Aerosol Technology E-Book

William C. Hinds

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 716

Veröffentlichungsjahr: 2012

Beschreibung

The #1 guide to aerosol science and technology -now better than ever Since 1982, Aerosol Technology has been the text of choice among students and professionals who need to acquire a thorough working knowledge of modern aerosol theory and applications. Now revised to reflect the considerable advances that have been made over the past seventeen years across a broad spectrum of aerosol-related application areas - from occupational hygiene and biomedical technology to microelectronics and pollution control -this new edition includes: * A chapter on bioaerosols * New sections on resuspension, transport losses, respiratory deposition models, and fractal characterization of particles * Expanded coverage of atmospheric aerosols, including background aerosols and urban aerosols * A section on the impact of aerosols on global warming and ozone depletion. Aerosol Technology, Second Edition also features dozens of new, fully worked examples drawn from a wide range of industrial and research settings, plus new chapter-end practice problems to help readers master the material quickly.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Preface to the First Edition

Preface to the Second Edition

List of Principal Symbols

Chapter 1: Introduction

1.1 Definitions

1.2 Particle Size, Shape, and Density

1.3 Aerosol Concentration

Problems

References

Chapter 2: Properties of Gases

2.1 Kinetic Theory of Gases

2.2 Molecular Velocity

2.3 Mean Free Path

2.4 Other Properties

2.5 Reynolds Number

2.6 Measurement of Velocity, Flow Rate, and Pressure

Problems

References

Chapter 3: Uniform Particle Motion

3.1 Newton’s Resistance Law

3.2 Stokes’s Law

3.3 Settling Velocity and Mechanical Mobility

3.4 Slip Correction Factor

3.5 Nonspherical Particles

3.6 Aerodynamic Diameter

3.7 Settling at High Reynolds Numbers

3.8 Stirred Settling

3.9 Instruments That Rely on Settling Velocity

3.10 Appendix: Derivation of Stokes’s Law

Problems

References

Chapter 4: Particle Size Statistics

4.1 Properties of Size Distributions

4.2 Moment Averages

4.3 Moment Distributions

4.4 The Lognormal Distribution

4.5 Log-Probability Graphs

4.6 The Hatch—Choate Conversion Equations

4.7 Statistical Accuracy

4.8 Appendix 1: Distributions Applied to Particle Size

4.9 Appendix 2: Theoretical Basis for Aerosol Particle Size Distributions

4.10 Appendix 3: Derivation of the Hatch–Choate Equations

Problems

References

Chapter 5: Straight-Line Acceleration and Curvilinear Particle Motion

5.1 Relaxation Time

5.2 Straight-Line Particle Acceleration

5.3 Stopping Distance

5.4 Curvilinear Motion and Stokes Number

5.5 Inertial Impaction

5.6 Cascade Impactors

5.7 Virtual Impactors

5.8 Time-of-Flight Instruments

Problems

References

Chapter 6: Adhesion of Particles

6.1 Adhesive Forces

6.2 Detachment of Particles

6.3 Resuspension

6.4 Particle Bounce

Problems

References

Chapter 7: Brownian Motion and Diffusion

7.1 Diffusion Coefficient

7.2 Particle Mean Free Path

7.3 Brownian Displacement

7.4 Deposition by Diffusion

7.5 Diffusion Batteries

Problems

References

Chapter 8: Thermal and Radiometric Forces

8.1 Thermophoresis

8.2 Thermal Precipitators

8.3 Radiometric and Concentration Gradient Forces

Problems

References

Chapter 9: Filtration

9.1 Macroscopic Properties of Filters

9.2 Single-Fiber Efficiency

9.3 Deposition Mechanisms

9.4 Filter Efficiency

9.5 Pressure Drop

9.6 Membrane Filters

Problems

References

Chapter 10: Sampling and Measurement of Concentration

10.1 Isokinetic Sampling

10.2 Sampling from Still Air

10.3 Transport Losses

10.4 Measurement of Mass Concentration

10.5 Direct-Reading Instruments

10.6 Measurement of Number Concentration

10.7 Sampling Pumps

Problems

References

Chapter 11: Respiratory Deposition

11.1 The Respiratory System

11.2 Deposition

11.3 Deposition Models

11.4 Inhalability of Particles

11.5 Respirable and Other Size-Selective Sampling

Problems

References

Chapter 12: Coagulation

12.1 Simple Monodisperse Coagulation

12.2 Polydisperse Coagulation

12.3 Kinematic Coagulation

Problems

References

Chapter 13: Condensation and Evaporation

13.1 Definitions

13.2 Kelvin Effect

13.3 Homogeneous Nucleation

13.4 Growth by Condensation

13.5 Nucleated Condensation

13.6 Condensation Nuclei Counters

13.7 Evaporation

Problems

References

Chapter 14: Atmospheric Aerosols

14.1 Natural Background Aerosol

14.2 Urban Aerosol

14.3 Global Effects

Problems

References

Chapter 15: Electrical Properties

15.1 Units

15.2 Electric Fields

15.3 Electrical Mobility

15.4 Charging Mechanisms

15.5 Corona Discharge

15.6 Charge Limits

15.7 Equilibrium Charge Distribution

15.8 Electrostatic Precipitators

15.9 Electrical Measurement of Aerosols

Problems

References

Chapter 16: Optical Properties

16.1 Definitions

16.2 Extinction

16.3 Scattering

16.4 Visibility

16.5 Optical Measurement of Aerosols

Problems

References

Chapter 17: Bulk Motion of Aerosols

Problems

References

Chapter 18: Dust Explosions

Problems

References

Chapter 19: Bioaerosols

19.1 Characteristics

19.2 Sampling

Problems

References

Chapter 20: Microscopic Measurement of Particle Size

20.1 Equivalent Sizes of Irregular Particles

20.2 Fractal Dimension of Particles

20.3 Optical Microscopy

20.4 Electron Microscopy

20.5 Asbestos Counting

20.6 Automatic Sizing Methods

Problems

References

Chapter 21: Production of Test Aerosols

21.1 Atomization of Liquids

21.2 Atomization of Monodisperse Particles in Liquid Suspensions

21.3 Dispersion of Powders

21.4 Condensation Methods

Problems

References

Appendices

Appendix A1. Useful Constants and Conversion Factors

Appendix A2. Some Basic Physical Laws

Index

Aerosol Technology

Copyright © 1999 by John Wiley & Sons, Inc. All rights reserved.

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 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, 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone]. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, [phone], fax [phone].

Library of Congress Cataloging-in-Publication Data

Hinds, William C. Aerosol technology : properties, behavior, and measurement of airborne particles / William C. Hinds. —2nd ed.p. cm. “A Wiley-Interscience publication.” Includes bibliographical references and index. ISBN 0-471-19410-7 (cloth : alk. paper) 1. Aerosols. 2. Aerosols—Measurement. I. Title. QC882.42.H56 1998 98-23683 648.5’3—dc21

PREFACE TO THE FIRST EDITION

Airborne particles are present throughout our environment. They come in many different forms, such as dust, fume, mist, smoke, smog, or fog. These aerosols affect visibility, climate, and our health and quality of life. This book covers the properties, behavior, and measurement of aerosols.

This is a basic textbook for people engaged in industrial hygiene, air pollution control, radiation protection, or environmental science who must, in the practice of their profession, measure, evaluate, or control airborne particles. It is written at a level suitable for professionals, graduate students, or advanced undergraduates. It assumes that the student has a good background in chemistry and physics and understands the concepts of calculus. Although not written for aerosol scientists, it will be useful to them in their experimental work and will serve as an introduction to the field for students starting such careers. Decisions on what topics to include were based on their relevance to the practical application of aerosol science, which includes an understanding of the physical and chemical principles that underlie the behavior of aerosols and the instruments used to measure them.

Although this book emphasizes physical rather than mathematical analysis, an important aspect of aerosol technology is the quantitative description of aerosol behavior. To this end I have included 150 problems, grouped at the end of each chapter. They are an important tool for learning how to apply the information presented in the book. Because of the practical orientation of the book and the intrinsic variability of aerosol properties and measurements, correction factors and errors of less than 5 percent have generally been ignored and only two or three significant figures presented in the tables.

Aerosol scientists have long been aware of the need for a better basic understanding of the properties and behavior of aerosols among applied professionals. In writing this book, I have attempted to fill this need, as well as the long-standing need for a suitable text for students in these disciplines. The book evolved from class notes prepared during nine years of teaching a required one-semester course on aerosol technology for graduate students in the Department of Environmental Health Sciences at Harvard University School of Public Health.

Chapters are arranged in the order in which they are covered in class, starting with simple mechanics and progressing to more complicated subjects. Particle statistics is delayed until the student has a preliminary understanding of aerosol properties and can appreciate the need for the involved statistical characterization. Applications are discussed in each chapter after the principles have been presented. The more complicated applications, such as filtration and respiratory deposition, are introduced as soon as the underlying principles have been covered. The operating principles of different types of aerosol measuring instruments are given in general terms so that one may correctly interpret data from them and explain the frequent differences in results between instruments. Discussion of specific instruments is limited because they change rapidly and are covered well in Air Sampling Instruments, 5th edition, ACGIH, Cincinnati, OH (1978). The latter (or any future edition) makes an excellent companion to this text. Several general references are given at the end of each chapter. Tables and graphs are provided in the appendix for general reference and for help in dealing with the problems at the end of each chapter.

While many people have contributed to this book, I would like to acknowledge particularly Klaus Willeke of the University of Cincinnati, who reviewed the manuscript and made many helpful suggestions; Kenneth Martin, who provided the SEM photos; and Laurie Cassel, who helped prepare and type the manuscript.

WILLIAM C. HINDS

Boston, MassachusettsFebruary 1982

PREFACE TO THE SECOND EDITION

More than 16 years have passed since the first edition of Aerosol Technology was published in 1982. During this time the field of aerosol science and technology has expanded greatly, both in technology and in the number of scientists involved. When the first edition was published there were two national aerosol research associations, now there are 11 with regular national and international meetings. Growth areas include the use of aerosols in high-technology material processing and the administration of therapeutic drugs, and there is an increased awareness of bioaerosols, aerosol contamination in microelectronic manufacturing, and the effect of aerosols on global climate. While the first edition proved to be popular and useful, and became a standard textbook in the field, changes in technology and growth of the field have created the need to update and expand the book.

The objective of the book has remained the same: to provide a clear, understandable, and useful introduction to the science and technology of aerosols for environmental professionals, graduate students, and advanced undergraduates. In keeping with changes in the field, this edition uses dual units, with SI units as the primary units and cgs units as secondary units. Besides updating and revising old material, I have added a new chapter on bioaerosols and new sections on resuspension, transport losses, respiratory deposition models, and fractal characterization of particles. The chapter on atmospheric aerosols has been expanded to include sections on background aerosols, urban aerosols, and global effects. There are 26 new examples and 30 new problems. The latest edition of Air Sampling Instruments remains an excellent companion book, as does Aerosol Measurement, by Willeke and Baron. Both provide greater depth and detail on measurement methods and instruments.

Of the many people who have helped with this edition. I would like to particularly acknowledge Janet Macher, Robert Phalen, and John Valiulis for reviewing specific chapters; Rachel Kim and Vi Huynh for typing manuscript changes; doctoral student Nani Kadrichu for entering the equations; and finally, my wife Lynda for her continued support during this long process.

WILLIAM C. HINDS

Los Angeles, California

LIST OF PRINCIPAL SYMBOLS

Chapter 1

Introduction

The microscopic particles that float in the air are of many kinds: resuspended soil particles, smoke from power generation, photochemically formed particles, salt particles formed from ocean spray, and atmospheric clouds of water droplets or ice particles. They vary greatly in their ability to affect not only visibility and climate, but also our health and quality of life. These airborne particles are all examples of aerosols. An aerosol is defined in its simplest form as a collection of solid or liquid particles suspended in a gas. Aerosols are two-phase systems, consisting of the particles and the gas in which they are suspended. They include a wide range of phenomena such as dust, fume, smoke, mist, fog, haze, clouds, and smog. The word aerosol was coined about 1920 as an analog to the term hydrosol, a stable liquid suspension of solid particles. Aerosols are also referred to as suspended particulate matter, aerocolloidal systems, and disperse systems. Although the word aerosol is popularly used to refer to pressurized spray-can products, it is the universally accepted scientific term for particulate suspensions in a gaseous medium and is used in that sense in this book.

Aerosols are but one of the several types of particulate suspensions listed in Table 1.1. All are two-component systems having special properties that depend on size of the particles and their concentration in the suspending medium. All have varying degrees of stability that also depend on particle size and concentration.

TABLE 1.1 Types of Particulate Suspensions

An understanding of the properties of aerosols is of great practical importance. It enables us to comprehend the process of cloud formation in the atmosphere, a key link in the hydrological cycle. Aerosol properties influence the production, transport, and ultimate fate of atmospheric particulate pollutants. Measurement and control of particulate pollutants in the occupational and general environments require the application of this knowledge. Aerosol technology has commercial application in the manufacture of spray-dried products, fiber optics, and carbon black; the production of pigments; and the application of pesticides. Because the toxicity of inhaled particles depends on their physical as well as their chemical properties, an understanding of the properties of aerosols is required to evaluate airborne particulate hazards. The same knowledge is used in the administration of therapeutic aerosols for the treatment of respiratory and other diseases.