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POLYCOM high-pressure grinding roll
for the minerals industry
tk Polysius
POLYCOM high-pressure
grinding roll
The economic and gentle
processing solution
The high-pressure grinding roll has proven to be extremely effective for the grinding of
mineral raw materials. With numerous POLYCOM installations in different industrial sectors,
ThyssenKrupp Polysius is the worldwide market leader for this technology. Thanks to
the application of ultramodern production processes, the plants protect resources and
the environment and guarantee plant owners maximum productivity and economy of
operation. Sustainable product solutions that are required by clients all around the world.
The following features distinguish the
POLYCOM high-pressure grinding roll from
other grinding systems:
A hydropneumatic spring system builds
up a pressure of up to 250 MPa in the
layer of material between the rolls.
During operation of the machine it is
possible to alter the pressure and thus
change the product fineness.
The majority of high-pressure grinding rolls used in the minerals industry are made by
ThyssenKrupp Polysius. The POLYCOM operates convincingly all around the world,
comminuting copper ore, gold ore, iron ore, diamond ore, platinum ore, coal, granulated
blast furnace slag, limestone, cement clinker and other mineral raw materials.
Highly wear-resistant roll surfaces
achieve service life times of up to 10,000
hours when grinding abrasive hard rock.
When softer materials are involved, the
service life can even exceed 20,000
hours.
This type of mill offers the minerals industry numerous benefits:
Safe process technological design.
Low operating expenses: in comparison to other systems, both the power consumption
and the costs for wear parts are significantly lower.
The feeding device ensures that the
machine permanently runs with the
optimum filling level the precondition
for efficient operation and a high service
life of the rolls.
High throughput rates: a high-pressure grinding roll can replace several reduction
crushers. This reduces the space requirement.
Metallurgical advantages in the downstream process stages.
Shorter delivery, assembly and commissioning times than can be achieved with other
systems.
The mill feed material can be dry or moist,
with particle sizes ranging from below
1 mm to 75 mm.
If required, the material can be dried in
screens or air separators in a closed circuit
grinding system.
The new low-maintenance wear protection
systems for roll surfaces permit even the
most abrasive materials to be efficiently
ground.
Because of the short material dwell time
in the mill, the machine settings can be
quickly altered by the touch of a button,
making the process easy to control and
permitting rapid compensation for
fluctuations in the properties of the feed
material.
Modern, user-friendly regulating, monitoring
and control devices, combined with
advanced process technology, ensure
reliable and effective operation of the plant
and an efficient process cycle.
Comminution in the POLYCOM results in
a product that has a far higher percentage
of fines than could be achieved in a
conventional crusher.
Moreover, the coarser particles show
extensive cracking which reduces the
amount of grinding work to be performed in
the downstream mills and improves the
liberation of metal from the ore.
The benefits are particularly noticeable in
the heap leaching process, where the
POLYCOM product demonstrably increases
the yield and thus the operating economy of
the facility.
POLYCOM particle
size distribution.
The grinding elements of the high-pressure
grinding roll are two counter-rotating rolls,
between which the material is crushed. One
roll is designed as a fixed roll and the other
one as a floating roll.
The required comminution pressure is
transmitted by a hydraulic system via the
floating roll.
Material passing screen [%]
POLYCOM units are designed for throughput rates in excess of 5,000 tph.
The drive system can be equipped
with variable speed motors in order to
compensate for throughput variations in
the upstream and downstream process.
Compared to the
crusher product
(lower picture)
the POLYCOM
product (upper
picture) is extensively cracked.
Whereas the grinding action of a tube mill
involves a mixture of compressive and
shear forces, the POLYCOM imposes
virtually pure compressive force on the layer
of material between the rolls. The compression stress thus caused in a particle of
material is more than five times higher than
shear stress would be.
100
90
80
70
60
50
40
30
20
Product
of highpressure
grinding roll
Product of
crusher
10
Feed
material
0
0,01
0,1
10
100
Particle size [mm]
Innovative POLYCOM design
A guarantee for high availability and for
economical continuous operation
In order to fulfil the expectations placed on the high-pressure grinding roll, such as
long service lives of the roll surfaces,
optimum feed material pull-in capability for maximum throughput rates, even of moist
materials and
easy replacement of worn roll bodies,
the POLYCOM rolls have a length to diameter ratio of between 0.3 and 0.7.
This provides the following advantages:
large roll diameters allow the feeding of lumpy ores,
Autogenous wear protection: ground material
accumulates between the hard metal studs and thus
minimises the wear of the roll surface.
minimised wear costs,
thick roll tyres permit refurbishment of the roll bodies (a further wear-cost-reducing
aspect),
self-aligning roller bearings dimensioned for safe and reliable operation,
quick and safe mounting and dismounting of the gear unit during roll changes
because it is only bolted onto the shaft.
The fixed and floating rolls are both
mounted in bearing blocks. The self-aligning roller bearings, which compensate for
skewing of the rolls, have a multiple seal
system to prevent dust penetration and
grease loss. The bearing blocks of the fixed
roll are bolted onto the machine frame,
while those of the floating rolls travel in a
longitudinal slideway. The fixed and floating
rolls are of identical construction and can
therefore be interchanged.
The grinding force is transmitted to the
floating roll by four hydraulic cylinders. A
hydropneumatic spring system allows the
setting of different pressure characteristics
and different control methods to enable
optimum application of the grinding
pressure in the roll gap and to protect the
machine against possible overloading. The
floating roll automatically accommodates
to changes in feed material characteristics
by moving outwards or inwards. Spacers
prevent the rolls from touching.
Since the introduction of the POLYCOM,
the wear protection concept has been
constantly improved and adapted to the
requirements of the different industries.
In order to ensure uniform distribution of
the drive power to the two drive motors, the
vertical feed shaft can be equipped with
infeed guide plates to adjust the distribution
of material flowing through the mill. If this
feeding device is installed, the material
filling level is monitored by means of load
cells.
This version ensures a long service life and
therefore a high plant availability and the
lowest maintenance requirement. It also
enables moist and sticky materials to be
ground.
ThyssenKrupp Polysius offers:
forged, hardfaced roll bodies,
chill cast alloy tyres made of bainite,
The roll drive system consists of:
constant or variable-speed electric
motors V-belt connection to the gear
units up to a drive power of 300 kW per motor cardan shaft connection to the gear
units > 300 kW mechanical overload
coupling for protecting the gear unit and
planetary gear unit.
The feed chute is an important component
for the assurance of reliable and optimum
operation of a high-pressure grinding roll.
For moist and sticky feed materials (such
as iron ore concentrates), ThyssenKrupp
Polysius installs vertical feed chutes with
straight walls.
For lumpy feed materials, chutes that
assure mass flow are installed.
Self-aligning roller bearings compensate
skewing of the floating roll.
Principle of feed
shaft adjustment.
roll bodies made of compound casting
and
roll bodies with hard metal studs.
For abrasive materials, roll bodies with
surfaces protected against wear by hard
metal studs are generally used.
The design of the hard metal studs
(geometry, hardness and metallurgical
composition) and their arrangement on the
roll surface are selected to suit the operating conditions and feed materials.
Nowadays, roll service lives of up to
10,000 h for hard rock, up to 12,000 h for
diamond and iron ore and up to 30,000 h
for iron ore concentrate applications are
achieved. Depending on the operating
parameters, higher values are also
possible.
Roll body with hard
metal studs.
Application examples
High-pressure grinding rolls
in concentrator plants ...
Compared to crushers, the POLYCOM produces a significantly
higher percentage of fines. Moreover, the comminuted particles
have a large number of micro cracks. These product features
provide enormous economic and process technological benefits
for the various minerals applications ...
Comparison:
gold yield rate of a crusher
and of a POLYCOM.
Gold yield [%]
... for gold, platinum and copper ore
100
80
60
40
20
For many ores the POLYCOM is an economically superior concept
compared to conventional systems, such as reduction crushers or
SAG mills.
The prospect of achieving maximum increases in the throughput
of existing grinding plants also make the POLYCOM a popular
machine for plant extensions. Thanks to its low space requirement
and high capacity in relation to machine size, the POLYCOM can
be easily incorporated into existing plant configurations.
The POLYCOM also brings substantial benefits to the heap
leaching process. The yield of valuable substance and thus the
operating economy of the facility are significantly raised. The
ground material can either be conveyed directly to the heap or first
go through an agglomeration stage. If finer qualities are required,
the POLYCOM product is first screened.
The first step on the way to
gold jewellery is the liberation of
gold particles.
Copper ore comminution in South
America: Four POLYCOM systems
are used for primary grinding. Four
energy-saving, low-wear ball mills
are used for the wet process final
grinding throughput 108,000 (!)
tonnes of rock per day.
From the natural rock
via liberated copper to the
copper coin...
10
20
30
40
50
60
70
Yield period [days]
100
80
60
40
+10M
-10+20M
POLYCOM
Flotation
From mineral resource to finished product
20
Used as a primary grinding unit upstream of ball mills, the
POLYCOM can boost the throughput by 20 to 30 %.
Ground
platinum ore.
Gold yield [%]
-20+48M -48+100M -100+200M
Crusher
-200M
[Mesh]
for diamond ore
for iron ore
Breaking the diamond-bearing rock in a high-pressure
grinding roll is a gentle method of liberating the diamonds.
The iron ore industry uses the POLYCOM
as a reduction crusher for lump ore.
The surrounding rock is broken while the hard diamond
remains undamaged and is recovered in a downstream
process stage.
Its high throughput rates, combined with
the production of a high percentage of
fines, bring clear operating and capital cost
benefits: one POLYCOM can replace
several crushers.
This also significantly reduces the maintenance expenses of the plant.
For scientists they may be just the material with hardness value
10, but for the ancient Greeks they were the tears of the gods.
Today we know that every diamond was created billions of years
ago by enormous underground forces. They only see the light of
day if the lava of erupting volcanoes carries them to the earths
surface.
The main field of POLYCOM application is
the production of pellet feed: the high-pressure grinding roll, usually installed downstream of the ball mill and filtering stage,
grinds the filter product.
POLYCOM for diamond ore
liberation in South Africa.
POLYCOM for iron ore
comminution in Brazil.
The POLYCOM product is the basis for
manufacturing high-quality iron ore pellets.
POLYCOM and scrubber from
ThyssenKrupp Polysius: core process
technological components of a diamond
ore processing plant.
Pelletisation
From iron ore via
the molten metal to the
finished product.
10
11
Technical data
B
Securing the future
L2
Research and Development. ThyssenKrupp Polysius has the knowhow and the equipment (the
ThyssenKrupp Polysius research centre with its ultramodern machines is one of the worlds leading
development establishments for basic material technology) to provide a suitable plant concept for the
individual properties of the respective ore.
The ThyssenKrupp Polysius research centre is equipped
with POLYCOM units of different sizes for grinding tests in
open circuit or closed circuit grinding systems.
For the safe process-technological design of plants, it is
often enough to grind a small sample material quantity.
Material tests also provide definite predictions of wear.
No matter whether a new plant, the upgrading of
existing facilities or the opening up of new fields of
application for proven technologies and services is
concerned.
Optimally trained personnel
take care that optimum wear
protection is restored.
The ThyssenKrupp Polysius Service also focuses on preventive maintenance and
comprehensive training of the plant operators. Due to the numerous POLYCOM
applications installed, the customer profits also in the service sector from complex
experience, customer-specific service concepts and thus reliable plant operation for
long periods.
Within the framework of service contracts
service experts plan e.g. the exact life cycles of
the installed roll bodies thus ensuring as
a preventive measure free capacities in the
ThyssenKrupp Polysius workshops so that the
wear parts can be immediately refurbished.
High-performance simulation programs support the
selection of machines and systems and forecast the
energy requirements, mill circuit material balances,
wear rates etc., thus assuring future-oriented, customtailored plant solutions with the lowest possible
operating expenses.
Service. Worldwide. Our scope of the ThyssenKrupp Polysius services is so broad that customers all around the world are assured of
comprehensive support for their achievement of profitable plant operation. Such support is the basis for permanently maintaining and
strengthening the trust and loyalty of our customers.
Thanks to a global network of subsidiaries
and service centres, ThyssenKrupp Polysius
is able to refurbish POLYCOM roll bodies
quickly and without complications all
around the world.
Following the material analysis, the ores are compared
with the comprehensive ThyssenKrupp Polysius
material database to quickly and reliably obtain the data
regarding their grindability, hardness, abrasiveness and
agglomeration behaviour that are needed for designing
the plant configuration.
From laboratory-scale to industrial reality:
The mineral liberation analysis (MLA) specifies the
mineralogical properties of different sample materials
and provides important data for the layout and the
design of the high-pressure grinding roll. It uses the
scanning electron microscopy (REM) and the energydispersive X-ray spectroscopy (EDX).
The service centres located close to customers
in all important mining regions all around the
world and equipped with top-end workshop
machines perform the maintenance and
manufacturing of machines and components:
close to the plant site, quickly and expertly.
L1
L1
Size
Type
9/7
11/8
14/8
14/10 15/11 17/10 17/12
17/12
17/14
20/10
Roll diameter
mm
950
1100
1400
1410 1520 1700 1700
1700
1700
2000
Roll width
mm
650
800
800
950
1200
1400
1000
Grinding force
kN
2700
3400
4300
7000
8600
Motor power
kW
2 x 220
2 x 450
2 x 500
2 x 800
2 x 1600
L1
mm
1150
1300
1600
1720 1720 1900 1900
2100
2100
2100
L2
mm
3240
3750
3735
4305 4305 4490 5050
5530
5530
5950
mm
1860
2150
2164
2580 3030 3030 3030
3025
3500
3000
mm
1371
1685
1895
2095 2095 2220 2220
2390
2390
2760
mm
3910
4300
4580
4960 5870 5230 5010
5010
6260
5160
mm
6000
7000
7360
7860 9850 6800 8250
9600
10400
9270
10
Size
Type
1100 1000 1200
19/15
20/15
20/15
20/17
22/15
24/17
26/18
30/20
1850
2000
2000
2000
2200
2400
2600
3000
1500
1650
1550
1650
1750
2000
Roll diameter
mm
Roll width
mm
1500
Grinding force
kN
11000
13500
17000
20000
25000
Motor power
kW
2 x 1850
2 x 2500
2 x 2800
2 x 3400
2 x 5000
L1
mm
2200
2200
2200
2200
3000
3000
3500
2000
L2
mm
6020
6020
6550
6550
7725
7725
8500
9500
mm
3310
3460
3640
3640
3820
3820
4150
4600
mm
2635
2855
2795
2795
3160
3180
3510
3600
mm
6800
7000
6980
7100
7860
7860
9000
7400
mm
11300
12000
11300
11600
11600
11600
14000
14000
The stated dimensions are subject to alteration in the course of technical advancements.
