Computer Aided Process Design and Simulation

163 Pages·2017·1.02 MB·English

Computer Aided Process Design and
Simulation
Supplimentary Course material,
to be read along with prescribed text books
Dr. B. Nedumaran
Associate Professor in Chemical Engineering
Adama Science and Technology University, Ethiopia
October– 2017
2
© www.yamunacoachingcentre.in
Computer Aided Process Design and Simulation
Supplimentary Course material,to be read along with prescribed text books
Dr. B. Nedumaran
Associate Professor in Chemical Engineering
| $ e
March 2, 2018
Typeset with LATEX
3
Preface
With the advancement of in the field of electronics, communication, information
technology and computer science and engineering, it is really impossible to make
any engineering system without computational facility and decision support sys-
tems.
This book is intended for the course on Computer Aided Process Design and
SimulationaimedatintroducingsoftwareknowledgeonMATLAB,ASPEN-HYSYS,
ChemCAD for solving complex mathematical models developed for any real life
process system.
The book is organised in six chapters and an Apendix with chapter 1 introduc-
tion of computer Aided Process Engineering followed by numerical methods and
process modeling in second and third chapters. The fourth chapter deels with
presentation of various software available for the engineers to simulate the entire
system and the fifth chapter devoted for simulation laboratory exersices using
MATLAB solving linear, non-linear system of ordinary, differential and partial
differential equations and student exercises. Chapter 6, suggests the topics for
a group project with the application of programing skill using simulation soft-
ware as well as developing their own routines using programming languages and
MATLAB solvers. This will provide an opportunity to the students to select their
system and can simulate any kind of process plant including petroleum and
petrochemical sytems.
At the end (not so exhaustive) list of commonly used MATLAB commands are
provided as apendix will definitely help the reader as a ready reference.
Dr. B. Nedumaran
March 2, 2018
4
Contents
1 CAPE- An Introduction 9
2 Numerical methods 11
2.1 Single, first order ordinary differential equation (ODE) . . . . . . . . . 11
2.1.1 Euler Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2 Runge-Kutta Methods . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.3 Implicit Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 System of coupled first order ODE’s . . . . . . . . . . . . . . . . . . . . 15
2.2.1 Explicit Euler Method . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Higher Order Differential equations . . . . . . . . . . . . . . . . . . . . 18
2.4 Partial differential equations, PDE . . . . . . . . . . . . . . . . . . . . . 19
3 Process Modeling 23
3.1 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2 Types of Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.1 Fundamental Models . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.2 Empirical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.3 Steady State Model . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.4 Unsteady State or Dynamic Model . . . . . . . . . . . . . . . . . 24
5
6 CONTENTS
3.2.5 Lumped Parameter Model . . . . . . . . . . . . . . . . . . . . . . 25
3.2.6 Distributed Parameter Model . . . . . . . . . . . . . . . . . . . . 25
3.2.7 Dimensionless Model . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.8 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.9 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3 Uses of Mathematical Models . . . . . . . . . . . . . . . . . . . . . . . 26
3.4 Scope of Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.4.1 Principles of Formulation . . . . . . . . . . . . . . . . . . . . . 27
3.5 Fundamental Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.5.1 Continuity Equations . . . . . . . . . . . . . . . . . . . . . . . . 29
3.6 Perfectly Mixed Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.7 Flow through pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.7.1 Component Continuity Equations . . . . . . . . . . . . . . . . . 32
3.8 CSTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.9 PFR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.10 Energy Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.11CSTR with heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.12Models and Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4 Process Simulation 101
4.1 Simulation Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.1.1 Programing Languages and Simulation Software . . . . . . . . 101
4.1.2 Simulation–Definition . . . . . . . . . . . . . . . . . . . . . . . . 107
4.1.3 Need for Simulation software . . . . . . . . . . . . . . . . . . . . 107
4.2 Aspen-HYSYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
4.3 ChemCAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
CONTENTS 7
4.4 ProSim-II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.5 ChemSep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5 LABORATORY PRACTICE with MATLAB 111
5.1 Student Exercise – 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
5.2 Student Exercise – 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.3 Student Exercise – 3: Equation of State . . . . . . . . . . . . . . . . . 117
5.3.1 Van der Waal’s EOS . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.3.2 Redlich Kwong EOS . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.3.3 Soave Redlich Kwong EOS . . . . . . . . . . . . . . . . . . . . . 118
5.3.4 Peng Robinson EOS . . . . . . . . . . . . . . . . . . . . . . . . . 118
5.3.5 Peng Robinson Gasem EOS . . . . . . . . . . . . . . . . . . . . . 119
5.3.6 Beattie-Bridgeman EOS . . . . . . . . . . . . . . . . . . . . . . . 120
5.3.7 Benedict-Webb-Rubin EOS . . . . . . . . . . . . . . . . . . . . . 122
5.4 Student Exercise – 4: Differential Equations . . . . . . . . . . . . . . . 124
5.4.1 Solving First Order Differential Equations . . . . . . . . . . . . 124
5.4.2 Solving Second and Higher Order Differential Equations . . . . 125
5.4.3 Solving System of Differental Equations . . . . . . . . . . . . . 126
5.5 Student Exercise – 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
6 Projects 143
MATLAB COMMANDS 149
8 CONTENTS
Chapter 1
CAPE- An Introduction
With advancement in computational facilities and chemical process industries
tend to adapt more quantitative approch to problems in the design and operation
of real processes. Design of process plant involves Process synthesis with:
• Reaction Path Selection
• Material Balancing
• Species allocation
• Separation task selection and sequencing
• Auxiliary task assignment and process integration
• Evolutionary improvement of initial flowsheet
• Material and Energy Balances
• Equipment Sizing and Costing
• Economic evaluation
Mathematical models consists of set of linear, nonlinear, ordinary differential
and partial differential equations representing steady state and dynamic system
of real life plant. Obtaining solution for these equations with application of nu-
merical methods and manual calculation is a tedious process. With the help of
9
10 CHAPTER 1. CAPE- AN INTRODUCTION
computers and advanced process engineering software it is possible to integrate
to get the physico chemical properties, thermodynamic models and computer
aided solvers and simulate the plant condition easily before implementing the
actual process plant.
Computer aided design does not replace the process engineer completely, but
provide an opportunity to continuously improve the model and development of
new processes with reduced energy consumotion, higher yield and quality of the
product. Figure 1.1 indicate the integration of various stages to make a com-
prehencive Computer Aided Process Engineering approach.
The course objective is to provide the student with a clear understanding of
what is process design, simulation & process optimization and how these can
be employed to solve practical problems commonly encountered in process en-
gineering. Use of computer aided tools will play an important role. Students
are encouraged to use softwares such as MATLAB, ASPEN for solving their own
model equations and simulating their ideas in process systems.
Figure 1.1: Structure of CAD Model