通過降維法加速篩板洗滌器中顆粒清除的三維流場建模

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研究生：	黃筱涵 Huang, Siao-Han
論文名稱：	通過降維法加速篩板洗滌器中顆粒清除的三維流場建模 Accelerating 3D Flow Modeling for the Particles Scavenging in a Sieve Plate Scrubber via Dimension Reduction
指導教授：	鄭西顯 Jang, Shi-Shang
口試委員:	汪上曉 Wong, David Shan-Hill 姚遠 Yao, Yuan 錢義隆 Chien, I-Lung 康嘉麟 Kang, Jia-Lin
學位類別：	博士 Doctor
系所名稱：	工學院 - 化學工程學系 Department of Chemical Engineering
論文出版年：	2020
畢業學年度：	109
語文別：	英文
論文頁數：	73
中文關鍵詞：	計算機流體力學模擬、粒子清除、板式洗滌器、多相流、U型曲線、降維法
外文關鍵詞：	Computational Fluid Dynamics(CFD), Particle Removal, Plate Scrubber, Multiphase Flow, U-Shaped Curve, Dimension reduction
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本研究建立了一個篩板洗滌器的計算流體動力學（CFD）模型,用以預測其顆粒去除效率。該模型亦能模擬出擴散及慣性機制交互作用而產生的粒子清除效率U型曲線。然而,於流場中跟蹤粒子的計算相當複雜,且硬體設備效能需求高,若使用三維(3D)流場結構來進行建模的試誤將花費大量時間,這將不利於找到適當的模型設置及洗滌塔設計。
為降低軟體計算的複雜性及時長,本研究提出了降維法來簡化三維流場至二維(2D)流場,用以分析連續流場施予粒子的力在不同的組合下,對粒子清除效率的影響。降維法及用戶自定義模型的合理性是通過2D及3D流場的泡沫密度的一致性來進行驗證。其中,流體施予粒子的力組合在2D流場中被分析,模擬結果顯示除了拖曳力之外,還應包含其他力(例如:升力,壓力梯度力,虛擬質量力等),才能正確地模擬篩板上的粒子流動情形。該力組合亦使得模擬在各種操作條件下,得到與文獻中實驗數據相符的結果。出乎意料地,該模型預測出粒徑由0.1至3.0μm的顆粒去除效率呈現U形曲線,且該現象無法由關係式預測而得。本文的最後, 使用具有與2D模型相同設置的3D模型來驗證兩者清除效率的一致性。結果表明, 2D模型與3D模型的粒子清除效率預測結果相當接近。

In this thesis, a computational fluid dynamics (CFD) model of a sieve plate scrubber was built to predict its particle-removal efficiency and predict the U-shaped curve of the particle-removal efficiency as particles became smaller. Due to the complexity of particle tracking, it takes considerable time to simulate the model by using a three-dimensional (3D) structure, which is not conducive to finding the appropriate setting of particle forces. Instead, this work presented a dimension-reduction method to estimate the particle force setting by using a two-dimensional (2D) structure. The rationality of the dimension-reduction method and user-defined function was validated by the consistency in froth density for both 2D and 3D models at various air-inlet velocities. Furthermore, the result of the particle forces setting showed that besides the drag force, other forces, such as the lift force, pressure-gradient force, gravity force, and virtual mass force, should be employed in the CFD model to predict the particle-removal efficiency of the sieve plate scrubber. The prediction results of the 2D model remarkably match the particle-removal efficiency results of experimental data from the literature for various gas velocities and particle sizes. In addition, the model predicts the U-shaped curve of the particle-removal efficiency for the particle-diameter range from 0.1 to 3.0μm. Furthermore, a 3D model with the setting of the particle forces as in the 2D model was used to validate the consistency between the 2D and 3D models. The result showed that the particle-removal efficiency of the 3D model was considerably close to the prediction results of the 2D model.

Table of Content
謝誌    i
摘要    ii
Abstract    iii
Table of Content    iv
List of Figure    vi
List of Tables    viii
Chapter 1.    Introduction    1
1.1    Background    1
1.2    Literature Review    2
1.2.1    Particle Control Equipment    2
1.2.2    CFD Simulation of Particle Control Equipment    4
1.2.3    Research of Particle Scavenging Efficiency Estimation    5
1.2.4    Research of Sieve Plate CFD Simulation    6
1.2.5    Research of Deformed-Sieve Plate CFD Simulation    8
1.2.6    Research of 3D to 2D Model Simulation    11
1.2.7    The U-shaped Curve of Particle-Removal Efficiency    13
1.3    Motivation and Contribution    15
Chapter 2.    Mathematical Modeling    17
2.1    Introduction of Commercial CFD Software    17
2.2    CFD Modeling approach    18
2.2.1    Governing Equations    18
2.2.2    Viscous Model    19
2.2.3    Interphase Momentum Exchange Term    20
2.2.4    Surface Tension    21
2.3    Particle Motion    22
2.3.1    Drag Force    22
2.3.2    Lift Force    23
2.3.3    Virtual Mass Force and Pressure Gradient Force    23
2.3.4    Particle Collision, Breakup, and Coalescence    24
2.3.5    Discrete Random Walk Model    26
2.4    Solution Algorithm    27
Chapter 3.    Validation of the user-defined drag coefficient in 2D sieve tray    29
3.1    Introduction    29
3.2    Introduction for Previous Experiment for Sieve Plate Hydraulics    29
3.3    Simulation for Sieve Plate Hydraulics    31
3.4    Results and Discussion    35
3.4.1    Hydraulic Results of Sieve Tray    35
3.4.2    Particles Affect by the Primary Phase    39
3.5    Conclusion    41
Chapter 4.    Modeling on particle scavenging in a sieve plate scrubber    42
4.1    Introduction    42
4.2    Introduction for Previous Experiment of Sieve Particle Scavenging    42
4.3    Simulation for particle scavenging of the sieve plate    45
4.4    Results and Discussion    50
4.4.1    Grid Size Sensitivity    50
4.4.2    Validation of the Dimension-Reduction Method    51
4.4.3    Forces Acting on Particles    55
4.4.4    Effect of Particle Concentration on Particle-Removal Efficiency    58
4.4.5    Validation of Particle-Removal Efficiency    59
4.4.6    Comparison of 2D and 3D Models    62
Chapter 5.    Conclusion    64
Nomenclature    65
Appendix    68
Reference    70

 
List of Figure
Figure 1. Evolution of the CFD model of sieve tray    8
Figure 2. Structures of the deformed sieve tray (a) full open valve tray [24]; (b) ConCap tray [25]; (c) sieve-fixed valve tray [22]; (d) bubble cap tray [23]    10
Figure 3. Experiment system and simulation geometries of pseudo-2D turbulent fluidized bed [27]    12
Figure 4. 2D and 3D model of the Tray dryer system [28]    13
Figure 5. U-shaped curve of particle-removal efficiency in the sieve plate scrubber [3]    14
Figure 6. Modeling procedure    28
Figure 7. Probe layout on the third tray [20]    30
Figure 8. The structure of commercial-scale sieve tray    31
Figure 9. Aerial view of the sieve tray    32
Figure 10. Mesh display of 2D and 3D sieve tray    32
Figure 11. The flow direction of the air and liquid phase    34
Figure 12. The monitored region in Fluent    35
Figure 13. froth density vs. flow time    36
Figure 14. Liquid velocity profile of x-direction    37
Figure 15. The interaction between particles and the primary phase, the primary was set as (a)liquid phase; (b)air phase.    40
Figure 16. Snapshot of particle flows in the sieve tray    41
Figure 17. The experimental system presented by Taheri and Calvert [3]    43
Figure 18. Removal efficiency vs generalized parameter    44
Figure 19. 3D geometry and mesh of the half sieve plate model    46
Figure 20. Dimension transformed from 3D to 2D geometries    48
Figure 21: 2D flow direction and discrete-phase boundaries    48
Figure 22: Structural mesh of the sieve plate scrubber    49
Figure 23. Sensitivity of the froth-density prediction to the number of meshes for (a) 2D geometry and (b) 3D geometry (vG= 0.387 m/s)    51
Figure 24. Snapshots of the liquid volume fractions at various flow times (vG= 0.387 m/s) in the (a) 2D model (0–20 s) and (b) 3D model (0–50 s)    52
Figure 25. Comparing the results of the 2D model, 3D model, and experiment for various air-inlet velocities. (a) holes average air velocities; (b) froth densities    54
Figure 26. Particle-removal efficiency versus dp (vG= 0.387 m/s)    56
Figure 27. Transient particle-removal efficiency as a function of flow time at various particle concentrations (dp=2.28μm; vG= 0.387 m/s)    58
Figure 28. Comparison of the results of the experiment, correlation, and 2D simulation of the particle-removal efficiency for various particle diameters. Notably, vG= (a) 0.232 m/s, (b) 0.387 m/s, (c) 0.775 m/s.    59
Figure 29. Comparison of the results of the experiment, correlation, and 2D simulation of the particle-removal efficiency for particle diameters in small sizes.  vG= (a) 0.232 m/s, (b) 0.387 m/s, (c) 0.775 m/s in the U-shaped curve simulation.    61
Figure 30. Transient particle-removal efficiency as a function of flow time from the moment of particle injection a dp=1.5μm; b dp=2.28μm (vG=0.387ms)    63

 
List of Tables
Table 1. Correlations of liquid holdup for deformed sieve plate    11
Table 2. Specification of commercial-scale sieve plate tower    30
Table 3. The liquid velocity of the x-direction    37
Table 4. Comparing the results of the clear liquid height    38
Table 5. Comparing the results of the froth height    38
Table 6. Comparing the results of the froth density    38
Table 7: Particle injected condition    50
Table 8. Comparison table of the case number and the selection of particle force models (the symbol “o” represents the particle force model been selected)    55



                                

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