atox mill

ATOX Raw Mill ■

Compact design

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Suitable for grinding any raw material

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Outstanding performance record

Continuous improvement     L MAIN FEATURES     L     i • High-efficiencymill     M grinding all types of     w     A     R     X     O     T     A

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raw materials High-performance separator and optimized airflow ensure highseparation efficiency and low pressure loss. Compactdesign minimizes space requirements Noauxiliarymilldrive required Largerollerspermit coarse feed and ensureathick grinding bed Easyadaptableto highairflowrequired by specially wet or easy to grind materials Lowvibrationsdueto all impact forces and dynamic reactions being small and verticalandthuseasy to accommodate Segmentedwear parts for table and rollers allow use ofthemostwear resistant materials. Further,thesegmented wear parts are suitable for hardfacing Reversibleroller segmentsensurehigh material utilization

Introduction Vertical roller mills are widely accepted as the most efficient means of preparing kiln feed for the production of cement clinker. They are capable of preparing a wide range of feed materials to the required fineness in an energy efficient process. Although cement raw materials vary considerably in grindability, drying requirement and abrasion, the roller mill has the flexibility to be adapted to these variations, as well as other specific requirements. FLSmidth commenced the development of the ATOX mill around 1980. Continuous improvement of the ATOX raw mill has resulted in today’s compact construction featuring a unique design concept entailing a number of advantages enhancing the reliability and performance of the ATOX raw mill.

Working principle The ATOX mill uses pressure and shear generated between the rollers and the rotating table to crush and grind raw materials. Feed material is directed onto the grinding table by the feed chute. The rotation of 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 from the nozzle ring. The moisture in the materials is evaporated almost immediately while the finer portion of material is carried by the gas stream to the separator and the coarser portion is deflected directly back to the table. The separator allows material that has reached the required fineness to leave the mill, while it rejects oversized

Internal and external material circulation.

material and sends it back to the table for further grinding. The coarsest fraction of the material that spills over the dam ring may fall through the nozzle ring and be conveyed back to the feed material inlet by a mechanical recirculation system.

Applications and adaptability The ATOX raw mill has demonstrated to be suitable for grinding virtually all types of raw materials. • Grindability varying from very easy to grind to very hard to grind, say from less than 3 kWh/t to more than 11 kWh/t for the mill drive • Moisture in feed material varying from less than 1 % to more than 20 % • Materials varying from being nonabrasive to very abrasive • Feed materials varying from being nonsticky to very sticky Raw materials that are easy to grind, i.e. high capacity for the specific mill size, or with high moisture content may require an increased air flow through the mill. The ATOX mill is simply adapted to this situation being provided with an oversize nozzle ring and an oversize separator.

Basic design concept The grinding table of the ATOX raw mill has a flat horizontal grinding track encircled by

The three cylindrical rollers are rigidly connected  to a common centerpiece.

an adjustable dam ring and an adjustable nozzle ring equipped with an air guide cone. The dam ring is made of stacked bolted on segmented rings and is simply adjusted by adding or removing one or more segmented rings. The height of the dam ring determines the depth of the grinding bed on the table. The roller assembly is kept centered on the grinding table and prevented from 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 of each roller shaft. By this unique ATOX roller suspension the grinding forces are transmitted by the tension rods directly into the foundation

Toe-inofgrindingroller

a) Reaction force from grinding bed 

Design advantages With grinding track being horizontal and the center of gravity of the roller system only moving vertically all impact forces and dynamic reactions are mainly vertical and thus easy to accommodate. The extremely low mass of the roller suspension system means low total inertia and thereby low dynamic forces. In case of excessive vibrations of the roller system the lower inertia also limits the dynamic loads on the grinding table and trust bearing in the gear box as well on the surroundings. During grinding the force of reaction on the roller is located in front of the vertical line below the roller shaft, see a). In that position, however, the velocities of the roller and the table have different directions, see b), if the roller is placed traditionally, resulting in large axial loads on the roller bearing. Due to a patented toe-in of the rollers of the ATOX mill, the axial load is eliminated, see c), and the roller bearings are thus only exposed to well defined radial load ensuring significantly longer life of the spherical bearings.

b) Traditional design Roller tangential to grinding table. Significant axial force on roller bearings.

c) Patented toe-in of grinding roller.  Axial force on roller bearings eliminated.

 Atox mill easy to fit  into a constricted space.

the airflow below the grinding table and, further, to be fitted with an oversize nozzle ring. In consequence the standard ATOX mill can 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 airflow – only the nozzle ring and the separator must be adapted to the higher airflow. The ATOX raw mill is of a very compact design involving a space-saving arrangement of inlet ducts and, further, crane access for service is required in only one position. The ATOX mill is thus easy to fit into a constricted space. The very compact and efficient design of the ATOX mill offers a correspondingly low cost of foundation and mill building in case of clients demand for the latter.

Segmentation of wear parts means low risk of cracking, therefore extremely wear resistant wear parts for both roller and table can be used. Further, the segmented wear parts are suitable for hardfacing. Roller segments can be reversed enabling high material utilization to be achieved also in case of uneven wear. The ATOX mill has rollers with Features and larger diameter compared to the Components diameter of the table than most other vertical roller mills. Larger roller diameter Feed sluice permits operation with Compared to other a proportionally thicker types of sluices the simple rotary sluice grinding bed being less critical as regards uneven effectively keeps the wear and foreign bodies ingress of false air to in the mill feed. a minimum and The rollers of large furthermore provides diameter further allow a proa virtually constant portionally coarser mill feed, material flow to the Rotary sluice with removable walls for ease of maintenance. mill. To prevent build up of which reduces the requirements on pre-crushing. sticky material the sluice can The rollers of the ATOX mill are lifted be supplied in a design having the hydraulically before start, so no auxiliary mill option of heating of the rotor by hot gas drive is required. Requirement to the mill passing horizontally through the sluice hub. motor as regards starting torque is modest The sluice is provided with a circular outlet since it starts unloaded. flange, so it can always be aligned with an incoming belt conveyor. Further, the sluice is The roller suspension system of the ATOX mill permits the hot gas inlet section to be provided with removable side-walls for ease designed virtually without restrictions to of maintenance.

Optimized separation process The ATOX raw mill is provided with various mill inserts to achieve the most appropriate gas and material flow through mill. Thereby is achieved an optimum utilization of the built-in high-performance separator and a correspondingly high efficiency of the combined grinding and separation process. High performance gear unit  The standard main gear unit for an ATOX raw mill is the compact bevel-planetary type supplied by MAAG Gear.

Bevel- planetary gear type

The axial thrust bearing supporting the grinding table and the grinding force is a reliable hydrodynamic/semi-hydrostatic 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.

Reversing and replacement of roller  wear segments The roller wear segments can easily be reversed or replaced inside the mill, i.e. without taking the rollers out of the mill. The separator reject cone is provided with rail and trolley for that purpose.

Reversing or replacement  of roller wear segments.

Flowsheet Three-fansystem

(a)

Two-fansystem (b)

Material flow

Layout of a) three-fan   system and  b) two-fan system. System b) is provided  with feature to minimise handling of  rejected material with metallic objects.

Mill air flow

Material + air flow

There is a number of arrangements for raw material grinding systems involving vertical roller mills. The various systems are different as regards placing of gas conditioning tower and dedusting of the mill vent gas. However, they can all be categorized as either three-fan systems or two-fan systems. A three-fan system uses cyclones to dedust the mill vent gas. This arrangement reduces the operating suction and usually

also the gas volume for the filter, which may be either an electrostatic precipitator or a filter of the baghouse type. The two-fan system uses a dust collector – an electrostatic precipitator or a baghouse filter – which takes the mill exhaust gases directly, reducing the number of drives and simplifying the system. The type of system is selected based on specific plant conditions. However, the three-fan system is the most common of the two systems, providing better operational control with less interaction between operation of mill and kiln respectively. For the two fan system, the required size of filter must be foreseen for the total mill air flow, which is normally significantly higher than the kiln gas flow. Mill feed arrangements: Either of the two systems shown can be provided with basically two different arrangements for feeding of the raw materials to the mill. The most simple arrangement is the one that is shown in the flow sheet for the three fan system. When the metal detector for the mill feed material activates the change over gate at the mill inlet the feed material containing metallic objects will be rejected to a reject container, or simply to a reject pile. When a high amount of metal parts is foreseen in the mill feed, a refinery material system as shown in b) will be advantageous. This improved system comprises a reject bin, a small conveyor system and an additional metal detector. Material is extracted from this bin at a very low rate to a conveyor belt provided with a second metal detector. When metallic objects in the extracted material are detected a second change over gate will be activated to reject a small amount of material containing the metallic objects to a reject container or to a reject pile. Due to the low extraction rate from the reject bin the amount of material rejected to container or pile will thus be reduced to a minimum.

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ATOX Raw Mill 25

1

Mill motor

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Gear box

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Grinding table Grinding parts in wear resistant high chromium white cast iron

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Scrapers for external circulation Wear protected with Hardox 400 plate

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Bottom plate for mill Repairable Densit Wearflex 2000 lining

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Outlet for external material circulation

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Rotary feed sluice

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Feed chute Equipped with low friction stainless steel plates

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Mill house Weldable mild steel lining

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Nozzle ring

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Air guide cone Chromium carbide composite plate

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Segmented grinding roller assembly Grinding parts in wear resistant high chromium white cast iron

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Roller body Protection in chromium carbide composite plate

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Joint head Protection in chromium carbide composite plate

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Torque rod Protected with mild steel plate

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Buffer house for torque rod

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Air and material seal for t ension rod

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Tension rod

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Hydraulic cylinder with accumulators

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Variable speed drive for separator

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Cage rotor

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Guide vanes Chromium carbide composite plate

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Reject cone

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Area in cone below separation zone protected with Chromium carbide composite plate

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Mill and separator outlet

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4 5

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Dimensionsandcharacteristicsof ATOX raw mill and separator

ATOX Raw Mill Size

25 27.5 30 32.5 35 37.5 40 42.5 45 47.5 50 52.5 55 57.5 60

Separator

A mm

B mm

C mm

D mm

E mm

7115 7415 7380 8420 8920 9855 9885 11450 11915 12500 13000 13800 14505 15190 15875

Ø3550 Ø3900 Ø4360 Ø4694 Ø5050 Ø5380 Ø5700 Ø5960 Ø6324 Ø6694 Ø7070 Ø7440 Ø7810 Ø8190 Ø8570

6000 6000 6600 7600 8600 9600 9700 10300 10900 11500 12000 12700 13300 13900 14500

9200 10000 10500 11300 12400 13400 14050 15000 15900 16200 17150 17860 18600 19330 20070

3000 3500 3500 3800 4300 4800 4850 5150 5450 5750 6000 6350 6650 6950 7250

Power minimum installed, kW 665 844 1048 1280 1541 1832 2152 2505 2889 3307 3760 4248 4772 5333 5931

F mm

G mm

H mm

4030 4490 4950 5440 5960 6460 6970 7490 8020 8570 9130 9690 10260 10830 11450

4100 4600 5100 5500 6100 6600 7100 7600 8200 8700 9200 9800 10400 11000 11368

3220 3620 4040 4460 4930 5380 5850 6330 6790 7250 7780 8290 8270 9310 9650

Power, minimum installed, kW 45 56 69 83 99 116 136 156 179 204 232 260 292 326 361

Our 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 any time. Please contact us for specific information or data that may relate to your interests.

www.flsmidth.com Up-to-date addresses of worldwide subsidiaries and sales offices are available from our website

DENMARK

USA

INDIA

FLSmidth A/S Vigerslev Allé 77 DK-2500 Valby Copenhagen Tel: +45 36 18 10 00 Fax: +45 36 30 18 20 E-mail: [email protected]

FLSmidth Inc. 2040 Avenue C Bethlehem, PA 18017-2188 Tel: +1 610-264-6011 Tel: +1 800-523-9482 Fax: +1 610-264-6170 E-mail: [email protected]

FLSmidth Ltd. Capital Towers 180, Kodambakkam High Road Nungambakkam Chennai 600 034 Tel: +91 – 44-52 191234 Fax: +91 – 44-2827 9393 E-mail: [email protected]

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