Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2013 Granular mixing visualization and quantification in a double screw mixer Todd Arnold Kingston Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Mechanical Engineering Commons Recommended Citation Kingston, Todd Arnold, "Granular mixing visualization and quantification in a double screw mixer" (2013). Graduate Theses and Dissertations. 13578. https://lib.dr.iastate.edu/etd/13578 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Granular mixing visualization and quantification in a double screw mixer by Todd A. Kingston A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Mechanical Engineering Program of Study Committee: Theodore J. Heindel, Major Professor Robert C. Brown Thomas J. Brumm Iowa State University Ames, Iowa 2013 Copyright © Todd A. Kingston, 2013. All rights reserved. ii TABLE OF CONTENTS LIST OF FIGURES .............................................................................................................x LIST OF TABLES .............................................................................................................xx NOMENCLATURE ....................................................................................................... xxii Abbreviations ............................................................................................................... xxii Roman Symbols .......................................................................................................... xxiv Greek Symbols ............................................................................................................ xxvi ACKNOWLEDGEMENTS ......................................................................................... xxviii ABSTRACT .....................................................................................................................xxx CHAPTER 1: INTRODUCTION ........................................................................................1 1.1 Motivation ...................................................................................................................1 1.2 Goal and Objectives ....................................................................................................2 1.3 Practical Applications .................................................................................................4 1.4 Outline ........................................................................................................................5 CHAPTER 2: LITERATURE REVIEW .............................................................................7 2.1 Granular Mixing .........................................................................................................7 2.1.1 Single Phase and Multiphase Flows .....................................................................7 2.1.2 Terminology ..........................................................................................................9 2.1.3 History of Granular Mixing ................................................................................10 2.1.4 Importance ..........................................................................................................11 2.1.5 Granular Rheology ..............................................................................................12 2.1.6 Mixing Classification ..........................................................................................13 2.1.7 Mixing and Segregation ......................................................................................15 2.1.7.1 Mixing mechanisms ......................................................................................18 2.1.7.1.1 Diffusive Mixing .....................................................................................18 2.1.7.1.2 Shear Mixing ...........................................................................................19 2.1.7.1.3 Convective Mixing..................................................................................19 2.1.7.2 Rate of Mixing ..............................................................................................19 2.1.7.3 Particle Property Effects on Segregation ......................................................20 2.1.7.3.1 Particle Size ............................................................................................23 2.1.7.3.1.1 Trajectory segregation ......................................................................25 2.1.7.3.1.2 Segregation by Percolation ...............................................................25 iii 2.1.7.3.1.3 Elutriation Segregation .....................................................................27 2.1.7.3.2 Particle Shape..........................................................................................27 2.1.7.3.3 Particle Density .......................................................................................29 2.1.7.3.4 Cohesive Forces ......................................................................................29 2.1.7.3.4.1 Electrostatic Forces ...........................................................................30 2.1.7.3.4.2 Van der Waals Forces .......................................................................30 2.1.7.3.4.3 Liquid Bridge Forces ........................................................................31 2.1.7.4 Granular Packing ..........................................................................................34 2.1.7.5 Mixing Quantification...................................................................................35 2.1.7.6 Granular Sampling ........................................................................................38 2.1.8 Granular Mixing and Handling Equipment ........................................................41 2.1.8.1 Screw Conveyors ..........................................................................................44 2.1.8.2 Screw Feeders ...............................................................................................45 2.1.8.3 Screw Mixers ................................................................................................46 2.1.8.4 Screw Flighting Geometry ............................................................................47 2.1.9 Future of Granular Mixing ..................................................................................50 2.2 Digital Image Analysis Techniques ..........................................................................52 2.3 X-ray Visualization Techniques ...............................................................................54 2.3.1 X-ray Fundamentals ............................................................................................55 2.3.2 Radiography ........................................................................................................57 2.3.2.1 Tracer Particles .............................................................................................59 2.3.3 Stereography .......................................................................................................60 2.3.4 Computed Tomography ......................................................................................62 2.4 Biomass Thermochemical Conversion .....................................................................64 2.4.1 Motivation ...........................................................................................................65 2.4.2 Biomass ...............................................................................................................66 2.4.3 Thermochemical Conversion ..............................................................................66 2.4.3.1 Pyrolysis .......................................................................................................67 2.4.3.1.1 Slow pyrolysis .........................................................................................67 2.4.3.1.2 Fast pyrolysis ..........................................................................................68 2.4.3.1.2.1 Heat Transfer Requirements .............................................................69 2.4.3.1.2.2 Fast Pyrolysis Products .....................................................................70 2.4.3.1.3 Chemical Reactors ..................................................................................71 2.4.3.1.3.1 Screw Pyrolyzers ..............................................................................71 2.4.4 Bio-oil .................................................................................................................73 2.4.4.1 Applications for Bio-oil ................................................................................74 2.5 Summary ...................................................................................................................74 CHAPTER 3 EQUIPMENT, MATERIALS, AND METHODS ......................................76 3.1 Screw Mixer Design .................................................................................................76