超细颗粒声场流态化特性研究
文献类型：学位论文
| 作者 | 苏吉 |
| 学位类别 | 硕士 |
| 答辩日期 | 2010-06-07 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 朱庆山 |
| 关键词 | 超细颗粒 声场流态化 聚团尺寸 受力平衡模型 |
| 其他题名 | Fluidization behaviors of ultrafine particles in sound-assisted fluidized bed |
| 学位专业 | 化学工程 |
| 中文摘要 | 超细颗粒间存在较强的粘附力，流化过程中易产生节涌、沟流、聚团等不良行为，难以实现均匀稳定流态化。但是，随着超细粉体技术的发展以及对超细颗粒加工的需要，超细颗粒流态化技术的研究和应用日益受到人们的关注，特别是如何改善超细颗粒的流化质量正逐渐成为研究的重点和热点。本文通过冷态实验和理论模型推导相结合的方式，研究了超细铁矿颗粒在声场流化床中的流化特性，得到的主要结论如下：（1）在内径为40 mm的流化床中用平均粒径为7.45 μm的超细铁矿颗粒为实验物料，在声波频率为0-300 Hz，声压级为0-121 db，声波波形为正弦波、方波、斜波、三角波、sin(x)/x波的条件下，系统考察了声波对超细颗粒流化行为的影响。研究表明：① 超细颗粒达到均匀稳定的流化状态存在一个最优频率范围。声压一定时，最小流化速度随着声波频率的增大呈现先减小后增大的变化趋势；频率130 Hz时，最小流化速度最低，此时流化床中形成的聚团尺寸最小，流化效果最好。②声波频率一定时，随着声压级的增大，聚团尺寸减小，最小流化速度降低，流化质量逐渐改善。③ 声波频率和声压级一定时，正弦波的最小流化速度最小；三角波次之；方波、斜波、sin(x)/x不能实现均匀稳定的流态化。综合比较得出实验条件下的最佳声波参数为130 Hz，121 db的正弦波。 （2）对声场流化床中超细颗粒聚团进行受力分析，建立了计算聚团大小的受力平衡模型，当促进聚团破碎的力和促进聚团形成的力相等时，可以得出一定频率不同声压级下的聚团尺寸。此模型计算的结果与实验得到的聚团大小较为接近，说明声场流化床中对于聚团的受力分析是正确的。该模型不仅可以预测任意声压级下的聚团尺寸，而且可以反映出颗粒间相互作用对聚团大小的影响。 |
| 英文摘要 | It is well known that ultrafine particles are difficult to be fluidized due to their strong interparticle forces. The fluidization of ultrafine particles usually experiences several stages such as slugging, channeling, disrupting and agglomerating with increasing gas velocity. Recently, there are increasing demands on processing ultrafine particles by fluidized bed due to their industrial applications. Therefore, it is of great importance to further study the behaviors of ultrafine particles and explore the possibility to intensify the fluidization process of ultrafine particles. In the study, characteristics of ultrafine iron particles fluidization were investigated and a mathematical model was developed to predict the sizes of agglomerates in sound-assisted fluidized bed. The following major conclusions were obtained: (1) The fluidization behavior of ultrafine iron particles were investigated in a 40 mm I.D. fluidized bed at 0-300 Hz and 0-121 db, with the sine wave, square wave, ramp-up wave, triangle wave and sin(x)/x wave. It has been shown that: ① At a given sound pressure level, there was an optimal sound frequency (130 Hz), at which the effectiveness of sound wave in improving fluidization of ultrafine particles was most remarkable. ② At a given sound frequency, agglomerate size and the minimum fluidization velocity (umf) decreased with increasing sound pressure level. Consequently, the quality of fluidization improved with increasing sound pressure level. ③ Among different sound waves, sine wave showed the best improvement in fluidization, while the fluidization quality exhibited little improvement under square wave, ramp-up wave and sin(x)/x wave. Therefore, the best operation parameters were 121 db, 130 Hz and the sine. (2) A model of force balance was developed to predict the agglomerate size through analyzing the forces acting on agglomerate based on an assumption that the agglomerate will reach a stable size when the detached forces and adherent forces acting on agglomerate are equal. Agglomerate sizes calculated by the model showed well agreements with measurement, which demonstrated the effectiveness of the model for predicting agglomerate size in sound-assisted fluidized bed. |
| 语种 | 中文 |
| 公开日期 | 2013-09-17 |
| 页码 | 64 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1500]  |
| 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 | 苏吉. 超细颗粒声场流态化特性研究[D]. 中国科学院研究生院. 2010. |
入库方式： OAI收割
来源：过程工程研究所
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