Introduction to chemical engineering PDF

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This page intentionally left blank Introduction to Chemical Engineering Tools for Today and Tomorrow This page intentionally left blank Introduction to Chemical Engineering Tools for Today and Tomorrow 5th Edition Kenneth A. Solen Brigham Young University John N. Harb Brigham Young University John ...

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Introduction to Chemical Engineering Tools for Today and Tomorrow

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Introduction to Chemical Engineering Tools for Today and Tomorrow 5th Edition

Kenneth A. Solen Brigham Young University John N. Harb Brigham Young University

John Wiley & Sons, Inc.

ACQUISITIONS EDITOR MARKETING MANAGER EDITORIAL ASSISTANT SENIOR DESIGNER EXECUTIVE MEDIA EDITOR PRODUCTION MANAGER PRODUCTION EDITOR

Jennifer Welter Christopher Ruel Alexandra Spicehandler Kevin Murphy Thomas Kulesa Micheline Frederick Amy Weintraub

Cover Art: Courtesy of Terri Bateman and Mark A. Philbrick/BYU

This book was printed and bound by Hamilton Printing Company. The cover was printed by Hamilton Printing Company. This book is printed on acid free paper. ∞ Copyright © 2011 John Wiley & Sons, Inc. All rights reserved. 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 Sections 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, website 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 07030-5774, (201)748-6011, fax (201)748-6008, website http://www.wiley.com/go/permissions. “Evaluation copies are provided to qualified academics and professionals for review purposes only, for use in their courses during the next academic year. These copies are licensed and may not be sold or transferred to a third party. Upon completion of the review period, please return the evaluation copy to Wiley. Return instructions and a free of charge return shipping label are available at www.wiley.com/go/returnlabel. Outside of the United States, please contact your local representative.”

Library of Congress Cataloging in Publication Data: ISBN-13 978-0-470-88572-7

Printed in the United States of America 10 9 8 7 6 5 4 3 2 1

About the Authors

Kenneth A. Solen is the Jesse Knight Professor and past Department Chair of Chemical Engineering at Brigham Young University. He received his B.S. in chemical engineering (1968) from the University of California, Berkeley and worked for the Mobil Oil Company, Union Oil Company, and Shell Oil Company in brief internships. He then earned his M.S. in physiology (1972) and Ph.D. in chemical engineering (1974) from the University of Wisconsin, Madison. He was a research fellow at the University of Iowa Medical School and the University of Oregon Health Sciences Center before joining the faculty at Brigham Young University in 1976. He has taught a variety of undergraduate and graduate courses and has received the Chemical Engineering Department Outstanding Teaching Award 15 times, the Ira A. Fulton College of Engineering and Technology Outstanding Teaching Award, and the Brigham Young University Karl G. Maeser Excellence in Teaching Award. His interest in undergraduate education motivated his efforts in the creation of this book and the associated first-year course in chemical engineering. His research interests include artificial organs and blood-biomaterial interactions. John N. Harb is Professor of Chemical Engineering and Associate Dean of the Ira A. Fulton College of Engineering and Technology at Brigham Young University. He received his B.S. in chemical engineering (1983) from Brigham Young University, Provo and his M.S. (1986) and Ph.D. (1988) in chemical engineering at the University of Illinois, Urbana. Professor Harb has been actively involved in engineering education and has developed and delivered workshops for engineering educators as a representative of the Educational Research Methods Division of ASEE. He has coauthored a monograph on teaching (Teaching Through the Cycle), in addition to the present textbook. He has received several teaching awards, including awards for teaching first-year students. He conducts research in electrochemical engineering, which includes a wide range of topics of technological importance that are governed by electrochemical phenomena. Of particular interest are energy storage devices (e.g., batteries), micro- and nano-fabricated electrochemical devices and structures, and the fundamental processes that govern electrodeposition and dissolution. Brigham Young University (BYU), with its main campus in Provo, Utah, is a private university sponsored by the Church of Jesus Christ of Latter-day Saints. Although BYU grants M.S. and Ph.D. degrees and supports graduate scholarly research, its principal focus is on undergraduate education.

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To our wives, Linda and Ruth, for their love and support.

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Preface

To the Student Chemical engineers are making a difference in our world, and this book was written to introduce you to this exciting field. You will learn that chemical engineering is a broad and versatile discipline, that it is involved in producing the vast array of products in our everyday life, and that it plays a vital role in addressing the “Grand Challenges” of today and tomorrow, such as providing clean water, clean and sustainable energy, and improved medical care. As part of your introduction to chemical engineering, you will be led step by step through a chemical engineering project that illustrates important aspects of the discipline and how they are connected. At each step, you will be presented with a new aspect of chemical engineering and have the opportunity to use what you have learned to solve engineering problems and make engineering decisions. You will also read about the application of chemical engineering to issues such as providing humanitarian service, improving medical technology, and protecting our environment. This book is intended to help you as you decide on a career and contemplate the impact that you will make on the world. It is our hope that you will learn much, and that you will enjoy the experience. To the Instructor This book was written to address a number of needs of freshman students, including (among others) their need (1) for information to assist them in deciding whether to major in chemical engineering and (2) for help (for those who choose this major) in recognizing in later courses the connections between advanced topics and relationships to the whole discipline. INTENDED AUDIENCE This text is designed for an introductory course for first-year college students interested in chemical engineering, a course that would precede the traditional mass-andenergy-balance course taught early in the program (e.g., the sophomore year). Portions of this text may also be useful for the chemical engineering component of a broader freshmanlevel course examining multiple engineering fields. OBJECTIVE AND SCOPE This book is intended to help first-year college students experience chemical engineering to the fullest extent possible within the constraints of limited time and limited student background. Thus, it provides a broad, shallow sweep through the entire discipline and teaches freshmen how to solve engineering problems, including quantitative problems. Topics, carefully tailored to a level appropriate for beginning students, include material balances (steady reacting and non-reacting single systems), fluid flow (mechanical engineering equation only, including the sizing of pumps), mass transfer (diffusion and convection), chemical reactor design, heat transfer (including heat exchanger design), materials, and engineering economics. A number of qualitative treatments are also presented on topics such as problem solving, teamwork, and ethics, with appropriate homework assignments. Process control, a more advanced topic, is also introduced qualitatively.

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APPROACH AND ORGANIZATION The book leads the students from start to finish through a small design problem of a simple chemical process. In the first chapter, the student is asked to adopt the role of a chemical engineer on the job, and the design problem is introduced in the form of a memo from the student’s supervisor. Chemical engineering is defined, and its critical role in addressing the “Grand Challenges” of today and tomorrow is discussed. The second chapter introduces the concept and basic elements of chemical processes and their representation using process flow diagrams. Throughout the remainder of the book, the students are led step by step through the design problem from initial problem definition to economic evaluation. At each step along the way, the concepts, principles, and equations necessary to accomplish the task at hand are introduced, an additional feature of the design is completed, and the process flow diagram is expanded to include that new feature. Thus, the student can see how the various aspects of chemical engineering integrate together to comprise an entire chemical process. DESIGN PROBLEMS Besides the design problem that forms the central storyline throughout the book, two additional design problems in Chapter 14 serve as possible case studies. These team-based design problems, used by the authors for a number years, require the use of, and reinforce, the skills taught throughout the semester. Recently, we have also explored the use of “hands-on” projects that have been well-received by students (see the Instructor’s Manual). OUTCOMES AND BENEFITS The overview of chemical engineering presented in this text helps students to form a conceptual “skeleton” of the discipline. This overview helps students to make an informed decision regarding chemical engineering as a career choice. Also, students who continue with the major are provided with an overall view of the discipline that has traditionally been lacking. They can now recognize how their subsequent courses fit into the “big picture.” Their connection with their chemistry and physics courses is also enhanced as they recognize applications for those principles in their engineering field. Thus, this introductory course leads to a richer experience in later classes by providing both perspective and background – i.e., the “’skeleton” – around which technical depth or “meat” is organized and filled in during the study of advanced topics. Finally, this text enables students to begin their educational program with an integrated experience and then end in similar manner in their senior design course. NEW TO THIS EDITION This edition has an increased focus on contemporary applications of chemical engineering (humanitarian, biomedical, energy, etc.), as reflected by the new title (the title of previous editions was “Introduction to Chemical Process Fundamentals and Design”). • NAE’s “Grand Challenges”: The recommendations of the National Academy of Engineering have been added, along with brief statements about the leadership role of chemical engineering in addressing many of those challenges. • Contemporary Applications: Discussions have been added to the end of most chapters providing examples of how topics in the chapter are applied to current problems of society to help motivate student study of the topics. • Ethics: The AIChE Code of Ethics has been added, along with discussion and examples (including a homework exercise) illustrating its application.

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• Homework Problems: Additional homework problems have been added to support the new content and illustrate important applications. • Refinements: Corrections, clarifications, and improvements have been added as guided by our own experience and by feedback from students and colleagues. This included format changes that help students identify and locate key content. HALLMARK FEATURES Relevance: The text helps students recognize how what they are learning in their engineering, chemistry, and physics courses applies to professional practice and how chemical engineering will play a critical role in solving important global challenges. Problem-Solving: The content helps beginning students develop problem-solving skills, including the ability to solve quantitative problems appropriate for students at their level. Introduction to Design: Following the central storyline throughout the book, students are led step by step through a chemical engineering project, and perform a variety of design calculations as a basis for defining a new chemical process. Assessment, Practice, and Self-Study Resources: The text includes a variety of resources to help students learn the concepts and skills presented. • Reading Questions help students think about what they’ve read. • Homework Problems help students practice the skills that they’ve learned. Most problems are quantitative, but a number of problems require the students to reflect upon and write about what they’ve learned. • Case Studies give students the opportunity to apply what they’ve learned in a number of areas to the solution of a design problem. Spreadsheets: Students are introduced to spreadsheets, and homework problems throughout the book give the students practice with this tool. Engineering Teamwork, Ethics, and Creative Problem-Solving: These topics begin building the student’s ability to guide teams of peers to creative and ethical solutions. Introduction and Integration of Chemical Engineering Topics: The text provides an integrated, holistic view of chemical engineering. WEBSITE The Web site for this book, located at www.wiley.com/college/solen, includes the following helpful materials for instructors: Sample Syllabus with suggested course coverage and organization. Lecture Slides prepared by the authors for in-class use. Image Gallery with figures from the text, for making lecture slides or transparencies. Solutions Manual, including solutions to all problems in the book. Hands-on projects to complement the textbook material. Instructors who have adopted this book for their course may visit the Instructor portion of the Web site at www.wiley.com/college/solen to register for a password. ACKNOWLEDGMENTS Credit for this book goes to the students who inspired its conception and tested its effectiveness. In addition, a panel of insightful freshman students provided especially helpful feedback in the preparation of this new edition. Appreciation is also expressed for feedback from colleagues who used the book in their own classes. Finally, the authors will be grateful for further suggestions as development of the book continues.

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Contents

CHAPTER 1

WHAT IS CHEMICAL ENGINEERING? 1.1 Scenario: An Assignment 1 1.2 What is Chemical Engineering? 2 1.3 The Impact of Chemical Engineering 1.4 The Chemical Engineering Discipline Reading Questions 12 Homework Problems 12

CHAPTER 2

3 9

THE ROLE OF CHEMICAL PROCESSING 2.1 What is a Chemical Process? 13 2.2 Representing Chemical Processes Using Process Diagrams Reading Questions 25 Homework Problems 25

CHAPTER 3

1

SOLVING ENGINEERING PROBLEMS

13 16

29

3.1 Strategies for Solving Problems 29 3.2 Ethical Considerations in Solving Problems 33 3.3 The Use of Teams in Solving Problems 35 Reading Questions 40 Homework Problems 41

CHAPTER 4

DESCRIBING PHYSICAL QUANTITIES 4.1 Units 43 4.2 Some Important Process Variables Reading Questions 57 Homework Problems 58

CHAPTER 5

50

MATERIAL BALANCES

61

5.1 Conservation of Total Mass 61 5.2 Material Balances for Multiple Species 5.3 Material Balances: Summary 77 Reading Questions 79 Homework Problems 80

CHAPTER 6

SPREADSHEETS 6.1 The Calculation Scheme 6.2 Setting Up a Spreadsheet 6.3 Graphing 95

43

67

85 85 88

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Contents

Reading Questions Homework Problems

CHAPTER 7

98 99

FLUID FLOW

101

7.1 What is a Fluid? 101 7.2 The Concept of Pressure 101 7.3 Non-flowing Fluids 103 7.4 Principles of Fluid Flow 106 7.5 Pumps and Turbines 115 Reading Questions 121 Homework Problems 121

CHAPTER 8

MASS TRANSFER

125

8.1 Molecular Diffusion 125 8.2 Mass Convection 127 8.3 Mass Convection with Transfer Across Phase Boundaries 8.4 Multi-step Mass Transfer 131 Reading Questions 139 Homework Problems 139

CHAPTER 9

REACTION ENGINEERING

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9.1 Describing Reaction Rates 141 9.2 Designing the Reactor 146 Reading Questions 154 Homework Problems 155

CHAPTER 10

HEAT TRANSFER

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10.1 Energy Balances for Steady-State Open Systems 10.2 Applications of the Steady-State Energy Balance 10.3 Heat-Exchange Devices 173 Reading Questions 185 Homework Problems 186

CHAPTER 11

MATERIALS 11.1 Metals and Corrosion 11.2 Ceramics 192 11.3 Polymers 193 11.4 Composites 195 11.5 Strength of Materials Reading Questions 198 Homework Problems 199

CHAPTER 12

189 189

196

CONTROLLING THE PROCESS 12.1 12.2 12.3 12.4

157 164

The Need for Process Control 201 Feedback Control 203 Feedforward Control 205 Comparison of Strategies 206

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Contents

Reading Questions Homework Problems

CHAPTER 13

208 208

ECONOMICS 13.1 Costs 209 13.2 Profitability 211 13.3 Economics of the Acid-Neutralization Problem 13.4 Reporting the Results 214 Reading Questions 216 Homework Problems 216

CHAPTER 14

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CASE STUDIES 14.1 Using Engineering Teams for These Case Studies 14.2 Case Study 1: Manufacture of Aspirin 218 14.3 Case Study 2: Manufacture of Xylenes 221

INDEX

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217 217

225

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Symbols cA Cp DAB E Eˆ Ea Em Fweight g hm h H Hˆ k kr ko m mA m˙ m˙ A MWA n nA n˙ n˙A N˙ A N˙ A,x P Q˙ Q˙ conv Q˙ cond,x rcons,A r f orm,A rreact,A R Rcons,A R f orm,A T U Uˆ Uo v V Vˆ V˙ wf ws W˙ W˙ s

molar concentration of Species A heat capacity binary diffusivity of Species A in Species B energy specific energy activation energy of reaction modulus of elasticity weight gravitational acceleration mass-transfer coefficient heat-transfer coefficient enthalpy specific enthalpy thermal conductivity reaction rate constant frequency factor mass mass of Species A mass flow rate mass flow rate of Species A molecular weight of Species A moles moles of Species A molar flow rate molar flow rate of Species A molar transfer rate of Species A molar transfer rate of Species A in x direction pressure rate of heat transfer rate of convection heat transfer rate of conduction heat transfer in x direction molar rate of consumption of Species A molar rate of formation of Species A rate of reaction of Species A universal gas constant mass rate of consumption of Species A mass rate of formation of Species A temperature internal energy specific internal energy overall heat-transfer coefficient velocity volume specific volume volumetric flow rate work of friction per mass of fluid shaft work on a fluid per mass of fluid rate of work on a fluid rate of shaft work on a fluid

Dimensions

Sample Units

moles/volume energy/(mass·temperature) length2 /time energy energy/mass energy force/area force length/time2 length/time energy/(time·area·temperature) energy energy/mass energy/(length·temperature) variable variable (same as for kr ) mass mass mass/time mass/time mass/mole moles moles moles/time mole...