Mineral Processing Plant Design and Optimization Guide

Basdew Rooplal
Mining & Metallurgical Consultant
http://mineralprocessingconsultant.com/
PLANT DESIGN
CONSTRUCTION AND
OPERATION
PLANT OPTIMISATION
AND ENERGY EFFICIENCY
CONSIDERATIONS

CONTENTS
Plant Design Construction
and Operation
 Bench scale and pilot scale design
for comminution circuits
 Factors influencing the selection of
comminution circuits
 Types and characterisation of
crusher equipment and circuit
flowsheet
 Selection and sizing of primary
crusher
o Computer aided design of Jaw
Crusher
 Selection and sizing of
secondary and tertiary
crushers
o Optimising the Eccentric
speed of cone crusher
 Selection and sizing of High
pressure roll crushers
 Advancement in Screening
Technology.
2

CONTENTS
Plant optimisation and
energy efficiency
considerations
• Characterisation –
Understanding the ore body
and the Metallurgy
• Ore dressing studies – what is
involved.
• Blasting for improved mining
and comminution productivity
• Production planning for the
combined mine and
comminution operation
• Optimising lumps to fines ratio
in Iron Ore processing
• Reducing fines generation in
Coal Mining
• Profit based comminution
controls
• Increasing the energy
efficiency of Processing
3

BENCH SCALE AND PILOT SCALE
DESIGN FOR COMMINUTION
CIRCUITS
4http://mineralprocessingconsultant.com/

BENCH SCALE TESTWORK
Introduction
• The resistance of ore samples
to breakage (or hardness) is
measured through grindability
tests.
• Several grindability tests have
been developed over the years
for different applications and
each test has its own strengths
and weaknesses
• Grindability tests are a
compromise between test
costs and its deliverables.
• The highest degree of
deliverables and certainty is
achieved in a pilot plant, which
is also the most reliable test
procedure to determine the
resistance of ore samples to
grinding or hardness and is
also the most expensive.
5

SUMMARY OF
GRINDABILITY TESTS
6

GRINDABILITY TESTS
Bond Ball mill
Grindability
• The AG/SAG mill or HPGR
circuit products, which have
non-standard particle size
distribution.
• One of the keys of the Bond
work index success over
time has been its reliability
and reproducibility.
• The figure below shows that
the Ball Mill work index is
normally distributed with
AVG 14.6 and Median 14.8
7

GRINDABILITY TESTS
Bond Rod mill work
Index
• The rod mill work Index is
also normally distributed
with and average and
median of 14.8kWh/t
• It is common to observe
difference between the ball
and rod mill caused by
variation in ore hardness
• The test has been mainly
used for the design of rod
mill or primary ball mills.
8

GRINDABILITY TESTS
Bond low energy
impact test
• Consists of an apparatus with
two pendulum hammers
mounted on two bicycle
wheels, so as to strike equal
blows simultaneously on
opposite sides of each rock
specimen.
• The height of the pendulum is
raised until the energy is
sufficient to break the rock
specimen
• The test is generally performed
on 20 rocks
• One of the strengths of the
test is to measure the natural
dispersion in the sample.
• Another advantage of the test
is the coarse size 2 – 3 inches
which makes it unique in the
series of tests.
9

GRINDABILITY TESTS
SAG power index (SPI)
• SPI expressed in minutes , is
the time T necessary to
reduce the ore from P80 of
12.5mm to P80 of 1.7 mm
• The SPI has the advantage
of requiring low weight and
is suited for
geometallurgical mapping
of ore deposits
• SPI is widely used and
deposits can be compared
in terms of hardness and
variability, see fig below.
10

GRINDABILITY TESTS
JKTECH drop weight
test
• Developed by JKMRC
• Divided into 3 components:
• Test measures the resistance
to impact breakage of
coarse particles in the range
63 – 13.2 mm
• Then evaluates the
resistance to abrasion
breakage in the range 53 –
37.5 mm
• Finally the rock density of
20 particles is measured to
asses the average ore
density as well as its
dispersion.
11

GRINDABILITY TEST
JKTECH drop weight
test
• The test generates the
appearance function –
• E.g. the breakage pattern of
the ore under a range of
impact and abrasion
breakage conditions
• The appearance function can
be used in the JKSimMet
modelling and simulation
package to predict the ore
response to comminution
process
12

GRINDABILITY TESTS
JKTECH Drop weight
test
• Also part of these procedure is
the density determination of
20 rock samples, using water
displacement techniques.
• Figure 5 shows an ore
displaying a wide range of
densities.
• The density distribution of the
ore is important in AG/SAG
milling because
• It affects the bulk density of
the charge and associated
power draw
13

GRINDABILITY TESTS
JKTECH drop weight
test
• A great number of rock
weight tests have been
performed over the years
which allows for
comparison of ore types in
a data base.
• The frequency distribution
of the function ‘A x b’ from
JKTech is depicted in Fig 6
14

GRINDABILITY TESTS
JKTECH drop weight
test
• One of the interesting
features of the drop weight
test procedure is that it
provides a variation in rock
hardness by size from 13.2
to 63 mm.
• Fig 7 illustrates this at 3
different energy levels.
• 0.25 1.0 and 2.5 kWh/t
• For a very competent ore,
the curve will be nearly
horizontal, a non-
competent fractured ore
will show a high gradient
with increasing size
15

GRINDABILITY TESTS
SAG Mill
comminution test
• This is an abbreviated drop
weight test, which can be
performed at low cost on
small samples 19 – 22 mm
or drill cores.
• 5 kg of sample is normally
sufficient.
• The advantage of the SMC test
is that it generates the energy
versus breakage relationship
with as small quantity of
sample of a single size fraction.
• Because the test can be
performed on small rocks, it is
well suited for
geometallurgical mapping.
16

GRINDABILITY TESTS
MacPherson Autogenous
Grindability tests
• This is a continuous test
performed in a 46 cm semi-
autogenous mill with an 8%
ball charge.
• The pilot plant consists of a
feed hopper, cyclone, screen
and dust collector with a
control system to regulate the
charge volume and circulating
load.
• 100 to 175 kg of sample is
required with a top size
greater than 25 mm.
• The test is run continuously for
6 hours.
• The importance of reaching a
steady state in a grinding mill
is widely accepted, this test is
the only small scale test that
offers the option.
17

GRINDABILITY TESTS
MacPhersons Autogenous
grinding tests
• Throughput rates • Specific Energy
18

GRINDABILITY TEST
Media Competency
test
• There has been some
variations of media
competency test developed
over the years with the
assessment of media
survival in autogenous
milling being the main
objective.
• 104 to 165 mm rocks are
subjected to a tumble test
using 10 large rock in 5 size
fractions.
• The surviving rocks are
submitted to fracture energy
test procedure.
• This provides the relationship
between the first fracture
energy requirement and rock
size.
19

GRINDABILITY TESTS
High Pressure
Grinding Rolls
• HPGR are emerging as an
energy efficient alternative to
AG/SAG circuits.
• The traditional method for
testing is processing large
samples in a pilot scale.
• Several tests are performed to
asses the effect of operating
pressure and moisture content
on HPGR performance
• The power input is recorded
and presented below.
20

CRUSHABILITY TEST
Impact Crushability
• Gives a WI that can be applied
to 3 types of crushers
• Gyratory – WI can be used to
determine the horse power.
• Impactors – WI is an indication
of hardness
• Cone Crusher – rate the
material to determine the duty
of the crusher
21

CRUSHABILITY TESTS
Paddle Abrasion
• Results are in the form of
Abrasion Index and chemical
makeup of the material
• Tests are used to determine
whether an Impactor or cone
crusher is suitable.
• Can also be used to calculate
the approximate liner life for
the crusher
22

CRUSHABILITY TESTS
French Abrasion
• Gives an Abrasion and
Crushability Index
• Mainly used to estimate
hammer wear in the
Impactor application
Dynamic
Fragmentation
• Conducted for Impactor
application
• Measures the friability of
the material
• Dynamic fragmentation
number will indicate if the
Impactor is feasible for a
particular application.
23

DISCUSSION POINTS!
• Where can I apply Bench
scale and pilot scale
programs in my work
environment?
24

FACTORS INFLUENCING THE
SELECTION OF COMMINUTION
CIRCUITS

SELECTION OF
COMMINUTION CIRCUITS
• Geological Interpretation of
Drill core and Bulb Sample
• Mineralogical Analysis
• Chemical Analysis
• Physical Properties
• Circuit feed Parameters
• Sampling requirements
• Contiguous properties
• Feed and product
Specification
• Bond work Indices, Abrasion
Index, and specific power
consumptions
26

SELECTION OF
COMMINUTION CIRCUITS
• Circuit selection
• Metallurgical efficiency
• Cost Consideration
• Water supply
• Fine Grinding
• Plant layout
27

GEOLOGICAL
INTERPRETATION OF DRILL
CORE AND BULK SAMPLE
Information Gained
• Identification and relative
abundance of Mineral content
• Degree of Dissemination
• Type of Lithology
• Types of Alteration
• Degree of Oxidation
• Geotechnical Competence
• Hardness
Effect on Circuit
Selection
• Provides a guide to the types
of circuit required and the
types of samples required
based on precedent
• Determines the necessity of
separate plants to process
sulphide ores
• Provides a guide to the
selection of autogenous
grinding
28

MINERALOGICAL ANALYSIS
Information Gained
• Identification of ore and
gangue minerals and
middling association
• Liberation and Modal
Analysis
• Quantitative analysis –
QemScan
Effect on Circuit
Selection
• Determine Ratios of
reduction
• Feed and product size
analysis in primary ,
secondary and regrind
circuits
29

CHEMICAL ANALYSIS
Information Gained
• Identification of metallic ,
non-metallic and acid
generating constituents
Effect on Circuit
Selection
• Determining the
requirements of pre-
washing the ore
30

PHYSICAL PROPERTIES
Information Gained
• Hardness, Blockiness,
Friability, Quantification of
primary fines and clay
content
• Specific gravity of mineral
constituents
Effect on Circuit Selection
• Provides a guide to
potential problems in
Crushing Screening and
Grinding the ore with
respect to equipment
selection and Over
grinding and avoidance of
slimes generation with
respect to softer minerals.
31

CIRCUIT FEED PARAMETERS
Information Gained
• ROM top size parameters
• Primary crusher discharge
size analysis
• Throughput requirements
and schedules
• Mining Plans , Schedules,
methods and equipment
sizes
• Determines selection of
primary crushers and
necessity for pre-crushing
can influence this selection
by determination of the
product size at the required
throughput rate.
32

SAMPLING REQUIREMENTS
Information Gained
• Preliminary drill core for
resource definition and split
for bond work indices
• Whole core for Autogenous
Media Competency Index,
Impact crusher work indices
and fracture frequency
• Bulk Sample , large diameter
drill core, open pit or
underground for pilot plant
testing
Effect on Circuit
Selection
• Preliminary Assessment of
grinding requirements and ore
variability
• Power based methods for mill
sizing using results from
Bond , Impact and grinding
work indices
• Assist in definition of Pilot
plant test program and ore
Variability Characteristics
33

CONTIGUOUS PROPERTIES
Information Gained
• Definition of equipment
characteristics
Effect on Circuit
Selection
• Determines the utility of
equipment with respect to
its Inherent operating
behaviour, e.g. Autogenous
grinding mills grinding to a
natural grain size, SAG mills
breaking across grain
boundaries and rod mill
minimizing the creation of
fines
34

FEED AND PRODUCT
SPECIFICATION
Information Gained
• Definition of requirements
at each comminution stage
Effect on Circuit
Selection
• Influence of “Mine to Mill”
and choke feeding the
primary crusher on
subsequent stages
Performance
• Maximum feed top size in
relation to high aspect and
low aspect primary mills
• Use of HPGR
35

BOND WORK INDICES,
ABRASION INDEX, AND
SPECIFIC POWER
CONSUMPTIONS
Information Gained
• Calculation of specific power
consumption at each
comminution stage for
different ore types and
composites.
• Assessment of ore variability
• Checking on pilot plant test
data
• Assessment of risk or
contingency based on
samples selected according to
the mine plan
• Distribution of power
Confirmation of specific power
consumption and
contingencies for Process
design criteria
• Calculation of estimates for
media and liner wear.
• Estimation of mill power
requirements and distribution
of power between equipment
36

CIRCUIT SELECTION
Information Gained
• Assessment of Overall Power
requirements and power
efficiency for different circuit
options
• Assessment of Overall
Operating Availability for
different circuit options
• Determination of unit power
cost and demand for different
circuit options
Effect on Circuit
Selection
• Determination of the Most
economic option on the basis
of NPV of Capital and
Operating cost and circuit
availability for a fixed revenue
rate.
• Power efficiency should be
optimised in design for each
circuit option considered.
37

METALLURGICAL EFFICIENCY
Information Gained
• Definition of Optimum
comminution configuration
• Definition of feed rate
variation
• Selection of grinding media
Effect on Circuit
Selection
• Determination of necessity for
stage grinding and stage
concentration to optimise
mineral liberation and
recovery.
• Quantify the effect of feed rate
variations on the metallurgical
efficiency of down stream
processes.
38

COST CONSIDERATION
Information Gained
• Definition of Largest
practical equipment size
and design
• Differences between
comminution options
Effect on Circuit
Selection
• Effect of efficiency on
crushing and grinding
equipment E.g. Separation
of screening plant from
crushing plant.
• Feed arrangement
requirements
• Choke feeding crushers
39

WATER SUPPLY
Information Gained
• Definition of Process
alternatives
Effect on Circuit
Selection
• Determination of plant
location Namely, Mine
location, Applicability of dry
grinding, Pre-concentration
and use of sea water.
40

FINE GRINDING
Information Gained
• Determination of test
requirements, batch and /
or Pilot scale tests
Effect on Circuit
Selection
• Determination of Optimum
location of Fine grinding
application within the circuit
and definition of the types
of machines used.
41

PLANT LAYOUT
Information Gained
• Definition of Geographic
location, Climatic conditions,
Accessibility
• Definition of relative location
of Mine vs. Plant
• Definition of Operating
schedules and manpower
requirements
• Definition of expansion
potential
Effect on Circuit
Selection
• Determination of wet and dry
processes
• Determination of Physical sizes
of equipment and foot print of
the plant
• Determination of built-in
contingencies that allow for
future expansion
• Consideration for the addition
of equipment lines in the case
of larger plants.
42

DISCUSSION POINTS!
• Comments on pertinent
factors that was involved in
the selection of your plant
system.
• The pros and cons of the
current system, bottle
necks, etc.
43

TYPES AND CHARACTERISATION OF
CRUSHER EQUIPMENT AND CIRCUIT
FLOWSHEET

INTRODUCTION
Standard Equipment
• Crushing flowsheet and
equipment are selected to
prepare ore for downstream
purposes. Standard equipment
for the minerals industry has
been :
Jaw crushers
Gyratory crushers
Cone crushers
New Equipment
Water flush cone crushers
Vertical and horizontal
impactors
High pressure grinding rolls
45

FACTORS AFFECTING
CRUSHER SELECTION
• Plant throughput, ore
delivery schedules
• Size of feed
• Desired product size for
down stream processing
Ore characteristics:
Hard rock
Clay
Gravel
Variability
Climatic conditions
Down stream processes
46

PLANT THROUGHPUT AND
ORE DELIVERY SCHEDULES
• Forms the base line for
flowsheet design and
equipment selection
• Size type, number of stages
and number of crushers per
stage for an application can
be identified.
• E.g. A primary Jaw crusher
will be better suited for a
conventional underground
mining operation because:
Tonnages are typically lower
Feed material size is smaller
Less headroom and a smaller
excavation is required.
47

FEED SIZE
• The crusher selected must
be sized for throughput as
well as top size expected
from the mine.
• Smaller the crusher the
smaller the dimension of
the feed material that can
enter the crusher chamber.
• A balance between the plant
capacity and the size of the
crusher must be reached.
• In multi stage crushing circuits
the products of the preceding
stage will be the determining
factor in the selection of the
size of the crusher and the
crusher liner configuration.
48

PRODUCT SIZE
• The target product size
required from the crushing
circuit will determine the
number of crushing stages and
types of crushers to be used
for a specific application.
• E.g.. To produce a coarse
product a single stage crusher
may be required.
• To produce a 15 mm product a
two stage crushing may be
required.
• The ability to crush finer has
been required for specific
application.
• For fine product sizes in dry
process application flowsheet
have incorporated vertical
shaft impact crushers operated
in closed circuit with vibrating
screens.
49

ORE CHARACTERISTICS
• When selecting equipment for
inclusion in a crushing
flowsheet the following factors
should be considered:
• Hardness
• Toughness
• Abrasiveness
• Moisture content
• mineralisation
• Geologists should provide
info with regards to:
• Rock types
• Abundance of various rock
types LOM
• Short and long term delivery
schedules should then be
provided mining to adapt
circuit configuration for LOM
50

CLIMATIC CONDITIONS
• A dry warm climate will
allow for an unenclosed
installation.
• Colder wet climates will
require enclosures for
operator protection and
moisture problems.
• An enclosed crushing plant
also posed dust extraction
challenges.
51

DOWNSTREAM
PROCESSES
• Heap Leaching
• Crusher product size will
be specified for optimum
recovery
• Milling
• Type of grinding circuit
will influence the number
of crushing stages.
52

APPLICATION
Primary Crusher
• Purpose
• To reduce the ore to a size
amenable to secondary
crushing, SAG mill feed or
heap leach product
• Usually operated in open
circuit.
• Typical crushers used are
• Jaw
• Gyratory
• Horizontal impactors
• Rotary breakers
• Ratio of reduction 8:1
• Some form of scalping screen
may be installed in the case of
Jaw and Impact crushers
53

APPLICATION
Secondary Crushers
• Purpose
• To produce an intermediate or
final product
• Feed Size – typically between
200 & 75 mm depending on
primary crusher
• Vibrating screen may be
installed ahead to remove
product size material.
• Crusher types:
• Standard cone crusher –
traditionally
• Horizontal Impact crusher
as alternative
• HPGR recently for diamond
and iron ore
54

APPLICATION
Tertiary Crushers
• Purpose: Produce the final
product
• Feed : 37 mm
• Product : 12 mm
• Crusher type:
• Short head cone crusher
• Longer crusher chamber and
more even size distribution
• Usually operated in closed
circuit with a vibrating screen
• HPGR and Nordberg Water
Flush crushers have also been
used.
55

APPLICATION
Quaternary Crushing
• Purpose:
• To produce fine dry product
for downstream processing
• Vertical Impact Crusher has
been used at Newmont’s heap
leaching operation in
Uzbekistan.
• High speed crusher that used
high speed impact to effect
particle reduction
• Nordberg’s Gyradisc
crusher uses a combination
of impact and attrition to
effect particle size
reduction.
• Applied in the industrial
minerals and sand industry
to produce finished
products to 800 microns.
56

CRUSHER TYPES
• Jaw
• Gyratory
• Horizontal shaft impact
crushers
• Rotary breakers
• Roll Crushers
• Cone crushers
• Gyradisc crushers
• Vertical impact crusher
57

FLOWSHEET – TWO STAGE
CRUSHING (FINE PRODUCT)
58

TWO STAGE CRUSHING
(COARSE PRODUCT)
59

THREE STAGE CRUSHING
60

61

62

TWO STAGE WITH WATER
FLUSH CRUSHER
63

THREE STAGE CRUSHING –
GOLD HEAP LEACH
64

THREE STAGE CRUSHING AND
WATER FLUSH CRUSHER
65

WATER FLUSH CRUSHING
66

SABC CONFIGURATION
67

WITH VERTICAL SHAFT
IMPACTORS
68

DISCUSSION POINTS!
• What are the Problem areas of current equipment
installation?
69

SELECTION AND SIZING OF
PRIMARY CRUSHER

INTRODUCTION
• The rock / ore determines
the type of crusher
• The plant capacity
determines the size of
crusher
Family of primary
crushers
• Gyratory
• Double toggle Jaw
• Single toggle Jaw
• High speed roll crusher
• Low speed sizer
• Impactors
• Hammer mill
• Feeder breaker
71

HISTORY
72

MECHANICAL REDUCTION
METHODS
Four basic ways to
reduce a material
• Impact
• Attrition
• Shear
• Compression
73

COMPRESSION
• Done between two surfaces
• Gyratory and double toggle
jaw uses this method
Should be used when
• Material is hard and tough
• Material is abrasive
• Material is not sticky
• Uniform product with a
minimum of fines is desired
• The finished product is
relatively coarse > 38 mm
• Material will break cubically
74

IMPACT
• Refers to sharp ,
instantaneous impingement
of one moving object
against another
• Two types
• Gravity
• Dynamic
Conditions
• Cubical particles are needed
• Finished product must be well
graded
• Ore must be broken along
natural cleavage lines
• When material is too hard and
abrasive or high moisture
content
75

ATTRITION
• Scrubbing material between
two hard surfaces
• Hammer mills operate with
close clearance between
hammers and screen bars
and reduce by attrition
combined with shear and
impact reduction.
Conditions
• When material is friable and
non-abrasive
• When top size control is
not desired
• When maximum of fines is
required.
76

SHEAR
• Consists of trimming or
cleaving action
• Exploits the fact that the ratio
of compressive strength to
tensile and shear strength in
the majority or rocks is
approximately 10 : 1
• Low speed sizers break the
rock in tension and shear by
chopping action
Conditions
• When the material is
somewhat friable and has low
silica content
• When material is soft to
medium hardness
• For primary crushing with a
reduction ratio of 6 : 1
• When a minimum of fines is
desired
• When a relative coarse product
is desired > 38 mm
77

PRIMARY GYRATORY
CRUSHERS
• The main capacity
advantage offered is
centred around the
Archimedes principal
• They found that the
crushing chamber provides
more effective volume than
a rectangular volume
• The shaft grating speed
adds a third dimension to
crushing as opposed to
two dimensional crushing
78

GYRATORY CRUSHER
Advantages
• Designed for direct dump
from trucks Lowest
maintenance per ton
processed of any designed
crusher
• Can handle crushing ore
hardness up to 600 mPa
• Easy handling of tramp
material with hydraulic reiief
system
Disadvantage
• Highest installed capital
cost of any crusher design
79

JAW CRUSHER ANIMATION VIDEO 1

WORKING PRINCIPLES OF THE JAW
CRUSHER VIDEO 2

DOUBLE TOGGLE DESIGN
• The swing Jaw of the Standard
DT crusher pivots from an
overhead shaft .
• A Pitman hung from an
eccentric shaft transmits
motion through a pair of
toggles at the bottom of the
swing Jaw
• Swing Jaw motion is greatest
at the discharge opening.
• The hinge pin is located
behind the centreline of the
crusher zone and it causes
the swing Jaw to move
perpendicular to the fixed
Jaw.
• This arrangement provides
twice the force in crushing
• Typical duty is 350 MPa
82

DOUBLE TOGGLE JAW
Advantages
• Lower installed cost than a
Gyratory crusher
• Can handle high abrasion
with low maintenance
• Can handle tough crushing
application upto 600 MPa
nickel ores, iron ores, etc.
Disadvantages
• Same capacity limitations as
the single toggle aw crusher
• Substantially higher
installed cost than a single
toggle Jaw crusher
• Same crushing size
limitation as single toggle
Jaw crusher
83

SINGLE TOGGLE JAW
CRUSHER
• The rotation of the eccentric
shaft causes the swing Jaw
assembly to move in an
elliptical path.
• Maximum movement of the
swing jaw assembly occurs at
the top of the crushing
chamber with minimum
movement at the discharge
opening
• At all points in the crushing
chamber the crushing action
has both vertical and
horizontal components.
• Due to the rubbing action of
this type of jaw, jaw plate wear
is accelerated and power
efficiency is lowered because
the swing jaw is lifted on
every stroke.
84

SINGLE TOGGLE JAW
CRUSHER
Advantages
• Lower installed cost than a
double toggle
• Lower power usage than a
double toggle
• Can handle sticky, muddy
ore easier than a double
toggle or Gyratory
Disadvantages
• Normal economic maximum
capacity is 750 MTPH
• Duty of crusher is for light or
medium hard material
• Does not handle high abrasive
material as well as DT
• Requires feeder
• Primary crushing only
85

LOW SPEED SIZERS
• The low speed sizing
principle is the combination
of high torque / low roll
speeds.
• The interaction of tooth,
spacer and roll set up a
“sized void” which in turn
sizes the material
• Used for non-abrasive sticky
type material bet 200 - 400
MPa
• Application
• Medium hard limestone,
bauxite, kimberlite,
gypsum, clay, shale and
gold ore.
86

LOW SPEED SIZERS
Advantages
• Can handle high tonnages – 12
000 MTPH
• Low installation cost and
minimum head room required
• Low fines production
• Low power consumption
• Easy rejection of oversize feed
– using discharge gates
• Low reduction ratio
• Peak power loading up to 8
times installed power
• Not economic for low
tonnage unless the material
is very difficult to handle
87

SINGLE TOGGLE VS.
DOUBLE TOGGLE
• ST has a larger angle of nip,
the larger the nip angle the
harder to grip the material..
• ST – greatest movement at
the top
• DT – greatest movement at
the bottom
• ST – Movement of jaw is in
downward rolling direction
which gives a force feed
action assists in handling
sticky material
• Life of Jaw in ST is less than
DT
88

IMPACT CRUSHERS
• Utilized in soft, non-
abrasive application
• Crushing availability and
maintenance can
economically offset against
capital cost
89

OPERATION OF AN IMPACT
CRUSHER VIDEO 3

IMPACTOR ANIMATION VIDEO 4

IMPACT CRUSHER
Advantages
• Can handle larger size
reduction 1000 : 75
• High reduction ratio
compared to investment
cost
• Provides a high degree of
fines
• Can handle up to 2500
MTPH
Disadvantages
• Requires feeder
• Cannot handle tramp metal
• Higher power consumption
as more fines are produced
• High wear due to higher
silica content + 8%
92

FEEDER BREAKERS
• Are utilised in soft to
medium hard application
• Coarsely break material for
belt conveying
• Frequently used for
overburden and
underground duty
93

FEEDER BREAKER
Advantages
• Avoids costly site preparation
and civil work
• Can transfer and crush
material in a single machine
• Handles wet material with ease
• Very low headroom
• Can handle upto 2000 MTPH
Disadvantage
• Very low reduction ratio
• Crushing takes place in
breaker bars and chains
which causes wear.
94

PRIMARY CRUSHER
SELECTION CRITERIA
• Will it produce the desired
product size at required
capacity
• Will it accept the largest feed
size expected
• What is the capacity to handle
peak loads
• Will it choke or plug
• Is the crusher suited to the
type of crushing plant design
• Is the crusher suited for
underground or in-pit duty
• Can it handle tramp material
without damage
• How much supervision is
required
• How does the crusher resist
abrasive wear
• What is the power
consumption
95

PRIMARY CRUSHER
SELECTION CRITERIA
• Does the crusher operate
economically with
minimum maintenance
• Does the crusher have an
acceptable parts
replacement cost
• Does the crusher have easy
access to internal parts
• How does the initial cost of
the machine compare to
the long term operating
cost.
96

PRIMARY CRUSHER
SELECTION - CAPACITY
97

PRIMARY CRUSHER
SELECTION – FEED SIZE
98

PRIMARY CRUSHER
SELECTION – PRODUCT SIZE
99

PRIMARY CRUSHER
SELECTION – COMPRESSIVE
STRENGTH
100

PRIMARY CRUSHER
SELECTION – ABRASION
INDEX
101

PRIMARY CRUSHER
SELECTION – CLAY CONTENT
102

PRIMARY CRUSHER
SELECTION – UNDERGROUND
APPLICATION
103

PRIMARY CRUSHER
SELECTION – MOBILE PLANTS
104

COMPUTER AIDED DESIGN OF JAW
CRUSHER
http://mineralprocessingconsultant.com/ 105

COMPONENTS OF A JAW
CRUSHER
106

MATERIAL FOR
COMPONENTS OF JAW
CRUSHER
107

KINEMATIC ANALYSIS OF
JAW CRUSHER
• The geometry of the
moving Jaw results in a
movement change which
has a great effect on the
crushing action and particle
breakage.
• Based on the analysis of the
moving jaw movement, the
squeezing process and the
crushing force distribution,
the jaw plate wear on a
macroscopic scale level
aiming to predict the wear
distribution on the jaw plate
can be studied.
108

SWINGING JAW
MOVEMENT
• The reciprocating jaw MN
driven by the eccentric shaft
AB does kind of a periodic
plane swing movement.
• Jaw crusher can be
considered as a four bar
mechanism in which link AN
is the crank and OA is the
fixed link
109

• MN is the moving jaw and
OM is the toggle bar.
• In the analysis we are
intended to find out the
displacement, velocity and
acceleration of various
points on the swinging jaw
plate.
110

DATA EXTRACTED FROM
STANDARD JAW CRUSHER
• Length AN = 172 cm
• Length MN = 1085 cm
• Length OM = 455 cm
• Co-ordinates of A (45.3 ,
815.7)
• Crank angle rotates from 0
to 360 degrees
anticlockwise.
111

CRANK ANGLE VS. ANGLE
MADE BY MOVING JAW
112

CRANK ANGLE VS. ANGLE
BETWEEN MOVING JAW AND
Y AXIS
• The graph shows as the
moving Jaw approached its
counterpart which is
stationary it tends to be
vertical i.e. the angle
between the moving Jaw
and the Y axis decreases as
a result the crushed product
slips downwards.
113

VERTICAL DISPLACEMENT VS.
HORIZONTAL DISPLACEMENT
114

HORIZONTAL DISPLACEMENT
VS. CRANK ANGLE
115

DISPLACEMENT VS. CRANK
ANGLE
116

POINTS ON THE MOVING
JAW
• Every point on the moving
Jaw follows an elliptical
path
• When it moves towards the
fixed Jaw, it goes vertically
down and in the return
stroke it moves vertically up.
117

VERTICAL VELOCITY VS.
CRANK ANGLE
• The rate of change of
vertical velocity is greater
for the topmost point and
decreases downwards
118

HORIZONTAL VELOCITY
VS. CRANK ANGLE
• The rate of change of
horizontal velocity is greater
for the bottom most point
and decreases upwards
119

VELOCITY VS. CRANK
ANGLE
• The maximum rate of
change of final velocity is
greater for the points away
from the crank.
120

HORIZONTAL ACCELERATION
VS. CRANK ANGLE
• With progress from 0 to 360
degrees crank angle
rotation the horizontal
acceleration first increases
then decreases
121

VERTICAL ACCELERATION VS.
CRANK ANGLE
• With progress from 0 to 360
degrees crank rotation the
vertical acceleration first
decrease then increases
122

ACCELERATION VS. CRANK
ANGLE
• The maximum acceleration
is observed for the points
farthest away from the
crank angle
123

EFFECT OF SLIDING
MOTION ON JAW WEAR
• Breakage Analysis
• 3 types of Fracture
mechanisms are observed
• Abrasion
• Cleavage
• Shatter
124

BREAKAGE ANALYSIS
• The particle fracture
mechanism in the Jaw
crusher chamber is a
mixture of cleavage and
abrasion. The abrasion
fracture is caused with the
localised too much energy
input to the area directly
under the loading points
and the
• Friction between the Jaw
plates and the particle.
• The induced tensile stress
results in the cleavage
fracture.
125

CRUSHING PROCESS
• Theoretically a particle
inside the crusher is crushed
when it is compressed and
fails in tensile stress.
• In practice the particles also
undergo slipping motion
between the jaw plates
• The forces acting on the
element during the
crushing process is shown
below
126

CRUSHING PROCESS
• As the horizontal and
vertical velocities of the
moving jaw changes during
the crushing process, the
forces on the particle varies
at different times.
• When the component of the
vertical velocity is greater
than the components of the
horizontal velocity the
forces on the particle is
shown in Fig. 3.3 (a)
127

CRUSHING PROCESS
• When the component of the
vertical velocity is less than
the components of the
horizontal velocity the
forces are shown in Fig. 3.3
(b)
128

CRUSHING PROCESS
• By a resolution of forces
acting on the particle as
shown in figure 3.3. it can
be proved that conditions
for the particle to slip
against the fixed jaw plate is
much greater than with the
moving jaw plate. Condition
for slide between the
particle and the fixed jaw
plate is unavoidable
The chance for the particle
to slide is greater with the
fixed jaw than the moving
jaw.
Due to vertical motion
irregular geometry of
particles, a classification
process before the particle
fracture may exist during
close process in which the
particle adjustment may take
place.
129

WEAR ANALYSIS
• Squeezing and sliding are the
two principal factors affecting
the Jaw plates wear
• Squeezing plays the main role
at the top of the crusher and
the wear is small.
• As the particles move down
the crusher the probability of
slip increases and the wear
becomes more pronounced.
•
• At the middle lower part of
the crusher where the ratio
of the vertical distance to
the horizontal stroke
reaches a maximum value
resulting in maximum wear
of the crusher.
• The slide between the fixed
Jaw and particle is greater
compared to the moving
jaw hence the wear is
dominant in the fixed jaw.
130

DISCUSSION POINTS!
• What are the flaws of the
current primary crusher
installation?
• Where can we improve?
131

SELECTION AND SIZING OF
SECONDARY AND TERTIARY
CRUSHERS

INTRODUCTION
• Modern crushers have
increased in performance
• Evolved to focus greater on
the quality of desired
product
• More stringent
requirements are being
placed in terms of shape
and gradation.
• Proper size reduction results in
better recoveries
• In milling feed preparation,
the generation of fines and
total top size reduction results
in maximum mill productivity.
• Proper understanding of
crusher capabilities will
minimize both installation and
operating capabilities.
133

HOW THE SYMONS CONE CRUSHER
WORKS VIDEO 5

NEW GENERATION OF CONE
CRUSHERS VIDEO 6

CONE CRUSHERS
Modern Cone
crushers
• Increased performance
capabilities
• More power capabilities
• Larger in size
• Higher capacities
• Better product shape
• Higher percentage of final
product yield
New cone crushers
• Safer more reliable hydraulic
clamp and clearing system
to protect the crusher from
uncrushables and overload
conditions
• Adaptation of hydraulic
setting adjustment system in
the cone crusher design
improves overall efficiency
of crushing operation
136

NEW CONE CRUSHERS
• New generation of cone
crushers provide
• ease of operation
• Simple maintenance
• Uniform production
throughout the liner life
• High availability
• Technology has evolved to
include computer controls to
maximize and optimize
crusher performance based on
application requirements
• Modern devises provide real
time feedback :
• Power draw, cavity level,
crushing force, temperatures,
pressures, etc.
137

CONE CRUSHER
SELECTION CRITERIA
Information required
• Capacity required with
consideration for expected
availability
• Expected gradation and
product size
Material
characteristics
• Specific gravity
• Bulk density
• Impact work index
• Moisture content
• Abrasion index
• How the material breaks
• Small scale lab tests and full
scale pilot tests
138

CONE CRUSHER DESIGN
LIMITS
Design limits
• Volume limits
• Power limits
• Force Limits
139

DESIGN LIMITS - VOLUME
• Maximum rate of feed to
the cone crusher without
overfilling the cone crusher
feed hopper
• Function of
• Speed of the crusher
• Closed side setting CSS
• Head angle
• Material density
Defining variables
• Feed gradation
• Crusher chamber
configuration
• Transport of material
through the crusher cavity
• Fragmentation
characteristics
140

DESIGN LIMIT - POWER
• Power limit is reached when
average power draw kW
exceeds the installed motor
power of the crusher.
• Ore of high impact work
index or strong resistance
to fragmentation tend to
reach or exceed the power
limit easily.
• Pilot scale test work can
provide information
regarding power
consumption
141

DESIGN LIMIT – FORCE
FACTOR
• The force limit of a crusher
is reached when the
combined forces exerted
during crushing exceeds the
force available on the
machine to hold the
desired closed side setting.
• Force limits may be exceeded
due to
• uncrushables material entering
the crushing chamber
• Operating at a small closed side
setting
• Packing of wet sticky material
• High power draws
• Incorrect crushing cavity design
142

CONE CRUSHER SIZES AND
CAPACITY RANGES
143

SECONDARY CONE
CRUSHER SELECTION
• Ensure the feed material
does not exceed the
acceptable maximum size
for the crusher
• Determine the capacity
requirements at a given
closed side setting based
on a 4/6:1 reduction ratio.
Example
• maximum feed material
200mm
• Capacity 500 tph
• Table 1 : HP 300
• At 32 mm CSS the crusher is
unable to achieve a
minimum of 500 tph
• Table 1 : HP500
144

SECONDARY CONE
CRUSHER SELECTION
Correct cavity
configuration
• The cavity configuration has to
suit the feed gradation so that
the maximum crushing
performance and liner
utilisation is achieved
• Several cavity configurations
are available for cone crushers
to maximise performance.
• An improper liner
configuration applied can
create high crushing forces
leading to adjustment ring
movement , exceeding
crusher force limit.
145

CASE STUDY: HP700
REPLACING HAMMER MILL
Copper mine in
Portland
• Hammer mill used to
prepare rod mill feed
• Hammer mill replaced by
HP700 cone crusher
Results
• 20% gain in energy
efficiency
• By reducing the rod mill
feed from 80% passing 30
mm to 80% passing 14
mm.
146

CASE STUDY: HP700
147

CASE STUDY: HP700
148

THE PRE-CRUSHER
OPTION
• The most recent evolution for
pebble crushing finds a basis
in the presumption that the
most appropriate primary mill
feed contains a minimum
amount of critical size material.
• The initial feed of the primary
mill should dominantly consist
of fine and coarse material.
• Coarse material serves as
impact media and fines as
transport medium for down
stream processing.
• Pre-crushing targets to
convert the middling to fine
fraction.
149

CASE STUDY: PRE-
CRUSHING
Troilus Mine
• 150 – 50 mm is pre-crushed
using an HP 700 cone
crusher
• Production increase and
operating cost decreased.
Kidston Mine
• All primary crusher ore is pre -
screened to remove fines
• All +50 mm oversize is crushed
at maximum reduction ratio to
deliver maximum fines.
• Proved effective in boosting
milling productivity and
lowering operating cost.
150

TYPICAL PRE-CRUSHER
INSTALLATION
151

TRACK MOUNTED CONE CRUSHER
VIDEO 7
152
Selectionandsizingof
Secondaryantertiarycrushers

CASE STUDY : INFLUENCE OF
ECCENTRIC SPEED OF CONE
CRUSHER PRODUCTION AND
OPERATION
153

CASE STUDY : PILOT TEST
PROGRAM
• The research was performed in
Tampere, Finland using an HP
200 cone crusher
• The study can be separated
into three groups of test:
• Base tests
• Fixed tonnage tests
• Feed size distribution tests
• The base tests were used to
measure the crushers
maximum performance for a
given eccentric speed.
• The fixed tonnage tests
simulated operating conditions
where the feed rate to the
crusher is limited below the
maximum capacity based on
the base eccentric speed and
CSS
154

CASE STUDY : PILOT TEST
PROGRAM
• A third set of tests utilized a
different feed size in order
to verify results as well as
reducing the effect of top
size particles possibly being
inhibited to enter the
crushing cavity.
• The tests in each group
used the same
homogenous feed of known
characteristics with feed
sample being taken every
forth test for verification.
155

CASE STUDY: PILOT TEST
RESULTS
Overall
• Most of the data showed
clear trends in capacity,
power and discharge size
distribution as the eccentric
speed was varied.
Base testing results
• For the base testing where
each test was operated at the
optimal cavity level to develop
a baseline for maximum
production, the results
matched theory.
• As the eccentric speed was
increased the capacity
decreased in a nearly liner
manner.
156

CASE STUDY : BASE
TESTING RESULTS
• On average, the total
capacity tph fluctuated by
22.5% over a design speed
range of 34%.
• The increase in capacity but
decrease in reduction as the
speed is lowered results in
relatively low changes to
power draw as shown in
figure 2.
157

CASE STUDY: BASE
TESTING RESULTS
• For a base case testing with
a full cavity throughout, it
was seen that there was
slight benefits in
throughput and energy
efficiency when the crusher
was operated at near the
minimum design eccentric
speed.
• The higher capacity
outweighed the slight loss
in reduction through the
machine and the machine
was more mechanically
efficient at the lower
speeds.
• It was best to operate at the
low end of the speed range.
158

CASE STUDY: 32 MM CSS
PRODUCTION VS. SPECIFIC
ENERGY
159

CASE STUDY : 19 MM CSS
PRODUCTION VS. SPECIFIC
ENERGY
160

CASE STUDY: FIXED
TONNAGE TEST RESULTS
• The tests operated at a fixed
tonnage were conducted to
simulate a crushing application
where the crusher is not the
limiting equipment therefore
the tonnage to the crusher is
fixed by other plant limitations
therefore the crusher cannot
normally achieve a full choke
condition.
• The power draw of the
crusher dropped
significantly as the speed
decreased resulting in a
lower kW/t specific energy
through the machine.
• There was a major shift in
reduction through the
machine ‘
161

CASE STUDY: FIXED
• The tph of the -12.5 mm
product fell slightly as the
eccentric speed reduced
from the reference speed by
20%
• The phenomenon occurred at
the point where the cavity
level in the crusher could not
fill up half of the crushing
chamber and the discharge
became coarser
• While operating with a higher
cavity level was more efficient,
the crusher was more
mechanically efficient at the
lower speeds
162

CASE STUDY : FIXED
• For the fixed tonnage tests
there was a marked
improvement in the
variation of power draw as
the speed and cavity level
increased.
163

CASE STUDY : PRACTICAL
APPLICATION
• There are a number of uses for these
principles in a crushing plant. The
main points are as follows:
• Changing the speed to find a more
optimal setup than that supplied by
the manufacturer.
• Manipulating the speed based on
current static plant conditions,
• And dynamic control of eccentric
speed in a control system.
• The optimization of eccentric
speed may be beneficial
where feed conditions and
plant requirements change.
• Dynamically manipulating the
eccentric speed using a
variable frequency drive has
not been widely used.
164

CASE STUDY : PRACTICAL
APPLICATION
• A dynamic control system
can be used to vary the
speed resulting in benefits
to production and energy
efficiency.
• E.g. When the throughput
of the crusher is high it
could be operated most
efficiently in the lower
speed range.
• If the throughput requirements drop
for a short period of time it would
be more productive and efficient to
increase the speed of the crusher
and operate with a fuller chamber.
• An underlining benefit for greater
control of the crusher operation is
maintaining a choke fed condition,
which has benefit to production ,
operating cost and mechanical
health of the crusher.
165

DISCUSSION POINTS!
• Choke feeding in your
current application, the pros
and cons.
166

SELECTION AND SIZING OF HIGH
PRESSURE GRINDING ROLL
CRUSHERS

NEW CRUSHERS ON THE MARKET
VIDEO 8

HPGR INTRODUCTION
• HPGR are well established
in the cement industry for
the grinding of clinker,
limestone, slag and other
relatively non-abrasive
material.
• Minerals are 20 – 100 times
more abrasive than cement
raw materials.
• Acceptance by the minerals
industry has required the
development of special wear
protection surfaces and rapid
change out procedures for the
rolls.
• Range of grinding
• Coarse < 75 mm
• To grinding of fine
concentrate < 100 microns
169

HPGR INTRODUCTION
• Moisture content up to 12
%
• Machines are available with
capacities up to 3000 tph
• Installed power up to 6000
kW
170

HPGR INSTALLED IN
DIAMOND AND IRON ORE
INDUSTRIES
171

HPGR – L/D RATIOS
Length to Diameter
ratio
• Is it more advantageous to
design rolls with smaller
diameters and larger widths
or larger diameters and
smaller widths?
172

HPGR – L/D RATIO
• The decision as to which
approach to adopt is
capital.
• It has an impact not only on
the performance of the
crusher but also major
impact on the design of the
individual components and
on the general layout of the
unit.
• The minimum roll diameter
is prescribed by the outside
diameter of the bearings
and the thickness of the
bearing block.
• The bearings are sized
according to the installed
grinding force.
173

HPGR – L/D RATIO
• The size of the bearing
determines the shaft
diameter and pre-
determines the manner in
which the gear box and
shaft are to be connected.
• Larger rolls with low L/D ratios
offer greater freedom in
selecting the most appropriate
bearings.
• The larger roll diameter makes
the connection between the
shaft and the gear box simple
to execute. And allow large
gear boxes to be located on
one side to save space and
facilitate maintenance.
174

HPGR – ROLL DESIGN
• Three different roll designs
have been successfully
applied:
• Solid rolls
• Rolls with tyres
• Rolls with segmented liners
175

HPGR – CRITERIA FOR
SELECTING OPTIMUM DESIGN
• The balance between
operating and investment
cost
• The acceptable lifetime and
frequency of replacement
• The tolerable down time for
liner replacement
176

HPGR - COMPARISON
Tyres
• Lower investment cost
• No interfaces (joints)
• Longer lifetime
• Lower wear cost
• No pressure restriction
Segments
• Higher investment cost
• Joints between segments
require more maintenance
due to washouts
• Shorter lifetime
• Higher wear cost
• Only for low pressure
177

HPGR - WEAR
PROTECTION SURFACES
178

HPGR - WEAR PROTECTION
OF ROLL SURFACES
179

HPGR – KEY PARAMETERS
• Achieve the throughput
requirements and to
achieve the desired product
fineness
Throughput
• Function of roll dimension
• Type of roll surface
• Feed material properties
• For a given material and
roll dimension the
throughput is controlled by
the roll speed.
180

HPGR – KEY PARAMETERS
Product Fineness
• Controlled by the grinding
force applied to the
material bed between the
rolls.
• The grinding force creates
the pressure in the material
bed which causes micro-
cracks and breakage of the
particles.
• The correlation between
particle breakage and
grinding force required needs
to be determined for each
material
• Key parameters are
• Specific throughput rate
• Specific press force to be
applied to achieved the
desired comminution results
181

HPGR – THROUGHPUT
RATE VS. ROLL SPEED
182

HPGR – FEED MOISTURE
CONTENT VS. THROUGHPUT
RATE
183

HPGR – THROUGHPUT VS.
SIZE DISTRIBUTION
184

HPGR – PRODUCT
FINENESS
185

HPGR – PRODUCT OF
VARIOUS ORES
186

HPGR – ENERGY
CONSUMPTION VS. FORCE
187

HPGR – ENERGY INPUT VS.
ROLL SURFACE
188

HPGR - ENERGY INPUT
FOR VARIOUS ORES
189

HPGR – ENERGY INPUT VS.
GRINDING FORCE
190

HPGR WEAR FACTORS
191

HPGR – ROLL DIAMETER
VS. ROLL SPEED
192

HPGR - APPLICATION
193

HPGR – PEBBLE CRUSHER
194

HPGR – PRE-CRUSHER
195

HPGR – REPLACEMENT OF
3RD AND 4TH STAGE
196

DISCUSSION POINTS!
• Is it possible to include
HPGR in your circuit?
197

ORE CHARACTERISATION

CHARACTERISATION -
UNDERSTANDING THE ORE
BODY AND THE METALLURGY
• The best possible
characterisation of the ore
body will enhance the
ability to extract better
outcomes from a mine to
mill application.
• The greater data, the better
body. Properties.
• This characterisation is
important in developing
extraction and processing
strategies which enhance
the productivity gains
possible from a mine to
mill application (JKMRC
1998)
199

CHARACTERISATION -
• At its simplest ,
characterisation is about
developing the best possible
understanding of the ore body
, in particular its variability.
• One of the first
comprehensive
characterisation studies was
reported by Simkus and Dance
(1998) at the Highland Valley
Mine
Highlands Valley
• Had developed a program
mapping the hardness of
different ore types, since the
late 1970’s.
• By late 1990’s , drill monitors
were being used to provide an
estimate of ore hardness of
subsequent blasted ore.
• Ore was then tracked to
stockpiles using mine dispatch
systems and movement
through stockpiles was
modelled.
200

CHARACTERISATION -
• An image analysis system
was used to provide an
estimation of the feed size
distribution to the SAG
mills.
• Relationships were
developed between ore
hardness, feed size and mill
throughput.
• This approach provided a
strong ability to predict
expected mill throughput
information which could
then be utilised in process
control.
201

CHARACTERISATION -
Rock Mass Properties
• Standard rock mass
properties are usually
obtained as geotechnical
information from drill core
and include:
• Rock Mass Rating
• Rock quality designation
• Point load Index
• Young’s Modulus
• Poisson’s Ratio
• Unconfined Compressive
stress
• In-situ block size
• Joint spacing
202

CHARACTERISATION -
Metallurgical Process
Parameters
• These data typically include:
• Grades, including the grades
of gangue minerals and minor
elements
• Grindability data, principally
related to ore hardness, as
measured by bond work
indices and JKMRC grinding
model parameters,
• Flotation grade and
recovery data as
determined by laboratory
flotation tests
• Mineral liberation
• Lithology
• Geological Alteration
• Acid forming potential of
ore
203

CHARACTERISATION -
Predictive Models
• Models frequently used in
mine to mill studies include
• Mine block models
incorporating geotechnical
and geometallurgical
parameters.
• Blast fragmentation models
• Muck pile models
• Comminution models
• Models which predict the
final stockpile shape
resulting from open pit
blast are increasingly useful
when it is desirable to
understand where material
of different properties,
notably grade, reside in the
muck pile after blast.
204

CHARACTERISATION -
Conclusions
• The literature analysis suggests
that the tools required to
implement Mine to mill
approach are available in
acceptable form.
• Many of these hardware and
software tools are provided by
established suppliers and have
been successfully
implemented.
• Most tools are also subjected
to research and further
development
• The area of greatest need is
the availability of tools to
monitor mine to mill
outcomes.
• To date these have been
developed at individual sites
• More generic software tools
would be useful.
205

CASE STUDY: ANTAMINA BOOSTS
THROUGHPUT FOR HARD ORES

CASE STUDY: ANTAMINA
BOOSTS THROUGHPUT FOR
HARD ORES
Introduction
• The ore body that
Compania Minera Antamina
has been mining in Peru
since 2001 contains two
principal ore types, copper
molybdenum ores and
much harder copper zinc
ores which exist about 70 :
30 ratio.
• Historically the copper zinc
ores were processed at a far
slower rate and it was clear
that something needed to be
done.
• A collaboration between
Metso Process Technology
and Innovation and the Mine
began in 2007 which aimed to
optimise the entire
comminution process.
207

HARD ORES
• The team began by auditing
the drill and blast practice as
well as sampling the crushing
and grinding circuit.
• This helped them to develop
models that would reveal
what each step was achieving
and what could be tweaked to
improve performance
• The mine and the processing
plant was then benchmarked.
• The models were calibrated
and then a number of
scenarios of operating
strategies for both mine and
process plant were run.
• An in-depth review of existing
practices were carried out.
208

HARD ORES
• The ore was categorised in
varying groups of hardness.
• Blast practices were audited
and blast fragments were
measured which made it
possible to benchmark existing
practices, and to define the
main constraints related to
wall stability and control ore
dilution and environmental
aspects.
• Site specific models for the
comminution process was
created and it became evident
that the largest potential gains
to the blast could be found.
• The basic idea was to increase
the powder factor using more
explosives to create a finer
ROM fragmentation so that
downstream equipment would
treat the ore with ease.
209

HARD ORES
• In the drilling process the
drill pattern ( burden and
spacing) was reduced
• By maintaining the same
type and amount of
explosives in each drill
hole, the corresponding
blast powder factor rose
from 0.35 - 0.54 kg/ton
• In addition switching to
electronic detonators
proved to be more reliable
and ensured that blasts
went off according to plan.
• A pebble crusher was also
installed and modification
to the pulp lifters were
made.
210

HARD ORES
Conclusion
• Mine to mill optimisation work
increased throughput by 30 %
• Process plant improvements
contributed 10 % increase in
throughput
• Reduction in hardness of the
copper zinc ore contributed
15% to the increase in
throughput
• As of 2011 Antamina was
processing copper zinc ores at
an average rate of 4400 tons
per hour, up 60 % from the
performance prior to 2007
• The copper – molybdenum
ore also saw an increase to
4800 tons per hour.
211

CASE STUDY : BATU HIJAU
(INDONESIA)
PRODUCTION PLANNING FOR THE
COMBINED MINE TO MILL
OPERATION

CASE STUDY:
INTRODUCTION
• The Batu Hijau copper –
gold operation commenced
a mine to mill program in
2001 with the standard
initial objective:
• To modify blast practice to
improve SAG mill
throughput.
• The work presented spans
over 10 years of
development.
213

CASE STUDY BATU HIJAU
• Using rock mass
characterisation data, ore
hardness and blast design
data, simple regression
models were developed which
predicted SAG mill throughput.
• This was done for different
zones in the ore body
ultimately resulting in separate
throughput predictions for 16
ore body domains.
• JKSimMet was used to
enhance the initial
regression models in order
to more accurately predict
the expected SAG mill
throughput for the different
domains.
214

• Attention then turned to
developing the best
blasting practice for the
domains to reduce
fragmentation top size in
order to improve loading
rates in the pit and increase
grinding circuit throughput.
• Different blast designs were
developed for each domain.
• The modelling approach
also provided a basis for ore
scheduling and production
forecasting
215

• The second phase of the
study was based on
improving prediction of mill
throughput based on
improved orebody
characterisation.
• Improving prediction of
blasting performance and
refining mill models.
• The other major advance
has been the use of the
modelling approach for
both short and long term
production planning.
216

• In 2007 the equations
linking mill throughput to
measurable variables were
coded into the mine block
model so that throughput
predictions became a direct
output from the block
models.
• As previously the throughput
relations were based on
regression models of the tph
as a function of
characterisation variables.
• In effect the models
established a benchmark
performance which can be
expected when mining and
processing ore from different
domains.
217

Outcomes first phase
• Productivity gains of 10%
for loading rates in the pit
and 10-15% increases in
SAG mill throughput for the
individual ore domains were
reported. Some of the
important requirements for
the effective
implementation of the Batu
Hijau M2M
• Strategy included:
• The need for a dedicated team
of involved staff from geology,
mining, milling IT support
• Strong and on-going support of
senior management
• Best possible orebody
characterisation – an on-going
requirement with continuing
updating of the domain models
218

Outcome first phase
• Accurate models of blasting
and comminution to
establish expected
performance for each
domain and the best
balance in cost and effort
between blasting and
milling for each domain
219

Outcome second
phase
• The second phase of the Batu
Hijau study provides the basis
for a much wider range of
M2M applications than just
increasing SAG mill
throughput.
• There is a demonstrated
ability to predict mill
throughput over the long term
to +/-2% accuracy
• At the core of the latest
developments is a greater
ability to predict mill
throughput with
considerable accuracy for
different ore sources.
220

• The applications of that
capability include:
• The understanding of the
expected or benchmark
performance against which
actual performance can be
compared.
• Deviations from the
expected can be identified
and remedial action to
regain performance can be
better targeted
• The availability of a sound
basis on which
improvements in the
grinding circuit can be
identified, implemented
and measured
• A tool which is an integral
part of both long and
short term production
planning to achieve
required production rates
221

ORE DRESSING STUDIES – WHAT
IS INVOLVED

ODS - WHAT IS INVOLVED
Introduction
• Ore dressing studies the
body with respect to
metallurgical properties.
• In conjunction with the project
requirements, geologists and
mineral resource
management, a sampling
program is compiled for the
specific ore body.
• These samples are
characterised with respect to
various flowsheet and data
obtained from the
characterisation work is
analysed and evaluated to
improve the process recovery .
• This provides information with
regards to risk minimisation,
for both plant design
envelopes as well as
operational efficiency
223

ODS - KNOWLEDGE FLOW224

ODS - IN AN ORE BODY
DEVELOPMENT
225

ODS - GENERIC DIAGRAM
FOR SAMPLE
CHARACTERISATION
226

ODS - COMMINUTION
CHARACTERISATION
• Test work consists of a suit of
laboratory and pilot plant scale
tests
• Laboratory tests are typically
rock mechanic tests as used
by equipment manufacturers
to provide performance
guarantees for comminution
equipment.
• These also include drop
weight tests , a
methodology used to
determine the extent of
breakage resistance due to
impact and abrasion.
227

ODS - COMMINUTION
CHARACTERISATION
• Depending on the
requirement of the specific
ore dressing study, i.e.
feasibility study , pilot scale
tests can be conducted on
various comminution
equipment to validate
laboratory scale test results
and generate plant design
information.
• Samples can also be
provided to equipment
manufactures to conduct
their own tests
228

ODS - DATA ANALYSIS
AND INTERPRETATION
• The data generated from the
characterisation tests is
analysed and interpreted by
process specialists.
• This is a collaborated effort
amongst in-house specialists,
proprietary and commercial
software, research institutes,
and equipment manufactures
and suppliers.
• Interpretation in this context
means that key metallurgical
parameters are determined
and operating envelopes are
established.
• Also potentially problematic
ore types are identified and
process recommendations are
made.
229

ODS - DATA ANALYSIS
AND INTERPRETATION
• The output results in key
plant design information.
• E.g. comminution
characterisation predicts the
product size distribution
and mass balance via
simulation for scrubbing
and each of the crushing
stages.
230

ODS - INTEGRATION
• The role of the metallurgist is
key in generating the
flowsheet design knowledge
package through the
interaction with a variety of
process specialists and process
engineers.
• Important major ore related
problem areas within a specific
ore type are also highlighted.
• This means that such problem
areas and solutions are
integrated within the overall
process design.
• Depending on the phase of
the project the integration
process also includes a level of
simulation of the ore dressing
study, and derived flowsheet
options that resulted from the
characterisation of the various
ore types.
231

ODS - INTEGRATION
• Simulation enables critical
investigation of all system
attributes, and the ability of
the circuit design to deliver
finished product with out
recycling.
• Raw ore dressing information
and knowledge is traded off
against practical operational
constraints, which leads to a
fit-for-purpose design
• That has the best chance of
maximizing recovery of
minerals from in-situ
resources.
232

ODS - PLANT DESIGN
• To reduce the risk of selecting
incorrect equipment from a
vast array of possibilities a
formalised set of tools to
guide equipment selection and
plant design have been
developed
• These tools consist of
commercially available as well
as proprietary tools
• Process engineers are
provided with basic flow
diagrams and related
metallurgical parameters.
• The process engineer will then
expand on the original ore
dressing flowsheet provided
and develop a number of
flowsheet based on the project
requirements.
233

ODS - PLANT DESIGN
• Completed ore dressing
study assists the process
engineer to rapidly evaluate
scenarios using existing
models and create an
understanding of how the
metallurgical envelope of
characteristics develop
through the ore body.
• An evaluation of proposed
solutions against a
background of knowledge
derived from the study is then
conducted.
• The knowledge derived from
the study supports the
engineer in the design phase
and assists in reducing project
risk and increases confidence
in the approved flowsheet.
234

PROFIT BASED GRINDING
CONTROLS
Case Study : Sierrita
Program controller : Duval Corporation

CASE STUDY : SIERRITA
Introduction
• The comminution circuit
represents the largest user
of energy in the Mineral
Processing Industry
• As the grades of ore
reduces the economics of
energy usage becomes
more significant.
• Pertinent control theory for
the control of comminution
circuits has been known for
a long time but it is of
recent years that practical
techniques and robust
computer control
architectures for these
systems have become
available
236

Description of the
Plant
• Wet grinding circuit treats
90 000 stpd
• Sixteen x Allis-Chalmers
overflow ball mills are
operated in parallel in a
conventional closed circuit
wet grinding system.
• The very low grade ore,
variable crusher product,
and changes in ore
hardness produces
disturbances that upset the
performance of the
grinding circuit.
237

Instrumentation
• Variable feeder
• Feeder Weight
measurement system
• Feed water flow meter
• Sump water flow rate
• Sump level indicator
• Mill power draft
• Pump amperage
• Control valves to feed and
sump water
• All the other variables are
calculated using inferential
techniques
238

Process Analysis study
• Fig. 2 shows a schematic
diagram of a ball mill /
cyclone control system
• This diagram shows the
instrumentation and the
calculated variables use in
the control strategy.
• From the process analysis
study several objectives
were established.
239

Objectives
• Reduction of mill feed size
• Reduction of mill power
consumption
• Extending mill transport
conditions
• Investment in variable
speed drives
• Identification of proper
linking of manipulated
variables with control
variables
• Identification of inferred
measurements and signal
conditioning of the raw
measurements
240

Disturbances
• Mill feed particle size
distribution due to bin
segregation and crusher
circuit operation
• Ore hardness and ore
mineralogical structure and
composition due to natural
mining characteristics
• Pumping / classification
limitations and equipment
wear.
• Process analysis study showed
that the calculations of the
inferred calculated variables
can provide adequate
information for the
development of control
strategy
241

Design of the plant
control strategy
• Fig. 3 shows that for a given
ore there is a unique milling
rate to provide the grind size
that will yield maximum profit
under certain economic
conditions
• A higher milling rate can be
achieved with a coarser grind
which is off set by losses in
recovery due to poor liberation
• A finer grind producers
better recoveries but loss in
throughput rate.
• Swings outside the given
band produces losses
242

Design of plant
control strategy
• Fig. 4 shows the control
objectives and limiting
conditions that the control
system must overcome to
produce a profit.
• The main controller is the mill
load constraint controller for
safe operation followed by the
grind cut controller for
profitable operation
• The mill load constraint
controller involves the
changing mill transport
constraint and sets the
tonnage for feasible operation
243

Design of plant
control strategy
• The grind cut inferential
controller maintains the
optimal liberation, if process
operational limits permit.
• The curves depicted in fig. 3
and 4 are not unique and
are changing constantly.
• Thus the information must be
handled on a timely basis in a
computer system.
• The computer system will in
turn provide for adapting
values of the moving
constraint and set points. This
known as online adaptive
decision making or control.
244

Grinding controls
• The primary objective of the
grinding controls system is to
provide a flexible , adaptive,
easy to use system to:
• Maintain an optimal
throughput depending on the
ore conditions. This will
provide the downstream
process with a constant size
distribution for improved
recovery.
• Or to maintain a stable
operation while assisting
the operator in maximizing
the throughput, avoiding
frequent upsets or spills and
maintaining an adequate
grind.
245

Grinding controls
Simplified function
block control strategy
246

The four principle
controllers
• The ball mill load control
system
• The grind index control
strategy
• The ball mill transport
index control strategy
• Sump level controller
247

The ball mill load
controller
• This is the main controller
• Any additional capacity of
the ball mill depending on
the grind setting is sensed
by the ball mill load
controller and the feed rate
is increased.
248

Control Design
249

MAIN CONTROLLER
WINDOW DISPLAY
250

Computer Architecture
for plant management
251

Overall plant control
strategy
• The current objective of
increasing the recovery / profit
by running an optimal
throughput can be enhanced
by proper co-ordination of the
plant activities.
• Fig. 8 shows the computer
architecture used to integrate
the distributed control system
with process management
activities
• Four process control units are
networked to two operator
interface units.
• The plant host computer is
also used for engineering
analysis of operating and lab
oratory information with
statistical modelling, process
analysis and simulation and
reporting software packages.
252

Conclusions
• A profitability concept was
transformed into a feasible
mode of operation.
• The tonnage setting can be
safely pushed up to 400
stph from 250 stph while
maintaining metallurgical
performance.
253

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