环流流化床内大差异二元颗粒的流动机制研究

doi:10.11949/0438-1157.20250916

摘要/Abstract

摘要：

二元颗粒流化床广泛应用于生物质热解、煤化工、石油化工等领域。中心气升式环流流化床因其结构简单，操作方便等特点，非常适用于流化床的过程强化。重点考察了由FCC催化剂颗粒（细颗粒，d_p=90 μm）与分子筛颗粒（粗颗粒，d_p=1850 μm）构成的具有大尺度差异的混合二元颗粒体系在环流床和无内构件自由床中的流动特性。结果表明：对于单一细颗粒体系，环流床导流筒区域内的平均颗粒速度比自由床提高40% ~ 62.9%；环流床整体平均气泡尺寸比自由床小12.8% ~ 20.8%。对于混合颗粒体系，导流筒内构件的强化效果明显，其固含率径向分布较自由床更加均匀；颗粒速度分布与气泡尺寸分布不仅优于相同操作条件下的自由床，甚至优于单一细颗粒自由床。采用局部流化质量因子对环流床与自由床内的流化质量进行定量分析，相较于自由床，环流床内的流化质量提高了25% ~ 29.4%。

关键词: 流化床, 大差异颗粒, 多相流, 流化质量, 介尺度

Abstract:

At present, binary particle fluidized beds are widely used in fields such as biomass pyrolysis, coal chemical industry, and petrochemical industry. Draft tube fluidized beds (including draft tube internals) are widely used in the intensification process of fluidized beds due to their characteristics of simple structure and convenient operation. This paper focuses on investigating the flow characteristics of a binary particle system (mixed particle system) with large-scale differences, which is composed of FCC catalyst particles (fine particles, d_p=90 μm) and molecular sieve particles (coarse particles, d_p=1850 μm), in the draft tube fluidized bed and the free bed without internals. The results show that for the pure fine particle system, the average particle velocity in the draft tube region of the bed is 40% ~ 62.9% higher than that of the free bed; the overall average bubble size of the draft tube fluidized bed is 12.8% ~ 20.8% smaller than that of the free bed. For the Mixed particles system, the intensification effect of the draft tube internals is obvious, and its radial distribution of solid holdup is more uniform than that of the free bed; both the particle velocity distribution and the bubble size distribution are not only better than those of the free bed under the same operating conditions, but even better than those of the pure fine particle free bed. In conclusion, the local fluidization quality factor is used to quantitatively analyze the fluidization quality in the draft tube fluidized bed and the free bed. Compared with the free bed, the fluidization quality in the draft tube fluidized bed is improved by 25% ~ 29.4%.

Key words: fluidized-bed, large difference particles, multiphase flow, fluidization quality, mesoscale

中图分类号:

TQ 052.5

李凌宇, 金伟星, 吴兆龙, 卢春喜. 环流流化床内大差异二元颗粒的流动机制研究[J]. 化工学报, DOI: 10.11949/0438-1157.20250916.

Lingyu LI, Weixing JIN, Zhaolong WU, Chunxi LU. Study on flow mechanism of binary particles with large differences in draft tube fluidized beds[J]. CIESC Journal, DOI: 10.11949/0438-1157.20250916.

图/表 26

图1 底部流化床-顶部提升管实验装置示意图

Fig.1 Diagram of fluidized bed-riser equipment

图2 颗粒粒度分布

Fig.2 Particle size distribution

表1 颗粒基本物性参数

Table 1 Basic physical parameters of particles

颗粒种类	平均粒径/μm	颗粒堆积密度/(kg/m³)	颗粒密度/(kg/m³)	最小流化速度/(m/s)	带出速度/(m/s)
FCC	90	861	1440	0.036	0.4
分子筛	1875	745	1161	0.680	8.0

表2 自由床测点分布

Table 2 Distribution of measure point in free fluidized beds

序号	h/mm
1	380
2	680
3	940
4	1220

表3 环流床测点分布

Table 3 Distribution of measure point in draft tube fluidized beds

序号	h/mm	序号	h/mm	序号	h/mm
1	175	6	1030	11	2870
2	360	7	1400	12	350
3	525	8	1640	13	510
4	675	9	1900	14	670
5	830	10	2430	15	830

图3 光纤结构示意图

Fig.3 Structure diagram of the optical fiber probe

表4 光纤电压标定方程

Table 4 Calibration curve equations of OFP under different initial blending ratios

加入大颗粒质量分数	标定方程
x₀=0	$ε s = 0.864 1 + 375.91 e - 1.686 v$
x₀=0.3	$ε s = 0.6525 1 + 174.505 e - 1.946 v$

表4 光纤电压标定方程

Table 4 Calibration curve equations of OFP under different initial blending ratios

加入大颗粒质量分数	标定方程
x₀=0	$ε s = 0.864 1 + 375.91 e - 1.686 v$
x₀=0.3	$ε s = 0.6525 1 + 174.505 e - 1.946 v$

图4 光纤信号

Fig.4 Time sequence of the OFP data

图5 自由床固含率径的分布

Fig.5 Radial distribution of solid holdup in free bed

图6 环流床固含率的分布

Fig.6 Radial distribution of solid holdup in draft tube fluidized bed

图7 混合颗粒环流床固含率分布

Fig.7 Radial distribution of solid holdup in draft tube fluidized bed with Mixed particles

图8 混合颗粒局部组成分布

Fig.8 Local composition distribution of mixed particles

图9 环流床瞬时固含率

Fig.9 Instantaneous solid holdup in draft tube fluidized bed

图10 局部组成瞬时固含率

Fig.10 Local composition instantaneous solid holdup

图11 颗粒浓相体积分率

Fig.11 Volume fraction of dense particle

图12 自由床颗粒速度的分布

Fig.12 Distribution of particle velocity in free bed

图13 环流床颗粒速度的分布

Fig.13 Distribution of particle velocity in draft tube fluidized bed

图14 混合颗粒环流床颗粒速度的分布

Fig.14 Distribution of particle velocity in draft tube fluidized bed with Mixed particles

图15 自由床气泡尺寸的分布

Fig.15 Distribution of bubble size in free bed

图16 环流床气泡尺寸的分布

Fig.16 Distribution of bubble size in draft tube fluidized bed

图17 混合颗粒环流床气泡尺寸的分布

Fig.17 Distribution of bubble size in draft tube fluidized bed with Mixed particles

图18 气泡相体积分率

Fig.18 Volume fraction of bubble particle

图19 自由床动态流化质量因子的分布

Fig.19 Distribution of dynamic fluidization quality factor in free bed

图20 环流床动态流化质量因子的分布

Fig.20 Distribution of dynamic fluidization quality factor in draft tube fluidized bed

图21 混合颗粒动态流化质量因子的分布

Fig.21 Distribution of dynamic fluidization quality factor in draft tube fluidized bed with Mixed particles

图22 流化床平均流化质量

Fig.22 Average fluidization quality of fluidized bed

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