2
High-pressure roller grinding of cement clinker and hard brittle materials is a modern and very energy-efficient process. During its relatively short history, roller press technology has undergone significant development from a pre-grinding process to a range of applications including semi-finish grinding and finish grinding.
The HRP roller press developed by
FLSmidth ranks among the most advanced and efficient units available.
Its design incorporates the vast expe- rience and expertise gained since roller press technology was first introduced.
How it works
In high-pressure roller press comminution the feed material is exposed to very high pressure for a short time. The high pressure causes formation of microcracks in the feed particles and generates a substantial amount of fine material.
If the pressed material is fed directly to a ball mill, the power consumption required to produce finished cement will be much lower than that of a mill fed with unpressed material.
This makes it possible to increase the throughput of a given size ball mill and reduce the specific power consumption of the whole mill system.
A flexible solution
The roller press is a flexible solution, highly suitable both for upgrades and for new installations. Upgrading may increase capacity by up to 100 percent, while the total specific energy con- sumption of new installations may be reduced by 20-30 percent compared with conventional grinding systems.
The most typical process configurations are described in the following.
Besides the cost-saving features already mentioned, the HRP roller press is characterised by:
- long wear part life
- low operational and maintenance costs
- short shutdown for wear part replenishment

As the grinding efficiency of a roller press is about twice that of a ball mill, considerable energy savings can be achieved by substitu t ing roller pressing for ball mill grinding.
Basically, there are several different ways of incorporating a roller press in a grinding installation.
Pregrinding system
In the pregrinding system, the roller press is used for grinding fresh feed and a certain amount of recirculated pressed flakes. The roller-pressed material is finish ground in a conventional ball mill grinding circuit. Excessive flake recircu- lation may cause operational instability, so in practice the power consumption of the roller press is limited to approximately
5 kWh/t in the pregrinding mode.
Semi-finish grinding system
The semi-finish grinding system ensures better utilisation of the roller press. The roller press operates in closed circuit with two separators on top of each other – a static separator making both disagglomerating and a coarse separation, and a dynamic separator. Fines from the roller press circuit are finish ground in a one-compartment ball mill to the required fineness.
A very compact and energy-efficient semi-finish grinding installation can be attained by combining the roller press and the ball mill with a Sepax separator and our stabile RPGS separator.
The roller press then operates in closed circuit with the static separator working as both disagglomerator and coarse separator, while the ball mill operates in closed circuit with the high-efficiency dynamic separator in the Sepax top module. As the separator air is used for both separation stages, the overall quantity of air and the fan power consumption remain at a very low level.
Splitting the two circuits
For some applications it may be necessary to split the two circuits, for instance if drying in the roller press circuit and cooling in the ball mill circuit are required, or if one roller press is to serve two or more ball mills.
In that case the static separator is used as a stand-alone unit for the roller press circuit, and a standard high-efficiency
Sepax is used for the ball mill circuit.
Some types of feed material and some end products allow omitting the ball mill so that the roller press is used for finish grinding in a closed circuit with the dynamic Sepax separator on top of the static RPGS separator. When feasible, such a process configuration is very attractive in terms of operating and investment costs.
Roller press pregrinding
Roller press semi-finish grinding
Two-stage Sepax
Roller press finish grinding
Mill air flow
Seperator air flow
Material flow
3

4
6
3
5
4
1
12
13

14
9
2
10
7
8
11
1 Grinding rollers with welded hardface wear lining
2 Oil-lubricated spherical roller bearing
3 Planetary reduction gear
4 Torque arm arrangement
5 Safety release coupling
6 Main motor
7 Hydraulic pressurising cylinders
8 Nitrogen-filled bladder accumulators
9 Bottom frame
10 Top frame
11 End section
12 Hinged L-shape end section
13 Elastomer shear pad
14 Feed control gate
5

6
Drive configuration
Specific energy consumption, kWh/t
Ball mill
Roller press
Separator
Grit separator
Separator fan
Mill fan
Aux.
Total kWh/t
Closed circuit
37.5
–
1.2
–
2.3
0.8
1.2
43.0
The frame
The frame is built up of parts fitted together by removable pins. The upper and lower frame, linked by vertical end sections, together form a horizontal
U-frame. The U-frame is closed by an
L-shape end section that is hinged to the lower frame and folds down for easy removal of the roller assemblies.
This frame encloses and supports the bearing housings of the roller assemblies and carries the hydraulic cylinders of the pressurising device. The bearing housings slide on the lower frame.
The upper frame supports a feed box and the dust casing, which encloses the two roller bodies.
3500 Blaine
Pregrinding
28.0
4.8
1.2
–
2.3
0.6
1.6
38.5
Semi-finish
17.1
9.6
1.2
0.6
3.6
0.5
1.8
34.5
Rollers
One roller is fixed while the other is horizontally movable and is pressed towards the former by four hydraulic cylinders. The position of the movable roller depends on the characteristics of the material fed to the press. Spacer shims between the roller bearing housings prevent the rollers from touching each other when pressurised without feed and permit adjustment of the minimum gap.
Each of the two rollers has a separate drive. Each roller has a shaft mounted planetary reducer connected to the other reducer by a balanced torque arm system. The patented balanced torque arm system reduces foundation costs and complexity by taking the torque through the other reducer and not down to the foundation. Both drives include a safety release coupling between reducer and motor.
The roller press is equipped with a hydraulic pressure system which ensures that the pressing force is kept practically even during the comminution process. In addition, it protects the press against overloading.
Roller wear lining
The rollers are normally supplied with a wear lining of welded hardfacing mate- rial. The hardfacing can be applied to either a solid shaft or a shrink fit sleeve bandage. Worn grinding surfaces are replenished by welding. Spot repairs or complete resurfacing can be performed with the rollers in situ, if desired.

Feed control gate
To facilitate control of the “choke feed” press, FLS has introduced a motorised feed control gate located just above the roller surface. The feed control gate is only required for choke feed.
The gate is used for smoothening the feed start and is suitable for trimming the press to optimum operation, for example when producing different cement types. It is also used for adjusting the throughput or power consumption of presses working with feed material of varying draw-in characteristics and/or friction characteristics.
Controlled feed by belt conveyor
For roller presses used in semi-finish grinding systems, the controlled feed system greatly improves operational stability. The feeder ex traction rate may be controlled by the roller gap or the roller press power consumption to maintain constant and optimum operating conditions at varying material characteristics.
Local machine control
The roller press has its own local control panel (PLC), similar to other complex machines. The panel is connected to the central control system.
The panel is used for testing and running in the machine as well as for troubleshooting, independent of the central control system.
The control panel includes a display that indicates status of the machine and has facilities for starting and stopping, making parameter changes, etc. The local control panel is delivered ready for use, thus saving engineering time during installation.
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Feed control gate

Characteristics, type range and typical data
Press size
A m 2
0.60
0.90
1.25
1.60
2.00
2.50
3.00
3.60
Roller dimension
D x W cm x cm
117x51
136x66
148x85
160x100
174x115
192x130
212x141
230x157
Roller speed
(peripheral) m/sec
1.60
1.60
1.60
1.60
1.60
1.60
1.60
1.60
Capacity t/h
198
297
412
528
660
825
990
1188
Motor power kw
2x230
2x350
2x485
2x615
2x770
2x960
2x1150
2x1390
Dimensions
m 2 mm mm mm mm mm mm mm mm mm
0.60 1775 4040 1170 1615 2065 1060 1260 2275 2330
0.90 2050 4615 1440 1985 2540 1220 1420 2460 2580
1.25 2320 5225 1640 2260 2890 1370 1570 3110 2800
1.60 2545 5665 1815 2480 3175 1475 1675 3450 2800
2.00 2830 6280 2060 2820 3575 1615 1815 4090 3190
2.50 3100 6860 2265 3130 4070 1800 2000 4270 3510
3.00 3480 7600 2605 3450 4410 1915 2115 4715 3510
3.60 4015 8740 2810 3900 5000 1985 2185 4910 3510
Copyright © 2010 FLSmidth A/S. ALL RIGHTS RESERVED. FLSmidth is a (registered) trademark of FLSmidth A/S. This brochure makes no offers, representations or warranties (express or implied), and information and data contained in this brochure are for general reference only and may change at any time.
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FLSmidth A/S
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DK-2500 Valby
Copenhagen
Tel: +45 3618 1000
Fax: +45 3630 1820
E-mail: info@flsmidth.com
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