ATOX™ raw mill

Grinds virtually anything while saving space and energy

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An efficient, reliable performerVertical roller mills are widely acceptedas the most efficient means of prepar-ing most moist raw materials for the production of cement clinker. The flexible ATOX™ raw mill can prepare virtually any kiln feed material to your required fineness in an energy-efficient process – regardless of variations in grindability, drying requirements and abrasion. In fact, the ATOX can be adapted to a wide variety of specific requirements. Our continuous development of themill over the years has resulted intoday’s ATOX raw mill – a compact millfeaturing a unique design that deliverssuperior reliability and performance.

Working principleThe ATOX raw mill uses pressure andshear generated between the rollersand the rotating table to crush andgrind raw materials.

Feed material is directed onto thegrinding table by the feed chute. Therotation of the grinding table acceler-ates the material towards the grindingtrack and passes it under the rollers.Partially ground material passes overthe dam ring encircling the grindingtable and into the hot gas streamcoming from the nozzle ring.

The moisture in the materials evapo-rates almost immediately, while thefiner portion of material is carried bythe gas stream to the separator andthe coarser portion deflected directlyback to the table. The separator allowsmaterial that has reached the requiredfineness to leave the mill, while itrejects oversized material and sends itback to the table for further grinding.

The coarsest fraction of the materialthat spills over the dam ring may fallthrough the nozzle ring and be conveyed back to the feed material inlet by a mechanical recirculation system.

Key benefits- Handles all types of raw

material

- Reliable, long-lasting operation

- Big rollers reduce need for crushing

- Low installation costs

- Easy maintenance

- Easy, simple and flexible operation

- Steep particle size distribution of raw meal

- Low mill vibration

- Low specific energy consumption

100%

Recirculation10 - 25%

New feed100%

Feed chute

1500 - 3000%

Nozzle ring

45 - 60 m/s

200 - 300%100 -

200%

10 - 25%

Internal and external material circulation

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Many applications, many adaptationsThe ATOX raw mill has demonstratedits suitability for grinding virtually alltypes of raw materials:

- From very easy-to-grind to very hard-to-grind material – roughly from less than 3 kWh/t to more than 11 kWh/t

- From less than 1% moisture to more than 20% moisture in feed material

- From non-abrasive to very abrasive materials- From non-sticky to very sticky feed material

Raw materials that are easy to grind– for example, high capacity for thespecific mill size, or with high moisturecontent – may require an increased gasflow through the mill. The ATOX mill iseasily adapted to this situation, as itcomes with an oversize nozzle ring andan oversize separator.

Basic design conceptThe grinding table of the ATOX rawmill has a flat, horizontal grinding trackencircled by an adjustable dam ringand an adjustable nozzle ring equippedwith an air guide cone.

The dam ring is made up of stacked,bolted-on, segmented rings and is easily adjusted by adding or removing one or more segmented rings. The height of the dam ring determines the thickness of the grinding bed on the table.

The roller assembly is kept centred onthe grinding table and prevented fromrotating by three torque rods attached

to the mill housing. The grinding pressure is exerted hydraulically through three pull rods attached to the outer ends of each roller shaft. This unique ATOX roller suspension ensures the grinding forces are transmitted vertically by the pull rods directly into the hydraulic cylinder and foundation, and horizontally by the torque rods into the mill housing.

The latest generation separator islocated above the grinding rollers. Thehigh efficiency of the separator is dueto the rotor equipped with an outerring of louvre plates. The fineness iscontrolled by adjusting the rotor speed.

The three cylindrical rollers are rigidly connected to a

common centerpiece

Easy to accommodate force variationsSince the grinding track is horizontaland the centre of gravity of the rollersystem only moves vertically, all impactforces and dynamic reactions are mainly vertical and thus easy to accommodate. The extremely low mass of the rollersuspension system means low totalinertia and thereby low dynamic forces. In the event of excessive vibrations ofthe roller system, the lower inertia alsolimits the dynamic loads on the grinding table and thrust bearing in the gear box as well as on the surroundings. The variation in hydraulic force is greatly limited by means of the nitrogen-filled accumulators connected to the cylinders, which act as springs. Even though the variation in the grinding bed takes place during operation, the hydraulic force varies within only a few bars.

The horizontal force into the mill housing normally accounts for 10-15% of the hydraulic force. The required raw meal quality and capacity are obtained by easily adjusting the grinding pressure, separator speed, gas flow and dam ring height.

Great wear resistanceSegmentation of wear parts means low risk of cracking. Therefore, wear-resist ant but relatively brittle segments in HiCr for both the rollers and table can be used. Furthermore, the HiCr segments are suitable for repetitive hardfacing, resulting in double life of the hardfaced layer. In case of very abrasive materials, HiCr segments with embedded

ceramic inserts ensure considerably increased life. The segments must be replaced when worn out.

Roller segments can be reversed,enabling high material utilisation, alsoin case of uneven wear. The ATOX mill’s rollers are larger indiameter than most other vertical rollermills, compared to the diameter of thetable. This larger roller diameter meansthat operation with a proportionallythicker grinding bed is less critical asregards uneven wear and foreignbodies in the mill feed. The large diameter rollers further allowa proportionally coarser mill feed, which reduces the requirements of pre-crushing.

No auxiliary mill drive requiredThe rollers are lifted hydraulically before start, so no auxiliary mill drive is required. Starting torque requirements to the mill are modest, since it starts unloaded.

Low gas speed saves fan powerThe roller suspension system permitsthe hot gas inlet section to be designed

virtually, without restrictions to the gas flow below the grinding table.

The nozzle ring area is adjusted by inserting or removing shims on top of the vanes. Thereby the gas speed can be reduced to a minimum allowed by the amount of external circulation. The bene-fit of the low gas speed in the nozzle ring is a significant reduction in pressure loss across the nozzle ring and thus a signif-icant saving in power for the mill fan.

Maintain mill size for easy materialsThe beneficial design of the hot gas inlet with low pressure loss enables the mill to be fitted with an oversize nozzle ring. That makes the standard ATOX mill operate with the extra amount of gas required by specially wet or easy- to-grind materials. It is not necessary to involve a larger mill size just to accommodate the gas flow – only the nozzle ring and the separator must be adapted to the higher gas flow.

Due to the relative large diameter grinding rollers the ATOX can handle up to 200 mm feed lumps. This feature reduces energy and wear in the crusher.

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Hard-working features and components

HiCr segment HiCr with ceramic inserts

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The rotary feed sluice is an essentialpart of the ATOX raw mill installation.Its main functions are to ensure:

- Uniform flow of feed to the mill for stable mill operation

- Low ingress of false air to decrease fan kW usage and cost

The sluice handles all new feed andmaterial coming from the externalcirculation system. For normal raw mills this material flow accounts for 115-150% of the new feed rate; for bigger mills it can represent more than 1,000 t/h.

Compared to other types of feed sluices, the rotary sluice ensures a uniform feed of material to the feed table. This is crucial for stable mill operation, since lack of feed will lead to reduced grinding bed thickness and to a corresponding increase in vibration level. Therefore, the uniform feed rate keeps the grinding bed stable and the vibrations low, ensuring steady operation and high availability withoutrisk of mill stop.

The rotary sluice also minimises theamount of false 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 flow of cold air into the mill. As the gas flow to the mill inletmust be constant independent of theamount of false air, every percentagein false air savings through the sluiceresults in a considerable cost savings,due to less gas flow sucked out of themill and through the mill fan.

Optimum mill performance dependson optimum separator performance.Therefore the ATOX raw mill is equipped with the most updated version of the dynamic separator, which features:

- Cutsize and fineness adjusted by change in rotor speed- Low bypass to reject ensures high

separation efficiency

- Sharp separation curve ensures steep particle size distribution

- Effective top seal ensures raw meal without oversized particles

This highly efficient separator results inthe following benefits:

- Lowest specific power consumption for the mill motor

- Highest mill capacity

- Low sieve residue for 200 micron and good burnability of raw meal

- High grinding bed thickness and low vibrations- Lowest pressure loss across the nozzle ring due to low reject bypass

The required fineness of the raw mealis obtained by adjusting the rotor speed.

Optimised separation process

Efficient feed sluice

Rotor seal Seperator top view

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The FLSmidth rotary sluice delivers:

- Sturdy design and low speed- Alignment with feed belt- Split sluice for normal materials- Heated sluice for very sticky

materials- Friction coupling, preventing overload of sluice- Easy adjustment of sealing plates- Easy access and easy replacement

of wear parts

For trouble-free operation and longlife, the feed sluice’s design is based ona low-speed rotor. The low speed,ability to feed big lumps and high rateof feed material have resulted inrelatively big rotary sluices. Sluices forATOX raw mills are in the range Ø800to Ø2200 mm.

To ensure proper filling and distributioninside the rotary feed sluice, the sluiceand the incoming feed belt are aligned. The circular bottom flange of the sluice and feed chute to the mill enables proper connection, independent of the direction of the feeding belt relative to the ATOX mill.

In case extraordinary foreign bodiessuch as big wood blocks, timber orsimilar materials enter and block therotor in the feed sluice, frictioncoupling ensures that the sluice partsare not damaged. A speed monitorstops the material belt and preventsoverfilling of the sluice.

Large inspection doors enable thesluice to be easily cleaned andrestarted. For normal raw materials,the standard split sluice with steel-linedrotor and lined housing is the optimumsolution for steady operation and longlife. The split design of the housingenables easy access and inspection ofthe interior of the sluice. When one side is opened, rotor lining replace-ment is a quick and easy job. The condition of the housing lining should be checked and replaced whenever required.

To limit false air ingress, replaceable sealing plates at the tips of the rotor vanes can be adjusted to obtain a small gap between the rotor and housing.

The heated rotary sluice is also theright solution for sticky mill feed. Hotgas from the mill inlet is guided through the rotor, thus preventing the sticky material from caking onto the rotor. Due to the change in rotor design, hardfacing is used for this version.

Split sluice

Heated rotary sluice for sticky materials

Split sluice with removable walls for easy maintenance

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Bevel-planetary gear type

Replacing or reversing roller segments

Makes life simpletoday and tomorrow

High-performance gear unitThe standard main gear unit for an ATOX raw mill is the compact bevel-planetary type supplied by FLSmidth MAAG Gear.

The axial thrust bearing supporting thegrinding table and the grinding force isa reliable hydrodynamic/semi-hydro-static bearing of segmented design. All the thrust pads are immersed in an oil bath. The lubricant for the thrust pads and for the internal gearings/bearings is conditioned and filtered in a separate pump station.

Hydraulic stations protectedFor all ATOX mill installations the hydraulic and lubrication stations are located in indoor fascility. The benefit is that operation and maintenance takes place in clean and tempered conditions and that trouble free and long life can be obtained. Apart from the lubrication station for mill gear and grinding rollers also the hydraulic station for the tensioning system as well as pump station for the water injection is located in the hydraulic room.

Low civil costsThe very compact and efficient designof the ATOX mill offers a correspond-ingly low cost of foundation and millbuilding in case of clients’ demand forthe latter. The possibility of customer supplied parts adds to the goodeconomy of the ATOX raw mill.

Easy maintenanceThe ATOX mill housing and separator are equipped with doors for easy access in connection with inspection and maintenance of all mill and separator parts. For more comprehen-sive overhaul the large maintenance door outside the grinding rollers can be removed for 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 of the mill. The separator reject cone is provided with a rail and trolley for that purpose.

When hardfacing of HiCr roller and table segments is selected the main-tenance work is preferably carried out inside the mill. While maintenance drive for the table can be part of mill supply or installed when required, the maintenance drives for the individual grinding rollers are installed inside the mill. Normally both table and roller segments can be hardfaced simultane-ously 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 of an oil leak be replaced inside the mill due to the use of a split-seal design for the inner oil seal. Most vital mill parts are equipped with replaceable wear protection enabling long life even when abrasive raw materials are ground.

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The ATOX mill provides optimum operation for all kinds of raw material mixes and ensures a uniform product dried to the correct level.

Adapting to different conditions is easy. Simply utilise the included facilities for dam ring adjustment (grinding bed control) by installing ring segments of varying thickness.

To give the lowest pressure drop across the mill – making it possible to operate with a controlled amount of re-circulated material – the mill nozzle ring area can

be adjusted by means of shims. Opti-mising these conditions results in the lowest fan power consumption.

The hydraulic system for grinding pres-sure has been designed for operational flexibility. Grinding pressure can be varied over a wide range, making it possible to minimise the mill vibration level during operation.

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 flow rate can be adjusted from the control system in a step-less mode.To ensure easy and reliable operation, the FLSmidth automation control system offers several possibilities for control and surveillance. Several facilities can be useful in setting up the grinding system for the best and most energy-efficient operation.

Easy operation

Normally the grinding rollers will stayinside the ATOX mill several years untilremoval is required – typically becauseof preventive replacement of bearingsor because there are initial signs ofbearing deterioration, which requiresroller replacement.

The rail and hoist system on all largeATOX mills provides a relatively simpleway to remove the roller. With themaintenance door removed, the rail isbolted to the mill housing; for Atox47.5-50, it is bolted to the supportoutside the mill. In case the grindingroller opposite the door needs removal,the entire roller assembly is rotated onthe grinding table while turning themain gear manually or by means of amaintenance drive.

Roller removal

Beam and hoist installed for roller removal

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1 Mill motor

2 Gear box

3 Grinding table

4 Split scrapers for external circulation

5 Bottom plate for mill

6 Reject sluice

7 Rotary split sluice in heated or non heated version

8 Feed chute with heated bottom

9 Mill house with lining

10 Nozzle ring

11 Air guide cone

12 Segmented grinding roller

13 Roller hub and wear cover

14 Joint head

15 Torque rod

16 Connection to mill house

17 Air and material seal for tension rod

18 Tension rod

19 Hydraulic cylinder with accumulators

20 Variable speed drive for separator

21 Cage rotor

22 Guide vanes

23 Reject cone

24 Area in cone below separation zone protected with chromium carbide composite plate

25 Mill and separator outlet

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Three-fan systems most common

There are a number of arrangementsfor raw material grinding systemsinvolving vertical roller mills. Thevarious systems are different as regardsplacing of the gas conditioning towerand dedusting of the mill vent gas.However the most common solutiontoday is the so-called three-fan system.The three-fan system uses cyclones todedust the mill vent gas. This arrange-ment reduces the operating suctionand usually also the gas volume for thefilter, which may be either an electro-static precipitator or a filter of thebaghouse type.

The three-fan system provides the bestoperational control with less interac-tion between operation of mill and kilnrespectively. For the two-fan system, the required size of filter must be foreseen for the total mill gas flow, which is normally significantly higher than the kiln gas flow. As the mill requires significantly more gas than supplied by the kiln, a certain part of the gas flow is guided from the mill fan through the recirculation duct back to the mill.

The raw material feeding system isequipped with a magnet separator andmetal detector for protection of themill parts. In case the raw material issignificantly contaminated with metal,an optional secondary refinery systemcan be selected. The secondary systemreduces the material to be rejected toa minimum, and at the same time theintermediate bin can be used as storage for external material during maintenance of the mill.

Material flow Mill air flow Material + air flow

Three-fan system

Two-fan system

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Mill layout

As a one-source supplier of completeplants, FLSmidth supplies the ATOXraw mill as well as all other equipmentneeded for the raw mill department.Mill layout is based on a standardisedconcept and modules that ensure themost cost-effective raw mill installa-tion. Because gas enters the ATOX mill from one side, the ducting arrange-ment is as small as possible, resulting in a very compact layout.

The dimensioning and selection ofcyclones, mill fan and connectingducting are optimised for low energyconsumption.

The number of cyclones will be 2, 4 or6, increasing with the mill size. The raw material feeding and recirculation system is preferably placed at the left side of the ATOX mill, seen from the mill motor.

Lubrication stations for main gear,hydraulics and roller lubrication areplaced with the pump station insidethe structure, below the cyclones.The layout is furthermore prepared for easy access to machinery and components needing overhaul or replacement.

The mill is per default designed to beoperated without enclosure, and allmaintenance can be conducted bymobile crane. As grinding rollers aretaken out through the main mill door,only one small area is required next tothe mill for positioning of the rollerafter dismantling.

When required by environmental regulations, for instance noise emissions, the entire mill installation can be closed, even when not required from an operating and maintenance point of view.

When the installation is enclosed, ahoist and monorail is provided for lifting separator parts, feed sluice, mill motor and the top part of the mill gear box. The mill foundation is kept at floor level, ensuring easy access around the mill.

All equipment is located at floor level or above to avoid pits and thereby ensure easy cleaning and maintenance.The material reject system includes areject bin and subsequent metal separation and back-feeding arrange-ment for dust-free reject material handling.

A short belt conveyor feeding the milland receiving the reject material ensures that the mill can start up without involving the long preceding mill feed conveyor.

Project Centre Denmark FLSmidth A/SVigerslev Allé 77DK-2500 ValbyCopenhagenTel: +45 3618 1000Fax: +45 3630 1820 E-mail: info@flsmidth.com

Project Centre USAFLSmidth Inc. 2040 Avenue CBethlehem, PA 18017-2188Tel: +1 610-264-6011Fax: +1 610-264-6170E-mail: info-us@flsmidth.com

Project Centre IndiaFLSmidth Private LimitedFLSmidth House34, Egatoor, Kelambakkam(Rajiv Gandhi Salai, Chennai)Tamil Nadu – 603 103Tel: +91-44-4748 1000Fax: +91-44-2747 0301E-mail: indiainfo@flsmidth.com

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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.

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 4030 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

Dimensions and characteristics