Principles of Chemical Engineering Practice E-Book

George DeLancey

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 792

Veröffentlichungsjahr: 2013

Beschreibung

Enables chemical engineering students to bridge theory and practice

Integrating scientific principles with practical engineering experience, this text enables readers to master the fundamentals of chemical processing and apply their knowledge of such topics as material and energy balances, transport phenomena, reactor design, and separations across a broad range of chemical industries. The author skillfully guides readers step by step through the execution of both chemical process analysis and equipment design.

Principles of Chemical Engineering Practice is divided into two sections: the Macroscopic View and the Microscopic View. The Macroscopic View examines equipment design and behavior from the vantage point of inlet and outlet conditions. The Microscopic View is focused on the equipment interior resulting from conditions prevailing at the equipment boundaries. As readers progress through the text, they'll learn to master such chemical engineering operations and equipment as:

• Separators to divide a mixture into parts with desirable concentrations
• Reactors to produce chemicals with needed properties
• Pressure changers to create favorable equilibrium and rate conditions
• Temperature changers and heat exchangers to regulate and change the temperature of process streams

Throughout the book, the author sets forth examples that refer to a detailed simulation of a process for the manufacture of acrylic acid that provides a unifying thread for equipment sizing in context. The manufacture of hexyl glucoside provides a thread for process design and synthesis.

Presenting basic thermodynamics, Principles of Chemical Engineering Practice enables students in chemical engineering and related disciplines to master and apply the fundamentals and to proceed to more advanced studies in chemical engineering.

Leseprobe

Contents

Cover

Title Page

Copyright

Dedication

Preface

Content

Organization

Calculations

Part I: Macroscopic View

Chapter 1: Chemical Process Perspective

1.1 Some Basic Concepts in Chemical Processing

1.2 Acrylic Acid Production

1.3 Biocatalytic Processes—Enzymatic Systems

1.4 Basic Database

Problems

Chapter 2: Macroscopic Mass Balances

2.1 Chemical Processing Systems

2.2 Steady-State Mass Balances without Chemical Reactions

2.3 Steady-State Mass Balances with Single Chemical Reactions

2.4 Steady-State Mass Balances with Multiple Chemical Reactions

Problems

Chapter 3: Macroscopic Energy and Entropy Balances

3.1 Basic Thermodynamic Functions

3.1.1.1 Gibbs–Duhem Equation

3.2 Evaluation of H and S for Pure Materials

3.3 Evaluation of H and S Functions for Mixtures

3.4 Energy Flows and the First Law

3.5 Energy Balances Without Reaction

3.6 Energy Balances With Reaction-Ideal Solution

3.7 Entropy Balances

3.7.4 Process Efficiency

Problems

Chapter 4: Macroscopic Momentum and Mechanical Energy Balances

4.1 Momentum Balance

4.2 Mechanical Energy Balance

4.3 Applications to Incompressible Flow Systems

Problems

Chapter 5: Completely Mixed Systems—Equipment Considerations

5.1 Mixing and Residence Time Distributions—Definitions

5.2 Measurement and Interpretation of Residence Time Distributions

5.3 Basic Aspects of Stirred Tank Design

Problems

Chapter 6: Separation and Reaction Processes in Completely Mixed Systems

6.1 Phase Equilibrium: Single-Stage Separation Operations

6.2 Gas–Liquid Operations

6.3 Flash Vaporization

6.4 Liquid–Liquid Extraction

6.5 Adsorption

6.6 Single-Phase Stirred Tank Reactors

6.7 Chemical Reaction Equilibrium

Problems

Part II: Microscopic View

Chapter 7: Multistage Separation and Reactor Operations

7.1 Absorption and Stripping

7.2 Distillation

7.3 Liquid–Liquid Extraction

7.4 Multiple Reactor Stages

7.5 Staged Fixed-Bed Converters for Exothermic Gas Phase Reaction

Problems

Chapter 8: Microscopic Equations of Change

8.1 Mass Flux: Average Velocities and Diffusion

8.2 Momentum Flux: Stress Tensor

8.3 Energy Flux: Conduction

8.4 Balance Equations

8.5 Entropy Balance and Flux Expressions

8.6 Turbulence

8.7 Application of Balance Equations

Problems

Chapter 9: Nonturbulent Isothermal Momentum Transfer

9.1 Rectangular Models

9.2 Cylindrical Systems

9.3 Spherical Systems

9.4 Microfluidics—Gas Phase Systems

Problems

Chapter 10: Nonturbulent Isothermal Mass Transfer

10.1 Membranes

10.2 Diffusion Models for Porous Solids

10.3 Heterogeneous Catalysis

10.4 Transient Adsorption by Porous Solid

10.5 Diffusion with Laminar Flow

Problems

Chapter 11: Energy Transfer Under Nonturbulent Conditions

11.1 Conduction in Solids–Composite Walls

11.2 Thermal Effects in Porous Catalysts

11.3 Heat Transfer to Falling Film—Short Contact Times

11.4 Moving Boundary Problem

Problems

Chapter 12: Isothermal Mass Transfer Under Turbulent Conditions

12.1 Intraphase Mass.Transfer Coefficients

12.2 Interphase Mass Transfer Coefficients—Controlling Resistances

12.3 Measurement and Correlation of Mass Transfer Coefficients

12.4 Fixed Beds

12.5 Pipes

12.6 Particles, Drops, and Bubbles in Agitated Systems

12.7 Packed Towers—Gas Absorption

12.8 Applification of Experimental Mass Transfer Coefficients

Problems

Chapter 13: Interphase Momentum Transfer Under Turbulent Conditions

13.1 Pressure Drop in Conduits and Fixed Beds

13.2 Flow Over Submerged Spheres

Problems

Chapter 14: Interphase Energy Transfer Under Turbulent Conditions

14.1 Heat Transfer Coefficients—Analogy with Mass Transfer

14.2 Heat Exchangers

14.3 Multi-Tubular Catalytic Reactors

Problems

Chapter 15: Microscopic to Macroscopic

15.1 Macroscopic Mass Balance

15.2 Macroscopic Energy Balance

15.3 Macroscopic Mechanical Energy Balance

Problems

Appendix A: Periodic Table

Appendix B: Conversion Factors

Appendix C: Partial Database for Acrylic Acid Process

Appendix D: Some Mathematical Results

D.1 Divergence Theorem (GAUSS)

D.2 Coordinate Systems

D.3 Unit Vectors and Distance Metrics

D.4 Components of Rectangular Unit Vectors

D.5 Derivatives of Unit Vectors

Appendix E: Mass Balance in Cylindrical Coordinates and Laminar Flow in Z Direction

Nomenclature

Greek symbols

Superscripts

Subscripts

Overstrike

Underscore

Other

Vector

Tensors

References

Index

Cover image reprinted with permission of BASF: The Chemical Company. All rights reserved. Graph image reprinted with permission of Elsevier, Kovenklioglu and DeLancey, 1979.

Copyright © 2013 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

DeLancey, George, 1940-

Principles of chemical engineering practice / George DeLancey.

pages cm

Includes index.

ISBN 978-0-470-53674-2 (hardback)

1. Chemical engineering. I. Title.

TP155.D425 2012

660–dc23

2012047056

This book is dedicated to my darling wife, Lynn, who nurtured every page and every moment with her generosity, encouragement, and unfaltering support.

Preface

This book is about the application of scientific principles and engineering experience to chemical processing. Major chemical engineering operations are organized under the principles of analysis in order to facilitate the consideration of new technologies from a chemical engineering point of view.

New applications have emerged in chemical engineering practice. Microchemical systems, for example, require attention to design parameters not important at larger scales. The shift from commodity chemicals to chemical products by many smaller companies is creating a demand for chemical engineers with a broader view of design than the traditional capstone design experience (Cussler and Moggridge, 2001). Biocatalysis and the chiral technology industry call for the support of undergraduate curricula. Opportunities for the chemical engineering graduate in the development of medical devices and drug manufacture call for more emphasis on the life sciences and physiology.

There is therefore a call to introduce a degree of flexibility into traditional undergraduate chemical engineering curricula for those who wish to serve a broader industrial base. An alternative is to concentrate the basic chemical engineering training in a minimal core designed to secure the distinguishing technical character of the chemical engineer and to provide the ground both for further specialization in traditional chemical engineering and for coherent studies in other areas. The minimization decisions regarding the required topics and the depth of coverage are local decisions that reflect the mission of the program.

This text can support such a local decision process as a consolidation of normally separate courses in material and energy balances, transport phenomena, reactor design, and separations. While not a replacement for these courses, it is a functional treatment of the underlying skills that characterize them. The selection of major operations reflects the intention of establishing a minimum competency level required to be differentiated as a chemical engineer in an undergraduate engineering curriculum.

Although the book is primarily meant for chemical engineering undergraduates, it may be appropriate for conversion programs designed to prepare graduates of other engineering and science programs for matriculation in chemical engineering master's programs.

Graduate engineers in both academic and industrial positions may find it convenient to have a single resource with wide coverage.

Content

The principles referred to above consist of the conservation of mass, energy, and momentum at the macroscopic and microscopic levels as well as the principle of the increase of entropy and characterization of equilibrium states by equilibrium thermodynamics. The production of entropy provides an important measure of process efficiency and underpins the conservation laws by providing a theoretical foundation for the nonconvective flows. In addition, the balance equations and equilibrium relations are used to develop models of the chemical process operations from the rate or equilibrium stage point of view, respectively. Efficiency is a link between the two.

The chemical engineering operations that are discussed in the text are as follows:

SeparatorsHeat exchangers.

A process flow diagram for the manufacture of acrylic acid is presented at the outset and used for an introduction to chemical processing and equipment. Reference to the acrylic acid process is continued thereafter for presentation of new material in a process context. Example calculations in the text are compared with simulator results pertaining to equipment sizes and operating conditions in the acrylic acid plant.

Heuristics are regarded as fundamental tools and are stated extensively. They are used in calculations and are compared with some independent calculations. Degrees of freedom are employed throughout the earlier sections of the book.

Process control, economics, and safety are not included.

Organization

Two major divisions of the subject matter in the text are made on the basis of a macroscopic and a microscopic view: The balance equations for mass, energy, momentum, and entropy are applied at the macroscopic level confined to the equipment ports, through completely mixed and staged systems to the continuous variations within equipment (see Organization).

Organization.

The “macroscopic view” ensures the conservation of mass, energy, and momentum at the equipment and process levels with consideration only of the conditions at the entrances and exits of the process equipment. The exception is completely mixed systems where the uniform interior conditions appear at the outlet. The macroscopic view is taken at the level of process synthesis where the conditions are consistently set for each processing step to establish the overall process design and economics. The microscopic view is subsequently adopted to arrive at the detailed design of the processing equipment and the final economics. This viewpoint can provide conditions at every location within the equipment boundaries. For multistaged systems consisting of completely mixed subsystems, the conditions vary stepwise throughout the equipment. The microscopic view ensures the local conservation of mass, energy, and momentum. The macroscopic view is therefore the net effect of this local role, which can be seen by integration over the system volume, thereby “closing the circle.”

Calculations

Many examples are provided within the chapters throughout the text to elucidate the discussion. Two process-related threads are carried through the examples (see Tables 1.7 and 1.8) in order to provide a broad process perspective for the calculations. Questions for discussion and encouragement to complete the argument or calculation appear periodically. A variety of problems are suggested at the end of chapters in order to initiate the problem-solving activity as a learning tool and to provide experience with scientific and engineering databases. The collection can be augmented to meet specific course objectives or a desired orientation without modifications to the chapters.

Scientific Notebook (MacKichan Software) and Microsoft Excel are primarily used in the example calculations. Scientific Notebook was chosen because the students who used the notes had prior experience with this software in their mathematics courses and they preferred this software over others that were available to them. Moreover, this software is particularly compatible with the notation used throughout this book.

Excel was used because the ease with which objects could be moved on graphs, the magnification options, and the ability to construct multifunctional plots greatly facilitated stepping off stages and other graphical constructions. The tabular formulation of recursive calculations is readily accomplished in Excel.

Some experience with the use of this software in an introductory course is available in DeLancey (1999).

George DeLancey

Part I

Macroscopic View

1

Chemical Process Perspective

The objective of this chapter is to provide an introduction to chemical processing and chemical processing equipment and to establish a realistic context for much of the more quantitative developments of the same topics appearing in the remaining chapters. A preliminary design of an acrylic acid process (Turton et al., 2003) with a complete flow sheet and stream table provides this context. A connected set of examples and exercises concerned with equipment sizing, material and energy balances, or stream and operating conditions threaded throughout the text are related to the acrylic acid process. The location and nature of these examples are summarized in Table 1.7.

Catalytic aspects of chemical processing are raised in the acrylic acid process and in biocatalytic systems with an introduction to enzyme catalysis. Industrial biotransformations are discussed and the production of hexyl glucoside is selected to provide the context for a second connected thread of examples and exercises throughout the text. In contrast to the acrylic acid thread, this selection is based on a proposed new process with much less information. The examples are therefore in the categories of scale up and process development. The location and nature of the examples in the subsequent chapters are summarized in Table 1.8.

1.1 Some Basic Concepts in Chemical Processing

It will be useful in the following discussion to have in mind what is meant by equilibrium, the steady state, and driving force. These ideas primarily underpin the steps in chemical processing and fall into the three thermodynamic categories: thermal, chemical, and mechanical. The first two categories are discussed below. The third is left to the reader (see Problem 1.1).

Thermal

Refer to Figure 1.1a. Here we imagine that two fluids not necessarily of the same phase are introduced into the two chambers of a rigid insulated container with impermeable walls. The two chambers are separated by a rigid dimensionless barrier (to allow the transfer of heat without mass transfer) and the fluids fill the two mixed chambers. The temperature of the hot fluid (A) will decrease and the temperature of the cold fluid (B) will increase, each approaching the same temperature at the equilibrium state.

Figure 1.1 Rate and equilibrium in thermal processes.

If, on the other hand, the fluids are drawn at the same rate they are fed, they will reach a steady-state temperature that is constant throughout each phase except for a narrow region near the dimensionless diathermal wall where the temperature decreases continuously from the high to the low value. The same equilibrium temperature is approached from either side of the interface. The two phases are prevented from reaching the intermediate state by the continual replacement and removal of the transferred energy.

If the flows are stopped, the system will equilibrate as in Figure 1.1a. We therefore think of the steady state being subjected to a driving force proportional to the distance from equilibrium as in Figure 1.1c where the flux of thermal energy is the response to the force. Since each approaches zero together, we take the linear approximation that the flux is proportional to the force.

We can focus on one phase and think of the driving force as the distance from the equilibrium value or we can think of the overall driving force as the difference between the phase temperatures. Both driving forces refer to the same flow of energy at steady state and each approaches zero at equilibrium.

Chemical—Unreactive Reaction

Refer to Figure 1.2a. We again consider an insulated container with rigid impermeable walls. Here we charge the container with two immiscible liquid phases containing components that are partially soluble in both phases. We will assume for simplicity that the dissolution process of any one of the components in either phase involves no heat effect. Otherwise we would need to repeat the “thermal” discussion. We also assume that no reactions take place. Chemical reactions will be discussed separately.

Figure 1.2 Rates and equilibrium in chemical processes—interphase phenomena.

Similar to the temperature in thermal phenomena, the concentration of each species will increase or decrease until a steady value is reached in each phase. This is a state of interphase chemical equilibrium. A fundamental difference from the thermal case is that the values are not the same in each phase. Whereas the potential for the transfer of thermal energy is the temperature, thermodynamics tells us that the chemical potential is a function of the temperature, pressure, and composition in each phase.

If, as above, the fluids are withdrawn at the same rate they are fed, the concentrations will reach steady-state values that are constant throughout each phase, except for a narrow region near the dimensionless open barrier where the concentrations change stepwise to the vales in the companion phase.

If the flows are stopped, the system will equilibrate as in Figure 1.2a. We therefore think of the steady state being subjected to a driving force proportional to the distance from equilibrium as in Figure 1.2c where the flux of mass is the response to the force. Since each approaches zero together, we take the linear approximation that the flux of mass is proportional to the driving force.

We can focus on one phase and think of the driving force as the distance from the equilibrium value for that phase or we can think of the overall driving force as the difference between the phase compositions. Since the interphase equilibrium compositions are not the same, the overall driving force will need to be modified slightly to assure that the rate is the same as that calculated in either phase.

Chemical—Single Ideal Gas-Phase Reaction