Advanced Distillation Technologies: Design, Control

Advanced Distillation Technologies Design, Control and Applications Anton Alexandru Kiss

Contents Preface Acknowledgements

xiii xv

1 Basic Concepts in Distillation 1.1 Introduction 1.2 Physical Property Methods 1.3 Vapor Pressure 1.4 Vapor–Liquid Equilibrium and VLE Non-ideality 1.4.1 Vapor–Liquid Equilibrium 1.4.2 VLE Non-ideality 1.5 Relative Volatility 1.6 Bubble Point Calculations 1.7 Ternary Diagrams and Residue Curve Maps 1.7.1 Ternary Diagrams 1.7.2 Residue Curve Maps 1.8 Analysis of Distillation Columns 1.8.1 Degrees of Freedom Analysis 1.8.2 McCabe–Thiele Method 1.8.3 Approximate Multicomponent Methods 1.9 Concluding Remarks References

1 1 2 6 8 8 11 13 14 16 16 18 24 26 27 33 34 35

2 Design, Control and Economics of Distillation 2.1 Introduction 2.2 Design Principles 2.2.1 Operating Pressure 2.2.2 Heuristic Optimization

37 37 38 39 40

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2.3

2.4

2.5

2.2.3 Rigorous Optimization 2.2.4 Feed Preheating 2.2.5 Intermediate Reboilers and Condensers 2.2.6 Heat Integration Basics of Distillation Control 2.3.1 Single-End Control 2.3.2 Dual-End Control 2.3.3 Alternative Control Structures 2.3.4 Constraint Control 2.3.5 Multivariable Control Economic Evaluation 2.4.1 Equipment Sizing 2.4.2 Equipment Cost 2.4.3 Utilities and Energy Cost 2.4.4 Cost of Chemicals Concluding Remarks References

3 Dividing-Wall Column 3.1 Introduction 3.2 DWC Configurations 3.3 Design of DWCs 3.3.1 Heuristic Rules for DWC Design 3.3.2 Approximate Design Methods 3.3.3 Vmin Diagram Method 3.3.4 Optimal Design of a DWC 3.4 Modeling of a DWC 3.4.1 Pump-Around Model 3.4.2 Two Columns Sequence Model 3.4.3 Four Columns Sequence Model 3.4.4 Simultaneous Models 3.4.5 Simulation of a Four-Product DWC 3.4.6 Optimization Methods 3.5 DWC Equipment 3.5.1 Liquid/Reflux Splitter 3.5.2 Column Internals 3.5.3 Equipment Sizing 3.5.4 Constructional Aspects 3.6 Case Study: Separation of Aromatics 3.7 Concluding Remarks References

41 42 42 43 44 46 49 52 53 54 55 56 59 62 63 63 64 67 67 70 75 77 78 79 82 83 84 84 85 86 86 86 87 89 91 91 94 97 103 107

CONTENTS

ix

4 Optimal Operation and Control of DWC 4.1 Introduction 4.2 Degrees of Freedom Analysis 4.3 Optimal Operation and Vmin Diagram 4.4 Overview of DWC Control Structures 4.4.1 Three-Point Control Structure 4.4.2 Three-Point Control Structure with Alternative Pairing 4.4.3 Four-Point Control Structure 4.4.4 Three-Point Control Structure with Nested Loops 4.4.5 Performance Control of Prefractionator Sub-system using the Liquid Split 4.4.6 Control Structures Based on Inferential Temperature Measurements 4.4.7 Feedforward Control to Reject Frequent Measurable Disturbances 4.4.8 Advanced Control Techniques 4.5 Control Guidelines and Rules 4.6 Case Study: Pentane–Hexane–Heptane Separation 4.7 Case Study: Energy Efficient Control of a BTX DWC 4.7.1 Energy Efficient Control Strategies 4.7.2 Dynamic Simulations 4.8 Concluding Remarks References

111 111 112 114 117 118

126 127 128 129 132 135 139 148 149

5 Advanced Control Strategies for DWC 5.1 Introduction 5.2 Overview of Previous Work 5.3 Dynamic Model of a DWC 5.4 Conventional versus Advanced Control Strategies 5.4.1 PID Loops within a Multi-loop Framework 5.4.2 Linear Quadratic Gaussian Control 5.4.3 Generic Model Control 5.4.4 Multivariable Controller Synthesis 5.5 Energy Efficient Control Strategies 5.5.1 Background of Model Predictive Control 5.5.2 Controller Tuning Parameters 5.5.3 Dynamic Simulations 5.6 Concluding Remarks

153 153 154 156 163 163 165 167 167 171 173 175 176 180

120 121 121 122 123

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Notation References

181 183

6 Applications of Dividing-Wall Columns 6.1 Introduction 6.2 Separation of Ternary and Multicomponent Mixtures 6.3 Reactive Dividing-Wall Column 6.4 Azeotropic Dividing-Wall Column 6.5 Extractive Dividing-Wall Column 6.6 Revamping of Conventional Columns to DWC 6.7 Case Study: Dimethyl Ether Synthesis by R-DWC 6.8 Case Study: Bioethanol Dehydration by A-DWC and E-DWC 6.9 Concluding Remarks References

187 187 188 195 198 199 203 205

7 Heat Pump Assisted Distillation 7.1 Introduction 7.2 Working Principle 7.3 Vapor (Re)compression 7.3.1 Vapor Compression 7.3.2 Mechanical Vapor Recompression 7.3.3 Thermal Vapor Recompression 7.4 Absorption–Resorption Heat Pumps 7.4.1 Absorption Heat Pump 7.4.2 Compression–Resorption Heat Pump 7.5 Thermo-acoustic Heat Pump 7.6 Other Heat Pumps 7.6.1 Stirling Cycle 7.6.2 Vuilleumier Cycle 7.6.3 Brayton Cycle 7.6.4 Malone Cycle 7.6.5 Solid–Sorption Cycle 7.7 Heat-Integrated Distillation Column 7.8 Technology Selection Scheme 7.8.1 Energy Efficient Distillation Technologies 7.8.2 Multicomponent Separations 7.8.3 Binary Distillation 7.8.4 Selected Scheme Applications

229 229 231 232 233 233 234 234 234 235 236 240 240 241 241 242 242 244 245

212 223 223

246 249 254 263

CONTENTS

7.9

Concluding Remarks References

xi

265 265

8 Heat-Integrated Distillation Column 8.1 Introduction 8.2 Working Principle 8.3 Thermodynamic Analysis 8.4 Potential Energy Savings 8.4.1 Partial Heat Integrated Distillation Column (p-HIDiC) 8.4.2 Ideal Heat Integrated Distillation Column (i-HIDiC) 8.5 Design and Construction Options 8.5.1 Inter-coupled Distillation Columns 8.5.2 Distillation Column with Partition Wall 8.5.3 Concentric Distillation Column 8.5.4 Concentric Column with Heat Panels 8.5.5 Shell & Tube Heat-Exchanger Column 8.5.6 Plate-Fin Heat-Exchanger Column 8.5.7 Heat Transfer Means 8.6 Modeling and Simulation 8.7 Process Dynamics, Control, and Operation 8.8 Applications of HIDiC 8.9 Concluding Remarks References

271 271 273 277 280

9 Cyclic Distillation 9.1 Introduction 9.2 Overview of Cyclic Distillation Processes 9.3 Process Description 9.4 Mathematical and Hydrodynamic Model 9.4.1 Mathematical Model 9.4.2 Hydrodynamic Model 9.4.3 Sensitivity Analysis 9.5 Modeling and Design of Cyclic Distillation 9.5.1 Modeling Approach 9.5.2 Comparison with Classic Distillation 9.5.3 Design Methodology 9.5.4 Demonstration of the Design Procedure 9.6 Control of Cyclic Distillation

311 311 313 316 319 319 321 323 327 329 331 331 333 335

280 281 282 284 285 287 288 289 290 292 295 297 300 304 305

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9.7

9.8

Cyclic Distillation Case Studies 9.7.1 Ethanol–Water Stripping and Concentration 9.7.2 Methanol–Water Separation Concluding Remarks References

338 338 341 347 349

10 Reactive Distillation 10.1 Introduction 10.2 Principles of Reactive Distillation 10.3 Design, Control and Applications 10.4 Modeling Reactive Distillation 10.5 Feasibility and Technical Evaluation 10.5.1 Feasibility Evaluation 10.5.2 Technical Evaluation 10.6 Case Study: Advanced Control of a Reactive Distillation Column 10.6.1 Mathematical Model 10.6.2 Open-Loop Dynamic Analysis 10.6.3 Closed-Loop Performance 10.7 Case Study: Biodiesel Production by Heat-Integrated RD 10.8 Case Study: Fatty Esters Synthesis by Dual RD 10.9 Concluding Remarks References

353 353 354 357 362 364 364 367

378 383 387 388

Index

393

371 371 374 374

Preface Our modern society is currently facing an energy revolution, and it needs to identify properly the potential threats and use all the opportunities to meet the needs of the growing population. Accordingly, chemical engineers have embarked on a quest for shaping a much needed sustainable future—especially considering that chemical industry is among the most energy demanding sectors. Distillation is a thermal separation method widely applied in the chemical process industry as the separation technology of choice, despite its very low thermodynamic efficiency. Remarkably, almost every single product on the market includes components that went through a distillation column. Even now, when changing from fossil fuels to a bio-based economy, it is clear that in the next two decades distillation will retain its significance as the main method for separating mixtures—although this old workhorse of the chemical industry is facing some new big and bold challenges. Owing to the limitation of fossil fuels, the need for energy independence, and the environmental problem of the greenhouse gas effect, there is a considerable increasing interest in the research and development of integrated chemical processes that require less capital investment, reduced operating costs, and have high eco-efficiency. Energy efficient distillation is a hot topic in separation technology due to the key advantages of the integrated technologies, such as reduced investment costs and low energy requirements, as well as an increasing number of industrial applications. Although the research and development carried out at universities and industrial companies in this exciting field is expanding quickly, there is still no book currently available focusing on this important area in distillation technology—the largest consumer of energy in the chemical process industry.

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PREFACE

Therefore, we feel that there is a significant gap that can be addressed with this book and it will be of immense interest to a readership across the world. The book provides engineers with a wide and relatively deep insight into integrated distillations using non-conventional arrangements. Readers can learn from this material the background, recent developments, fundamental principles, design and simulation methods, detailed case studies of distillation processes, as well as expected future trends. We believe that the abundant valuable resources included here— relevant equations, diagrams, figures, and references that reflect the current and upcoming integrated distillation technologies—will be of great help to all readers from the (petro-)chemical industry, bio-refineries, and other related areas. This book is the first comprehensive work about advanced distillation technologies, covering many important topics such as key concepts in distillation technology, principles of design, control, equipment sizing and economics of distillation, DWC design and configurations, optimal operation, controllability and advanced control strategies, industrial and pilot-scale DWC applications (in ternary separations, azeotropic distillation, extractive distillation, and reactive distillation), HIDiC design and configurations, heat pump assisted applications, cyclic distillation, and reactive distillation. Each chapter is independently written and consists typically of an introduction, working principle, process design, modeling and simulation, process control and operation, specific equipment, industrial and applied research examples, concluding remarks, as well as a comprehensive list of useful references for further reading. Note that the author is aware about the unavoidable presence of some minor mistakes. That is why I would like to express my gratitude for every observation and suggestion towards further improving this material.