Title Page
ABSTRACT
Contents
Chapter 1 : Introduction 22
1.1. Background 25
1.2. Research Motivation 29
1.3. Research Objectives 30
1.4. Organization of Dissertation 31
References 33
Chapter 2 : Literature Review 35
2.1. Diethylene Glycol 35
2.1.1. Basic characteristics of diethylene glycol 35
2.1.2. Thermo-Oxidation Degradation of Glycols 42
2.2. Slurry recycling process in solar cell production 44
2.2.1. Wafer Slicing Process 44
2.2.2. The stability of SiC particles in Suspension. 46
2.2.3. Carrier Fluid(Suspension Agent for slurry) 50
2.2.4. Slurry Recycling Process 52
2.3. Pervaporation 56
2.3.1. Overview of Pervaporation 56
2.3.2. Mechanism of Transport for pervaporation 61
References 64
Chapter 3 : Pervaporative dehydration of diethylene glycol (DEG) through a hollow fiber membrane 67
3.1. Abstract 67
3.2. Introduction 68
3.3. Materials and Methods 71
3.3.1. Materials 71
3.3.2. Membrane module preparation 73
3.3.3. Pervaporation 74
3.4. Results and discussion 77
3.4.1. Effect of feed composition 77
3.4.2. Effect of feed temperature 83
3.5. Conclusions 92
References 94
Chapter 4 : Development of High efficiency Coolant (DEG) Recycle System (Pilot scale test) 96
4.1. Abstract 96
4.2. Introduction 97
4.3. Filiteration System 101
4.3.1. Experimental 101
4.3.2. Results and Discussion 110
4.4. Dehydration Membrane System 117
4.4.1. Experimental 117
4.4.2. Results and discussion 120
4.5. Effect of recycled DEG on silicon wafers for solar cells (Wire-Sawing Test of Recycled DEG) 123
4.5.1. Experimental 123
4.5.2. Results and discussion 124
4.6. Conclusions 126
References 127
Chapter 5 : Model Simulation of Hollow Fiber Membrane Pervaporative Dehydration Performance with Diethylene Glycol (DEG) 129
5.1. Abstract 129
5.2. Introduction 130
5.3. Simulation Model 133
5.3.1. Mass and heat balances over differential element volume in the unit membrane module 133
5.3.2. Batch process 137
5.4. Experimental 145
5.4.1. Membranes 145
5.4.2. Membrane module preparation 145
5.4.3. Pervaporation 146
5.5. Results and Discussion 147
5.5.1. Determination of permeation parameters and verification of the simulation model 147
5.5.2. Simulation of the pervaporation process 150
5.6. Conclusions 170
Nomenclature 172
References 173
Chapter 6 : Conclusions 175
국문요약 179
Publications 183
Patents 184
Table 1.1. Slurry consumption during wire sawing (500 MW/year, 78 wires sawing equipments base) 29
Table 2.1. Applications of diethylene glycol 38
Table 2.2. Physical properities of diethylene glycol 39
Table 2.3. Comparison of the physical properties of glycols and water 40
Table 2.4. Specification of fresh DEG 41
Table 2.5. Composition of impurities in fresh DEG 41
Table 2.6. Worldwide commercialization technology of Slurry Recycle System 55
Table 2.7. Industrial suppliers of pervaporation systems 60
Table 3.1. Comparison of the physical properties of DEG and water 87
Table 4.1. Estimated Cost Savings Analysis for "N" company (500 MW/year wafer production base) 100
Table 4.2. Compositions of waste coolant derived from each process 102
Table 4.3. Size distribution of particles in waste coolant (2nd Decanter Oil)(이미지참조) 102
Table 4.4. Experimental procedures of the pilot system 107
Table 4.5. Flux variations before and after backwashing 111
Table 4.6. Operating conditions for the production of recycled coolant 112
Table 4.7. Characteristics of recycled coolant after filtration 113
Table 4.8. Classification of chemicals for removal of foulants 115
Table 4.9. Variation of flux and quality of recycled coolant after cleaning test 115
Table 4.10. Classification according to CIP sequence 115
Table 4.11. Composition of recycled DEG (after final purification) 122
Table 4.12. Specifications of R-DEG for wafering slurry 122
Table 4.13. Estimate of the total forecast time for production 122
Table 4.14. Mixing ratio of slurry in wafer sawing test 124
Table 4.15. Line test results of recycled DEG by a local company 125
Table 5.1. Operation parameters used in both the simulation and experiment 148
Table 5.2. Base Parameters for simulation of the batch pervaporation process 155
Table 5.3. Total pumping rate of feed with connection mode 159
Table 5.4. The result of simulations for pervaporative dehydration at different feed flow rates 162
Table 5.5. The results of simulations for pervaporative dehydration at different maximum temperature drops 166
Figure 1.1. Process steps from chunks to clean silicon wafers 24
Figure 1.2. A schematic drawing of wafer slicing process 24
Figure 1.3. Existing slurry regeneration system for SiC recovery and the scope of this research 32
Figure 1.4. Schematic flow chart of the DEG recycling process (Hybrid membrane system) 32
Figure 2.1. Chemical structure of diethylene glycol (CAS#111-46-6) 35
Figure 2.2. Comparative hygroscopicities of various glycols at 21℃ 36
Figure 2.3. Viscosities of aqueous diethylene glycol solutions 37
Figure 2.4. Therm-oxidation degradation of ethylene glycol 43
Figure 2.5. Possible reaction scheme for the cyclodehydration of DEG 43
Figure 2.6. Therm-oxidation degradation of Propylene glycol 43
Figure 2.7. Schematic drawing of multi-wire saw and illustration of the cutting process in one sawing channel 44
Figure 2.8. Schematic diagram of SiC surface functional groups 48
Figure 2.9. Zeta potential of SiC particles at various pH values 48
Figure 2.10. Sedimentation behaviour of Slurry A dispersions [fresh DEG (pH=6.88) 45% + fresh SiC 55%, by sonication], Evolution of transmission profiles with time at 2300xg, 25℃ 49
Figure 2.11. Sedimentation behaviour of Slurry B dispersions [denaturated DEG (pH=3.13) 45% + fresh SiC 55%, by sonication], Evolution of transmission profiles with time at 2300xg, 25℃ 49
Figure 2.12. Overview of Slurry Recycling Process in "N" company 54
Figure 2.13. Schematic diagram of pervaporation process 57
Figure 2.14. The effect of (a) permeate pressure and (b) feed pressure on the flux of hexane through a rubbery pervaporation membrane 58
Figure 2.15. Mass transport through a solution diffusion membrane in pervaporation 62
Figure 3.1. Structure of the pervaporation hollow fiber membrane 72
Figure 3.2. Braid-reinforced pervaporation hollow fiber membrane 73
Figure 3.3. Schematic representation of the pervaporation apparatus 74
Figure 3.4. Plots of the total permeation rate and separation factor as a function of the water content in the feed at 353 K 81
Figure 3.5. Plots of the permeation rates of individual components as a function of the water content in the feed 81
Figure 3.6. Water flux as a function of the feed composition at different feed temperatures 82
Figure 3.7. Water content in the feed mixture in the feed tank as a function of the permeating time at different feed temperatures 82
Figure 3.8. Plots of the total permeation rate and separation factor as a function of the feed temperature with a water content of 1 wt. % in the feed 84
Figure 3.9. Permeation rates of individual components as a function of the feed temperature with a water content of 1 wt. % in the feed 89
Figure 3.10. Parameters used in the water flux equation as a function of the feed temperature 89
Figure 3.11. Comparison of the calculated and experimentally obtained total fluxes as a function of the water content in the feed at a feed temperature of 353 K 91
Figure 3.12. Comparison of the calculated and experimentally obtained permeation rates as a function of the water content in the feed at different feed temperatures 91
Figure 4.1. Process concept for used DEG recycling. 99
Figure 4.2. Size distribution of particle in waste coolant (2nd Decanter Oil), Beckman Coulter LS 13 320, Laser Diffraction Particle Size Analyzer(이미지참조) 102
Figure 4.3. Individual ceramic membrane fiber (100㎚) 104
Figure 4.4. Cross-section of ceramic fiber with magnified view of asymmetric pore structure 104
Figure 4.5. Ceramic membrane module 105
Figure 4.6. Schematic design of the pilot scale filtration system 106
Figure 4.7. Ceramic membrane pilot scale filtration system 106
Figure 4.8. Schematic design of modified pilot system with CIP tanks 108
Figure 4.9. Modified automation pilot scale filtration system 109
Figure 4.10. Flux variations before and after backwashing with time 112
Figure 4.11. Comparison of feed and permeate samples after filtration 113
Figure 4.12. Change of membrane surface by CIP 116
Figure 4.13. Schematic diagram of pervaporation system 119
Figure 4.14. Pilot-scale pervaporation system 119
Figure 4.15. Water content vs. operation time for pilot scale test [1~4th : The Pilot system is installed by PC2 membrane (effective area : 5.57㎡)] manufactured by SepraTek(이미지참조) 121
Figure 5.1. Mass and heat transfer across the membrane during flow through the differential unit volume of a single hollow fiber in the membrane module 134
Figure 5.2. Module configuration in the batch pervaporation process 139
Figure 5.3. Finite difference grid used in the numerical solution 140
Figure 5.4. Comparison of simulated feed compositions to experimental data with permeation time in the dehydration of DEG at various feed temperatures through hollow fiber membrane module with a membrane area of 0.16 ㎡ 149
Figure 5.5. Simulated feed compositions in the feed tank with permeation time at various feed temperatures in the dehydration of DEG through a hollow fiber membrane module composed of 10 commercial unit modules, each with a... 153
Figure 5.6. Simulation results of pervaporative dehydration of DEG through 10 hollow fiber membrane modules connected in series at various feed temperatures 154
Figure 5.7. Simulation results of pervaporative dehydration of DEG through 10 hollow fiber membrane modules connected in series at various feed flow rates 157
Figure 5.8. Simulation of pervaporative dehydration of DEG through 10 hollow fiber membrane modules connected in parallel at various feed flow rates per unit module and comparison to the series module configuration 160
Figure 5.9. Calculated constituent module numbers in series and parallel module assemblies with feed flow rate per unit module for pervaporative dehydration of DEG 163
Figure 5.10. Simulation of pervaporative dehydration of DEG through the module assemblies determined in Figure 5.9 at different feed flow rates per unit module 167
Figure 5.11. Calculated constituent module numbers in series and parallel module assemblies with max. temperature drop of feed stream in module assembly for pervaporative dehydration of DEG 168
Figure 5.12. Simulation of pervaporative dehydration of DEG through module assemblies determined in Figure 5.10 at different max. temperature drops of feed stream in module assembly 169