ATOX™ raw mill
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Grinds virtually anything while saving space and energy Key benets - Handles all types o raw material - Reliable, long-lasting operation - Big rollers reduce need or crushing - Low installation costs - Easy maintenance - Easy, simple and fexible operation - Steep particle size distribution o raw meal - Low mill vibration - Low specic energy consumption
An ecient, reliable perormer Vertical roller mills are widely accepted as the most ecient means o preparing most moist raw materials or the production o cement clinker. The fexible ATOX™ raw mill can prepare virtually any kiln eed material to your required neness in an energy-ecient process – regardless o variations in grindability, drying requirements and abrasion. In act, the ATOX can be adapted to a wide variety o specic requirements. Our continuous development o the mill over the years has resulted in today’s ATOX raw mill – a compact mill eaturing a unique design that delivers superior reliability and perormance.
The moisture in the materials evaporates almost immediately, while the ner portion o material is carried by the gas stream to the separator and the coarser portion defected directly back to the table. The separator allows material that has reached the required neness to leave the mill, while it rejects oversized material and sends it back to the table or urther grinding. The coarsest raction o the material that spills over the dam ring may all through the nozzle ring and be conveyed back to the eed material inlet by a mechanical recirculation system.
Working principle The ATOX raw mill uses pressure and shear generated between the rollers and the rotating table to crush and grind raw materials.
100%
Feed material is directed onto the grinding table by the eed chute. The rotation o the grinding table accelerates the material towards the grinding track and passes it under the rollers. Partially ground material passes over the dam ring encircling the grinding table and into the hot gas stream coming rom the nozzle ring.
Recirculation 10 - 25% New feed 100%
100 200%
200 300%
Feed chute
1500 - 3000% Nozzle ring
45 - 60 m/s
Internal and external material circulation
10 - 25%
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Many applications, many adaptations The ATOX raw mill has demonstrated its suitability or grinding virtually all types o raw materials: - From very easy-to-grind to very hard-to-grind material – roughly rom less than 3 kWh/t to more than 11 kWh/t - From less than 1% moisture to more than 20% moisture in eed material - From non-abrasive to very abrasive materials - From non-sticky to very sticky eed material Raw materials that are easy to grind – or example, high capacity or the specic mill size, or with high moisture content – may require an increased gas fow through the mill. The ATOX mill is easily adapted to this situation, as it comes with an oversize nozzle ring and an oversize separator.
The three cylindrical rollers are rigidly connected to a common centerpiece
Basic design concept The grinding table o the ATOX raw mill has a fat, horizontal grinding track encircled by an adjustable dam ring and an adjustable nozzle ring equipped with an air guide cone. The dam ring is made up o stacked, bolted-on, segmented rings and is easily adjusted by adding or removing one or more segmented rings. The height o the dam ring determines the thickness o the grinding bed on the table. The roller assembly is kept centred on the grinding table and prevented rom rotating by three torque rods attached
to the mill housing. The grinding pressure is exerted hydraulically through three pull rods attached to the outer ends o each roller shat. This unique ATOX roller suspension ensures the grinding orces are transmitted vertically by the pull rods directly into the hydraulic cylinder and oundation, and horizontally by the torque rods into the mill housing. The latest generation separator is located above the grinding rollers. The high eciency o the separator is due to the rotor equipped with an outer ring o louvre plates. The neness is controlled by adjusting the rotor speed.
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Hard-working eatures and components Easy to accommodate orce variations Since the grinding track is horizontal and the centre o gravity o the roller system only moves vertically, all impact orces and dynamic reactions are mainly vertical and thus easy to accommodate. The extremely low mass o the roller suspension system means low total inertia and thereby low dynamic orces. In the event o excessive vibrations o the roller system, the lower inertia also limits the dynamic loads on the grinding table and thrust bearing in the gear box as well as on the surroundings. The variation in hydraulic orce is greatly limited by means o the nitrogen-lled accumulators connected to the cylinders, which act as springs. Even though the variation in the grinding bed takes place during operation, the hydraulic orce varies within only a ew bars. The horizontal orce into the mill housing normally accounts or 10-15% o the hydraulic orce. The required raw meal quality and capacity are obtained by easily adjusting the grinding pressure, separator speed, gas fow and dam ring height.
Great wear resistance Segmentation o wear parts means low risk o cracking. Thereore, wear-resistant but relatively brittle segments in HiCr or both the rollers and table can be used. Furthermore, the HiCr segments are suitable or repetitive hardacing, resulting in double lie o the hardaced layer. In case o very abrasive materials, HiCr segments with embedded
HiCr segment
HiCr with ceramic inserts
ceramic inserts ensure considerably increased lie. The segments must be replaced when worn out.
virtually, without restrictions to the gas fow below the grinding table.
Roller segments can be reversed, enabling high material utilisation, also in case o uneven wear. The ATOX mill’s rollers are larger in diameter than most other vertical roller mills, compared to the diameter o the table. This larger roller diameter means that operation with a proportionally thicker grinding bed is less critical as regards uneven wear and oreign bodies in the mill eed. The large diameter rollers urther allow a proportionally coarser mill eed, which reduces the requirements o pre-crushing.
No auxiliary mill drive required The rollers are lited hydraulically beore start, so no auxiliary mill drive is required. Starting torque requirements to the mill are modest, since it starts unloaded. Low gas speed saves an power The roller suspension system permits the hot gas inlet section to be designed
The nozzle ring area is adjusted by inserting or removing shims on top o the vanes. Thereby the gas speed can be reduced to a minimum allowed by the amount o external circulation. The benet o the low gas speed in the nozzle ring is a signicant reduction in pressure loss across the nozzle ring and thus a signiicant saving in power or the mill an.
Maintain mill size or easy materials The benecial design o the hot gas inlet with low pressure loss enables the mill to be tted with an oversize nozzle ring. That makes the standard ATOX mill operate with the extra amount o gas required by specially wet or easyto-grind materials. It is not necessary to involve a larger mill size just to accommodate the gas fow – only the nozzle ring and the separator must be adapted to the higher gas fow. Due to the relative large diameter grinding rollers the ATOX can handle up to 200 mm eed lumps. This eature reduces energy and wear in the crusher.
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Optimised separation process
Rotor seal
Optimum mill perormance depends on optimum separator perormance. Thereore the ATOX raw mill is equipped with the most updated version o the dynamic separator, which eatures: - Cutsize and neness adjusted by change in rotor speed - Low bypass to reject ensures high separation eciency
Seperator top view
- Sharp separation curve ensures steep particle size distribution - Eective top seal ensures raw meal without oversized particles This highly ecient separator results in the ollowing benets: - Lowest specic power consumption or the mill motor - Highest mill capacity
- Low sieve residue or 200 micron and good burnability o raw meal - High grinding bed thickness and low vibrations - Lowest pressure loss across the nozzle ring due to low reject bypass The required neness o the raw meal is obtained by adjusting the rotor speed.
Ecient eed sluice The rotary eed sluice is an essential part o the ATOX raw mill installation. Its main unctions are to ensure: - Uniorm fow o eed to the mill or stable mill operation - Low ingress o alse air to decrease an kW usage and cost The sluice handles all new eed and material coming rom the external circulation system. For normal raw mills this material fow accounts or 115-150% o the new eed rate; or bigger mills it can represent more than 1,000 t/h.
Compared to other types o eed sluices, the rotary sluice ensures a uniorm eed o material to the eed table. This is crucial or stable mill operation, since lack o eed will lead to reduced grinding bed thickness and to a corresponding increase in vibration level. Thereore, the uniorm eed rate keeps the grinding bed stable and the vibrations low, ensuring steady operation and high availability withoutrisk o mill stop. The rotary sluice also minimises the amount o alse air entering the mill. Due to the high underpressure in the
range 40-70 mbar inside the raw mill, even small gaps at the inlet will cause a considerable fow o cold air into the mill. As the gas fow to the mill inlet must be constant independent o the amount o alse air, every percentage in alse air savings through the sluice results in a considerable cost savings, due to less gas fow sucked out o the mill and through the mill an.
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The FLSmidth rotary sluice delivers: -
Sturdy design and low speed Alignment with eed belt Split sluice or normal materials Heated sluice or very sticky materials - Friction coupling, preventing overload o sluice - Easy adjustment o sealing plates - Easy access and easy replacement o wear parts Split sluice
Split sluice with removable walls or easy maintenance
For trouble-ree operation and long lie, the eed sluice’s design is based on a low-speed rotor. The low speed, ability to eed big lumps and high rate o eed material have resulted in relatively big rotary sluices. Sluices or ATOX raw mills are in the range Ø800 to Ø2200 mm. To ensure proper lling and distribution inside the rotary eed sluice, the sluice and the incoming eed belt are aligned. The circular bottom fange o the sluice and eed chute to the mill enables proper connection, independent o the direction o the eeding belt relative to the ATOX mill. In case extraordinary oreign bodies such as big wood blocks, timber or similar materials enter and block the rotor in the eed sluice, riction coupling ensures that the sluice parts are not damaged. A speed monitor stops the material belt and prevents overlling o the sluice.
Heated rotary sluice or sticky materials
Large inspection doors enable the sluice to be easily cleaned and restarted. For normal raw materials, the standard split sluice with steel-lined rotor and lined housing is the optimum solution or steady operation and long lie. The split design o the housing enables easy access and inspection o the interior o the sluice. When one side is opened, rotor lining replacement is a quick and easy job. The condition o the housing lining should be checked and replaced whenever required. To limit alse air ingress, replaceable sealing plates at the tips o the rotor vanes can be adjusted to obtain a small gap between the rotor and housing. The heated rotary sluice is also the right solution or sticky mill eed. Hot gas rom the mill inlet is guided through the rotor, thus preventing the sticky material rom caking onto the rotor. Due to the change in rotor design, hardacing is used or this version.
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Makes lie simple today and tomorrow High-perormance gear unit The standard main gear unit or an ATOX raw mill is the compact bevelplanetary type supplied by FLSmidth MAAG Gear. The axial thrust bearing supporting the grinding table and the grinding orce is a reliable hydrodynamic/semi-hydrostatic bearing o segmented design. All the thrust pads are immersed in an oil bath. The lubricant or the thrust pads and or the internal gearings/bearings is conditioned and ltered in a separate pump station.
Hydraulic stations protected For all ATOX mill installations the hydraulic and lubrication stations are located in indoor ascility. The benet is that operation and maintenance takes place in clean and tempered conditions and that trouble ree and long lie can be obtained. Apart rom the lubrication station or mill gear and grinding rollers also the hydraulic station or the tensioning system as well as pump station or the water injection is located in the hydraulic room. Low civil costs The very compact and ecient design o the ATOX mill oers a correspondingly low cost o oundation and mill building in case o clients’ demand or the latter. The possibility o customer supplied parts adds to the good economy o the ATOX raw mill.
Easy maintenance The ATOX mill housing and separator are equipped with doors or easy access in connection with inspection and maintenance o all mill and separator parts. For more comprehensive overhaul the large maintenance door outside the grinding rollers can be removed or crane access. When the grinding wear parts eventually get partly or completely worn out, the roller segments can easily be reversed or replaced inside the mill, without taking the rollers out o the mill. The separator reject cone is provided with a rail and trolley or that purpose.
Bevel-planetary gear type
When hardacing o HiCr roller and table segments is selected the maintenance work is preerably carried out inside the mill. While maintenance drive or the table can be part o mill supply or installed when required, the maintenance drives or the individual grinding rollers are installed inside the mill. Normally both table and roller segments can be hardaced simultaneously shortening the maintenance time to a minimum. For the grinding rollers in the ATOX 27.5 and bigger mills, the rotary oil seals can in case o an oil leak be replaced inside the mill due to the use o a split-seal design or the inner oil seal. Most vital mill parts are equipped with replaceable wear protection enabling long lie even when abrasive raw materials are ground.
Replacing or reversing roller segments
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Roller removal Normally the grinding rollers will stay inside the ATOX mill several years until removal is required – typically because o preventive replacement o bearings or because there are initial signs o bearing deterioration, which requires roller replacement. The rail and hoist system on all large ATOX mills provides a relatively simple way to remove the roller. With the maintenance door removed, the rail is bolted to the mill housing; or Atox 47.5-50, it is bolted to the support outside the mill. In case the grinding roller opposite the door needs removal, the entire roller assembly is rotated on the grinding table while turning the main gear manually or by means o a maintenance drive. Beam and hoist installed or roller removal
Easy operation The ATOX mill provides optimum operation or all kinds o raw material mixes and ensures a uniorm product dried to the correct level.
be adjusted by means o shims. Optimising these conditions results in the lowest an power consumption.
Adapting to dierent conditions is easy. Simply utilise the included acilities or dam ring adjustment (grinding bed control) by installing ring segments o varying thickness.
The hydraulic system or grinding pressure has been designed or operational fexibility. Grinding pressure can be varied over a wide range, making it possible to minimise the mill vibration level during operation.
To give the lowest pressure drop across the mill – making it possible to operate with a controlled amount o re-circulated material – the mill nozzle ring area can
The mill is equipped with a water injection system to improve the grinding conditions, should this be required due to dry or unstable raw materials. The
water fow rate can be adjusted rom the control system in a step-less mode. To ensure easy and reliable operation, the FLSmidth automation control system oers several possibilities or control and surveillance. Several acilities can be useul in setting up the grinding system or the best and most energyecient operation.
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20
25
22
21
1
Mill motor
2
Gear box
3
Grinding table
4
Split scrapers or external circulation
5
Bottom plate or mill
6
Reject sluice
7
Rotary split sluice in heated or non heated version
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Feed chute with heated bottom
9
Mill house with lining
10 Nozzle ring
7
11 Air guide cone 12 Segmented grinding roller 13 Roller hub and wear cover
24
14 Joint head 15 Torque rod
23
16 Connection to mill house 17 Air and material seal or tension rod
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18 Tension rod
8
19 Hydraulic cylinder with accumulators 20 Variable speed drive or separator 21 Cage rotor 22 Guide vanes
12
23 Reject cone
13 15
14 17
24 Area in cone below separation zone protected with chromium carbide composite plate
16 11
25 Mill and separator outlet
10 18
3
4 5
6
2 19 1
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Three-an systems most common There are a number o arrangements or raw material grinding systems involving vertical roller mills. The various systems are dierent as regards placing o the gas conditioning tower and dedusting o the mill vent gas. However the most common solution today is the so-called three-an system. The three-an system uses cyclones to dedust the mill vent gas. This arrangement reduces the operating suction and usually also the gas volume or the lter, which may be either an electrostatic precipitator or a lter o the baghouse type.
Three-an system
The three-an system provides the best operational control with less interaction between operation o mill and kiln respectively. For the two-an system, the required size o lter must be oreseen or the total mill gas fow, which is normally signicantly higher than the kiln gas fow. As the mill requires signicantly more gas than supplied by the kiln, a certain part o the gas fow is guided rom the mill an through the recirculation duct back to the mill.
Two-an system
Material fow
Mill air fow
Material + air fow
The raw material eeding system is equipped with a magnet separator and metal detector or protection o the mill parts. In case the raw material is signicantly contaminated with metal, an optional secondary renery system can be selected. The secondary system reduces the material to be rejected to a minimum, and at the same time the intermediate bin can be used as storage or external material during maintenance o the mill.
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Mill layout
As a one-source supplier o complete plants, FLSmidth supplies the ATOX raw mill as well as all other equipment needed or the raw mill department. Mill layout is based on a standardised concept and modules that ensure the most cost-eective raw mill installation. Because gas enters the ATOX mill rom one side, the ducting arrangement is as small as possible, resulting in a very compact layout. The dimensioning and selection o cyclones, mill an and connecting ducting are optimised or low energy consumption. The number o cyclones will be 2, 4 or 6, increasing with the mill size. The raw material eeding and recirculation system is preerably placed at the let side o the ATOX mill, seen rom the mill motor. Lubrication stations or main gear, hydraulics and roller lubrication are placed with the pump station inside the structure, below the cyclones. The layout is urthermore prepared or easy access to machinery and components needing overhaul or replacement. The mill is per deault designed to be operated without enclosure, and all maintenance can be conducted by mobile crane. As grinding rollers are taken out through the main mill door, only one small area is required next to the mill or positioning o the roller ater dismantling.
When required by environmental regulations, or instance noise emissions, the entire mill installation can be closed, even when not required rom an operating and maintenance point o view. When the installation is enclosed, a hoist and monorail is provided or liting separator parts, eed sluice, mill motor and the top part o the mill gear box. The mill oundation is kept at foor level, ensuring easy access around the mill.
All equipment is located at foor level or above to avoid pits and thereby ensure easy cleaning and maintenance. The material reject system includes a reject bin and subsequent metal separation and back-eeding arrangement or dust-ree reject material handling. A short belt conveyor eeding the mill and receiving the reject material ensures that the mill can start up without involving the long preceding mill eed conveyor.
Dimensions and characteristics Atox Raw Mill
Separator Power
Power
minimum
minimum
A
B
C
D
E
installed,
F
G
H
installed,
Size
mm
mm
mm
mm
mm
kW
mm
mm
mm
kW
25
7115
Ø3550
6000
9200
3000
665
403 0
4100
3220
45
27.5
7415
Ø3900
6000
10000
3500
844
4490
4600
3620
56
30
7380
Ø4360
6600
10500
3500
1048
4950
5100
4040
69
32.5
8420
Ø4694
7600
11300
3800
1280
5440
5500
4460
83
35
8920
Ø5050
8600
12400
4300
1541
5960
6100
4930
99
37.5
9855
Ø5380
9600
13400
4800
1832
6460
6600
5380
116
40
9885
Ø5700
9700
14050
4850
2152
6970
7100
5850
136
42.5
11450
Ø5960
10300
15000
5150
2505
7490
7600
6330
156
45
11915
Ø6324
10900
15900
5450
2889
8020
8200
6790
179
47.5
12500
Ø6694
11500
16200
5750
3307
8570
8700
7250
204
50
13000
Ø7070
12000
17150
6000
3760
9130
9200
7780
232
52.5
13800
Ø7440
12700
17860
6350
4248
9690
9800
8290
260
55
14505
Ø7810
13300
18600
6650
4772
10260
10400
8270
292
57.5
15190
Ø8190
13900
19330
6950
5333
10830
11000
9310
326
Copyright © 2011 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.
Project Centre Denmark FLSmidth A/S Vigerslev Allé 77 DK-2500 Valby Copenhagen Tel: +45 3618 1000 Fax: +45 3630 1820 E-mail: in
[email protected]
Project Centre USA FLSmidth Inc. 2040 Avenue C Bethlehem, PA 18017-2188 Tel: +1 610-264-6011 Fax: +1 610-264-6170 E-mail: in
[email protected]
Project Centre India FLSmidth Private Limited FLSmidth House 34, Egatoor, Kelambakkam (Rajiv Gandhi Salai, Chennai) Tamil Nadu – 603 103 Tel: +91-44-4748 1000 Fax: +91-44-2747 0301 E-mail: indiain
[email protected]
www.fsmidth.com
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