本研究探討於掃流微過濾裝置中通入氣體對過濾效能之提升，並探討操作條件對多相流(固、液、氣三相)掃流微過濾之濾速與濾餅性質之影響。實驗中使用平均孔徑為0.1μm的醋酸纖維膜(Mixed cellulose ester) 過濾平均粒徑為0.4μm之聚甲基丙烯酸甲酯(PMMA)粒子，故粒子只能附著於薄膜表面，形成濾餅層。在多相流之微過濾實驗中，改變通入之氣體流量、過濾壓差、液體速度、進料濃度等變因，量測其對於濾速，濾餅量與過濾阻力之變化。實驗結果顯示，多相流之過濾程序中濾餅之成長是可逆的，濾餅量與濾速取決於最終之操作條件。當通氣量越大時，穩定濾速會越高，但提昇之效率仍然有其最終極限。經改變各種操作變因，都發現平均過濾比阻值並無顯著的變化，故濾餅成長量為影響過濾速度的最主要因素，而濾餅成長量可以由本研究提出之模式估計。在本研究之操作條件範圍內，氣體速度為0.12 m/s之濾速為無通氣時的2倍；液體速度或過濾壓差提高5倍皆可提升濾速1.5倍；但是懸浮液濃度增加5倍後，濾速僅為原來的1/3。總而言之，通入氣泡可以有效提升掃流微過濾之效能。

The efficiency enhancement in cross-flow microfiltration of submicron particles by air-bubble injection is studied. The effects of operating conditions, such as flow rates of suspension and air, filtration pressure and suspension concentration, etc., on the cake properties and filtration rate are also discussed. A filter membrane, made of mixed cellulose ester, with a mean pore size of 0.1mm is used to filter 0.4 mm PMMA particles; therefore, particles may be deposited on the membrane surface to form a filter cake. The results show that the cake formation in multiphase filtration process is reversible, and the pseudo-steady filtration rate increases with increasing air-bubble flow rate. However, the increase in filtration rate is more significant under lower air-bubble flow rate. Since the average specific filtration resistance of cake varies slightly within the operating conditions of this study, the cake mass plays the major role in determining filtration resistance and filtration rate. The cake mass can be related to the ratio of wall shear stress to filtration rate based on the proposed model. The filtration rate at the gas velocity of 0.12 m/s is double compared to that in the case of no air injection. The filtration rate is 1.5-fold when liquid velocity increases from 0.1 to 0.5 m/s or filtration pressure increases from 20 to 100 kPa. However, the filtration rate becomes 1/3 when PMMA concentration increases from 0.1 to 0.5wt%. In general, the injection of air-bubble can significantly enhance filtration efficiency in cross-flow microfiltration of fine particles.

目 錄
誌 謝.......Ⅰ
摘 要.......II
目 錄.......IV
圖目錄.......VII
表目錄.......XII


第一章  緒  論.......1
1-1  前言.......1
1-2  研究動機與目標.......3

第二章  文 獻 回 顧.......6
2-1  掃流微過濾之特性.......6
2-2  過濾阻塞模式.......8
2-3  結垢與臨界濾速.......10
2-4  在過濾程序中通入氣體對結垢與過濾的影響.......15

第三章  理  論.......21
3-1  掃流過濾模組中力的分析.......22
3-2  粒子於膜面上堆積與力之解析.......23
3-2.1  流體在平行濾面方向 (x方向) 之拉曳力，Ft.......25
3-2.2  流體在垂直濾面方向 (y方向) 之拉曳力，Fn.......27
3-2.3  慣性浮昇力，Fl.......27
3-2.4  淨重力，Fg.......29
3-2.5 粒子間之交互作用力，Fi.......29
3-2.6 氣泡與粒子間之交互作用力，Fb.......33
3-3  粒子之黏著機構.......39
3-4  單成份掃流微過濾之模式探討.......39

第四章  實驗裝置與步驟.......42
4-1  實驗物料與濾材.......42
4-1.1  懸浮液.......42
4-1.2  氣體.......42
4-1.3  濾材.......42
4-2  掃流過濾裝置.......43
4-3  分析儀器.......45
4-4  實驗步驟.......46

第五章  實驗結果與討論.......48
5-1多相流動對於掃流微過濾的影響.......48
5-2氣體量對掃流微過濾的影響.......50
5-2.1  氣體量對濾速的影響.......50
5-2.2  氣體量對單位濾餅量與濾餅厚度的影響.......56
5-2.3  氣體量對平均過濾比阻與平均孔隙度的影響.......58
5-3  單成份懸浮液於多相流動中之掃流過濾特性.......61
5-3.1  液體速度對於多相流動中之掃流過濾的影響.......61
5-3.2  過濾壓差對於多相流動中之掃流過濾的影響.......65
5-3.3  懸浮液濃度對於多相流動中之掃流過濾的影響.......69
5-4  阻力分析.......75
5-5  多相流動中剪應力之變化.......80

第六章  結  論.......82

符 號 說 明.......84

參 考 文 獻.......89

附  錄.......94

圖 表 目 錄

圖目錄

第一章
Fig.1-1 The classification of membrane filtration process........2

Fig. 1-2 Schematics of dead-end filtration and cross-flow filtration........3

第二章
Fig.2-1 Fouling schematics........10

Fig.2-2 Coordinate system and sketch of a spherical foulant particle rolling due to viscous shear flow over a permeable surface with two characteristic roughness heights........12

Fig2-3 I Two-phase flow inside pipes........17

第三章
Fig3-1 Schematics of cross-flow filtration with aeration........21

Fig3-2 Schematics of shell momentum balance for a rectangular element in cross-flow filter........22

Fig.3-3 Force exerted on a depositing particle in the cross-flow microfiltration.	.......26

Fig.3-4 Interaction energy of Van der Walls force and electrical double layer repulsive force under different distance.	.......30

Fig.3-5 Separated horizontal flow model. Simultaneous gas/liquid flow in (a)is considered a the combination of gas and liquid flow, as in(b) and (c)........34

Fig.3-6 The resistance of microfiltration........41

第四章
Fig.4-1 A schematic diagram of cross-flow filtration system........44

第五章
Fig.5-1 Decay of filtration rates during cross-flow microfiltration under various aeration condition........49

Fig.5-2 Time courses of filtration rates during cross-flow microfiltration under various gas velocities........50

Fig.5-3 Pseudo steady state filtration rates during cross-flow microfiltration under different gas velocities........51

Fig.5-4 Effect of pseudo steady state filtration rates on the efficiency under different gas velocity........52

Fig.5-5 Bubble size distributions under different gas velocities........55

Fig.5-6 Bubble frequency distribution under different gas velocities........55

Fig.5-7 Cake mass under different gas velocities........56

Fig.5-8 Pseudo-steady cake thickness under different gas velocities........57

Fig.5-9 Average porosity of cake under various gas velocities........58

Fig.5-10 Image of filtration cake under different gas velocities  (a) 0.02 m/s (b) 0.04 m/s (c) 0.08 m/s (d) 0.12 m/s........	59


Fig. 1-2 Schematics of dead-end filtration and cross-flow filtration.	3
第二章
Fig.2-1 Fouling schematics.	10

Fig.2-2 Coordinate system and sketch of a spherical foulant particle rolling due to viscous shear flow over a permeable surface with two characteristic roughness heights.	12

Fig2-3 I Two-phase flow inside pipes.	17
第三章
Fig3-1 Schematics of cross-flow filtration with aeration.	21

Fig3-2 Schematics of shell momentum balance for a rectangular element in cross-flow filter.	22

Fig.3-3 Force exerted on a depositing particle in the cross-flow microfiltration.	26

Fig.3-4 Interaction energy of Van der Walls force and electrical double layer repulsive force under different distance.	30

Fig.3-5 Separated horizontal flow model. Simultaneous gas/liquid flow in (a)is considered a the combination of gas and liquid flow, as in(b) and (c).	34

Fig.3-6 The resistance of microfiltration.	41
第四章
Fig.4-1 A schematic diagram of cross-flow filtration system..	44

第五章
Fig.5-1 Decay of filtration rates during cross-flow microfiltration under various aeration condition..	49

Fig.5-2 Time courses of filtration rates during cross-flow microfiltration under various gas velocities..	50

Fig.5-3 Pseudo steady state filtration rates during cross-flow microfiltration under different gas velocities.	51

Fig.5-4 Effect of pseudo steady state filtration rates on the efficiency under different gas velocity.	52

Fig.5-5 Bubble size distributions under different gas velocities.	55

Fig.5-6 Bubble frequency distribution under different gas velocities..	55

Fig.5-7 Cake mass under different gas velocities.	56

Fig.5-8 Pseudo-steady cake thickness under different gas velocities.	57

Fig.5-9 Average porosity of cake under various gas velocities.	58

Fig.5-10 Image of filtration cake under different gas velocities  (a) 0.02 m/s (b) 0.04 m/s (c) 0.08 m/s (d) 0.12 m/s.	59

Fig.5-11 The top view of membrane surface after filtration experiment (ug=0, ul=0.1 m/s, DP=20 kPa). (5,000 X).	60



Fig.5-12 The top view of membrane surface after filtration experiment (ug=0.12 m/s, ul=0.1 m/s, DP=20 kPa). (5,000 X) 	60

Fig.5-13 Average specific filtration resistance under different gas velocities.	61

Fig.5-14 Pseudo steady state filtration rates during cross-flow microfiltration under different liquid velocities.	62

Fig.5-15 Bubble frequency distribution under different liquid velocities.	63

Fig.5-16 Average specific filtration resistance under different liquid velocities.	64

Fig.5-17 Cake mass under different liquid velocities.	64

Fig.5-18 The pseudo-steady cake thickness under different liquid velocities .	65

Fig.5-19 Cake mass under different filtration pressure.	66

Fig.5-20 The pseudo-steady cake thickness under different filtration pressure.	66

Fig.5-21 The average specific filtration resistance under different filtration pressure.	67

Fig.5-22 The pseudo steady state filtration rates during cross-flow microfiltration under different filtration pressure.	68

Fig.5-23 Bubble frequency distribution under different filtration pressure.	69

Fig.5-24 Decay of filtration rates during cross-flow microfiltration under various feed concentration..	70
Fig.5-25 Cake mass under various feed concentration.	71

Fig.5-26 The pseudo-steady cake thickness under different various feed concentration.	71

Fig.5-27 The pseudo steady state filtration rates during cross-flow microfiltration under various feed concentration.	72

Fig.5-28 Bubble frequency distribution under various feed concentration.	73

Fig.5-29 Cake mass and the average specific filtration resistance under various feed concentration.	74

Fig.5-30 Image of filtration cake under various feed concentration (a) 0.1 % (b) 0.2 % (c) 0.3 % (d) 0.4 % (e) 0.5 %.	74

Fig.5-31 The side view of membrane surface after filtration experiment (ug=0, ul=0.1 m/s, DP=20 kPa). (5,000 X).	76

Fig.5-32 The side view of membrane surface after filtration experiment (ug=0.12 m/s, ul=0.1 m/s, DP=20 kPa). (5,000 X).	76

Fig.5-33 Cake resistances at the pseudo-steady state in cross-flow microfiltration under different gas velocities .	77

Fig.5-34 Comparison of the cake resistances at the pseudo-steady state in cross-flow microfiltration under different liquid velocities.	78

Fig.5-35 Cake resistances at the pseudo-steady state in cross-flow microfiltration under different filtration pressure.	78


Fig.5-36 Cake resistances at the pseudo-steady state in cross-flow microfiltration under various feed concentration.	79

Fig.5-37 A plot of wc v.s τzy/qs under various liquid velocity.	81

附錄

Fig.A-1.1 The SEM picture of PMMA powder. ( ×50KX )	94

Fig.A-1.2 Particle size distribution of PMMA powder. (MP-1000).	95

Fig.A-1.3 Particle size distribution of PMMA powder. (MP-1000).	95

Fig.A-2.1 The top view of the mixed cellulose ester membrane by SEM(30,000X)..	97

Fig.A-2.2 The side view of the mixed cellulose ester membrane by SEM (30,000X)..	97

Fig.B-1.1 The bubble of image (operating in 0.4％PMMA，ul=0.1m/s，ug=0.04m/s，DP=20kPa )..98
Fig.B-1.2 Bubble size distribution of Air..	99








表目錄
Table. 3-1 Values from Lockhart and Martinelli .	37

Table. 3-2 Exponent for Two-Phase Correlation. .	38

Table. 4-1 The operating conditions used in this study. .	44

Table. 5-1 The injection factor under different gas velocities. .	53

附錄
Table. B-1 Calculated Bubble size distribution. .	99

Table. B-2 Calculated shear stress under various gas velocity...	101

Table. B-3 Calculated shear stress under various liquid velocity. 	102

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