Chemical Process Retrofitting and Revamping
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Preface xv
PART I OVERVIEW
1 Introduction 3
G.P. Rangaiah
1.1 Chemical Process Plants 3
1.2 Process Retrofitting and Revamping 4
1.3 Stages in Process Retrofitting/Revamping Projects 6
1.4 Conceptual Process Design for Process Retrofit/Revamp Projects 8
1.5 Research and Development in Process Retrofit/Revamp 9
1.6 Scope and Organization of this Book 12
1.7 Conclusions 16
References 17
2 Project Engineering and Management for Process Retrofitting and Revamping 19
C.C.S. Reddy
2.1 Introduction 19
2.2 Key Differences between Revamp and Grassroots Designs 20
2.3 Revamp Design Methodology 20
2.4 Project/Process Engineering and Management of Revamp Projects 24
2.4.1 Revamp Objectives and Pre-Feasibility Study 24
2.4.2 Conceptual Design (Pre-FEED) 24
2.4.3 FEED (Front End Engineering Design) 31
2.4.4 Detailed Engineering, Procurement and Construction 33
2.4.5 Project Completion 35
2.5 Key Elements of Project Management 35
2.5.1 Project Schedule 39
2.5.2 Project Execution and Progress Monitoring 39
2.5.3 Project Cost Control 40
2.5.4 Risk Management 41
2.5.5 Final Project Deliverables 41
2.6 Revamp Options for Process Equipment 41
2.7 Conclusions 53
Acronyms 53
References 54
3 Process Safety in Revamp Projects 57
Raman Balajee and C.C.S. Reddy
3.1 Introduction 57
3.2 Lessons from Past Process Safety Incidents 59
3.3 Preliminary Hazard Review during Conceptual Design 60
3.3.1 Risk Matrix for Qualitative Judgments 61
3.3.2 What-If and Process Safety Check Lists 62
3.3.3 Plot Plan and Layout Review 63
3.3.4 Area Classification Reviews 65
3.3.5 Pressure Relief System Considerations 66
3.3.6 Fire Safety for Revamp Projects 72
3.4 Process Hazard Analysis (PHA) 74
3.4.1 Process Plant Hazard Review using HAZOP 74
3.4.2 Failure Modes and Effects Analysis (FMEA) Tool 79
3.4.3 Instrumented Protective System Design 81
3.4.4 Fault Tree Analysis 82
3.4.5 Event Tree Analysis 84
3.4.6 Layer of Protection Analysis (LOPA) 85
3.4.7 Safety Instrumented System (SIS) Life Cycle 88
3.5 Revision of PSI and Operator Induction 88
3.6 Pre-Start-up Safety Review (PSSR) 90
3.7 Management of Change (MOC) 91
3.8 Conclusions 92
Acronyms 93
Exercises 94
References 95
PART II TECHNIQUES FOR RETROFITTING AND REVAMPING
4 Mathematical Modeling, Simulation and Optimization for Process Design 99
Shivom Sharma and G.P. Rangaiah
4.1 Introduction 99
4.2 Process Modeling and Model Solution 101
4.2.1 Process Modeling 101
4.2.2 Model Solution 103
4.2.3 Model for Membrane Separation of a Gas Mixture 104
4.3 Process Simulators and Aspen Custom Modeler 107
4.4 Optimization Methods and Programs 108
4.5 Interfacing a Process Simulator with Excel 112
4.6 Application to Membrane Separation Process 113
4.7 Conclusions 116
Acronyms 116
Appendix 4A: Implementation of Membrane Model in ACM 117
Appendix 4B: Interfacing of Aspen Plus v8.4 with Excel 2013 119
Appendix 4C: Interfacing of Aspen HYSYS v8.4 with Excel 2013 122
Exercises 125
References 125
5 Process Intensification in Process Retrofitting and Revamping 129
D.P. Rao
5.1 Introduction 129
5.1.1 Retrofitting and Revamping 129
5.1.2 Evolution of Chemical Industries and Process Intensification 130
5.1.3 Flow Chemistry 130
5.2 Methods of Process Intensification 130
5.2.1 Intensification of Rates 131
5.2.2 Process Integration 132
5.3 Alternatives to Conventional Separators 132
5.3.1 Rotating Packed Beds (HIGEE) 133
5.3.2 HIGEE with Split Packing 134
5.3.3 Zigzag HIGEE 135
5.3.4 Multi-rotor Zigzag HIGEE 136
5.3.5 Applications of HIGEE for Retrofitting 137
5.3.6 Podbielniak Centrifugal Extractor 138
5.3.7 Annular Centrifugal Extractor 139
5.3.8 Adsorbers 140
5.4 Alternatives to Stirred Tank Reactor (STR) 142
5.4.1 HEX Reactor 142
5.4.2 Advanced-flowTM Reactor (AFR) 143
5.4.3 Agitated Cell Reactor (ACR) 145
5.4.4 Oscillatory-flow Baffled Reactors (OBR) 146
5.4.5 Spinning Disc Reactor (SDR) 147
5.4.6 Spinning Tube-in-tube Reactor (STTR) 148
5.4.7 Stator-rotor Spinning Disc Reactor (Stator-rotor SDR) 150
5.4.8 Reactor Selection 150
5.4.9 Microchannel Devices 151
5.5 Process Integration 151
5.5.1 Heat and Mass Integration 152
5.5.2 Reactive Separations 152
5.5.3 Hybrid Separation 153
5.5.4 Conversion of Crosscurrent into Countercurrent Process 153
5.5.5 Process-specific Integration 154
5.5.6 In-line Processing 157
5.5.7 Twister® - A Supersonic Separator 158
5.6 Fundamental Issues of PI 159
5.7 Future of PI 159
5.8 Conclusions 160
Acknowledgement 160
Appendix 5A: Monographs, Reviews and Some Recent Papers 160
References 163
6 Using Process Integration Technology to Retrofit Chemical Plants for Energy Conservation and Wastewater Minimization 167
Russell F. Dunn and Jarrid Scott Ristau
6.1 Introduction 167
6.1.1 Heat Integration Networks 168
6.1.2 Water Recycle Networks 169
6.2 Graphical Design Tools for Retrofitting Process for Energy Conservation by Designing Heat Exchange Networks 170
6.2.1 The Temperature-Interval Diagram (TID) 171
6.2.2 The Heat Pinch Composite Curves (Temperature-Enthalpy Diagrams) 172
6.2.3 The Enthalpy-Mapping Diagram (EMD) 174
6.2.4 Identifying Heat Integration Matches Using the TID and EMD 174
6.2.5 Graphical Tools Facilitate HEN Design for Large-scale Industrial Problems 177
6.3 Graphical Design Tools for Retrofitting Processes for Wastewater Reduction by Designing Water Recycle Networks 179
6.3.1 The Material Recycle Pinch Diagram 179
6.3.2 The Source-Sink Mapping Diagram 181
6.3.3 Suggested Guidelines for Identifying Water Recycle Matches Using the Material Recycle Pinch Diagram and Source-Sink Mapping Diagrams 181
6.4 Conclusions 182
Appendix 6A: Illustrating the Water Recycle Network Design Guidelines 183
Exercises 188
References 190
7 Heat Exchanger Network Retrofitting: Alternative Solutions via Multi-objective Optimization for Industrial Implementation 193
B.K. Sreepathi and G.P. Rangaiah
7.1 Introduction 193
7.2 Heat Exchanger Networks 196
7.2.1 Structural Representation 198
7.3 HEN Improvements 199
7.4 MOO Method, HEN Model and Exchanger Reassignment Strategy 203
7.4.1 Multi-objective Optimization 203
7.4.2 HEN Model 205
7.4.3 Exchanger Reassignment Strategy (ERS) 206
7.5 Case Study 208
7.6 Results and Discussion 208
7.6.1 Simple Retrofitting 209
7.6.2 Moderate Retrofitting 211
7.6.3 Complex Retrofitting 214
7.6.4 Comparison and Discussion 216
7.7 Conclusions 218
Appendix 7A: Calculation of Nodal Temperatures 218
Exercises 221
References 221
8 Review of Optimization Techniques for Retrofitting Batch Plants 223
Catherine Azzaro-Pantel
8.1 Introduction 223
8.2 Batch Plant Typical Features 224
8.3 Formulation of the Batch Plant Retrofit Problem 228
8.3.1 Design versus Retrofitting Problem 228
8.3.2 Design/Retrofit Problems: A Four-Level Framework 229
8.4 Methods and Tools for Retrofit Strategies 230
8.4.1 General Comments 230
8.4.2 Key Approaches in Batch Plant Retrofitting: Deterministic vs Stochastic Methods 238
8.4.3 New Trends in Batch Plant Retrofitting: Steps for More Sustainable Processes 242
8.5 Conclusions 243
References 244
PART III RETROFITTING AND REVAMPING APPLICATIONS
9 Retrofit of Side Stream Columns to Dividing Wall Columns, with Case Studies of Industrial Applications 251
Moonyong Lee, Le Quang Minh, Nguyen Van Duc Long, and Joonho Shin
9.1 Introduction 251
9.2 Side Stream Column 254
9.2.1 Side Stream Configuration 254
9.2.2 Heuristic Rules for the Use of SSCs 256
9.2.3 Pros and Cons of SSC 257
9.2.4 Design of SSC 257
9.3 Dividing Wall Column 258
9.3.1 Introduction 258
9.3.2 Design and Optimization of DWC 259
9.4 Retrofit of an SSC to a DWC 260
9.4.1 Introduction 260
9.4.2 Design and Optimization of Retrofitted DWC 260
9.4.3 Column Modification and Hardware 263
9.5 Case Studies of Industrial Applications 266
9.5.1 Acetic Acid Purification Column 266
9.5.2 n-BuOH Refining Column 271
9.6 Other Case Studies 275
9.6.1 Ethylene Dichloride (EDC) Purification Column 275
9.6.2 Diphenyl Carbonate (DPC) Purification Column 276
9.6.3 Other SSCs 277
9.7 Conclusions 277
Acknowledgements 278
Nomenclature 278
References 279
10 Techno-economic Evaluation of Membrane Separation for Retrofitting Olefin/Paraffin Fractionators in an Ethylene Plant 285
X.Z. Tan, S. Pandey, G.P. Rangaiah, and W. Niu
10.1 Introduction 285
10.2 Olefin/Paraffin Separation in an Ethylene Plant 287
10.3 Membrane Model Development 289
10.3.1 Membrane Modeling 289
10.3.2 Assumptions for Membrane Separation Simulation 291
10.4 Retrofitting a Distillation Column with a Membrane Unit 292
10.4.1 HMD Modeling and Simulation 292
10.4.2 Techno-economic Feasibility of Retrofit Operation 296
10.5 Formulation of Multi-objective-Optimization Problem 300
10.6 Results and Discussion 304
10.6.1 Case 1: HMD System for EF (Assuming Credit for Reboiler Duty) 304
10.6.2 Case 2: HMD System for EF (Assuming Reboiler Duty as Cost) 306
10.6.3 Case 3: HMD System for PF 308
10.7 Conclusions 310
Appendix 10A: Membrane Model Validation 310
Appendix 10B: Costing of HMD System 312
Exercises 315
References 315
11 Retrofit of Vacuum Systems in Process Industries 317
C.C.S. Reddy and G.P. Rangaiah
11.1 Introduction 317
11.2 Vacuum-generation Methods 318
11.3 Design Principles and Utility Requirements 320
11.3.1 Suction Load of Vacuum System 320
11.3.2 Steam Jet Ejectors 323
11.3.3 Liquid Ring Vacuum Pumps 325
11.3.4 Dry Vacuum Pumps 326
11.4 Chilled-water Generation 326
11.5 Optimization of Vacuum System Operating Cost 328
11.6 Case Study 1: Retrofit of a Vacuum System in a Petroleum Refinery 332
11.6.1 Analysis of the Results 335
11.7 Case Study 2: Retrofit of a Surface Condenser of a Condensing Steam Turbine 341
11.8 Conclusions 342
Nomenclature 343
Exercises 344
References 345
12 Design, Retrofit and Revamp of Industrial Water Networks using Multi-objective Optimization Approach 347
Shivom Sharma and G.P. Rangaiah
12.1 Introduction 347
12.2 Mathematical Model of a Water Network 350
12.3 Water Network in a Petroleum Refinery 352
12.4 Multi-objective Optimization Problem Formulation 352
12.5 Results and Discussion 355
12.5.1 Water Network Design 355
12.5.2 Retrofitting Selected Water Networks for Change in Environmental Regulations 358
12.5.3 Retrofitting Selected Water Networks for Increase in Hydrocarbon Load 363
12.5.4 Revamping Selected Water Networks for Change in Environmental Regulations 365
12.5.5 Revamping Selected Water Networks for Increase in Hydrocarbon Load 367
12.5.6 Comparison of Retrofitting and Revamping Solutions 369
12.6 Conclusions 369
Acknowledgement 370
Nomenclature 370
Exercises 371
References 372
13 Debottlenecking and Retrofitting of Chemical Pulp Refining Process for Paper Manufacturing - Application from Industrial Perspective 375
Ajit K. Ghosh
13.1 Introduction 375
13.2 Fundamentals of Chemical Pulp Refining 376
13.2.1 Refining Effects on Various Chemical Pulp Types 377
13.2.2 Effects of Refining on Pulp and Paper Properties 378
13.3 Theories of Chemical Pulp Refining 380
13.3.1 Specific Edge Load Theory 381
13.3.2 Specific Surface Load Theory 382
13.3.3 Frequency and Intensity or Severity of Impact 382
13.3.4 The 'C' Factor 383
13.4 Types of Commercial Refiners 384
13.5 Laboratory and Pilot-scale Refining Investigation 384
13.6 Case Studies of Retrofitting Refining Process for Paper Mills 386
13.6.1 Case A: Retrofitting of Existing Refiners to Debottleneck Output of a Modern Paper Machine 386
13.6.2 Case B: Retrofitting of Existing Refiners of a Paper Machine to Switch from 'Flat' to 'Semi-extendable' Sack Kraft Papers 402
13.7 Conclusions 406
Exercises 407
References 408
Index 410
1
Introduction
G.P. Rangaiah
Department of Chemical & Biomolecular Engineering, National University of Singapore, Singapore
1.1 Chemical Process Plants
There are a wide range of chemical process industries such as agrochemicals, ceramics, cement, cosmetics, fragrances and flavors, food and drinks, glass, industrial gases, industrial/inorganic chemicals, leather, mineral processing, nuclear, oil and gas, paper and pulp, paints and pigments, petrochemicals, pharmaceuticals, polymers, rubber, soap and detergent, specialty chemicals, synthetic fibers, sugar, vegetable oils and water. Many of these involve continuous processes whereas some are batch processes. New process plants continue to be designed and built, relatively more in developing countries, to produce useful and valuable products required by the society. These are usually designed and their economic viability assessed assuming a plant life of 10 to 20 years. However, chemical plants, once built, continue to operate for very much longer than this assumed plant life.
Thus, chemical process plants in operation have been increasing steadily in the world. They were designed in the past few years or even decades, perhaps optimally for the economic, technological and societal conditions at that time. Obviously, technological knowledge has been advancing since the existing plants were designed. In addition, economic and societal conditions are dynamic and change over time for one reason or other. For example, energy prices and global warming concerns have increased substantially; new and better technologies (such as catalysts, process equipment and their internals), separation processes and intensified processes as well as simulation and optimization techniques are being continually developed and improved through research and industrial implementation.
Hence, it is imperative to review regularly the performance of the existing plants and assess the possibilities for their improvement. This can be for one or more of the following objectives (Grossmann et al., 1987; Rong et al., 2000).
- To reduce energy required and/or operating cost
- To improve conversion and/or selectivity of reactions
- To increase production/throughput of the process
- To use feed of different quality and/or alternative feed
- To meet new specifications of product(s)
- To produce new products
- To enhance the control of the process
- To improve the safety, reliability and flexibility of the process
- To reduce the adverse impact of the process on the environment.
The first and relatively simple step is to optimize and set the operating conditions such as temperature, pressure and flow rate in the existing process for the chosen objective (for example, energy required and operating cost). This is often referred to as operation optimization, and involves analysis of the process and use of optimization techniques. In operation optimization, there is no change in process configuration or equipment. It can be performed off-line or on-line because of frequent changes in the operating environment of the process (such as product requirements and prices). On-line optimization is also known as real time optimization. Process improvement by operation optimization is limited because of constraints imposed by current process configuration, equipment and/or technology employed. It is thus necessary to consider modifications in all these for improving the current process substantially.
1.2 Process Retrofitting and Revamping
Process retrofitting and revamping refers to making suitable changes and/or additions to existing process configuration and equipment. It may involve new technology such as membrane separation or reactive distillation to supplement or replace distillation. One example of equipment and configuration changes in a process is heat exchanger network retrofitting, which involves area additions in existing exchangers and/or installation of new exchangers for increased energy recovery and re-use. Obviously, process retrofitting and revamping should maximize the use of the existing equipment in the plant as much as possible.
Analysis, simulation and optimization techniques could be used to achieve the chosen objective of process retrofitting/revamping. However, process retrofitting/revamping is more than operation optimization because the former considers changes to the process configuration and equipment in addition to operating conditions. Hence, solving a process retrofitting/revamping problem and implementing the solution found are more complex and challenging than those in the case of operation optimization.
Is there some difference between process retrofit and revamp? According to oxforddictionaries.com, revamp is to give a new and improved form, structure or appearance (to something), and retrofit is to provide (something) with a component or accessory not fitted during manufacture. Although these two meanings seem to be similar, process retrofit perhaps refers to adding new equipment to the existing process and so its scale, complexity and capital cost are relatively lower. On the other hand, process revamp involves changes in configuration and so its scale, complexity and capital cost are more. Currently, retrofit and revamp are often used synonymously in the chemical engineering literature although some practitioners use retrofit for smaller projects (that is, investment) and revamp for bigger projects.
In the technical literature, Rong et al. (2000) state that the main objectives of process retrofits include increasing the production capacity, efficiently processing new feedstock, utilizing new process technologies, reducing environmental impact, and reducing operating costs. According to Smith (2005), the motivation to retrofit (or revamp) an existing plant could be to increase capacity, allow for different feed or product specifications, reduce operating costs, improve safety and reduce environmental emissions. Kemp (2007), in the glossary of terms, defines retrofit or revamp as any change to an existing chemical process. On the other hand, Towler and Sinnott (2012) state that revamps fall into two categories: debottlenecking (discussed below) and retrofitting, which implies the former is not within the scope of retrofitting.
Should we distinguish retrofit/retrofitting and revamp/revamping? It is perhaps desirable for clarity and consistency. As suggested by Rao in Chapter 5, retrofitting can be used to mean adding to or replacing the whole or part of one type of equipment with a better alternative, and revamping for reorganizing the process involving several process steps (thus different equipment types). This indicates that retrofitting is smaller in scale, complexity and capital cost compared with revamping. Thus, the suggested distinction between retrofit and revamp is consistent with the use of these terms by some practitioners.
One of the purposes of process changes is to increase the plant throughput (that is, increasing production rate without any change in feed, process performance or product quality). This specific activity is referred to as debottlenecking. This common term in process industries is related to a bottle's neck, which is generally narrow and limits the flow rate through it. Obviously, the neck has to be widened for increasing the flow rate. Similarly, in debottlenecking of an operating process, equipment/operation limiting the throughput is identified and then it is suitably modified for increasing the production rate. In this way, process capacity can be increased by 5 to 20%, with much smaller capital investment compared with building new facilities. This is possible because of the spare size/capacity available in many items of the existing equipment because of design margins used at the time of their design and fabrication. It is possible to increase the throughput by modifying one (type of) equipment or several types of equipment. Thus, debottlenecking can be achieved by retrofit or revamp. In other words, one objective of retrofit or revamp can be debottlenecking. Recall that retrofit and revamp can be for any of the reasons listed in the previous section. For specificity and clarity, debottlenecking (and not retrofit or revamp) should be used if the sole objective of process changes is an increase in the plant throughput. Note it is different from plant expansion, wherein there are no existing items of equipment to be considered and generally no space restrictions.
How is process retrofit/revamp different from operation optimization? Unlike the operation optimization, retrofit/revamp design will have more degrees of freedom (that is, variables related to existing equipment changes and to new equipment) and more combinations to be considered for optimization. Hence, it is much more challenging than operation optimization. However, retrofit/revamp design can improve the process significantly compared with operation optimization.
Analysis and solution of a process retrofit/revamp problem will require simulation and optimization. Hence, computational techniques for process simulation and optimization find applications in process retrofit and revamp. However, appropriate models have to be developed for process retrofit/revamp, and the resulting optimization problems have more constraints and are more challenging than are operation optimization problems.
1.3 Stages in Process Retrofitting/Revamping Projects
There are five main stages in the industrial retrofit/revamp projects. These are: (1)...
