基于图像处理的增压流化床气泡行为的实验研究

论文总字数：30226字

摘 要

面对日益严重的CO₂排放问题，结合CO₂捕集的增压流化床富氧燃烧成为下一代有潜力的洁净煤燃烧技术。增压流化床锅炉作为增压富氧燃烧技术的关键部件，其相关设计参数的研究显得尤为重要。本文研究了高温、高压下流化床的临界流化速度，以及不同操作参数下床层的鼓泡特性。

本文利用热态增压流化床实验台测量了0.85-1.0mm、0.3-0.35mm石英砂以及0.1-0.15mm铁粉颗粒的临界流化速度，研究温度、压力、颗粒粒径、流化气氛对临界流化速度的影响。研究结果表明：在相同的温度下，临界流化速度随着压力的增加而减小；在相同的压力下，临界流化速度随着温度的升高而减小；此外，临界流化速度还与颗粒粒径有关，并随着粒径的增大而增大，而与流化气氛无关。并拟合出适用于高温、高压下流化床临界流化速度计算的关联式，运用该公式计算的预测值与实验值的误差均在15%之内。

本文在多功能可视化增压流化床实验平台上研究了增压流化床的鼓泡特性，获得了0.2-0.25mm石英砂的最小鼓泡速度。在300-800℃、0.1-0.6MPa范围内，利用高速摄像机获得了气泡图像，对气泡形状、平均尺寸、气泡频率等气泡特性进行了系统研究。研究表明：最小鼓泡速度随温度、压力、流化气氛的变化规律与临界流化速度的结论一致；随着流化数的增加，气泡形状由规则的球形或椭球形逐渐变得不规则，且合并趋势明显，难以辨识；气泡的尺寸随着压力增以及温度升高而逐渐减小，然而流化数增大会导致气泡直径的增大。对于气泡频率的统计可以发现，随流化数增加，气泡频率上升；随环境压力和温度的上升，气泡频率均呈现不同程度的下降。

关键词：增压流化床；速度；图像；气泡

ABSTRACT

In the face of the increasingly serious problem about the emission of the carbon dioxide, the oxy-fuel combustion in pressurized fluidized bed combined with the capture of carbon dioxide has become the next generation of potential technology in the combustion of clean coal. The pressurized fluidized bed boiler is the key component of the pressurized oxy-fuel combustion technology, whose related design parameters are important especially. In this paper, the minimum fluidization velocity of the fluidized bed under high temperature and high pressure and the characteristics of bubbling in the bed under different operating parameters are studied.

In this paper, the minimum fluidization velocity of 0.85-1.0mm, 0.3-0.35mm quartz sand and 0.1-0.15mm iron powder particles are measured by hot pressurized fluidized bed. The effects of temperature, pressure, particle size and fluidization atmosphere on the minimum fluidization velocity is studied. The result shows that the minimum fluidization velocity decreases with the increase of the pressure at the same temperature. Under the same pressure, the minimum fluidization velocity decreases with the increase of the temperature. In addition, the minimum fluidization velocity is also associated with particle size, and increases with the increasing of particle size, and has nothing to do with the fluidization atmosphere. And the fitting formula for the minimum fluidization velocity of the fluidized bed under high temperature and high pressure is fitted. The error between the experimental value and the predicted value calculated by this formula is within 15%.

In this paper, the characteristics of bubbling in the pressurized fluidized bed are studied on the multi-functional visualized pressurized fluidized bed, and the minimum bubbling velocity of 0.2-0.25mm quartz sand is obtained. In the range of 300-800 ℃ and 0.1-0.6MPa, the images of bubble are obtained by high speed camera, the characteristics of bubble such as bubble shape, average size and bubble frequency are systematically studied. The results show that the change of the minimum bubbling velocity with the temperature, pressure and fluidization atmosphere is consistent with the conclusion of the minimum fluidization velocity. With the increase of the fluidization number, the shape of bubble becomes irregular from the regular spherical or ellipsoid shape and difficult to identify, the merging trend is obvious. The size of the bubble increases with the increase of pressure and temperature, but the increase of the fluidization number will lead to the increase of the bubble diameter. For the statistics of the bubble frequency, It can be found that with the fluidization number increases, the bubble frequency increases; with the ambient pressure and temperature rise, the bubble frequency shows a different degree of decline.

KEY WORDS: Pressurized fluidized bed; velocity; image;；bubble

目 录

摘 要 I

ABSTRACT II

第一章 绪论 1

1.1 引言 1

1.2 课题的研究背景 1

1.3 国内外研究现状 4

1.3.1 临界流化速度 4

1.3.2 鼓泡特性 5

1.4 研究目的与研究内容 6

1.4.1 研究目的 6

1.4.2 研究内容: 7

第二章 实验及测试系统 8

2.1 实验装置 8

2.1.1 增压流化床试验台 8

2.1.2 可视化增压流化床试验台 9

2.2 实验操作过程 9

2.2.1 临界流化速度 9

2.2.2 研究气泡行为特性 10

2.3 气体物性参数修正 10

2.3.1 气体黏度修正 10

2.3.2 气体密度的修正 10

第三章 流动特性分析 12

3.1测试方法 12

3.2 影响因素 13

3.2.1 颗粒粒径对临界流化速度的影响 13

3.2.2 气体气氛对临界流化速度的影响 14

3.2.3 压力对临界流化速度的影响 14

3.2.4 温度对临界流化速度的影响 15

3.3计算公式拟合 16

第四章 鼓泡特性分析 19

4.1 最小鼓泡速度 19

4.2气泡形态 21

4.3 气泡直径 22

4.4 气泡频率 23

第五章 总结与展望 25

5.1 总结 25

5.2 需要进一步完善和开展的工作： 25

致 谢 26

参考文献 27

第一章 绪论

1.1 引言

自工业革命以来，人类在工业生产过程中过多地燃烧化石燃料（煤炭、石油和天然气），导致大量温室气体排入大气，全球的CO₂浓度急剧升高，在1870年时CO₂的浓度尚且为288 ppm，然而到2013年时，该数值已经飙升至395 ppm^[1]，全年平均气温也提高了近1K，温室效应将引发一系列错综复杂的气候变化问题，因此控制全球温室气体，尤其是控制CO₂的排放已经成为当前人类生存和发展的主题之一。近年来，世界各国相继制定了多项减排温室气体的量化目标，我国也针对此采取了一系列措施。在2009年的哥本哈根气候变化峰会上，中国政府作出承诺，相比于2005年时的单位国内生产总值造成CO₂的排放量，到2020年将下降到40-45%。2014年，中国和美国发表了关于气候变化的联合声明，其中中国预计在2030左右使CO₂排放量达到顶峰，且将计划到2030年，使非化石能源占一次能源消费的比重提高到20%左右。研究与发展控制温室气体的技术对实现温室气体减排目标、保护全球气候具有十分重要的意义^[2]。

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