper, Euler-Euler method, k-ε standard turbulence model and Syamlal-o ' Brien drag model of multiphase flow are used to simulate the cold flow of the compact fluidized bed by using ANASY 15.0. The fluidization process of the lower bubbling fluidized bed under different operating conditions, the velocity distributions of the upper riser and the pressure distributions of the compact fluidized bed are studied, and the simulation results are compared with the experimental results in order to verify with the simulation results. It is concluded that the simulation results are roughly the same as those presented by the experimental results, but there are still some differences between them due to the simplification of the simulation.

Key words: Compact fluidized bed; Euler-Euler model; Numerical Simulation; Fluent; Flow characteristics

目 录

摘要 I

Abstract II

第一章 绪论 1

1.1 研究背景与意义 1

1.1.1 研究背景 1

1.1.2 研究意义 1

1.2 国内外研究现状 1

1.2.1 CO₂捕集技术与钙循环过程 1

1.2.2 流化床的多相流模拟 2

1.3 研究对象介绍 3

1.4 研究内容与思路 3

第二章 叠式流化床数值建模 5

2.1 数学模型 5

2.1.1 多相流模型 5

2.1.2 曳力模型 5

2.2 模拟对象的构建与边界条件 7

2.2.1 模型简化 7

2.2.2 网格划分 8

2.2.3 边界条件 9

2.2.4 求解器设置 10

2.3 本章小结 11

第三章 典型工况结果分析 12

3.1 鼓泡流化床流化过程 12

3.2 快速提升管流场分析 13

3.3 叠式流化床压力分布 13

3.4 叠式流化床固相颗粒分布 15

3.5 本章小结 20

第四章 不同工况与结构的比较讨论 21

4.1 不同工况的结果比较 21

4.1.1 快速提升管流线与整体压力分布比较 21

4.1.2 叠式流化床内压差比较 22

4.1.3 氧化钙入口局部比较 23

4.2 不同结构的结果比较 23

4.2.1 鼓泡流化床的流化过程比较 24

4.2.2 快速提升管流线与整体压力分布比较 26

4.2.3 叠式流化床内压差比较 26

4.3 本章小结 27

第五章 结论与展望 29

5.1 全文总结 29

5.2 展望 29

致谢 31

参考文献 32

第一章 绪论

1.1 研究背景与意义

1.1.1 研究背景

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