Contents 1 Introduction 1 1.1 Removal of Particles from Gases 1 1.1.1 Filtration 2 1.1.2 Wet Scrubbers 5 1.1.3 Centrifugal/Cyclonic Devices 5 1.1.4 Knock-out Vessels and Settling Chambers 6 1.2 A Closer Look at Centrifugal Gas Cleaning Devices... 6 1.2.1 Applications of Centrifugal Separators 8 1.2.2 Classification of Centrifugal Separators 11 1.2.3 Two Main Classes - Cyclones and Swirl Tubes 13 2 Basic Ideas 15 2.1 Gas Flow 15 2.1.1 Swirling Flow 15 2.1.2 Static and Dynamic Pressure 17 2.2 Particle Motion 19 2.3 Particle Size 24 2.3.1 Definitions of Particle Size 24 2.3.2 Particle Size Distribution 25 2.4 Particle Density 29 Appendix 2A Ideal Vortex Laws from the Navier-Stokes Equations 30 Appendix 2B Common Models Functions for Particle Size Distribution 33 2B.1 The Normal Distribution 34 2B.2 The Log-Normal Distribution 34 2B.3 The Rosin-Rammler Distribution 35 3 How Cyclones Work 37 3.1 Flow in Cyclones 37 3.1.1 Gas Flow Pattern 37 3.1.2 Particle Flow 40 3.2 Separation Efficiency 41 3.2.1 Overall Separation Efficiency 41 3.2.2 Grade-Efficiency 42 3.2.3 Converting Between Overall Efficiency and Cut Size 44 3.3 Pressure Drop 45 Appendix 3A Worked Example: Calculating a Grade-Efficiency Curve 46 Solution 46
XVIII Cyclone Flow Pattern and Pressure Drop 49 4.1 Discussion 49 4.1.1 Flow Pattern 49 4.1.2 Pressure Drop 51 4.2 Models for the Flow Pattern 53 4.2.1 n-type Model 55 4.2.2 Barth 56 4.3 Models for the Pressure Drop 59 4.3.1 Models Based on Estimating the Dissipative Loss 59 4.3.3 Core Model 61 4.3.3 Purely Empirical Models 66 4.4 Model Assumptions in Light of CFD and Experiment 67 4.5 Overview 71 Appendix 4A Worked Example for Calculating Cyclone Pressure Drop 72 Solution 72 Appendix 4B The Meissner and Loftier Model 74 Cyclone Separation Efficiency 77 5.1 Discussion 77 5.2 Models 78 5.2.1 Equilibrium-orbit Models: the Model of Barth 78 5.2.2 Time-of-Flight Models 81 5.2.3 Hybrid Models: the Models of Dietz and of Mothes and L6ffler83 5.2.4 Comparing the Models 84 5.3 Comparison of Model Predictions with Experiment 85 5.3.1 Agreement with Experiment in General 85 5.3.2 A Case Study: the Effect of Cyclone Length 86 5.4 Overview 89 Appendix 5 A Worked Example for the Prediction of Cyclone Separation Performance 90 Solution 90 Appendix 5B The Cyclone Efficiency Models of Dietz and of Mothes and Ldffler 93 The Muschelknautz Method of Modeling 97 6.1 Basis of the Model 98 6.2 Computation of the Cut-Point of the Inner Vortex, x so 103 6.3 Computation of Efficiency at Low Solids Loadings 105 6.4 Determining if the Mass Loading Effect will Occur 107 6.5 Overall Separation Efficiency when c o > C O L 107 6.6 Computation of Pressure Drop 108 Appendix 6A Example Problems 110 6A.1 Simulation of Data from Hoffmann et al. (2001) 110 6A.2 Simulation of the Data from Obermair and Staudinger (2001). 113 6A.3 Simulation of the Data from Greif (1997) 115
XIX Appendix 6B Incorporation of the 'Inner Feed' 117 7 Computational Fluid Dynamics 123 7.1 Simulating the Gas Flow Pattern 124 7.1.1 Setting up the Finite Difference Equations 124 7.1.2 Turbulence Models 126 7.1.3 Simulations 127 7.2 Simulating the Particle Flow....' 131 7.2.1 Eulerian Modeling 131 7.2.2 Lagrangian Particle Tracking 132 7.2.3 Simulations 132 Appendix 7A: Transport Equations 134 8 Dimensional Analysis and Scaling Rules 137 8.1 Classical Dimensional Analysis 138 8.1.1 Separation Efficiency 138 8.1.2 Pressure Drop 141 8.2 Scaling Cyclones in Practice 142 8.2.1 Approximately Constant Stkso over a Wide Range of Re 142 8.2.2 Eu only Weakly Dependent on Re 144 8.2.3 Some other Considerations 145 8.2.4 Stk-Eu Relationships 145 Appendix 8A. Inspecting the Equations of Motion 147 8A.1 Equation of Motion for the Gas 147 8A.2 Equation of Motion for a Particle 148 Appendix 8B. Sample Cyclone Scaling Calculations 148 8B.1 Calculating the Inlet Velocity in a Scale Model Required for Re Similarity 148 8B.2 Predicting Full-Scale Cyclone Performance using a Scale Model 149 9 Other Factors Influencing Performance 155 9.1 The Effect of Solids Loading 155 9.1.1 Effect on Separation Efficiency of Cyclones 155 9.1.2 Models for the Effect on Separation Efficiency of Cyclones... 156 9.1.3 Effect on the Separation Efficiency of Swirl Tubes 162 9.1.4 Effect on the Pressure Drop of Cyclones 163 9.1.5 Effect on the Pressure Drop Across Swirl Tubes 164 9.1.6 Computing the Performance of a Cyclone with High Loading. 164 9.2 The Effect of the Natural Vortex Length 165 9.2.1 The Nature of the Vortex End 166 9.2.1 The Significance of the Vortex End 168 9.2.2 Models for the Natural Vortex Length 169 Appendix 9 A Predicting the Effect of Solids Loading on Cyclone Efficiency.. 170
XX Appendix 9B Predicting the Effect of Loading on Cyclone Pressure Drop 173 10 Measurement Techniques 175 10.1 Gas Flow Pattern 176 10.2 Pressure Drop 179 10.3 Particle Flow 180 10.4 Overall Separation Efficiency 180 10.4.1 On-line Sampling of Solids '. 182 10.5 Grade-Efficiency 184 10.5.1 On-Line vs. Off-Line Size Analysis 184 10.5.2 Sample Capture and Preparation 185 10.5.3 Methods for Size Analysis 186 Appendix 10A Estimate of Errors 190 11 Underflow Configurations and Considerations 193 11.1 Underflow Configurations 193 11.2 Importance of a Good Underflow Seal 197 11.2.1 Inleakage Example 199 11.3 Upsets Caused by 'too Good' an Underflow Seal 200 11.4 Second-Stage Dipleg Solids 'Backup' 203 11.5 Hopper 'Crossflow' 205 11.6 Hopper Venting Options 207 Appendix 11A Dipleg Calculation 210 Solution 210 Appendix 1 IB Moment Balance on Flapper Valve Plate 210 11B.1 Example 213 12 Some Special Topics 215 12.1 Cyclone Erosion 215 12.1.1 Inlet'Target Zone* 215 12.1.2 Lower Cone Section 217 12.1.3 Erosion Protection 221 12.2 Critical Deposition Velocity 232 12.3 High Vacuum Case 233 12.3.1 Application to Cyclone or Swirl Tube Simulation 234 Appendix 12A Worked Example for Calculation of the Critical Deposition Velocity 235 Solution 235 Appendix 12B Worked Example Taking Into Account Slip in Calculation of the Cut Size 236 Solution 236 13 Demisting Cyclones 239 13.1 Liquid Creep and 'Layer Loss' 240 13.2 Demisting Cyclone Design Considerations 241
XXI 13.3 Some Vapor-Liquid Cyclone Design Geometries and Features 243 13.4 Estimating Inlet Drop Size for Two-Phase Mist-Annular Flow 248 13.4.1 Estimating Drop Size Distribution 251 13.5 Modeling the Performance of Vapor-Liquid Cyclones 252 13.5.1 Computation of Cut Size 252 13.5.2 Computation of Efficiency at Low Inlet Loadings 253 13.5.3 Criteria for Determining if'mass loading' ('Saltation') Occurs 253 13.5.4 Overall Separation Efficiency when c o > c ol 254 Appendix 13A Example Calculations of Droplet Sizes in Pipe Flow 255 13A.1 Finding the Mean Droplet Size 255 13A.2 Finding the Droplet Size Distribution 256 Appendix 13B Flow Distribution in Parallel Demisting Cyclones 256 13B.1 Calculation of Flow Distribution 261 13B.2 Calculation of the Liquid Level Difference between the Front and Back Cyclones 261 14 Foam-Breaking Cyclones 263 14.1 Introduction 263 14.2 Some Design Considerations and Factors Influencing Behavior 265 14.3 Applications 268 14.3 Estimating Submergence Required to Prevent Gas 'Blow Out' 272 Appendix 14A Example Computation of Submergence Required to Prevent Underflow Gas 'Blow Out' 274 Solution 274 15 Design Aspects 277 15.1 Cylinder-on-Cone Cyclones with Tangential Inlet 277 15.1.1 Some Standard Cyclone Designs 277 15.1.2 Design of the Inlet 278 15.1.3 Design of the Cone Section 282 15.1.4 Solids Outlet Configurations 284 15.1.5 Vortex Finder Geometries 286 15.1.6 Cyclone Length 290 15.1.7 Cyclone Operating Conditions 291 15.2 Design of Swirl Tubes with Swirl Vanes 292 15.2.1 Design of the Inlet Vanes 292 15.2.2 Calculation of Inlet 'Throat' Area For a Vane-Type Inlet Device 293 15.2.3 Length of the Swirl Tube Body and the Solids Exit 295 Appendix 15A Example Calculation of the Throat Area 296 Solution 296 16 Multicyclone Arrangements 299 16.1 Cyclones in Series 299
XXII 16.2-Cyclones in Parallel 300 Appendix 16A Example Calculation for Multicyclone Arrangements 308 Solution 309 List of Symbols 313 Greek and Other: 315 Subscripts: 316 Superscripts 318 ListofTradenames 319 References 321 Index 325
PPN: 099876892 Titel: Gas cyclones and swirl tubes : principles, design and operation / Alex C. Hoffmann; Louis E. Stein. - Berlin : Springer, 2002 ISBN: 3-540-43326-0 Bibliographischer Datensatz im SWB-Verbund