Table of Contents

Preface xxiii

Acknowledgments xxv

About the Author xxvii

Nomenclature xxix

Chapter 1. Introduction to Separation Process Engineering 1

1.0 Summary—Objectives 1

1.1 Importance of Separations 1

1.2 Concept of Equilibrium 3

1.3 Mass Transfer Concepts 4

1.4 Problem-Solving Methods 5

1.5 Units 6

1.6 Computers and Computer Simulations 7

1.7 Prerequisite Material 7

1.8 Other Resources on Separation Process Engineering 9

References 10

Problems 11

Chapter 2. Flash Distillation 13

2.0 Summary—Objectives 13

2.1 Basic Method of Flash Distillation 13

2.2 Form and Sources of Equilibrium Data 15

2.3 Binary VLE 17

2.4 Binary Flash Distillation 26

2.5 Multicomponent VLE 32

2.6 Multicomponent Flash Distillation 36

2.7 Simultaneous Multicomponent Convergence 40

2.8 Three-Phase Flash Calculations 45

2.9 Size Calculation 45

2.10 Using Existing Flash Drums 50

References 51

Problems 52

Appendix A. Computer Simulation of Flash Distillation 62

     Lab 1. Introduction to Aspen Plus 62

     Lab 2. Flash Distillation 69

Appendix B. Spreadsheets for Flash Distillation 72

Chapter 3. Introduction to Column Distillation 75

3.0 Summary—Objectives 75

3.1 Developing a Distillation Cascade 75

3.2 Tray Column Distillation Equipment 82

3.3 Safety 85

3.4 Specifications 86

3.5 External Column Balances 88

References 92

Problems 92

Chapter 4. Binary Column Distillation: Internal Stage-by-Stage Balances 99

4.0 Summary—Objectives 99

4.1 Internal Balances 99

4.2 Binary Stage-by-Stage Solution Methods 103

4.3 Introduction to the McCabe-Thiele Method 109

4.4 Feed Line 113

4.5 Complete McCabe-Thiele Method 120

4.6 Profiles for Binary Distillation 123

4.7 Open Steam Heating 125

4.8 General McCabe-Thiele Analysis Procedure 129

4.9 Other Distillation Column Situations 134

4.10 Limiting Operating Conditions 141

4.11 Efficiencies 143

4.12 Subcooled Reflux and Superheated Boilup 145

4.13 Simulation Problems 146

4.14 New Uses for Old Columns 148

4.15 Comparisons between Analytical and Graphical Methods 149

References 150

Problems 150

Appendix A. Computer Simulation of Binary Distillation 165

     Lab 3. Binary Distillation 165

Appendix B. Spreadsheet for Binary Distillation 169

Chapter 5. Introduction to Multicomponent Distillation 171

5.0 Summary—Objectives 171

5.1 Calculational Difficulties of Multicomponent Distillation 171

5.2 Profiles for Multicomponent Distillation 176

5.3 Stage-by-Stage Calculations for CMO 181

References 186

Problems 187

Appendix A. Simplified Spreadsheet for Stage-by-Stage Calculations

     for Ternary Distillation 192

Chapter 6. Exact Calculation Procedures for Multicomponent Distillation 195

6.0 Summary—Objectives 195

6.1 Introduction to Matrix Solution for Multicomponent Distillation 195

6.2 Component Mass Balances in Matrix Form 196

6.3 Initial Guesses for Flow Rates and Temperatures 200

6.4 Temperature Convergence 201

6.5 Energy Balances in Matrix Form 203

6.6 Introduction to Naphtali-Sandholm Simultaneous Convergence Method 206

6.7 Discussion 207

References 208

Problems 208

Appendix. Computer Simulations for Multicomponent Column Distillation 214

     Lab 4. Simulation of Multicomponent Distillation 214

     Lab 5. Pressure Effects and Tray Efficiencies 216

     Lab 6. Coupled Columns 220

Chapter 7. Approximate Shortcut Methods for Multicomponent Distillation 223

7.0 Summary—Objectives 223

7.1 Total Reflux: Fenske Equation 223

7.2 Minimum Reflux: Underwood Equations 228

7.3 Gilliland Correlation for Number of Stages at Finite Reflux Ratios 231

References 234

Problems 235

Chapter 8. Introduction to Complex Distillation Methods 241

8.0 Summary—Objectives 241

8.1 Breaking Azeotropes with Hybrid Separations 241

8.2 Binary Heterogeneous Azeotropic Distillation Processes 243

8.3 Continuous Steam Distillation 251

8.4 Pressure-Swing Distillation Processes 257

8.5 Complex Ternary Distillation Systems 259

8.6 Extractive Distillation 266

8.7 Azeotropic Distillation with Added Solvent 272

8.8 Distillation with Chemical Reaction 274

References 277

Problems 278

Appendix A. Simulation of Complex Distillation Systems 292

     Lab 7. Pressure-Swing Distillation for Separating Azeotropes 292

     Lab 8. Binary Distillation of Systems with Heterogeneous Azeotropes 295

     Lab 9. Simulation of Extractive Distillation 298

Appendix B. Spreadsheet for Distillation curve Generation for Constant

     Relative Volatility at Total Reflux 302

Chapter 9. Batch Distillation 303

9.0 Summary—Objectives 303

9.1 Introduction to Batch Distillation 303

9.2 Batch Distillation: Rayleigh Equation 305

9.3 Simple Binary Batch Distillation 307

9.4 Constant-Mole Batch Distillation 312

9.5 Batch Steam Distillation 314

9.6 Multistage Binary Batch Distillation 317

9.7 Multicomponent Simple Batch Distillation and Residue Curve Calculations 321

9.8 Operating Time 324

References 326

Problems 326

Appendix A. Calculations for Simple Multicomponent Batch Distillation and

     Residue Curve Analysis 334

Chapter 10. Staged and Packed Column Design 337

10.0 Summary—Objectives 337

10.1 Staged Column Equipment Description 338

10.2 Tray Efficiencies 344

10.3 Column Diameter Calculations 351

10.4 Balancing Calculated Diameters 356

10.5 Sieve Tray Layout and Tray Hydraulics 358

10.6 Valve Tray Design 364

10.7 Introduction to Packed Column Design 366

10.8 Packings and Packed Column Internals 366

10.9 Packed Column Design: HETP Method 368

10.10 Packed Column Flooding and Diameter Calculation 371

10.11 Economic Trade-Offs for Packed Columns 378

10.12 Choice of Column Type 379

10.13 Fire Hazards of Structured Packings 381

References 382

Problems 385

Appendix. Tray and Downcomer Design with Computer Simulator 392

     Lab 10. Detailed Design 392

Chapter 11. Economics and Energy Efficiency in Distillation 397

11.0 Summary—Objectives 397

11.1 Equipment Costs 397

11.2 Basic Heat Exchanger Design 404

11.3 Design and Operating Effects on Costs 406

11.4 Changes in Plant Operating Rates 414

11.5 Energy Reduction in Binary Distillation Systems 415

11.6 Synthesis of Column Sequences for Almost Ideal Multicomponent Distillation 419

11.7 Synthesis of Distillation Systems for Nonideal Ternary Systems 425

11.8 Next Steps 429

References 430

Problems 431

Chapter 12. Absorption and Stripping 439

12.0 Summary—Objectives 440

12.1 Absorption and Stripping Equilibria 441

12.2 McCabe-Thiele Solution for Dilute Absorption 444

12.3 Stripping Analysis for Dilute Systems 446

12.4 Analytical Solution for Dilute Systems: Kremser Equation 447

12.5 Efficiencies 452

12.6 McCabe-Thiele Analysis for More Concentrated Systems 453

12.7 Column Diameter 457

12.8 Dilute Multisolute Absorbers and Strippers 458

12.9 Matrix Solution for Concentrated Absorbers and Strippers 460

12.10 Irreversible Absorption and Cocurrent Cascades 463

References 465

Problems 466

Appendix. Computer Simulations of Absorption and Stripping 474

     Lab 11. Absorption and Stripping 474

Chapter 13. Liquid-Liquid Extraction 481

13.0 Summary—Objectives 481

13.1 Introduction to Extraction Processes and Equipment 481

13.2 Equilibrium for Dilute Systems and Solvent Selection 486

13.3 Dilute, Immiscible, Countercurrent Extraction 489

13.4 Immiscible Single-Stage and Crossflow Extraction 499

13.5 Concentrated Immiscible Extraction 502

13.6 Immiscible Batch Extraction 506

13.7 Extraction Equilibrium for Partially Miscible Ternary Systems 508

13.8 Mixing Calculations and the Lever-Arm Rule 511

13.9 Partially Miscible Single-Stage and Crossflow Systems 513

13.10 Partially Miscible Countercurrent Extraction 516

13.11 Relationship Between McCabe-Thiele and Triangular Diagrams for Partially

     Miscible Systems 522

13.12 Minimum Solvent Rate for Partially Miscible Systems 523

13.13 Extraction Computer Simulations 525

13.14 Design of Mixer-Settlers 526

References 537

Problems 538

Appendix. Computer Simulation of Extraction 545

     Lab 12. Extraction 545

Chapter 14. Washing, Leaching, and Supercritical Extraction 551

14.0 Summary—Objectives 551

14.1 Generalized McCabe-Thiele and Kremser Procedures 551

14.2 Washing 552

14.3 Leaching 559

14.4 Introduction to Supercritical Fluid Extraction 565

References 568

Problems 568

Chapter 15. Introduction to Diffusion and Mass Transfer 575

15.0 Summary−Objectives 576

15.1 Molecular Movement Leads to Mass Transfer 577

15.2 Fickian Model of Diffusivity 578

15.3 Values and Correlations for Fickian Binary Diffusivities 593

15.4 Linear Driving-Force Model of Mass Transfer for Binary Systems 601

15.5 Correlations for Mass Transfer Coefficients 615

15.6 Difficulties with Fickian Diffusion Model 626

15.7 Maxwell-Stefan Model of Diffusion and Mass Transfer 627

15.8 Advantages and Disadvantages of Different Diffusion and Mass Transfer Models 641

15.9 Useful Approximate Values 642

References 642

Problems 643

Appendix. Spreadsheets for Examples 15-10 and 15-11 650

Chapter 16. Mass Transfer Analyses for Distillation, Absorption, Stripping, and Extraction 653

16.0 Summary—Objectives 653

16.1 HTU-NTU Analysis of Packed Distillation Columns 653

16.2 Relationship of HETP and HTU 661

16.3 Correlations for HTU Values for Packings 663

16.4 HTU-NTU Analysis of Absorbers and Strippers 670

16.5 HTU-NTU Analysis of Cocurrent Absorbers 675

16.6 Prediction of Distillation Tray Efficiency 677

16.7 Mass Transfer Analysis of Extraction 679

16.7.4.3 Conservative Estimation of Mass Transfer Coefficients for Extraction 689

16.8 Rate-Based Analysis of Distillation 690

References 693

Problems 695

Appendix. Computer Rate-Based Simulation of Distillation 702

     Lab 13. Rate-Based Modeling of Distillation 702

Chapter 17. Crystallization from Solution 705

17.0 Summary–Objectives 706

17.1 Basic Principles of Crystallization from Solution 706

17.2 Continuous Cooling Crystallizers 712

17.3 Evaporative and Vacuum Crystallizers 722

17.4 Experimental Crystal Size Distribution 729

17.5 Introduction to Population Balances 734

17.6 Crystal Size Distributions for MSMPR Crystallizers 736

17.7 Seeding 750

17.8 Scaleup 755

17.9 Batch and Semibatch Crystallization 756

17.10 Precipitation 761

References 764

Problems 765

Appendix. Spreadsheet 772

Chapter 18. Melt Crystallization 773

18.0 Summary–Objectives 773

18.1 Equilibrium Calculations for Melt Crystallization 774

18.2 Suspension Melt Crystallization 780

18.3 Introduction to Solid-Layer Crystallization Processes: Progressive Freezing 793

18.4 Static Solid-Layer Melt Crystallization Process 808

18.5 Dynamic Solid-Layer Melt Crystallization 809

18.6 Zone Melting 819

18.7 Post-Crystallization Processing 824

18.8 Scaleup 827

18.9 Hybrid Crystallization–Distillation Processes 828

18.10 Predictions 833

References 834

Problems 836

Chapter 19. Introduction to Membrane Separation Processes 841

19.0 Summary—Objectives 844

19.1 Membrane Separation Equipment 844

19.2 Membrane Concepts 847

19.3 Gas Permeation (GP) 850

19.4 Osmosis and Reverse Osmosis (RO) 865

19.5 Ultrafiltration (UF)` 881

19.6 Pervaporation 891

19.7 Bulk Flow Pattern Effects 902

References 905

Problems 907

Appendix A. Spreadsheet for Crossflow GP 918

Chapter 20. Introduction to Adsorption, Chromatography, and Ion Exchange 923

20.0 Summary—Objectives 924

20.1 Adsorbents and Adsorption Equilibrium 924

20.2 Solute Movement Analysis for Linear Systems: Basics and

     Applications to Chromatography 935

20.3 Solute Movement Analysis for Linear Systems: Temperature and

     Pressure Swing Adsorption and Simulated Moving Beds 942

20.4 Nonlinear Solute Movement Analysis 963

20.5 Ion Exchange 970

References 978

Problems 980

Chapter 21. Mass Transfer Analysis of Adsorption, Chromatography, and Ion Exchange 991

21.0 Summary—Objectives 991

21.1 Mass and Energy Transfer in Packed Beds 991

21.2 Mass Transfer Solutions for Linear Systems 1000

21.3 Nonlinear Systems 1008

21.4 Checklist for Practical Design and Operation 1019

References 1021

Problems 1022

Appendix. Aspen Chromatography Simulator 1030

     Lab AC1. Introduction to Aspen Chromatography 1031

     Lab AC2. Convergence for Linear Isotherms 1035

     Lab AC3. Convergence for Nonlinear Isotherms 1036

     Lab AC4. Cycle Organizer 1038

     Lab AC5. Flow Reversal 1041

     Lab AC6. Ion Exchange 1045

     Lab AC7. SMB and TMB 1048

     Lab AC8. Thermal Systems 1051

Answers to Selected Problems 1057

Appendix A. Aspen Plus Troubleshooting Guide for Separations 1063

Appendix B. Instructions for Fitting VLE and LLE Data with Aspen Plus 1067

Appendix C. Unit Conversions and Physical Constants 1071

Appendix D. Data Locations 1073

Index

About the Author

Phillip C. Wankat, Clifton L. Lovell Distinguished Professor of Chemical Engineering Emeritus at Purdue University, has served as director of undergraduate degree programs at Purdue's School of Engineering Education. His research interests include adsorption, large-scale chromatography, simulated moving bed systems, distillation, and improvements in engineering education. His teaching, research, and service awards have included Purdue's College of Education's 2007 Distinguished Education Alumni Award, the Morrill award (Purdue University's highest faculty award), and the 2016 AIChE Warren K. Lewis award.