TEACH YOURSELF THE BASICS OF ASPEN PLUS

TEACH YOURSELF THE BASICS OF ASPEN PLUS

TEACH YOURSELF THE BASICS OF ASPEN PLUS RALPH SCHEFFLAN Chemical Engineering and Materials Science Department Stevens Institute of Technology A JOHN WILEY & SONS, INC., PUBLICATION

Copyright 2011 by John Wiley & Sons, Inc. All rights reserved. A joint publication of the American Institute of Chemical Engineers and John Wiley & Sons, Inc. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400, fax 978-750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, 201-748-6011, fax 201-748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at 877-762-2974, outside the United States at 317-572-3993 or fax 317-572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: Schefflan, Ralph. Teach yourself the basics of Aspen Plus / Ralph Schefflan. p. cm. Includes bibliographical references and index. ISBN 978-0-470-56795-1 (pbk.) 1. Chemical-process Computer simulation. 2. Chemical process control Computer programs. 3. Aspen Plus. I. Title. TP155.7.S28 2010 660.280113 dc22 2010019514 Printed in the United States of America obook ISBN: 978-0-470-91006-1 epdf ISBN: 978-0-470-91004-7 epub ISBN: 978-0-470-92285-9 10987654321

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CONTENTS PREFACE xiii 1 INTRODUCTION TO ASPEN PLUS 1 1.1 Starting Aspen Plus / 2 1.2 Graphic Users Interface / 3 1.3 Next Button / 4 1.4 Setup Specifications Display / 5 1.5 Simulation Options / 6 1.6 Units / 6 1.7 Components / 8 1.8 Properties / 10 1.9 Streams / 12 1.10 Blocks / 14 1.11 Viewing Results / 14 1.12 Object Manager / 16 1.13 Plotting Results / 17 References / 19 2 PROPERTIES 21 2.1 Pure Component Data Banks / 21 2.2 Property Analysis / 24 2.3 Property Estimation / 25 vii

viii CONTENTS 2.4 Workshops / 34 References / 35 3 THE SIMPLE BLOCKS 37 3.1 Mixer/Splitter Blocks / 37 3.1.1 Mixer Block / 37 3.1.2 Fsplit Block / 38 3.2 Simple Separator Blocks / 39 3.2.1 Sep Block / 40 3.2.2 Sep2 Block / 41 3.3 Some Manipulator Blocks / 42 3.3.1 Dupl Block / 42 3.3.2 Mult Block / 44 3.4 Workshops / 45 4 PROCESSES WITH RECYCLE 49 4.1 Blocks with Recycle / 50 4.2 Heuristics / 53 4.3 Workshops / 54 References / 58 5 FLOWSHEETING AND MODEL ANALYSIS TOOLS 59 5.1 Introduction to Fortran in Aspen Plus / 59 5.2 Basic Interpreted Fortran Capabilities / 60 5.2.1 Primary Fortran Operators / 61 5.2.2 Precedence of Calculations / 61 5.2.3 Statement Format / 62 5.2.4 Program Logic Control / 62 5.3 Sensitivity Function / 63 5.4 Design Specification / 65 5.5 Calculator Function / 67 5.6 Transfer Function / 69 5.7 Workshops / 71 References / 72 6 THE DATA REGRESSION SYSTEM 73 6.1 Parameters of Equations of State / 74 6.2 Parameters of Activity Coefficient Equations / 76 6.3 Basic Ideas of Regression / 77 6.4 Mathematics of Regression / 80

CONTENTS ix 6.4.1 Newton Raphson Method for Solution of Nonlinear Equations / 80 6.4.2 Direct Optimization of an Objective Function / 81 6.5 Practical Aspects of Regression of VLE or LLE Data / 82 6.5.1 Regression of VLE Data / 82 6.5.2 Regression of LLE Data / 85 6.6 Workshops / 87 References / 90 7 FLASHES AND DECANTER 93 7.1 Flash2 Block / 93 7.2 Flash3 Block / 96 7.3 Decanter Block / 99 7.4 Workshops / 101 References / 103 8 PRESSURE CHANGERS 105 8.1 Pump Block / 105 8.2 Compr Block / 105 8.3 MCompr Block / 107 8.4 Pipelines and Fittings / 107 8.5 Workshops / 109 Reference / 110 9 HEAT EXCHANGERS 111 9.1 Heater Block / 112 9.2 Heatx Block / 115 9.3 Mheatx Block / 118 9.4 Workshops / 118 References / 121 10 REACTORS 123 10.1 RStoic Block / 123 10.2 RYield Block / 125 10.3 REquil Block / 126 10.4 RGibbs Block / 128 10.5 Reactions for the Rigorous Models / 129 10.5.1 Equilibrium Class / 130 10.5.2 Powerlaw Class / 130 10.5.3 Langmuir Hinshelwood Hougen Watson Class / 133

x CONTENTS 10.5.4 Generalized Langmuir Hinshelwood Hougen Watson Class / 134 10.6 RCSTR Block / 134 10.7 RPlug Block / 135 10.8 RBatch Block / 138 10.9 Workshops / 139 References / 144 11 MULTISTAGE EQUILIBRIUM SEPARATORS 145 11.1 Basic Equations / 145 11.2 The Design Problem / 148 11.3 A Three-Product Distillation Example / 150 11.4 Preliminary Design and Rating Models / 154 11.4.1 DSTWU / 154 11.4.2 Distl / 156 11.5 Rigorous Models / 157 11.5.1 RadFrac / 158 11.5.2 Extract / 164 11.6 BatchSep / 167 11.7 Workshops / 170 References / 173 12 PROCESS FLOWSHEET DEVELOPMENT 175 12.1 Heuristics / 175 12.2 Example: The Production of Styrene / 176 12.3 A Model with Basic Blocks / 177 12.4 Properties / 177 12.5 Rigorous Flash and Decanter / 178 12.6 Analyzing the Rigorous Distillation / 181 12.7 Integrating the Rigorous Distillation Into the Flowsheet / 181 12.7.1 Selection of a Tear Stream / 183 12.7.2 Sequence of Calculations / 183 12.8 Reactor Feed / 183 12.9 Miscellaneous Considerations / 185 12.10 Workshops / 185 Reference / 189 13 OPTIMIZATION 191 13.1 Optimization Example / 192 13.2 Workshops / 195 References / 198

CONTENTS xi 14 COMPLEX EQUILIBRIUM STAGE SEPARATIONS 199 14.1 Energy Integration Applications / 199 14.2 Homogeneous Azeotropic Distillation / 202 14.3 Extractive Distillation / 203 14.4 Heterogeneous Operations / 205 14.5 Workshops / 207 References / 211 INDEX 213

PREFACE During my years working as a chemical engineer in development laboratories, process engineering groups, and plant startup and support operations, the most frequently referenced documents were process flow diagrams (PFDs), which contain the material and energy balances and the basic process design information. Equally important were process and instrument diagrams (P&IDs), which contain details of all equipment, all controls, all instruments, and all lines (i.e., process, instrument, and utilities). Process simulation software is an excellent tool for producing high-quality PFDs, and when integrated with computer-aided design software, facilitates the production of P&IDs. There are several process simulation software systems available to the chemical engineering community, and Aspen Plus is arguably the most popular. Teach Yourself the Basics of Aspen Plus evolved from two graduate courses that I taught at Stevens Institute of Technology over the past 20-odd years. The first course, ChE662, is an introduction to steady-state chemical process simulation, which is usually taken by graduate students and is organized around a series of workshops that introduce Aspen Plus functionality. Occasionally, undergraduates are enrolled and typically experience difficulties in the thermodynamics of phase equilibrium and parameter estimation, due to limitations in their undergraduate courses. The second course, ChE612, deals with the analysis and design of complex equilibrium stage processes and with difficult multicolumn problems such as, extractive distillation systems. Over time, the course evolved from the use of stand-alone two- and three-phase flashes, decantation, and two-phase distillation software, to their equivalent blocks in Flowtran and later, Aspen Plus. The idea for this book originated from my observations of students in these courses. I noted that after an initial period dedicated to learning the basics of how to navigate, locate material, and enter data into Aspen Plus, students could proceed through the exercises, within the workshops, mostly on their own. I would give an introductory lecture for each subject studied, show examples, and provide individual help on the xiii