This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Membrane distillation crystallization‑performance enhancement and scaling control Chen, Guizi 2014 Chen, G. (2014). Membrane distillation crystallization‑performance enhancement and scaling control. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/62561 https://doi.org/10.32657/10356/62561 Downloaded on 01 Oct 2021 00:28:43 SGT MEMBRANE DISTILLATION CRYSTALLIZATION MEMBRANE DISTILLATION CRYSTALLIZATION - CHEN GUIZI 2014 PERFORMANCE ENHANCEMENT AND SCALING - PERFORMANCE ENHANCEMENT AND SCALING CONTROL CONTROL CHEN GUIZI SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING NANYANG TECHNOLOGICAL UNIVERSITY 2014 MEMBRANE DISTILLATION CRYSTALLIZATION - PERFORMANCE ENHANCEMENT AND SCALING CONTROL CHEN GUIZI CHEN GUIZI School of Civil and Environmental Engineering A thesis submitted to the Nanyang Technological University in fulfillment of the requirements for the degree of Doctor of Philosophy 2014 Acknowledgements ACKNOWLEDGEMENTS First of all, I would like to express my sincere appreciation and deep gratitude to my supervisors, Associate Professor Wang Rong and Professor Anthony G. Fane. Their supports, scientific guidance and valuable advice throughout the project helped me to overcome difficulties and reach a new high in my career. It is lucky for me to work with both of them—their exceptional intelligence and academic integrity have given me substantial influence, for now and forever. My special thanks go to Professor W.B. Krantz, for his brilliant advice on research and technical writing skills. During discussing with Prof. Krantz, I gained not only the sparkling inspirations and knowledge, but also confidence and optimistic nature that has an enormous influence on me. I am grateful to Environment and Water Industry Program Office (EWI) for providing the scholarship and funding, to Singapore Membrane Technology Centre (SMTC) for providing a workplace equipped with necessary facilities and Siemens Water Technology (SWT) for membrane supply. Special thanks are due to Dr. Lu Yinghong and Deric Lim (Final Year Project students) for their helps and support in the experimental part; and Dr. Yang Xing for her kind guidance and help on technical writing skill, without which I would not be able to accomplish PhD work and this thesis smoothly. Many thanks go to my friends and staff from SMTC, Chun Heng, Zhang Yuan, Lauren, Chen Lin, Wei Jing, Saren, Amir, Shuwen, Jingsong, Shuren, Ziggy and my former colleague Yuhui, Guangzhi, Elizabeth, Guoqiang etc. for their sharing of knowledge and kind assistance on various issues. Without their friendship and help, I would not have such an enjoyable postgraduate student life. I Acknowledgements Lastly, I would like to thank my dearest parents and my husband for offering me unlimited moral support, perseverance and encouragement, being with me whenever frustrations/difficulties were met. Also, special thanks to my unborn baby, maybe mum can’t offer you the best physical environment and has to take you to work every day, but mum hope you can acquire strong mind, optimism and painstaking. Mum and Dad love you forever. II Publications PUBLICATIONS In Journals Guizi Chen, Xing Yang, Rong Wang, Anthony G. Fane, Performance enhancement and scaling control with gas bubbling in direct contact membrane distillation, Desalination, 308 (2013): 47-55. Guizi Chen, Yinghong Lu, William B. Krantz, Rong Wang, Anthony G. Fane, Optimization of operating conditions for a continuous membrane distillation crystallization process with zero salty water discharge, Journal of Membrane of Science, 450 (2014): 1-11. Guizi Chen, Yinghong Lu, Xing Yang, Rong Wang, Anthony G. Fane, Quantitative study on the crystallization induced scaling in high concentration direct contact membrane distillation (DCMD), Industrial & Engineering Chemistry Research 53 (2014): 15656–15666. Guizi Chen, Xing Yang, Yinghong Lu, Rong Wang, Anthony G. Fane, Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration, Journal of Membrane Science, 470 (2014):60- 69. At International Conferences Guizi Chen, Yinghong Lu, Xing Yang, Rong Wang, Anthony G. Fane, Quantitative study on crystallization induced scaling in high concentration direct contact membrane distillation (DCMD) (oral presentation). The 10th International Congress on Membranes and Membrane Processes (ICOM), July 20-25, 2014, Suzhou, China. III Table of contents TABLE OF CONTENTS ACKNOWLEDGEMENTS ..................................................................................... I PUBLICATIONS ................................................................................................... III ABSTRACT ......................................................................................................... VIII LIST OF SYMBOLS ................................................................................................ X LIST OF FIGURES ............................................................................................ XVI LIST OF TABLES .............................................................................................. XXII CHAPTER 1 ............................................................................................................. 1 INTRODUCTION .................................................................................................... 1 1.1 Background ............................................................................................. 1 1.2 Challenges for high concentration MD/MDC ...................................... 2 1.3 Objectives of this thesis .......................................................................... 3 1.4 Scope of this research ............................................................................. 3 1.5 Organization of this thesis ..................................................................... 4 CHAPTER 2 ............................................................................................................. 6 LITERATURE REVIEW ........................................................................................ 6 2.1 Introduction to membrane distillation ................................................. 6 2.1.1 MD configurations ........................................................................... 6 2.1.2 Heat transfer & temperature polarization (TP) effect ..................... 8 2.1.3 Mass transfer & concentration polarization (CP) effect ............... 10 2.1.4 Benefits and limitations of MD ...................................................... 12 2.2 Membrane distillation at high salt concentrations ............................ 13 2.2.1 Lower vapor pressure ..................................................................... 13 2.2.2 More serious TP effect ................................................................... 14 2.2.3 Slight change in CPC ..................................................................... 14 2.2.4 Dramatic flux decline owing to fouling/scaling ............................. 14 2.3 Methods for performance enhancement and scaling control in membrane process........................................................................................... 16 2.3.1 Addition of gas bubbles in the feed side ......................................... 17 2.3.2 Attaching a vibration system to the membrane module ................. 18 2.3.3 Applying an ultrasound system for cleaning fouled membrane ..... 23 IV Table of contents 2.4 Investigation and measurement of membrane fouling/scaling ......... 24 2.4.1 Direct observation through/above the membrane .......................... 25 2.4.2 Laser triangulometry and optical laser sensors ............................ 26 2.4.3 Ultrasonic time-domain reflectometry (UTDR) ............................. 27 2.4.4 Electrical impedance spectroscopy ................................................ 28 2.4.5 Crystallization kinetics ................................................................... 28 2.5 Crystallization and coupled process of membrane and crystallization operations ......................................................................................................... 29 2.5.1 Basic concepts of crystallization .................................................... 29 2.5.2 Coupled processes of membrane and crystallization operations ... 33 2.6 The MDC process and recent works ................................................... 38 2.7 Summary ............................................................................................... 41 CHAPTER 3 ........................................................................................................... 43 PERFORMANCE ENHANCEMENT AND SCALING CONTROL WITH GAS BUBBLING IN DIRECT CONTACT MEMBRANE DISTILLATION . 43 3.1 Introduction .......................................................................................... 43 3.2 Theory and methodology ..................................................................... 45 3.2.1 Mass and heat transfer analysis in DCMD .................................... 45 3.2.2 Flux decline in a high concentration DCMD ................................. 46 3.3 Experimental ......................................................................................... 47 3.3.1 Material properties and MD module specifications ...................... 47 3.3.2 Bubble-assisted DCMD process set up .........................................