论文总字数：33482字

摘 要

湿颗粒广泛存在于工业生产中，随着工业技术的发展，湿颗粒对于生产过程的影响渐渐增加，它与干颗粒的流化行为有着诸多的不同，已有针对干颗粒的研究并不能简单地应用于湿颗粒生产实践中。Geldart-D类湿颗粒流化的研究才刚刚兴起，许多流化动力学特性还不清楚。混合特性是流化床动力学特性的重要方面，本文对此开展了实验工作。本文搭建了截面140mm×70mm，高500mm由有机玻璃构成的小型气固鼓泡流化床，采用图像法和插板隔板取样法两种实验方法，对湿颗粒在流化床中的混合情况展开了系统的研究。分别讨论了不同密度，不同比例，不同粒径，不同初始位置等单一影响因素对于湿颗粒混合的影响，并将结果与干颗粒的混合情况进行对比。使用高速数码相机记录混合过程，先对混合的情况做初步的定性分析，同时设计了一种带有梳形插板的插板隔板取样器，对流化床内颗粒进行采样，使用示踪颗粒比例分布和Lacey混合指数对混合情况进行了定量分析。研究发现：对于异重颗粒，同样气速条件下，在混合过程前期，湿颗粒的混合明显要优于干颗粒，这是因为湿颗粒间的粘连作用，可以使得轻质颗粒被床内颗粒循环更好的裹挟带入床下部，利于混合；但随着时间的发展，在混合过程后期，湿颗粒的混合要劣于干颗粒，这同样与液桥粘性力有关，湿颗粒聚团块难以被打散，导致床内局部混合指数降低，从而整体混合效果下降。

增加含液量在一定条件下有利于颗粒混合；密度对湿颗粒混合的影响很大，轻质颗粒容易聚集在床层上部，重质颗粒与之相反，停留在床层下部，形成分离现象；示踪颗粒在所有颗粒中所占比例越高，混合情况越好；小粒径湿颗粒的混合比大粒径颗粒混合更好；湿颗粒混合初始位置对混合结果影响较大，轻质的示踪颗粒在底部的混合结果较在顶部更优。最后，我们对比了两种混合方法得出的结果发现，图像法对于干颗粒基本能够反映混合快慢情况，但由于湿颗粒的沾壁因素，容易失真，须多次试验才能得出可靠结论；插板取样法可以较真实的反映混合情况，但取样工作较为繁琐，工作负荷较大。

关键词：气固流化床；湿颗粒；混合；图像法；插板隔板取样法

ABSTRACT

Wet particles exist widely in industrial production, with the development of industrial technology, wet particles’ impact on the production process of gradually increased, it has a lot of differences with dry fluidized flow behavior, the existing theory for dry particles can not be simply applicated in the wet particle production practice. The study of Geldart-D type wet particle fluidization is just emerging, and many of the characteristics of fluidization dynamics are still not clear. Mixing characteristics is an important aspect of the dynamic characteristics of the fluidized bed, and the experimental work is carried out in this paper. In this paper, we build a small gas solid bubbling fluidized bed whichconsists oforganic glass,itssection is 140mm * 70mm,and it is 500mm high, we usetwo experimental approaches,one is image method and another one is plug in board sampling method, to research the mixing condition of wet particles in a fluidized bed. The influences of different densities, different proportions, different sizes and different initial positions on the mixing of wet particles are discussed, and the results are compared with the mixing of dry particles. Using a high-speed camera to record the mixing process, firstly for the mixed situation, we have preliminary qualitative analysis. Meanwhile, the design of the a with comb shaped in plate in clapboard sampler and sampling of particles in the fluidized bed, using tracer particles proportion distribution and Lacey mixed exponential to conduct a quantitative analysis on the mixing. Research shows for different heavy particles, the same gas velocity conditions, in the early stage of the mixing process, wet granular mixture was obviously superior to the dry particles. This is because of the wet particle adhesion, can the light particles are fluidized bed particle circulation better coerced into the lower part of the bed, to mix; however, with the time development, in the latter part of the mixing process, wet granular mixing inferior to dry particles, the same with the viscous force of liquid bridge on, wet granular poly mass to be scattered, lead to the decrease of the bed local mixing index, it reduces the overall mixing effect.

The increase of liquid volume in certain conditions conducive to mixed particles containing; effects of density on particles mixed wet large, light particles tend to aggregate in the upper part of the bed, heavy particles and instead, stay in the lower part of the bed, forming a separation phenomenon; tracer particles in all the particles in the proportion of the higher, better mixing; small sized wet particles mixed than large particles mixed better; wet particles mixed initial position of mixed results larger, light tracer particles in the bottom of the mixed results are at the top of the better. Finally, we compared the two hybrid methods that results found that the image method for dry particles can basically reflect the mixing speed, but due to the wet granular staining the wall factors, easy to distortion, to be repeated trials in order to draw reliable conclusions; plug in board sampling method can a real reflection of the mixing, but sampling is more complicated and larger workload.

Keywords: gas-solid fluidized bed, wet particle, mixing, Image method, plug in board sampling method

目 录

摘 要 I

ABSTRACT II

第一章 前 言 1

1.1 课题的研究背景及意义 1

1.2 课题的国内外研究现状和问题 2

1.3 本实验的研究内容 4

第二章 颗粒混合特性的实验研究 5

2.1 实验系统 5

2.1.1 实验流程 5

2.1.2 空气供给系统 5

2.1.3 流化床体 6

2.1.4 高速照相机图像采集系统 6

2.1.5 补液装置 6

2.2 实验颗粒性质 6

2.3 实验方法 7

2.3.1 国内外的方法使用情况 7

2.3.2 本实验使用的方法 7

第三章 湿流化床基础流动特性研究 8

3.1 气固鼓泡流态化介绍 8

3.2 颗粒堆积角 8

3.3 湿颗粒理论 9

3.4 干湿颗粒流型分析 10

3.5 干湿颗粒压力曲线分析 11

3.6 最小流化速度 12

3.7 小结 13

第四章 图像法实验结果与分析 14

4.1 不同密度颗粒混合 14

4.2 不同比例颗粒混合 15

（1）比例对干颗粒混合的影响 15

（2）比例对湿颗粒混合的影响 15

4.3 不同粒径颗粒混合 16

（1）粒径对干颗粒混合的影响 17

4.4 不同初始位置颗粒混合 18

（1）不同初始位置对干颗粒混合的影响 18

（2）不同初始位置对湿颗粒混合的影响 19

第五章 取样法实验结果与分析 21

5.1 实验过程 21

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