Description
Book SynopsisThe use of control systems is necessary for safe and optimal operation of industrial processes in the presence of inevitable disturbances and uncertainties. Plant-wide control (PWC) involves the systems and strategies required to control an entire chemical plant consisting of many interacting unit operations. Over the past 30 years, many tools and methodologies have been developed to accommodate increasingly larger and more complex plants.
This book provides a state-of-the-art of techniques for the design and evaluation of PWC systems. Various applications taken from chemical, petrochemical, biofuels and mineral processing industries are used to illustrate the use of these approaches. This book contains 20 chapters organized in the following sections:
- Overview and Industrial Perspective
- Tools and Heuristics
- Methodologies
- Applications
- Emerging Topics
With contributions from the leading researchers and industrial
Trade Review
Review copy sent 25/04/12: Book News
Table of Contents
Preface
Section I: Overview and Perspective
1 Introduction
1.1 Background 1
1.2 Plant-Wide Control 2
1.3 Scope and Organization of the Book 4
References 10
2 Industrial Perspective on Plant-Wide Control
2.1 Introduction 1
2.2 Design Environment 3
2.3 Disturbances and Measurement System Design 6
2.4 Academic Contributions 8
2.5 Conclusions 11
References 12
Section II: Tools and Heuristics
3 Control Degrees of Freedom Analysis for Plant-Wide Control of Industrial Processes
3.1 Introduction 2
3.2 Control Degrees of Freedom (CDOF) 4
3.3 Computation Methods for Control Degrees of Freedom (CDOF): A Review 7
3.4 Computation of CDOF Using Flowsheet-Oriented Method 14
3.4.1 Computation of Restraining Number for Unit Operations 16
3.5 Application of Flowsheet-Oriented Method to Distillation Columns and the Concept of Redundant Process Variables 19
3.6 Application of Flowsheet-Oriented Method to Compute CDOF to Complex Integrated Processes 22
3.7 Conclusions 23
References 24
4 Selection of Controlled Variables Using Self-Optimizing Control Method
4.1 Introduction 2
4.2 General Principle 4
4.3 Brute-Force Optimization Approach for CV Selection 8
4.4 Local Methods 11
4.4.1 Minimum Singular Value (MSV) Rule 12
4.4.2 Exact Local Method 14
4.4.3 Optimal Measurement Combination 16
4.4.3.1 Null Space Method 16
4.4.3.2 Explicit Solution 17
4.4.3.3 Toy Example 19
4.5 Branch and Bound Methods 21
4.6 Constraint Handling 23
4.7 Case Study: Forced Circulation Evaporator 26
4.8 Conclusions and Discussion 32
4.9 Acknowledgements 34
References 34
5 Input-Output Pairing Selection for Design of Decentralized Controller
5.1 Introduction 2
5.1.1 State of the Art 3
5.2 Relative Gain Array and Variants 5
Steady-State RGA 6
5.2.2 Niederlinski Index 8
5.2.3 The Dynamic Relative Gain Array 9
5.2.4 The Effective Relative Gain Array 11
5.2.5 The Block Relative Gain 12
5.2.6 Relative Disturbance Gain Array 14
5.3 µ-Interaction Measure 15
5.4 Pairing Analysis Based on the Controllability and Observability 17
5.4.1 The Participation Matrix 17
5.4.2 The Hankel Interaction Index Array 19
5.4.3 The Dynamic Input-Output Pairing Matrix 19
Input-Output Pairing for Uncertain Multivariable Plants 21
RGA in the Presence of Statistical Uncertainty 22
RGA in the Presence of Norm-Bounded Uncertainties 23
DIOPM and the Effect of Uncertainty 26
Input-Output Pairing for Nonlinear Multivariable Plants 28
5.6.1 Relative Order Matrix 29
5.6.2 The Nonlinear RGA 30
5.7 Conclusions and Discussion 31
References 33
6 Heuristics for Plantwide Control
6.1 Introduction 2
6.2 Basics of Heuristic Plantwide Control 4
6.2.1 Plumbing 5
6.2.2 Recycle 6
6.2.2.1 Effect of Recycle on Time Constants 6
6.2.2.2 Snowball Effects in Liquid Recycle Systems 7
6.2.2.3 Gas Recycle Systems 8
6.2.3 Fresh Feed Introduction 8
6.2.3.1 Ternary Example 9
6.2.3.2 Control Structures 11
6.2.3.3 Ternary Process with Altered Volatilities 12
6.2.4 Energy Management and Integration 12
6.2.5 Controller Tuning 13
6.2.5.1 Flow and Pressure Control 13
6.2.5.2 Level Control 14
6.2.5.3 Composition and Temperature Control 16
6.2.5.4 Interacting Control Loops 17
6.2.6 Throughput Handle 18
6.3 Application to HDA Process 18
6.3.1 Process Description 19
6.3.2 Application of Plantwide Control Heuristics 20
6.3.2.1 Throughput Handle 20
6.3.2.2 Maximum Gas Recycle 20
6.3.2.3 Component Balances (Downs Drill) 20
6.3.2.4 Flow Control in Liquid Recycle Loop 21
6.3.2.5 Product Quality and Constraint Loops 21
6.4 Conclusion 21
7 Throughput Manipulator Location Selection for Economic Plantwide Control
7.1 Introduction 2
7.2 Throughput Manipulation, Inventory Regulation and Plantwide Variability Propagation 3
7.3 Quantitative Case Studies 6
7.3.1 Case Study I: Recycle Process 7
7.3.1.1 Alternative Control Structures 7
7.3.1.2 Quantitative Back-Off Results 8
7.3.1.3 Salient Observations 10
7.3.2 Case Study II: Recycle Process with Side Reaction 11
7.3.2.1 Economically Optimal Process Operation 11
7.3.2.2 Self Optimizing Variables for Unconstrained Degrees of Freedom 14
7.3.2.3 Plantwide Control System Design 15
7.3.2.4 Dynamic Simulation Results 18
7.4 Discussion 19
7.5 Conclusions 23
7.6 Acknowledgments 23
7.7 Supplementary Information 23
References 24
8 Influence of Process Variability Propagation in Plant-Wide Control
8.1 Introduction 2
8.2 Theoretical Background 5
8.3 Local Unit Operation Control 12
8.3.1 Heat Exchanger 12
8.3.2 Extraction Process 13
8.4 Inventory Control 15
8.4.1 Pressure Control in Gas Headers 15
8.4.2 Parallel Unit Operations 17
8.4.3 Liquid Inventory Control 18
Plant-Wide Control Examples 21
8.5.1 Distillation Column Control 21
8.5.2 Esterification Process 22
8.6 Conclusion 25
References 27
Section III: Methodologies
9 A Review of Plant-Wide Control Methodologies and Applications
9.1 Introduction 1
9.2 Review and Approach-Based Classification of PWC Methodologies 3
9.2.1 Heuristics-Based PWC Methods 4
9.2.2 Mathematical-Based PWC Methods 6
9.2.3 Optimization-Based PWC Methods 8
9.2.4 Mixed PWC Methods 9
9.3 Structure-Based Classification of PWC Methodologies 12
9.4 Processes Studied in PWC Applications 14
9.5 Comparative Studies on Different Methodologies 16
9.6 Concluding Remarks 18
References 20
10 Integrated Framework of Simulation and Heuristics for Plant-Wide Control System Design
10.1 Introduction 1
10.2 HDA Process: Overview and Simulation 2
10.2.1 Process Description 2
10.2.2 Steady-State and Dynamic Simulation 4
10.3 Integrated Framework Procedure and Application to HDA Plant 5
10.4 Evaluation of the Control System 17
10.5 Conclusions 18
References 20
11 Economic Plantwide Control
Introduction 1
Control Layers and Time Scale Separation 3
Plantwide Control Procedure 7
Degrees of Freedom for Operation 9
11.5 Skogestad’s Plantwide Control Procedure 12
Top-Down Part 12
Discussion 29
Conclusion 30
REFERENCES 30
12 Performance Assessment of Plant-Wide Control Systems
12.1 Introduction 2
12.2 Desirable Qualities of a Good Performance Measure 4
12.3 Performance Measure Based on Steady State: Steady-State Operating Cost/Profit 5
12.4 Performance Measures Based on Dynamics 6
12.4.1 Process Settling Time Based on Overall Absolute Component Accumulation 6
12.4.2 Process Settling Time Based on Plant Production 7
12.4.3 Dynamic Disturbance Sensitivity (DDS) 8
12.4.4 Deviation from the Production Target (DPT) 8
12.4.5 Total Variation (TV) in Manipulated Variables 10
12.5 Application of the Performance Measures to the HDA Plant Control Structure 11
12.5.1 Steady-State Operating Cost 12
12.5.2 Process Settling Time Based on Overall Absolute Component Accumulation 12
12.5.3 Process Settling Time Based on Plant Production 13
12.5.4 Dynamic Disturbance Sensitivity (DDS) 14
12.5.5 Deviation from the Production Target (DPT) 15
12.5.6 Total Variation (TV) in Manipulated Variables 15
12.6 Application of the Performance Measures for Comparing PWC Systems 15
12.7 Discussion and Recommendations 17
12.7.1 Disturbances and Set-Point Changes 17
12.7.2 Performance Measures 19
12.8 Concluding Remarks 21
References 21
Section IV: Applications Studies
13 Design and Control of a Cooled Ammonia Reactor
13.1 Introduction 2
13.2 Cold-Shot Process 4
13.2.1 Process Flowsheet 4
13.2.2 Equipment Sizes, Capital and Energy Costs 6
13.3 Cooled-Reactor Process 7
13.3.1 Process Flowsheet 7
13.3.2 Reaction Kinetics 9
13.3.3 Optimum Economic Design of the Cooled-Reactor Process 10
13.3.3.1 Effect of Pressure 10
13.3.3.2 Effect of Reactor Size 12
13.3.4 Comparison of Cold-Shot and Cooled-Reactor Processes 12
13.4 Control 13
13.5 Conclusion 16
13.6 Acknowledgement 16
References 16
14 Design and Plant-Wide Control of a Biodiesel Plant
14.1 Introduction 1
14.2 Steady-State Plant Design and Simulation 4
14.2.1 Process Design 4
14.2.1.1 Feed and Product Specifications 4
14.2.1.2 Reaction Section 5
14.2.1.3 Separation Section 6
14.2.2 Process Flowsheet and HYSYS Simulation 8
14.3 Optimization of Plant Operation 10
14.4 Application of IFSH to Biodiesel Plant 12
14.5 Validation of the Plant-Wide Control Structure 18
14.6 Conclusions 20
References 20
15 Plant-Wide Control of a Reactive Distillation Process
15.1 Introduction 2
15.2 Design of Ethyl Acetate Reactive-Distillation Process 3
15.2.1 Kinetic and Thermodynamic Models 3
15.2.2 The Process Flowsheet 4
15.2.3 Comparison of the Process Using Either Homogeneous or Heterogeneous Catalyst 6
15.3 Control Structure Development of the Two Catalyst Systems 8
15.3.1 Inventory Control Loops 8
15.3.2 Product Quality Control Loops 10
15.3.3 Tuning of the Two Temperature Control Loops 12
Closed-Loop Simulation Results 13
15.3.5 Summary of PWC Aspects 15
15.4 Conclusions 17
References 17
16 Control System Design of a Crystallizer Train for Para-Xylene Recovery
16.1 Introduction 3
16.1 Process 5
16.2 Description 5
16.2.1 Para-Xylene Production Process 5
16.2.2 Para-Xylene Recovery Based on Crystallization Technology 6
16.3 Process Model 8
16.3.1 Crystallizer (Units 1–5) 8
16.3.2 Cyclone Separator (Units 9, 11) 10
16.3.3 Centrifugal Separator (Units 8, 10) 11
16.3.4 Overall Process Model 12
16.4 Control System Design 14
16.4.1 Basic Regulatory Control 14
16.4.2 Steady State Optimal Operation Policy 15
16.4.2.1 Maximization of Para-Xylene Recovery 15
16.4.2.2 Load Distribution 17
16.4.3 Design of Optimizing Controllers 19
16.4.3.1 Multiloop Controller 20
16.4.3.2 Multivariable Controller 20
16.4.3.3 Simulation 21
16.4.4 Incorporation of Steady State Optimizer 22
16.4.4.1 LP Based Steady State Optimizer 22
16.4.4.2 Simulation 24
16.4.5 Justification of MPC Application 25
16.5 Conclusions 26
16.6 5.A Linear Steady State Model and Constraints 27
References 29
17 Modeling and Control of Industrial Off-Gas Systems
17.1 Introduction 3
17.2 Process Description 5
Off-Gas System Model Development 7
17.3.1 Roaster off-Gas Train 8
17.3.2 Furnace Off-Gas Train 12
17.4 Control of Smelter Off-Gas Systems 14
17.4.1 Roaster Off-Gas System 15
17.4.1.1 Degree of Freedom Analysis 15
17.4.1.2 Definition of Optimal Operation 16
17.4.1.3 Optimization 17
17.4.1.4 Production Rate 19
17.4.1.5 Structure of the Regulatory and Supervisory Control 21
17.4.1.6 Validation of the Proposed Control Structure 22
17.4.2 Furnace Off-Gas System 22
17.4.2.1 Manipulated Variables and Degree of Freedom Analysis 22
17.4.2.2 Definition of Optimal Operation 23
17.4.2.3 Optimization 24
17.4.2.4 Production Rate 26
17.4.2.5 Structure of the Regulatory and Supervisory Control Layer 27
17.4.2.6 Validation of the Proposed Control Structures 28
17.5 Conclusion 28
Notation 29
Subscripts 32
References 33
Section V: Emerging Topics
18 Plant-Wide Control via a Network of Autonomous Controllers
18.1 Introduction 2
18.2 Process and Controller Networks 7
18.2.1 Representation of Process Network 7
18.2.2 Representation of Control Network 10
Plant-Wide Stability Analysis Based on Dissipativity 13
18.4 Controller Network Design 18
18.4.1 Transformation of the Network Topology 18
Plant-Wide Connective Stability 25
18.4.3 Performance Design 27
18.5 Case Study 31
18.5.1 Process Model 32
18.5.2 Distributed Control System Design 34
18.6 Discussions and Conclusion 35
References 40
19 Co-Ordinated, Distributed Plant-Wide Control
19.1 Introduction 2
Co-Ordination Based Plant-Wide Control 8
19.2.1 Price-Driven Co-Ordination 11
19.2.1.1 The Price Decomposition Principle 11
19.2.1.2 Algorithm 12
Price-Driven Co-Ordination Procedure: 14
19.2.1.4 Summary 15
19.2.2 Augmented Price-Driven Method 15
19.2.2.1 The Newton Based Price Update Method as a Negotiation Principle 17
19.2.3 Resource Allocation Co-Ordination 18
19.2.3.1 Resource Allocation Principle 18
19.2.3.2 Algorithm and Interpretation 18
19.2.4 Prediction-Driven Co-Ordination 21
19.2.4.1 Prediction-Driven Principle 21
19.2.4.2 Algorithm and Interpretation 23
19.2.4.3 Prediction Driven Co-Ordination Procedure 23
19.2.5 Economic Interpretation 24
19.3 Case Studies 25
19.3.1 A Pulp Mill Process 25
19.3.1.1 Problem Formulation 25
Plant-Wide Coordination and Performance Comparison 27
19.3.2 A Forced-Circulation Evaporator System 29
19.3.2.1 Problem Formulation 30
Plant-Wide Co-Ordination and Performance 32
19.4 The Future 34
References 38
20 Determination of Plant-Wide Control Loop Configuration and Eco-Efficiency
20.1 Introduction 1
20.2 Relative Gain Array (RGA) and Relative Exergy Gain Array (REA) 4
20.2.1 Relative Gain Array (RGA) 4
20.2.2 Relative Exergy Array (REA) 6
20.2.2.1 Exergy 6
20.2.2.2 Relative Exergy Array 8
20.3 Exergy Calculation Procedure 10
20.4 Case Study 13
20.4.1 Distillation Column 13
20.4.2 Case Study 2 15
20.5 Summary 19
References
