非球形湿颗粒导向管喷动流化床流动特性

doi:10.11949/0438-1157.20240292

摘要/Abstract

摘要：

实际工业生产中颗粒多为非球形颗粒，对颗粒形状效应和液相作用机制的研究不足，是导向管喷动流化床在颗粒涂层改性、包膜等工业应用的关键限制因素。选取粒径、密度相似的球形和圆柱形非球形颗粒为实验物料，对比两种颗粒在不同气速和雾滴引入量下的压力脉动信号频谱分析、信息熵分析，并结合床内气固流动对流型进行划分，绘制非球形湿颗粒流动相图，进而探究喷动流化过程中颗粒形状效应及液相作用机制。相比于球形颗粒，粒径、密度相似的非球形颗粒有较小的最小喷动速度，在喷动过程中有两个及以上较低的主频峰且信息熵较大，显示出非球形颗粒在系统内较高的混乱程度，颗粒之间摩擦、碰撞等降低了导向管内颗粒的固体循环速率。液体的引入增大了环形区颗粒间液桥力，使最小流化速度变大，但液体挥发引起喷动气量增大，使最小喷动速度与最小喷动流化速度减小。在喷动流化流型下引入液体，球形颗粒导向管两端压降Δp_DT的脉动主频降低，而非球形颗粒Δp_DT的主频升高。而且非球形颗粒黏附液体后频谱分析结果显示幅值较大的单一主频峰，表明非球形湿颗粒压力脉动规律性的增强。

关键词: 喷动流化床, 导向管, 非球形, 湿颗粒, 液相效应

Abstract:

Most of the particles in industrial production have a non-spherical shape. However, the study of particle shape effect and liquid phase mechanism is insufficient, which is the main limiting factor for the application of draft tube spout-fluid bed in particle coating. In this study, the spherical and non-spherical cylindrical particles with similar particle size and density were selected as experimental materials. The pressure pulsation signal spectrum analysis and information entropy analysis of the two types of particles under different gas velocities and droplet introduction amounts were compared, and it is divided based on the gas-solid flow convection pattern in the bed. Meanwhile, the effect of particle shape and liquid phase under spouted-fluidized state were clarified by signal analysis method. The results show that non-spherical particles have a smaller minimum spouting velocity, multiple main frequency peaks and higher information entropy than spherical particles. These indicate that non-spherical particles have a high degree of chaos in the system. The solid circulation rate is reduced due to the friction and collision between particles in the draft tube. The minimum spouting velocity and the minimum spout fluidizing velocity are decrease owing to the introduction of liquid in the bed. Meanwhile, the liquid bridging force between particles is increased in the annular region, resulting in an increasing of the minimum fluidization velocity. However, the gas velocity is increased with the evaporating of liquid, resulting in a decrease in the minimum spouting velocity and the minimum spouting fluidization velocity. Due to the introduction of liquid during the spouted-fluidized flow pattern, the dominant frequency of pressure drop Δp_DT is reduced for the spherical particle. However, the dominant frequency of pressure drop Δp_DT is increased for the non-spherical particle. Moreover, owing to the liquid adhering, the spectrum analysis of non-spherical particles show a single dominant frequency peak with a larger amplitude. This indicates an enhanced regularity of pressure fluctuations for non-spherical wet particles.

Key words: spout-fluid bed, draft tube, non-spherical, wet particle, liquid phase effect

中图分类号:

TQ 051.13

战德康, 孙腾, 王香竹, 吴明周, 吴曼, 郭庆杰. 非球形湿颗粒导向管喷动流化床流动特性[J]. 化工学报, 2024, 75(6): 2166-2179.

Dekang ZHAN, Teng SUN, Xiangzhu WANG, Mingzhou WU, Man WU, Qingjie GUO. Flow characteristics of non-spherical wet particles in a draft tube spout-fluid bed[J]. CIESC Journal, 2024, 75(6): 2166-2179.

图/表 19

图1 导向管喷液喷动流化床实验装置示意图1—空气压缩机;2—减压阀;3—转子流量计;4—管式加热炉;5—液体储槽;6—蠕动泵;7—气体及液体喷嘴;8—温控箱;9—气体分布板;10—玻璃视窗;11—导向管;12—加热带;13—测量孔;14—数据采集卡;15—计算机;16—除尘器

Fig.1 Schematic diagram of experimental device of spout-fluid bed with nozzle spray1—air compressor; 2—pressure reducing valve; 3—rotor flowmeter; 4—tubular heating furnace; 5—liquid storage tank; 6—peristaltic pump; 7—gas and liquid nozzle; 8—temperature control box; 9—gas distribution plate; 10—glass window; 11—guide pipe; 12—heating belt; 13—measuring hole; 14—data acquisition card; 15—computer; 16—dust collector

表1 实验所用颗粒的物理性质

Table 1 Physical properties of particles used in experiment

颗粒	形状	当量直径d_p/mm	颗粒密度ρ_p/(kg/m³)	堆积密度ρ_b/(kg/m³)	球形度	Geldart分类
尼龙6	圆柱	2.62	1140	778	0.71	Geldart D
PE	球形	2.80	1050	800	1.00	Geldart D

表2 实验所用气体的物理性质

Table 2 Physical properties of gases used in experiment

气体	密度ρ/ (kg/m³)	比热容c_p /（kJ/(kg·K)）	热导率λ/ （W/(m·K)）	黏度μ/(Pa·s)
空气	1.205	1.013	2.59×10²	1.81×10^-5

表3 实验所用液体的物理性质

Table 3 Physical properties of liquid used in experiment

液体	密度ρ/(kg/m³)	比热容c_p / （kJ/(kg·K)）	黏度μ/(Pa·s)
去离子水	998.2	4.183	1×10^-3

表4 本实验操作参数值

Table 4 Values of each operation parameter in this experiment

实验参数	符号	数值
静床高/mm	H₀	140
夹带高度/mm	H_d	25
喷口直径/mm	D_i	8
导向管内径/mm	D_d	25
床层温度/K	T	293,323
喷液量/(ml/min)	L	3
雾化气流速/(m/s)	U_L	5
喷动气流速/(m/s)	U_s	0~35
流化气流速/(m/s)	U_f	0~0.7

图2 导向管喷动流化床不同流型气固流动结构

Fig.2 Gas-solid flow structure of different flow patterns in spout-fluid bed with draft tube

图3 鼓泡流化状态的压降特性（Us=10 m/s，Uf=0.3 m/s，T=293 K）

Fig.3 Pressure drop characteristics of bubbling fluidization state

图4 射流流化状态的压降特性（Us=10 m/s，Uf=0.5 m/s，T=293 K）

Fig.4 Pressure drop characteristics of jet fluidization state

图5 不稳定喷动状态的压降特性（Us=20 m/s，Uf=0.6 m/s，T=293 K）

Fig.5 Pressure drop characteristics of unstable spouting state

图6 充气喷动状态的压降特性（Us=30 m/s，Uf=0.2 m/s，T=293 K）

Fig.6 Pressure drop characteristics of aerated spout state

图7 喷动流化状态的压降特性（Us=30 m/s，Uf=0.6 m/s，T=293 K）

Fig.7 Pressure drop characteristics of spouted-fluidized state

图8 不同颗粒气固流动流型

Fig.8 Gas-solid flow pattern of different particles

图9 喷动流化流型下不同颗粒不同喷动气速条件下导向管内压降信号功率谱密度分布

Fig.9 Power spectral density distribution of pressure drop signal in draft tube under different particle and different spouting gas velocity conditions

图10 喷动流化流型不同气速条件下球形颗粒和非球形颗粒信息熵对比

Fig.10 Comparison of information entropy between spherical particles and non-spherical particles under different gas velocities of spouted-fluidized flow patterns

图11 两种颗粒喷动流化流型下固定喷动气速压降熵值随流化气速的变化

Fig.11 Variation of pressure drop entropy of fixed spouting velocity with fluidizing gas velocity under two particle spouted-fluidized flow patterns

图12 两种颗粒喷动流化流型下固定流化气速信息熵值随喷动气速的变化

Fig.12 Change of fixed fluidization gas velocity information entropy with spouting gas velocity under two particle spouted-fluidized flow patterns

图13 球形颗粒与非球形圆柱颗粒喷液量为3 ml/min时不同气速下流型

Fig.13 Flow patterns of spherical particles and non-spherical cylindrical particles with spray volume of 3 ml/min at different gas velocities

图14 不同颗粒喷动流化流型引入液滴导向管两端压降信号功率谱密度分布的变化

Fig.14 Change of power spectral density distribution of pressure drop signal at both ends of droplet draft tube introduced by different particle spouted-fluidized flow patterns

图15 不同颗粒喷动流化流型引入液滴导向管两端压降的变化

Fig.15 Pressure drop changes at both ends of droplet draft tube introduced by different particle spouted-fluidized flow patterns

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