Characteristics on gushing in tower bubbling fluidized bed

doi:10.11949/j.issn.0438-1157.20170364

Abstract

Abstract:

In order to enhance the solid-gas contact, a new bubbling fluidized bed with tower reactor is designed. The fuel reactor is divided into several chambers along the bed height direction by internal air distributor with caps. In the period of fluidization, a special phenomenon is caused by slugging, which could be named “gushing”. The forming and disappearing of gushing can be recorded on the basis of image with a digital video camera. By using fast Fourier transform (FFT) and wavelet packet transform methods, the pressure fluctuation signal is analyzed to investigate the characteristics on gushing, including fluidization conditions, dominant frequency and energy mode of gushing. The results showed that gushing fluidization appears under the fluidization number of 3.47 in this reactor. Its cycle period is lasting 1-2 s and dominant frequency is around 0.1-0.5 Hz. Changing of reactor structure, like adding one distributor to reach two chambers, adjusting the aspect ratio of lower chamber to be 3:1 and enlarging the valve opening on caps of distributors, is the better structures for gushing fluidization. Therefore, in order to obtain a satisfactory gushing property in the reactor, the inlet gas velocity and reactor structure must be kept in a suitable condition.

Key words: bubbling fluidized bed, tower reactor, gushing, spectral analysis, wavelet analysis

摘要：

为强化气固接触，提出了一种新型塔式鼓泡循环床反应器，采用多个带有风帽的中间分布板、沿床层高度方向将反应器分隔成若干腔室，流化过程中形成一种特殊的涌渗（gushing）现象；依据连续拍照所得图像，基于快速傅里叶变换和小波包变换的方法，对床内压力脉动信号进行分析，研究涌渗产生和消亡条件，频率和能量大小，以期掌握涌渗的形成规律。结果表明，此反应器内流化数为3.47时涌渗产生明显，周期性寿命为1~2 s，频率分布于0.1~0.5 Hz区域；保持流化风速不变，改变反应器结构，加入一层中间分布板构成双腔室、调整下腔室高径比为3：1以及适当增大风帽开孔率时，涌渗主频明显，能量适中，涌渗效果得到优化。因此，塔式鼓泡流化床内的涌渗流动特性取决于流化风速以及塔式鼓泡床的几何结构。

关键词: 鼓泡流化床, 塔式反应器, 涌渗, 频谱分析, 小波分析

CLC Number:

TQ053.5

ZHU Xiao, SHEN Laihong. Characteristics on gushing in tower bubbling fluidized bed[J]. CIESC Journal, 2017, 68(11): 4112-4120.

朱晓, 沈来宏. 塔式鼓泡流化床内的涌渗流动特性[J]. 化工学报, 2017, 68(11): 4112-4120.

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