Cyclohexane-water dispersion behaviour including benzoic acid mass transfer by influence of different types of stirrers [Elektronische Ressource] : experiments and CFD simulation = Cyclohexan-water-Dispergierverhalten einschließlich Benzoesäure-Stoffaustausch unter dem Einfluss verschiedener Rührertypen / by Laila Mahmod Nabhan Abu-Farah

Fawzi Rouzeik

Informations

• Publié par: universitat_duisburg-essen
• Publié le: 01 janvier 2010
• Nombre de lectures: 35
• Langue: English
• Poids de l'ouvrage: 70 Mo

Extrait

Cyclohexane/Water Dispersion Behaviour Including Benzoic Acid
Mass Transfer by Influence of Different Types of Stirrers –
Experiments and CFD Simulation

(Cyclohexan/Wasser Dispergierverhalten einschließlich Benzoesäure-
Stoffaustausch unter dem Einfluss verschiedener Rührertypen –
Experimente und CFD-Simulation)


by
Laila Mahmod Nabhan Abu-Farah (Jordan-Zarqa)

Thesis submitted to the Institute of Chemical Engineering,
Faculty of Chemistry at Universität Duisburg-Essen, in partial
fulfilment of the requirements of the degree of
Dr. rer. nat.




Approved by the examination committee on July 14, 2010:
Chair : Prof. Dr. G. Jansen
Advisor : Prof. Dr. A. Schönbucher
Reviewer : Prof. Dr. F. Bandermann




Essen, 2010

































Declaration

I declare here that I have written this thesis on my own. The literature and
technical aids used have been completely indicated.



Essen, 28.05.2010 Signature:






















































Acknowledgements

First, I wish to express my deep gratitude and appreciation to my advisor
Prof. Dr. Axel Schönbucher for his guidance and support in the course of this
work. He has given me helpful advice on approaching and performing
challenging tasks.

I am very grateful to Prof. Dr. F. Bandermann for his accepting the task of
co-examiner of this thesis and for investing time in reading and discussion this
thesis, I appreciate him for providing me with valuable ideas and useful
information.

I am obliged to Prof. Dr. G. Jansen for taking over the position of chairman
of the examination board.

I would like to thank Dr. Wolfgang Laarz for his support and advice as well
as his help to build up the experimental setup. I would like to thank Peter
Sudhoff for his help with the computer cluster and the staff of the Institute. Also
my thanks go to Mrs. Lieselotte Schröder for her help in the administrative
matters and her support in many other things.

Especial hearty and gratitude thanks go to my husband Dr.rer.nat.-Eng.
Fawzi Al-Qaessi for his endless help, advice, encouragement and support
through my project work and patience during the course of my life. Also, to our
sons Sadid and Noor for providing me so much love. I was always glad to know
that they are with me.

I want to thank my parents, brothers and sisters for giving me support in any
way I needed it before and during the time of this work. Their love and strong
belief in me has always strengthened my self-confidence.


































Table of Contents
Abstract XIII
Nomenclature XVII
1. INTRODUCTION 1
2. THEORY AND IMPORTANT ASPECTS 5
2.1 Scope of mixing 5
2.2 Mixing procedure 6
2.3 Miscible and immiscible liquids 6
2.4 Fundamentals and Phenomena in immiscible liquid-liquid systems 7
2.4.1 Drop dispersion and breakup 8
2.4.2 Drop coalescence 9
2.4.3 Drop size 10
2.4.4 Dispersion time 12
2.4.5 Holdup of the dispersed phase 12
2.4.6 Complete and uniform dispersion velocity 13
2.5 Interphase mass transfer 14
2.5.1 Solute concentration 15
2.5.2 Mass transfer coefficient 16
2.5.3 Interfacial area 17
2.6 Types of agitators 20
2.7 Impeller selection for immiscible liquid–liquid system 20
2.8 Flow patterns 21
2.9 Batch and continuous modes for immiscible liquids 26
2.10 Computational fluid dynamics (CFD) for multiphase flow 27
2.11 CFD developments and applications 30
2.11.1 Mathematical and discretisation methods 30
2.11.1.1 Finite difference method 31
2.11.1.2 Finite element method 31
VII
Table of Contents VIII
2.11.1.3 Finite volume method 32
2.11.2 Iterative solution strategy 32
2.11.3 Validation 33
2.12 Calculation methods of the flow patterns by CFD 33
2.12.1 Sliding mesh 33
2.12.2 Rotating frame 34
2.12.3 Multiple reference frames 34
2.13 Features of ANSYS CFX-11 software 34
2.13.1 Geometry and mesh generation 35
2.13.1.1 Cell types 35
2.13.2 Physics definition pre-processor 36
2.13.3 Numerical methodology by CFX solver 36
2.13.3.1 Coupled solver 37
2.13.3.2 Solver manager 38
2.13.4 Post-processing 39
3. EXPERIMENTS 40
3.1 Liquid-Liquid multiphase components 40
3.2 Experimental setup 41
3.3 Measuring methods 43
3.3.1 Visualization method 43
3.3.2 Particle Vision Microscope (PVM) 45
3.3.2.1 Image analysis procedure 47
3.3.3 Sampling withdrawal method 47
3.3.3.1 Measuring procedure for the cyclohexane volume fraction 48
3.3.4 Chemical analysis method 49
3.3.5 Photographic–light-cut method 51
3.3.5.1 Schematic setup 51
3.3.5.2 Measuring procedure of the tracer particles 52
3.3.5.3 Analysis procedure for tracer particles velocity 53



Table of Contents IX
4. CFD SIMULATION AND SUBMODELS 54
4.1 Geometry and mesh generation 54
4.2 Type of simulation 57
4.3 Multiphase cyclohexane/water flow modelling 57
4.3.1 Inhomogeneous model 58
4.3.2 Free surface flow model 59
4.3.3 Submodels 60
4.3.3.1 Fluid buoyancy model 60
4.3.3.2 Turbulent k-epsilon model 61
4.3.3.3 Sliding mesh model 63
4.3.3.4 Interphase momentum transfer models 64
4.3.3.4.1 Interphase transfer Particle model 64
4.3.3.4.2 Interphase drag force model 65
4.3.3.4.2.1 Ishii-Zuber drag model 66
4.3.3.4.2.2 Algebraic slip model 68
4.4 Domain conditions 73
4.4.1 General conditions 73
4.4.2 Initial conditions 73
4.4.3 Boundary conditions 75
4.4.3.1 Wall top 75
4.4.3.2 Bottom and cylindrical walls 75
4.4.3.3 Shaft and impeller 75
4.4.3.4 Periodic interface boundary 75
4.4.3.5 General grid interface (GGI) 76
4.4.3.6 Fluid-fluid interfaces 76
4.4.3.7 Rotor-stator 76
4.5 Solution algorithm 77
5. RESULTS AND DISCUSSION 78
5.1 Flow field visualisation of cyclohexane /water dispersion 78
5.1.1 Anchor impeller 78

Table of Contents X
5.1.2 Rushton turbine impeller (RTI) 81
5.1.2.1 Effect of RTI bottom clearance 82
5.1.3 Propeller impeller 87
5.1.4 Pitched blade turbine impeller (PBT) 90
5.2 Dispersed droplets - shape and size distribution 93
5.2.1 Influence of the RTI clearance 93
5.2.2 Influence of the percentage of the dispersed phase 95
5.2.3 Influence of the stirrer type 97
5.2.4 Sauter mean droplet diameter 100
5.3 Experiment and CFD simulation for holdup (volumetric fraction)
profiles of cyclohexane 113
5.3.1 Cyclohexane dispersion with anchor impeller 113
5.3.1.1 Axial profile 113
5.3.1.2 Radial profile 115
5.3.1.3 Anchor velocity for complete and uniform dispersion 1