Distillation Principles and Practice

JOHANN STICHLMAIR PHD, is the Emeritus of the Institute of Plant and Process Technology, Technical University of Munich. He is the winner of the Arnold Eucken Award 1978, the Emil Kirschbaum Medal 2003 and the Arnold Eucken Medal 2008 of the German Association of Chemical Engineers. He was also honored in a special session at the AIChE National Meeting in 2004.

HARALD KLEIN PHD, is the current head of the Institute of Plant and Process Technology at the Technical University of Munich. His research is based on modeling and simulation of chemical processes, equipment design as well as thermodynamic property data.

SEBASTIAN REHFELDT PHD, is a senior lecturer for equipment design and process design at the Technical University of Munich. His research concentrates on gas-liquid contact apparatus and heat exchangers.

1 Introduction 1

1.1 Principle of Distillation Separation 1

1.2 Historical 3

2 Vapor-Liquid Equilibrium 7

2.1 Basic Thermodynamic Correlations 7

2.1.1 Measures of Concentration 7

2.1.2 Equations of State (EOS) 8

2.1.3 Molar Mixing and Partial Molar State Variables 12

2.1.4 Saturation Vapor Pressure and Boiling Temperature of Pure Components 13

2.1.5 Fundamental Equation and the Chemical Potential 14

2.1.6 Gibbs-Duhem Equation and Gibbs-Helmholtz Equation 17

2.2 Calculation of Vapor-Liquid Equilibrium in Mixtures 18

2.2.1 Basic Equilibrium Conditions 18

2.2.2 Gibbs Phase Rule 19

2.2.3 Correlations for the Chemical Potential 19

2.2.4 Calculating Activity Coefficients with the Molar Excess Free Energy 23

2.2.5 Thermodynamic Consistency Check of Molar Excess Free Energy and Activity Coefficients 28

2.2.6 Iso-fugacity Condition 30

2.2.7 Fugacity of the Liquid Phase 30

2.2.8 Fugacity of the Vapor Phase 31

2.2.9 Vapor-Liquid Equilibrium Using an Equation of State 32

2.2.10 Fugacity of Pure Liquid as Standard Fugacity: Raoult’s Law 47

2.2.11 Fugacity of Infinitely Diluted Component as Standard Fugacity: Henry’s Law 48

2.2.12 Correlations describing the Molar Excess Free Energy and Activity Coefficients 49

2.2.13 Using Experimental Data of Binary Mixtures for Correlations Describing the Molar

Excess Free Energy and Activity Coefficients .55

2.2.14 Vapor-Liquid Equilibrium Ratio of Mixtures 59

2.2.15 Relative Volatility of Mixtures 59

2.2.16 Boiling Condition of Liquid Mixtures 61

2.2.17 Condensation (Dew Point) Condition of Vapor Mixtures .62

2.3 Binary Mixtures and Phase Diagrams 81

2.3.1 Boiling Curve Correlation 81

2.3.2 Condensation (Dew Point) Curve Correlation 83

2.3.3 (p, x, y)-Diagram.84

2.3.4 (T, x, y)-Diagram 84

2.3.5 McCabe-Thiele Diagram 86

2.3.6 Boiling and Condensation Behavior of Binary Mixtures 86

2.3.7 General Aspects of Azeotropic Mixtures 90

2.3.8 Limiting Cases of Binary Mixtures 104

2.4 Ternary Mixtures 114

2.4.1 Boiling and Condensation Conditions of Ternary Mixtures 114

2.4.2 Triangular Diagrams 116

2.4.3 Boiling Surfaces 116

2.4.4 Condensation Surfaces 122

2.4.5 Derivation of Distillation Lines .123

2.4.6 Examples for Distillation Lines 128

3 Single Stage Distillation and Condensation 137

3.1 Continuous Closed Distillation and Condensation 137

3.1.1 Closed Distillation of Binary Mixtures 137

3.1.2 Closed Distillation of Multicomponent Mixtures 140

3.2 Batchwise Open Distillation and Open Condensation 152

3.2.1 Binary Mixtures .152

3.2.2 Ternary Mixtures 157

3.2.3 Multicomponent Mixtures 167

3.3 Semi-continuous Single Stage Distillation 169

3.3.1 Semi-continuous Single Stage Distillation of Binary Mixtures 169

4 Multistage Continuous Distillation (Rectification) 173

4.1 Principles 173

4.1.1 Equilibrium-Stage Concept 176

4.1.2 Transfer-Unit Concept 177

4.1.3 Comparison of Equilibrium-Stage and Transfer-Unit Concepts 180

4.2 Multistage Distillation of Binary Mixtures 181

4.2.1 Calculations Based on Material Balances 182

4.2.2 Calculation Based on Material and Enthalpy Balances 189

4.2.3 Distillation of Binary Mixtures at Total Reflux and Reboil .192

4.2.4 Distillation of Binary Mixtures at Minimum Reflux and Reboil 198

4.2.5 Energy Requirement for Distillation of Binary Mixtures.204

4.3 Multistage Distillation of Ternary Mixtures 206

4.3.1 Calculations Based on Material Balances 208

4.3.2 Distillation of Ternary Mixtures at Total Reflux and Reboil 215

4.3.3 Distillation of Ternary Mixtures at Minimum Reflux and Reboil 224

4.3.4 Energy Requirement of Ternary Distillation 248

4.4 Multistage Distillation of Multicomponent Mixtures 255

4.4.1 Rigorous Column Simulation 256

5 Reactive Distillation, Catalytic Distillation 283

5.1 Fundamentals 284

5.1.1 Chemical Equilibrium 284

5.1.2 Stoichiometric Lines 284

5.1.3 Non-Reactive and Reactive Distillation Lines .287

5.1.4 Reactive Azeotropes 289

5.2 Topology of Reactive Distillation Lines 293

5.2.1 Reactions in Ternary Systems 293

5.2.2 Reactions in Ternary Systems with Inert Components 295

5.2.3 Reactions with Side Products 297

5.2.4 Reactions in Quaternary Systems.298

5.3 Topology of Reactive Distillation Processes 298

5.3.1 Single Product Reactions 300

5.3.2 Decomposition Reactions.302

5.3.3 Side Reactions 306

5.4 Arrangement of Catalysts in Columns 307

5.4.1 Homogeneous Catalyst.307

5.4.2 Heterogeneous Catalyst 308

6 Multistage Batch Distillation 313

6.1 Batch Distillation of Binary Mixtures 314

6.1.1 Operation with Constant Reflux 315

6.1.2 Operation with Constant Distillate Composition 318

6.1.3 Operation with Minimum Energy Input 323

6.1.4 Comparison of Energy Requirement for Different Modes of Distillation.327

6.2 Batch Distillation of Ternary Mixtures 327

6.2.1 Zeotropic Mixtures 328

6.2.2 Azeotropic Mixtures 332

6.3 Batch Distillation of Multicomponent Mixtures 336

6.4 Influence of Column Liquid Hold-up on Batch Distillation 337

6.5 Processes for Separating Zeotropic Mixtures by Batch Distillation 340

6.6 Processes for Separating Azeotropic Mixtures by Batch Distillation 341

6.6.1 Processes in One Distillation Field 342

6.6.2 Processes in Two Distillation Fields 343

6.6.3 Process Simplifications 348

6.6.4 Hybrid Processes 348

7 Energy Economization in Distillation 357

7.1 Energy Requirement of Single Columns 358

7.1.1 Reduction of Energy Requirement 358

7.1.2 Reduction of Exergy Losses 359

7.2 Optimal Separation Sequences of Ternary Distillation 363

7.2.1 Process and Energy Requirement of the a-Path 363

7.2.2 Process and Energy Requirement of the c-Path.365

7.2.3 Process and Energy Requirement of the Preferred a/c-Path 366

7.3 Modifications of the Basic Processes 368

7.3.1 Material (Direct) Coupling of Columns.368

7.3.2 Processes with Side Columns 370

7.3.3 Thermal (Indirect) Coupling of Columns 386

7.4 Design of Heat Exchanger Networks 390

7.4.1 Optimum Heat Exchanger Networks 392

7.4.2 Modifying the Optimum Heat Exchanger Network 397

7.4.3 Dual Flow Heat Exchangers Networks 401

7.4.4 Process Modifications 401

8 Industrial Distillation Processes 407

8.1 Constraints for Industrial Distillation Processes 407

8.2 Fractionation of Binary Mixtures 412

8.2.1 Recycling of Diluted Sulfuric Acid 412

8.2.2 Ammonia Recovery from Waste Water 414

8.2.3 Hydrogen Chloride Recovery from Inert Gases .416

8.2.4 Linde Process for Air Separation 418

8.2.5 Process Water Purification 421

8.2.6 Steam Distillation 425

8.3 Fractionation of Multicomponent Zeotropic Mixtures 429

8.3.1 Separation Paths 429

8.3.2 Processes with Side Columns 431

8.4 Fractionation of Heterogeneous Azeotropic Mixtures 435

8.5 Fractionation of Azeotropic Mixtures by Pressure Swing Processes 436

8.6 Fractionation of Azeotropic Mixtures by Addition of an Entrainer 439

8.6.1 Processes for Systems without Distillation Boundary 440

8.6.2 Processes for Systems with Distillation Boundary 443

8.6.3 Hybrid Processes.455

8.7 Industrial Processes of Reactive Distillation 469

8.7.1 Synthesis of MTBE 469

8.7.2 Synthesis of Mono-Ethylene Glycol 471

8.7.3 Synthesis of TAME 473

8.7.4 Synthesis of Methyl-Acetate 474

9 Design of Mass Transfer Equipment 481

9.1 Types of Design 482

9.1.1 Tray Columns.482

9.1.2 Packed Columns 484

9.1.3 Criteria for Use of Tray or Packed Columns 486

9.2 Design of Tray Columns 487

9.2.1 Design Parameters of Tray Columns 487

9.2.2 Operating Region of Tray Columns 489

9.2.3 Two-Phase Flow on Trays 497

9.2.4 Mass Transfer in the Two-Phase Layer on Column Trays 518

9.3 Design of Packed Columns 533

9.3.1 Design Parameters of Packed Columns 534

9.3.2 Operating Region of Packed Columns 545

9.3.3 Two-Phase Flow in Packed Columns .548

9.3.4 Mass Transfer in Packed Columns 568

9.4 Appendix to Chapter 9: Pressure Drop in Packed Beds 587

10 Control of Distillation Processes 601

10.1 Control Loops 602

10.1.1 Single Control Loop 602

10.1.2 Ratio Control Loop 604

10.1.3 Disturbance Feed Forward Control Loop 604

10.1.4 Cascade Control Loop 605

10.2 Single Control Tasks for Distillation Columns 605

10.2.1 Liquid Level Control 605

10.2.2 Split Stream Control 606

10.2.3 Pressure Control 611

10.2.4 Product Concentration Control 613

10.3 Basic Control Configurations of Distillation Columns 613

10.3.1 Basic Control Systems without Composition Control 617

10.3.2 One-Point Composition Control Configurations 623

10.3.3 Two-Point Composition Control Configurations 626

10.4 Application Ranges of the Basic Control Configurations 629

10.4.1 Impact of Split Parameters according to Split Rule 2.629

10.4.2 Sharp Separations of Ideal Mixtures with Constant Relative Volatility at Minimum

Reflux and Boilup Ratio 639

10.4.3 Extended Application Ranges of the Basic Control Configurations 643

10.5 Examples for Control Configurations of Distillation Processes 646

10.5.1 Azeotropic Distillation Process by Pressure Change.646

10.5.2 Distillation Process for Air Separation 647

10.5.3 Distillation Process with a Main and a Side Column 649

10.5.4 Azeotropic Distillation Process by Using an Entrainer 650

10.6 Control Configurations for Batch Distillation Processes 651

Index 655

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