# Energy and Process Integration

## Description

Optimization of the use of energy is of fundamental importance, particularly in view of the increasing tensions between energy supply and demand which the world now faces. Chemical processes in general, and distillation processes in particular, account for a significant fraction of the world's energy usage. For example, distillation processes account for around 3% of the energy utilization in the US. There is thus a significant incentive to so design systems that energy utilization is minimized. Much progress has been made by the application of simple methods such as pinch technology (see for instance B. Linnhoff and R. Smith, Section 1.7 of the Heat Exchanger Design Handbook, also published by Begell House), but the problems encountered in complex distillation systems are such that a much higher level approach is needed.

Both authors, Michael Georgiadis and Efstratios Pistikopoulos are from the Centre for Process Systems Engineering (CPSE) at Imperial College. CPSE is an international leader in the areas of process simulation, optimization and control. Once can confidently expect that the application of techniques of the type described in this volume will make an important contribution to making the best use of mankind's increasing scarce energy resources.

© 2006

## Table of Contents:

2 The Generalized Modular Framework: Fundamentals and Representation of Process Units

2.1 Generalized Modular Framework Fundamentals

2.1.1 The GMF Structural Model

2.1.2 The GMF Physical Model

2.1.3 The GMF Mathematical Model Formulation

2.2 Synthesis Procedure in the GMF

2.3 GMF Simple Distillation Column Representation

2.3.1 GMF Physical Modelling Issues Revisited

2.3.2 GMF Simple Distillation Column Structural Model

2.3.3 GMF Physical Model For Distillation Columns

2.4 Case Study: Binary Distillation Column

2.4.2 GMF Problem Formulation

2.4.3 Problem Solution and Results

3 Synthesis of Simple Distillation Column Sequences

3.1 Simple Distillation Column Sequencing

3.1.1 Superstructure Methods for Simple Column Sequencing

3.2 GMF Structural Model For Simple Distillation Column Sequences

3.2.1 GMF Propositional Logic Expressions - Stage 1

3.2.2 GMF Structural Integer Constraints - Stage 2

3.3 Case Study: Ternary Simple Distillation Sequencing

3.3.2 GMF Problem Formulation - Stage 3

3.3.3 Problem Solution and Results

3.4 Case Study: Quaternary Simple Distillation Sequencing

3.4.2 GMF Problem Formulation - Stage 3

3.4.3 Problem Solution and Results

4 Synthesis of Heat Integrated Distillation Column Sequences

4.1 Heat Integrated Distillation Column Sequencing

4.1.1 Superstructure Methods for HI Simple Column Sequencing

4.2 The GMF Heat Integration Block

4.2.1 HI Block Structural Representation

4.2.2 HI Block Physical Representation

4.3 GMF Structural Model For HI Simple Column Sequences

4.3.1 GMF Propositional Logic Expressions - Stage 1

4.3.2 GMF Structural Integer Constraints - Stage 2

4.4 Case Study: Ternary HI Simple Column Sequencing

4.4.2 GMF Problem Formulation - Stage 3

4.4.3 Problem Solution and Results

4.5 Case Study: Quaternary HI Simple Column Sequencing

4.5.2 GMF Problem Formulation - Stage 3

4.5.3 Problem Solution and Results

5 Synthesis of Complex Distillation Column Sequences

5.1 Complex Distillation Column Sequencing

5.1.1 Superstructure Methods for Complex Distillation Sequencing

5.2 GMF Structural Model For Ternary Complex Distillation Column Sequences

5.2.1 GMF Module Rearrangement

5.2.2 GMF Ternary Complex Distillation Column Superstructure

5.2.3 GMF Propositional Logic Expressions - Stage 1

5.2.4 GMF Structural Integer Constraints - Stage 2

5.3 Case Study: Ternary Complex Distillation Sequencing

5.3.2 GMF Problem Formulation - Stage 3

6 Enhanced GMF for Distillation Column Representation

6.1 GMF Physical Model Enhancement

6.2 Principles of Collocation Methods For Distillation

6.2.1 Orthogonal Collocation (OC)

6.2.2 Orthogonal Collocation On Finite Elements (OCFE)

6.3 Coupling GMF and OC For Distillation

6.4 Coupling GMF and OCFE For Distillation

6.5 Case Study: Enhanced GMF Binary Distillation Column

6.5.1 GMF/OC Formulation and Results

6.5.2 GMF/OCFE Formulation and Results

7 Enhanced GMF for the Synthesis of Distillation Column Sequences

7.1 Enhanced GMF for the Simple Distillation Column Sequencing

7.1.1 GMF/OC Simple Column Sequencing Formulation and Results

7.1.2 GMF/OCFE Simple Column Sequencing Formulation and Results

7.2 Enhanced GMF for the HI Simple Distillation Column Sequencing

7.2.1 GMF/OC HI Column Sequencing Formulation and Results

7.2.2 GMF/OCFE HI Column Sequencing Formulation and Results

7.3 Enhanced GMF for the Complex Distillation Column Sequencing

7.3.1 GMF/OC Complex Column Sequencing Formulation and Results

7.3.2 GMF/OCFE Complex Column Sequencing Formulation and Results

8 Other Process Synthesis Applications

8.1 Acetone recovery system

8.2 Ethylbenzene production

8.3 Ethylene glycol production

8.4 Synthesis of heat exchanger networks with mixed streams and variable heat capacities

A The Generalized Modular Framework

A.1 GMF Representation of Units

A.2 Phase Defining Constraints

A.3 Driving Force Constraints

A.4 Simple Distillation Column Statistics - Trayed Model

A.5 Simple Distillation Column Statistics - GMF Model

B GMF Representation of Ternary Complex Column Sequences

B.1 Rearranged GMF Ternary Complex Column Sequences

B.2 STN Representation of GMF Complex Column Sequences

C Enhanced GMF Physical Model

C.1 GMF/OC Distillation Column Degrees Of Freedom

C.2 GMF/OCFE Distillation Column Degrees Of Freedom

D Mass/Heat Exchange Hyperstructure Model for Acetone Recovery Example