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Reactive Distillation Design and Control

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$144.99

Reactive Distillation Design and Control

William L. Luyben, Cheng-Ching Yu

ISBN: 978-0-470-37779-6 March 2009 608 Pages

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Description

After an overview of the fundamentals, limitations, and scope of reactive distillation, this book uses rigorous models for steady-state design and dynamic analysis of different types of reactive distillation columns and quantitatively compares the economics of reactive distillation columns with conventional multi-unit processes. It goes beyond traditional steady-state design that primarily considers the capital investment and energy costs when analyzing the control structure and the dynamic robustness of disturbances, and discusses how to maximize the economic and environmental benefits of reactive distillation technology.

Preface xvii

1 Introduction 1

1.1 History 2

1.2 Basics of Reactive Distillation 3

1.3 Neat Operation Versus Excess Reactant 7

1.4 Limitations 8

1.4.1 Temperature Mismatch 8

1.4.2 Unfavorable Volatilities 9

1.4.3 Slow Reaction Rates 9

1.4.4 Other Restrictions 9

1.5 Scope 9

1.6 Computational Methods 10

1.6.1 Matlab Programs for Steady-State Design 10

1.6.2 Aspen Simulations 10

1.7 Reference Materials 11

Part I Steady-State Design of Ideal Quaternary System 15

2 Parameter Effects 17

2.1 Effect of Holdup on Reactive Trays 20

2.2 Effect of Number of Reactive Trays 22

2.3 Effect of Pressure 24

2.4 Effect of Chemical Equilibrium Constant 27

2.5 Effect of Relative Volatilities 29

2.5.1 Constant Relative Volatilities 30

2.5.2 Temperature-Dependent Relative Volatilities 30

2.6 Effect of Number of Stripping and Rectifying Trays 32

2.7 Effect of Reactant Feed Location 33

2.7.1 Reactant A Feed Location (NFA) 33

2.7.2 Reactant B Feed Location (NFB) 35

2.8 Conclusion 36

3 Economic Comparison of Reactive Distillation with a Conventional Process 37

3.1 Conventional Multiunit Process 38

3.1.1 Assumptions and Specifications 38

3.1.2 Steady-State Design Procedure 40

3.1.3 Sizing and Economic Equations 42

3.2 Reactive Distillation Design 43

3.2.1 Assumptions and Specifications 44

3.2.2 Steady-State Design Procedure 45

3.3 Results for Different Chemical Equilibrium Constants 47

3.3.1 Conventional Process 47

3.3.2 Reactive Distillation Process 54

3.3.3 Comparisons 61

3.4 Results for Temperature-Dependent Relative Volatilities 61

3.4.1 Relative Volatilities 62

3.4.2 Optimum Steady-State Designs 64

3.4.3 Real Chemical Systems 69

3.5 Conclusion 70

4 Neat Operation Versus Using Excess Reactant 71

4.1 Introduction 72

4.2 Neat Reactive Column 72

4.3 Two-Column System with Excess B 75

4.3.1 20% Excess B Case 76

4.3.2 10% Excess B Case 78

4.4 Two-Column System with 20% Excess of A 81

4.5 Economic Comparison 85

4.6 Conclusion 86

Part II Steady-State Design of Other Ideal Systems 87

5 Ternary Reactive Distillation Systems 89

5.1 Ternary System without Inerts 90

5.1.1 Column Configuration 90

5.1.2 Chemistry and Phase Equilibrium Parameters 90

5.1.3 Design Parameters and Procedure 92

5.1.4 Effect of Pressure 94

5.1.5 Holdup on Reactive Trays 94

5.1.6 Number of Reactive Trays 94

5.1.7 Number of Stripping Trays 94

5.2 Ternary System with Inerts 99

5.2.1 Column Configuration 99

5.2.2 Chemistry and Phase Equilibrium Parameters 99

5.2.3 Design Parameters and Procedure 100

5.2.4 Effect of Pressure 102

5.2.5 Control Tray Composition 103

5.2.6 Reactive Tray Holdup 105

5.2.7 Effect of Reflux 107

5.2.8 Chemical Equilibrium Constant 109

5.2.9 Feed Composition 109

5.2.10 Number of Reactive Trays 113

5.2.11 Number of Rectifying and Stripping Trays 113

5.3 Conclusion 116

6 Ternary Decomposition Reaction 119

6.1 Ternary Decomposition Reaction: Intermediate-Boiling Reactant 120

6.1.1 Column Configuration 120

6.1.2 Chemistry and Phase Equilibrium Parameters 120

6.1.3 Design Parameters and Procedure 121

6.1.4 Holdup on Reactive Trays 123

6.1.5 Number of Reactive Trays 124

6.1.6 Number of Rectifying and Stripping Trays 126

6.1.7 Location of Feed Tray 126

6.2 Ternary Decomposition Reaction: Heavy Reactant with Two-Column Configurations 127

6.2.1 Column Configurations 127

6.2.2 Chemistry and Phase Equilibrium Parameters 128

6.2.3 Design Parameters and Procedure 128

6.2.4 Reactive Holdup 129

6.2.5 Number of Reactive Trays 131

6.2.6 Number of Rectifying Trays 132

6.3 Ternary Decomposition Reaction: Heavy Reactant with One-Column Configurations 134

6.3.1 Feasibility Analysis 134

6.3.2 Column Configuration 139

6.3.3 Design Parameters and Procedure 139

6.3.4 Reactive Tray Holdup 139

6.3.5 Number of Reactive Trays 139

6.3.6 Number of Rectifying Trays 140

6.3.7 Location of Feed Tray 143

6.3.8 Comparison Between These Two Flowsheets 143

6.4 Conclusion 143

Part III Steady-State Design of Real Chemical Systems 145

7 Steady-State Design for Acetic Acid Esterification 147

7.1 Reaction Kinetics and Phase Equilibria 147

7.1.1 Reaction Kinetics 147

7.1.2 Phase Equilibria 149

7.2 Process Flowsheets 153

7.2.1 Type I Flowsheet: MeAc 153

7.2.2 Type II Flowsheet: EtAc and IPAc 156

7.2.3 Type III Flowsheet: BuAc and AmAc 157

7.3 Steady-State Design 158

7.3.1 Design Procedure 158

7.3.2 Optimized Design 160

7.4 Process Characteristics 168

7.4.1 Type I: MeAc 168

7.4.2 Type II: EtAc and IPAc 168

7.4.3 Type III: BuAc and AmAc 170

7.5 Discussion 175

7.6 Conclusion 177

8 Design of Tame Reactive Distillation Systems 179

8.1 Chemical Kinetics and Phase Equilibrium 180

8.1.1 Chemical Kinetics 180

8.1.2 Phase Equilibrium Using Aspen Plus 181

8.1.3 Conceptual Design 186

8.2 Component Balances 194

8.3 Prereactor and Reactive Column 195

8.3.1 Base Case Design of Reactive Column 195

8.3.2 Effect of Design Parameters on Reactive Column 199

8.4 Pressure-Swing Methanol Separation Section 208

8.5 Extractive Distillation Methanol Separation Section 209

8.6 Economic Comparison 210

8.7 Conclusion 212

9 Design of MTBE and ETBE Reactive Distillation Columns 213

9.1 MTBE Process 213

9.1.1 Phase Equilibrium 214

9.1.2 Reaction Kinetics 214

9.1.3 Aspen Plus Simulation Issues 214

9.1.4 Setting up the Aspen Plus Simulation 215

9.1.5 Effect of Design Parameters 221

9.1.6 Chemical Equilibrium Model 229

9.2 ETBE Process 231

9.2.1 Kinetic Model 231

9.2.2 Process Studied 232

9.2.3 User Subroutine for ETBE 232

9.2.4 Chemical Equilibrium Model 234

9.2.5 Effects of Design Parameters 236

9.3 Conclusion 237

Part IV Control of Ideal Systems 239

10 Control of Quaternary Reactive Distillation Columns 241

10.1 Introduction 242

10.2 Steady-State Design 243

10.3 Control Structures 245

10.4 Selection of Control Tray Location 246

10.5 Closed-Loop Performance 247

10.5.1 CS7-R Structure 247

10.5.2 CS7-RR Structure 248

10.6 Using More Reactive Trays 249

10.6.1 Steady-State Design 249

10.6.2 SVD Analysis 250

10.6.3 Dynamic Performance of CS7-RR 253

10.7 Increasing Holdup on Reactive Trays 254

10.8 Rangeability 256

10.9 Conclusion 259

11 Control of Excess Reactant Systems 261

11.1 Control Degrees of Freedom 261

11.2 Single Reactive Column Control Structures 263

11.2.1 Two-Temperature Control Structure 265

11.2.2 Internal Composition Control Structure 272

11.3 Control of Two-Column System 278

11.3.1 Two-Temperature Control 279

11.3.2 Temperature/Composition Cascade Control 285

11.4 Conclusion 292

12 Control of Ternary Reactive Distillation Columns 293

12.1 Ternary System without Inerts 293

12.1.1 Column Configuration 293

12.1.2 Control Structure CS1 296

12.1.3 Control Structure CS2 300

12.1.4 Control Structure CS3 303

12.2 Ternary System with Inerts 310

12.2.1 Column Configuration 310

12.2.2 Control Structure CS1 310

12.2.3 Control Structure CS2 314

12.2.4 Control Structure CS3 320

12.2.5 Conclusion for Ternary A + B <=> C System 322

12.3 Ternary A <=> B + C System: Intermediate-Boiling Reactant 324

12.3.1 Column Configuration 324

12.3.2 Control Structure CS1 326

12.3.3 Control Structure CS2 329

12.3.4 Control Structure CS3 334

12.4 Ternary A <=> B + C System: Heavy Reactant with Two-Column Configuration 334

12.4.1 Column Configuration 334

12.4.2 Control Structure CS1 334

12.4.3 Control Structure CS2 335

12.5 Ternary A <=> B + C System: Heavy Reactant With One-Column Configuration 342

12.5.1 Column Configuration 342

12.5.2 Control Structure CS1 342

12.5.3 Control Structure CS2 344

12.5.4 Control Structure CS3 345

12.5.5 Conclusion for Ternary A <=> B + C System 352

Part V Control of Real Systems 353

13 Control of Reactive Distillations for Acetic Acid Esterification 355

13.1 Process Characteristics 355

13.1.1 Process Studies 355

13.1.2 Quantitative Analysis 356

13.2 Control Structure Design 362

13.2.1 Selection of Temperature Control Trays 363

13.2.2 Control Structure and Controller Design 366

13.2.3 Performance 368

13.2.4 Alternative Temperature Control Structures 376

13.3 Extension to Composition Control 380

13.4 Conclusion 388

14 Plantwide Control of Tame Reactive Distillation System 389

14.1 Process Studied 389

14.1.1 Prereactor 390

14.1.2 Reactive Column C1 391

14.1.3 Extractive Column C2 391

14.1.4 Methanol Recovery Column C3 397

14.2 Control Structure 397

14.2.1 Prereactor 397

14.2.2 Reactive Distillation Column C1 399

14.2.3 Extractive Distillation Column C2 399

14.2.4 Methanol Recovery Column C3 401

14.3 Results 403

14.4 Conclusion 406

15 Control of MTBE and ETBE Reactive Distillation Columns 407

15.1 MTBE Control 407

15.1.1 Steady State 407

15.1.2 Control Structure with C4 Feedflow Controlled 408

15.1.3 Control Structure with Methanol Feedflow Controlled 416

15.2 ETBE Control 418

15.2.1 Control Structure with Flow Control of C4 Feed 419

15.2.2 Control Structure with Flow Control of Ethanol Feed 424

Part VI Hydrid and Nonconventional Systems 429

16 Design and Control of Column/Side Reactor Systems 431

16.1 Introduction 431

16.2 Design for Quaternary Ideal System 433

16.2.1 Assumptions and Specifications 434

16.2.2 Reactor and Column Equations 435

16.2.3 Design Optimization Procedure 436

16.2.4 Results and Discussion 437

16.2.5 Reactive Column with Optimum Feed Tray Locations 445

16.3 Control of Quaternary Ideal System 446

16.3.1 Dynamic Tubular Reactor Model 446

16.3.2 Control Structures 447

16.4 Design of Column/Side Reactor Process for Ethyl Acetate System 458

16.4.1 Process Description 458

16.4.2 Conceptual Design 459

16.5 Control of Column/Side Reactor Process for Ethyl Acetate System 474

16.5.1 Determining Manipulated Variables 475

16.5.2 Selection of Temperature Control Trays 479

16.5.3 Controller Design 481

16.5.4 Performance 481

16.5.5 Extension to Composition Control 485

16.5.6 Comparison with Reactive Distillation Temperature Control 485

16.6 Conclusion 485

17 Effects of Boiling Point Rankings on the Design of Reactive Distillation 487

17.1 Process and Classification 487

17.1.1 Process 487

17.1.2 Classification 490

17.2 Relaxation and Convergence 492

17.3 Process Configurations 495

17.3.1 Type I: One Group 496

17.3.2 Type II: Two Groups 501

17.3.3 Type III: Alternating 507

17.4 Results and Discussion 511

17.4.1 Summary 511

17.4.2 Excess Reactant Design 514

17.5 Conclusion 518

18 Effects of Feed Tray Locations on Design and Control of Reactive Distillation 519

18.1 Process Characteristics 519

18.1.1 Modeling 521

18.1.2 Steady-State Design 522

18.1.3 Base Case 522

18.1.4 Feed Locations Versus Reactants Distribution 523

18.1.5 Optimal Feed Locations 527

18.2 Effects of Relative Volatilities 529

18.2.1 Changing Relative Volatilities of Reactants 529

18.2.2 Changing Relative Volatilities of Products 530

18.2.3 Summary 532

18.3 Effects of Reaction Kinetics 533

18.3.1 Reducing Activation Energies 533

18.3.2 Effects of Preexponential Factor 536

18.4 Operation and Control 538

18.4.1 Optimal Feed Location for Production Rate Variation 538

18.4.2 Control Structure 539

18.4.3 Closed-Loop Performance 541

18.5 Conclusion 544

Appendix Catalog of Types of Real Reactive Distillation Systems 545

References 563

Index 573