PHD THESIS: Energy generation and recovery by Pressure Retarded Osmosis (PRO): Modeling and experiments. Thesis submitted by Khaled Touati for the degree of Doctor of Industrial Engineering in the University of Valladolid. Supervised by: Fernando Tadeo 2015 Acknowledgements I would like to express my appreciation to the following persons, who have helped me during the years of my PhD candidature. To my supervisor, Professor Fernando Tadeo, for his kind help, advices, patience, supervision, and this important opportunity he gave me. To the reviewers of the thesis, Professors Mohamed Safi, Hamza Elfil and Joon Ha Kim, for their time, feedback and nice comments. To the members of the jury, for their willingness and feedback. To my colleagues from the H2Ocean project for their support. To my colleagues from the department of Systems Engineering and Automatic Control of the University of Valladolid (Spain). To my colleagues from Fraunhofer Institute for Interfacial Engineering and Biotechnology, especially Dr. Thomas Schiestel and Christopher Haenel. To my colleagues from the center of researches and water technologies (CeRTE) – BorjCedria (Tunisia) for their support and encouragements. To my parents for their patience and support during my entire career. To my wife Zainab for the support, care and patience. To all the members of my family. To my friends, Haithem, Walid, Borhane, Saber, Klai, Mohamed SBS, Hassan, Seddik, Rochdi, and others for their help and advices. To the person who changed my life, Abdullah Al Harari. i Contenu Aknowledgements Contents Chapter 1 : Introduction 1. Problem statement .................................................................................................................................................. 1 2. Pressure Retarded Osmosis (PRO).................................................................................................................... 1 3. Objectives of the thesis .......................................................................................................................................... 2 4. Organization of the dissertation ......................................................................................................................... 3 Chapter 2: Pressure Retarded Osmosis: State of the art 1. Introduction ................................................................................................................................................................ 7 2. Salinity gradient energy ......................................................................................................................................... 7 3. Gibbs free energy of mixing ................................................................................................................................. 9 4. Pressure Retarded Osmosis .............................................................................................................................. 10 4.1 Osmotic processes ....................................................................................................................................... 10 4.1.1 Reverse Osmosis ...................................................................................................................................... 10 4.1.2 Forward Osmosis ..................................................................................................................................... 11 4.1.3 Pressure Retarded Osmosis ................................................................................................................ 11 4.2 Basic concept of Pressure Retarded Osmosis .................................................................................. 11 4.2.1 Water and salt fluxes across a PRO membrane ............................................................................ 12 4.2.2 Concentration polarization................................................................................................................... 15 4.2.3 PRO power density ................................................................................................................................. 17 4.3 Developments of PRO ................................................................................................................................ 19 4.3.1 Temporal sequence of the PRO development ............................................................................... 19 4.3.2 PRO models development ..................................................................................................................... 22 4.3.3 PRO membrane development ............................................................................................................. 25 4.4 Integration of PRO with desalination systems ................................................................................ 31 4.5 PRO limitations and suggested solutions........................................................................................... 42 4.5.1 Membrane fouling .................................................................................................................................... 42 4.5.2 Membrane scaling .................................................................................................................................... 45 4.5.3 Concentration polarization................................................................................................................... 47 4.5.4 Membrane deformation ......................................................................................................................... 47 4.6 PRO cost ........................................................................................................................................................... 47 iii 4.7 Environmental impact ............................................................................................................................... 51 5. Final consideration and Conclusions ............................................................................................................ 53 Chapter 3: Water flux and power density in PRO 1. Problem statement ............................................................................................................................................... 65 1. Problem statement ............................................................................................................................................... 66 2.1 Basic models for water and salt fluxes ................................................................................................ 66 2.2 Concentration polarization ...................................................................................................................... 67 2.2.1 Internal concentration polarization (ICP) ....................................................................................... 68 2.2.2 External concentration polarization (ECP) ..................................................................................... 69 2.3 Model of the water flux Jw ......................................................................................................................... 71 2.4 Model of the temperature profile through the membrane ......................................................... 72 3. Materials and methods ................................................................................................................................... 77 3.1 Model validation ........................................................................................................................................... 77 3.1 Model validation ........................................................................................................................................... 77 3.1 Model validation ........................................................................................................................................... 77 4. Results and discussion ................................................................................................................................... 79 4.1 Model validation ........................................................................................................................................... 79 4.2 Effect of the concentrations of feed and draw solutions ............................................................. 82 4.3 Effect of the flow rate velocity ................................................................................................................ 84 4.4 Effect of the bulk temperatures on the membrane temperature distribution ................... 85 4.5 Effect of the bulk temperatures on the membrane parameters ............................................... 86 4.5.1 Effect of the temperatures on the water permeability coefficient A ...................................... 86 4.5.2 Effect on the salt permeability coefficient B .................................................................................... 88 4.5.3 Effect on the structure parameter s ..................................................................................................... 89 4.6 Study of the reverse solute diffusion .................................................................................................. 91 5 Conclusions ......................................................................................................................................................... 94 Chapter 4: Effect of the Reverse Salt Flux on PRO 1.