Principles of Mineral Processing

610 Pages·2003·9.135 MB·610\610

by  Fuerstenau, Maurice C., Han, Kenneth N. (Eds.)

Principles of
Mineral
Processing
Edited by
Maurice C. Fuerstenau and Kenneth N. Han
Published by the
Exploration, Inc.
Society for Mining, Metallurgy, and Exploration, Inc. (SME)
8307 Shaffer Parkway
Littleton, Colorado, USA 80127
[phone] / [phone]
www.smenet.org
SME advances the worldwide mining and minerals community through information exchange and
professional development. SME is the largest association of minerals professionals.
Copyright (cid:164) 2003 Society for Mining, Metallurgy, and Exploration, Inc.
All Rights Reserved. Printed in the United States of America.
Information contained in this work has been obtained by SME, Inc. from sources believed to be
reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any
information published herein, and neither SME nor its authors shall be responsible for any errors,
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No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form
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the approval or endorsement of SME.
ISBN 0-87335-167-3
Library of Congress Cataloging-in-Publication Data.
Principles of mineral processing / [edited by] Maurice C. Fuerstenau
p. cm.
Includes bibilographical references and index.
ISBN 0-87335-167-3
1. Ore dressing. 2. Hydrometallurgy. I. Fuerstenau, Maurice C.
TN500.P66 2003
622'.7--dc21 2002042938
. . . . . . . . . . . . . .
Preface
The world is faced with opportunities and challenges that require ever-increasing amounts of raw
materials to fuel various industrial sectors, and, at the same time, meet environmental constraints asso-
ciated with excavating and processing these raw materials. In addition, gradual depletion of mineral
resources and the necessity of handling more complex forms of resources, primary and secondary, have
led to challenges in the development of state-of-the-art technologies that are metallurgically efficient
and environmentally friendly. Unquestionably, technology advances are the key to sustaining a suffi-
cient supply of necessary raw materials.
To advance the technology in the production of material resources, nations look to practicing and
future engineers. Current and future mineral processing engineers must obtain sound and rigorous
training in the sciences and technologies that are essential for effective resource development. Many
industrial and academic leaders have recognized the need for more textbooks and references in this
important area. This was the driving force for writing a comprehensive reference book that covers
mineral processing and hydrometallurgical extraction.
This book was written first to serve students who are studying mineral processing and hydro-
metallurgy under various titles. We also hope that the book will serve as a valuable reference to
many industrial practitioners in the mineral processing field. In the chapters that follow, you will
find first principles that govern various unit operations in mineral processing and hydrometallurgy,
along with examples to illustrate how fundamental principles can be used in real-world applications.
In general, the volume covers topics in the order of the usual processing sequence. Comminution, the
breakage of rocks and other materials, is covered in such a way that the fundamental principles can
be used not only in mineral processing but also in other relevant areas such as chemical engineering
and pharmaceutical fields.
Understanding the characteristics of particles and the separation of particulate materials from
one another is of ultimate importance. Separation technologies based on properties such as magne-
tism, electrical properties, and surface properties of various minerals are present along with industrial
examples.
Because most mineral processing unit operations take place in water as a medium, understand-
ing how solids can best be separated from water is of industrial importance. Efficiently using water
during effective solid–liquid separation is often vital to the success of the overall mineral beneficiation
operation.
With computer application technologies continuing to emerge rapidly, the mineral industry has
made tremendous advances in its industrial production. Plant automation and control often play a vital
role in the overall success of the plant operation. The chapter on comminution covers some of these
innovations in automation.
ix
Once desired minerals are recovered from the undesired portion of an ore deposit, chemical treat-
ment to unlock the desired metal elements from various minerals is necessary. Hydrometallurgical
treatment for the chemical release of metal elements from various minerals is presented along with
fundamental water chemistry and kinetic principles.
We are fortunate that many world-class authorities in various areas of mineral processing have
joined this endeavor, and we thank them for their participation. We would also like to take this oppor-
tunity to thank the staff of the Society for Mining, Metallurgy, and Exploration, Inc., for their support in
producing this book.
x
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Contents
LIST OF AUTHORS vii
PREFACE ix
CHAPTER 1 INTRODUCTION 1
Maurice C. Fuerstenau and Kenneth N. Han
Goals and Basics of Mineral Processing 1
Metallurgical Efficiency 1
Economic Concerns 3
Unit Operations 4
Examples of Mineral Processing Operations 5
Environmental Consequences of Mineral Processing 8
CHAPTER 2 PARTICLE CHARACTERIZATION 9
Richard Hogg
Particle Characteristics 9
Mathematical Treatment of Particle Distributions 14
Measurement of Particle Characteristics 29
Comparison and Interconversion of Particle Size Data 53
Appendix 2.1: Moment Determination and Quantity Transformation
from Experimental Data 54
Appendix 2.2: Combination of Sieve and Subsieve Size Data 54
CHAPTER 3 SIZE REDUCTION AND LIBERATION 61
John A. Herbst, Yi Chang Lo, and Brian Flintoff
Introduction 61
Fundamentals of Particle Breakage 63
Comminution Equipment 79
Comminution Circuits 94
Process Control in Comminution 100
Financial Aspects of Comminution 113
Symbol Glossary 115
CHAPTER 4 SIZE SEPARATION 119
Andrew L. Mular
Introduction 119
Laboratory Size Separation 121
Sedimentation Sizing Methods 127
iii
Industrial Screening 129
Size Classification 148
CHAPTER 5 MOVEMENT OF SOLIDS IN LIQUIDS 173
Kenneth N. Han
Introduction 173
Dynamic Similarity 173
Free Settling 174
Particle Acceleration 179
Particle Shape 181
Hindered Settling 183
CHAPTER 6 GRAVITY CONCENTRATION 185
Frank F. Aplan
Introduction 185
The Basics of Gravity Separation 188
Float–Sink Separation 195
Jigs 202
Flowing Film Concentrators, Sluices, and Shaking Tables 206
Centrifugal Devices 212
Pneumatic Devices 212
Process Selection and Evaluation 214
CHAPTER 7 MAGNETIC AND ELECTROSTATIC SEPARATION 221
Partha Venkatraman, Frank S. Knoll, and James E. Lawver
Introduction 221
Review of Magnetic Theory 221
Conventional Magnets 228
Permanent Magnets 232
Superconducting Magnets 236
Electrostatic Separation 239
CHAPTER 8 FLOTATION 245
Maurice C. Fuerstenau and Ponisseril Somasundaran
Surface Phenomena 245
Flotation Reagents 252
Chemistry of Flotation 259
Flotation Machines 292
Column Flotation 296
Flotation Circuits 299
CHAPTER 9 LIQUID–SOLID SEPARATION 307
Donald A. Dahlstrom
Introduction 307
Major Influences on Liquid–Solid Separation 309
Liquid–Solid Separation Equipment 317
Gravitational Sedimentation 317
Filtration 322
Basic Guidelines for Application 334
iv
Gravity Sedimentation Applications 336
Continuous Vacuum Filtration 346
Batch Pressure Filters 357
CHAPTER 10 METALLURGICAL BALANCES AND EFFICIENCY 363
J. Mark Richardson and Robert D. Morrison
Terminology 363
Applications 366
Types of Balances 368
Calculation Methods 376
Data 385
CHAPTER 11 BULK SOLIDS HANDLING 391
Hendrik Colijn
Theory of Solids Flow 391
Design of Storage Silos and Hoppers 393
Feeders 397
Mechanical Conveying Systems 402
Pneumatic Conveying Systems 407
Instrumentation and Control 408
CHAPTER 12 HYDROMETALLURGY AND SOLUTION KINETICS 413
Kenneth N. Han and Maurice C. Fuerstenau
Introduction 413
Solution Chemistry 414
Electrochemistry 434
Reaction Kinetics 442
Shrinking Core Models 454
Reactor Design 462
Recovery of Metal Ions from Leach Liquor 479
CHAPTER 13 MINERAL PROCESSING WASTES AND THEIR REMEDIATION 491
Ross W. Smith and Stoyan N. Groudev
Liquid Wastes 491
Contaminated Soils 503
Solids Disposal and Long-term Management of Tailings Impoundments 509
CHAPTER 14 ECONOMICS OF THE MINERALS INDUSTRY 517
Matthew J. Hrebar and Donald W. Gentry
Supply-Demand Relationships 517
Distinctive Features of the Minerals Industry 520
Mineral Project Evaluation 522
INDEX 561
v
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CHAPTER 1
Introduction
Maurice C. Fuerstenau and Kenneth N. Han
The term mineral processing is used in a broad sense throughout this book to analyze and describe the
unit operations involved in upgrading and recovering minerals or metals from ores. The field of mineral
processing is based on many fields of science and engineering. Humanities and social science have also
become an integral part of this technology because mineral processing, like many other technologies, is
carried out to improve human welfare. In addition, environmental science and engineering have become
inseparable components; the steps involved in mineral processing have to be founded not only on sound
scientific and technological bases but on environmentally acceptable grounds as well.
GOALS AND BASICS OF MINERAL PROCESSING
In the traditional sense, mineral processing is regarded as the processing of ores or other materials to
yield concentrated products. Most of the processes involve physical concentration procedures during
which the chemical nature of the mineral(s) in question does not change. In hydrometallurgical
processing, however, chemical reactions invariably occur; these systems are operated at ambient or
elevated temperatures depending on the kinetics of the processes.
The ultimate goal in the production of metals is to yield metals in their purest form. Mineral
processing plays an integral part in achieving this objective. Figure 1.1 shows a generalized flow
diagram for metals extraction from mining (step 1) through chemical processing. Steps 2 and 3 involve
physical processing and steps 5 and 7 involve low-temperature chemical processing (hydrometallurgy).
All four steps are considered part of mineral processing. High-temperature smelting and refining (pyro-
metallurgy), steps 4 and 6, are not included under the heading of mineral processing.
Table 1.1 specifies processing routes from ore to pure metal for a number of metals. Note that
processing routes can be quite different and that more than one route may be possible for many of
these metals. For example, in the extraction of copper or gold from low-grade ores, dump or heap
leaching is commonly practiced. The choice of this leaching practice is frequently driven by the overall
economics of the operation. Because crushing and grinding of ores are quite expensive, leaching of ores
in large sizes is attractive compared to the leaching of finely ground ores, even though the overall
recovery of metals from the leaching of fine particles is, in general, much greater than that obtained
with large particles. The introduction of this innovative leaching process has made feasible the mining
of many mineral deposits that could not be processed economically through conventional technologies.
METALLURGICAL EFFICIENCY
One of the most important and basic concepts in mineral processing is metallurgical efficiency. Two
terms are commonly used to describe the efficiency of metallurgical processes: recovery and grade.
These phenomena are illustrated in the generalized process presented in Figure 1.2. In this example,
100 tph of ore are being fed into a concentration operation that produces 4.5 tph of concentrate and
1
2 | PRINCIPLES OF MINERAL PROCESSING
FIGURE 1.1 Generalized flowchart of extraction of metals
TABLE 1.1 Processing sequence(s) for a number of selected metals
Steps Involved in the Processing Route
(see Figure 1.1)
Metal Associated Major Minerals 1 2 3 4 5 6 7 8
Iron Hematite, Fe2O3; magnetite, Fe3O4 x x x x x x
Aluminum Gibbsite, Al2O3-3H2O; diaspore, Al22O3×H2O x x x x x
Copper Chalcopyrite, CuFeS2; chalcocite, Cu2S x x x x x x x
Zinc Sphalerite, ZnS x x x x x x
x x x x x x x
Lead Galena, PbS x x x x x x
Gold Native gold, Au x x x x x x
x x* x x x
Platinum Native platinum, Pt; platinum sulfides x x x x x x
Silver Native silver, Ag x x x x x x
*Only crushing is practices; grinding is usually omitted.
INTRODUCTION | 3
FIGURE 1.2 A simple material balance for a unit operation
TABLE 1.2 U.S. total and recycled supply of selected metals in 1996
Total Supply, Recycled Supply,
Metal million t metal content million t metal content % Recycled
Iron and steel 183 72 39
Aluminum 8.34 3.29 39
Copper 3.70 1.30 35.1
Lead 1.63 1.09 66.8
Zinc 1.45 0.379 26.1
Chromium 0.48 0.098 20.5
Magnesium 0.205 0.0709 35
Gold 516 t* 150 t* 29
Source: U.S. Bureau of Mines (1997).
*Value for 1995.
95.5 tph of tailings. In upgrading this process, then, 1.0 tph of the desired material, A, is introduced
into the unit operation and 0.9 tph (4.5 × 0.2) of this material reports to the concentrate, resulting in
90% recovery (0.9/1.0 × 100). The grade of the mineral, A, has been improved from 1% to 20%. The
term percent recovery refers to the percentage of the valuable material reporting to the concentrate with
reference to the amount of this material in the feed. Note that obtaining the highest possible recovery is
not necessarily the best approach in a concentration process. High recovery without acceptable grade
will lead to an unsalable product and is therefore unsatisfactory.
Mineral processing engineers are responsible for optimizing processes to yield the highest possible
recovery with acceptable purity (grade) for the buyers or engineers who will treat this concentrate
further to extract the metal values. To achieve this goal, economic assessments of all possible techno-
logical alternatives must be conducted.
ECONOMIC CONCERNS
Table 1.2 summarizes the total U.S. supply and recycled supply of selected metals in 1996. The total
supply of iron and steel includes supply from primary and secondary sources as well as imports; these
two metals represent by far the largest of commodities produced and consumed, followed by
aluminum, copper, and lead. Note that the recycled supply of these metals from processing scrap is
strikingly high. In addition, the tonnage of precious metals consumed is rather small. However,
because of the high prices of precious metals, their monetary value is substantial. For example, the
monetary value of 516 t of gold was $12.8 billion in 1996, compared to $10.7 billion for 5.3 million t of
copper and lead.