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Forward Osmosis Desalination Process: Modelling and Simulation

  • Boram Gu (대학원 화공생명공학과 화공생명공학전공)

초록/요약

It is admitted that potable water becomes shorter as population has increased drastically. Thus, many researchers have tried to solve this problem through sea water desalination. Among many desalination methods, FO process has recently received considerable attention. This is because it does not require any external energy for separation such as hydraulic pressure in RO process and sensible heating energy in MD process. In this study, models of three types of FO modules are developed in 2-dimension. Since actual behaviours of flow inside the modules are complicated, balance models are simplified using several assumptions. Based on the simplified balance equations, water flux is predicted by considering ECP and ICP phenomena according to membrane orientations. The performance of the FO modules under various operating conditions and design parameters is investigated by the developed model. The module and the operating condition should be carefully chosen according to the desired performance. Therefore, the developed model and the simulation results in this work can be applied to designing the FO module and finding the optimal operating conditions for future research. Furthermore, a draw solute separation process using a vacuum membrane distillation (VMD) is suggested and analysed. It is expected to lower the required energy by applying the VMD process to separation of the volatile draw solute from the FO process. In the results, concerning the energy consumption, the VMD process needs about 370kWh/m3 for thermal energy (heating fluids) and about 2kWh/m3 for electric energy (vacuum pump). The VMD process for desalination can compete with RO process on energy consumption under the suggested cases in this study.

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목차

CONTENTS
CHAPTER I. INTRODUCTION
CHAPTER II. THEORY
1 Classification of Osmotic Process - 7 -
2 Process Description - 10 -
3 Forward Osmosis Membrane and Module - 13 -
3.1 Plate-and-frame module - 13 -
3.2 Modified spiral-wound module - 15 -
3.3 Hollow fibre module - 17 -
CHAPTER III. MODEL DEVELOPEMENT
1 Theoretical Background - 20 -
1.1 General flux equation - 20 -
1.2 Concentration polarization - 21 -
1.2.1 External concentration polarization (ECP) - 21 -
1.2.2 Internal concentration polarization (ICP) - 25 -
2 Modelling and Numerical Solution Procedure - 28 -
2.1 Model Equations - 28 -
2.2 Numerical Procedure - 34 -
3 Modelling Procedure for FO Modules - 36 -
3.1 Discretisation for plate-and-frame module - 36 -
3.2 Discretisation for hollow fibre module - 37 -
3.3 Discretisation for modified spiral-wound module - 38 -
3.3.1 Discretisation for envelope-outside-zone - 42 -
3.3.2 Discretisation for envelope-inside-zone - 43 -
CHAPTER IV. PARAMETER ESTIMATION
1 Plate-and-Frame (PNF) Module - 47 -
2 Modified Spiral-Wound (MSW) Module - 50 -
3 Hollow Fibre Module - 53 -
CHAPTER V. SIMULATION RESULTS: MEMBRANE PROCESS
1 Plate-and-frame (PNF) Module - 57 -
1.1 Comparison of flow directions - 61 -
1.2 Comparison of membrane orientations - 66 -
1.3 Energy requirement for PNF module - 69 -
1.4 Effects of membrane size - 72 -
2 Modified Spiral-wound (MSW) Module - 75 -
2.1 Structural effects by winding membranes - 75 -
2.2 Effects of operating conditions - 81 -
2.3 Energy requirement for MSW module - 85 -
2.4 Effect of membrane leaves - 87 -
2.5 Comparison of PNF and MSW modules - 89 -
3 Hollow Fibre (HF) Module - 92 -
3.1 Comparison of flow directions and feed location - 95 -
3.2 Energy requirement for HF module - 98 -
3.3 Effects of module configurations - 100 -
CHAPTER VI. FEASIBILITY ANALYSIS: DRAW SOLUTE SEPARATION USING VACUUM MEMBRANE DISTILLATION
1 Objectives - 103 -
2 Process Description - 104 -
3 Model Equations - 107 -
4 Simulation Results and Discussions - 113 -
CHAPTER VII. CONCLUSIONS

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