添加内构件对粘性颗粒流化质量的改善
文献类型：学位论文
| 作者 | 刘勤 |
| 学位类别 | 硕士 |
| 答辩日期 | 2000-07-13 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 李洪钟 |
| 关键词 | 粘性颗粒 流态化 改善 多孔板式内构件 桨式内构件 孔桨式内构件 |
| 其他题名 | Improvement of fluidization quality of cohesive particles by internals |
| 学位专业 | 化学工艺 |
| 中文摘要 | 本文主要考察了在粘性颗粒气固流化床中添加多孔板式内构件、桨式内构件和孔桨式内构件对流化质量的影响规律。实验物料是平均粒径2.67μm的Al_2O_3颗粒。实验利用压力传感器采集床层压力脉动信号，利用光纤探头测量床层局部空隙率以及气泡住处作为评价流化质量的标准。本文分析了粘性颗粒流化床的床层运动规律以及添加内构件后对流化状态的影响。粘性颗粒在流化过程中容易出现节涌、沟流等不正常现象，只有在较高的表观气速下才能以聚团流化的形式达到比较稳定的流化状态。在流化床内添加内构件提高流化质量的作用表现在一个方面：能够破碎气泡与聚团、限制气泡长大；能有效地消除不正常现象，稳定流化状态；并且能够提高床层内气体含率，从而增强了气固接触效率。实验表明，添加多孔板式内板件对粘性颗粒流化状态的改善效果不理想。对沟流等不正常现象没有明显的抑制，气泡尺寸没有明显减小，等等。添加开孔率50%，孔径3mm的多孔板式内构件时的流化状态甚至比自由床更差。添加桨式内构件的流化实验表明，桨式内构件是一种性能良好的粘性颗粒流化床内构件。其性能明显优于多孔板式内构件。表明在节涌、沟流现象得到抑制；表现最小流化速度降低，压降曲线线形较好；床膨胀比自由床有了明显的提高。本文设计了一种新型的内构件——孔桨式内构件，实验表明孔桨式内构件是一种优良的粘性颗粒流化床内构件，能显著提高粘性颗粒流化质量。主要表现在：①节涌与沟流消失；②压降曲线线形符合理想压降曲线；③床层膨胀提高，床层内气体含量增大；④床层中气泡的数量减少，尺寸缩小，说明流化状态向散式流化靠近。对结构参数的考察表明，桨叶越来越多，内构件对流化质量的改善性能越好；桨叶的倾角应该大于60°；对孔桨式内构件开孔率的实验表明，开孔率在20-25%效果最好。对添加内构件的数量的考察表明，添加多片内构件比添加一片内构件对流化质量的改善效果更好。 |
| 英文摘要 | In order to improve the fluidization quality of cohesive particles, the traditional porous-plate internals, the remiform internals and the porous-remiform internals have been investigated. Cohesive γ-Al_2O_3 particles were employed as the experimental material. Pressure sensor has been used to collect the pressure fluctuation signals; and two optical fiber sensors have been used to obtain the fluctuation information of local voidage, bubble size and velocity. In the first part of this paper, the motion behaviors of cohesive particles have been recognized. Due to the diversity in the physical and superficial properties, some abnormal behaviors such as slugs, channels and de-fluidization usually were observed during the process of fluidization. When the superficial gas velocity is increased to a much higher value, cohesive particles can be fluidized in the form of agglomerates. The internals can improve fluidization quality in three ways: Firstly, internals can break up the bubbles and agglomerates, and the size of bubbles and agglomerates can be decreased. Secondly, internals can dispel those abnormal behaviors and stabilize the fluidization state. Thirdly, internals can increase the ratio of gas phase in the fluidized bed, and then improve the contact efficiency between gas phase and solids. Experimental results showed that the porous-plate internals was not a good internals for improving fluidization quality of cohesive particles. Those abnormal phenomena can't be controlled and the bubble size can't be decreased. Some of the experimental porous-plate internals such as the No.D-d3-a50 performed more badly than free fluidized bed. The remiform internals is a good internals for improving the fluidization quality of cohesive particles. It performed much better than the former, but still had some defects. Those abnormal phenomena are controlled. Comparing with free fluidized bed, the incipient fluidization velocity becomes lower, the bed expansion becomes higher, and the style of pressure drop curve is more close to that of idealized fluidization. A new type of internals, which is called porous-remiform internals, was designed and has been researched with experiments. Experimental result shows that the porous-remiform internals can improve fluidization quality markedly, and it is the best one of the three types of internals. When it is used, slug and channel disappear, the style of pressure drop curve is looked like the ideal pressure drop curve, the bed expansion augment and the bubble size and number of bubbles are decreased markedly. In summary, the fluidized status is closed up to the particular fluidization by using the remiform-porous internals. After the effect of structure parameters is investigated, it is found that with increase of the number of blades, fluidization quality is improved. Besides, the obliquity of blade must be higher than 60 degree, and the porosity of the remiform-porous internals must be under the range of 20-25%. The effect of number of internals is investigated. The performance of several internals is better than that of one internal. |
| 语种 | 中文 |
| 公开日期 | 2013-09-26 |
| 页码 | 103 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1938]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 刘勤. 添加内构件对粘性颗粒流化质量的改善[D]. 中国科学院研究生院. 2000. |
入库方式： OAI收割
来源：过程工程研究所
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