OK vertical roller mill
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Quality & profit improving features Main features - OK vertical roller mills use 30-50% less energy than ball mill systems - Simple layout and fewer machines in the mill circuit ensure high run-factor and low maintenance costs - E xcellent drying capability when grinding blast furnace slag or blended cements with wet components - Roller and table profile improve operating stability and reliability - Consistent cement quality with easy to adjust quality parameters - S pecial design features for iron removal during slag grinding minimise wear - O ptimal wear-protection on all internal surfaces - Space-saving design reduces civil construction costs - Flexibility to operate with two or four rollers guarantees long term availability
OK 36-4 mill under erection
Application advantages Proven commercially, the OK mill is the premier roller mill for finish grinding of portland cement, slag and blended cements. With a 30-45% reduction in the energy requirements for cement grinding and 40-50% for slag as compared with traditional ball mill operations, the OK mill can contribute significantly to your profitability and competitiveness. The design combines the drying, grinding and separation processes into just one unit, thus simplifying the plant lay-
out. A low noise level makes outdoor installation feasible, substantially reducing civil construction costs and improving the working environment. Because of its highly effective drying performance, the OK mill is a natural choice for grinding blended cements with one or more wet components. Design advantages The OK mill uses a hydro-pneumatic system to press its grinding rollers against the material bed on the rotating grinding table.
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Product
The grooved roller profile has two grinding zones, an inner and an outer. This creates a high and concentrated grinding pressure on the outer path, allowing air to escape into the grooved centre. The inner path serves to prepare the grinding bed, by compressing the feed material as it moves under the rollers into the high pressure grinding zone.
Feed inlet
Rotary feed sluice Separator
Segmented roller wear parts are made of the hardest possible material without risk of cracking and are very well suited for hard facing. Re-positioning of rollers is possible for evening out wear. These features ensure maximum longevity. Operating advantages The rollers are in a lifted position when the mill is started, ensuring trouble-free start-up. This eliminates the need for an auxiliary drive. A control system monitors the machinery and facilitates operation.
Grinding roller Nozzle ring Grinding table Roller stopper Main hydraulic loading system
Roller shape & curved table profile
Main hydraulic loading system
Swing-out system for roller replacement
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Mill design for versatile applications, simple operation and long life
Clinker, gypsum, slag, additive
3
1 OK mill
4 Finished product Cold air intake
Hot air for drying
2 Dynamic separator
2
3 Bag filter
1
4 Fan
5
5 Magnetic separator
Nozzle
Table
Nozzle ring bypass system For slag grinding, a specially designed nozzle ring bypass allows the iron particles to segregate through nozzles without airflow and subsequently be removed by a magnetic separator to minimise wear of the mill internals.
Air inlet
Discharge chute for iron particles
To magnetic separator Mill arrangement and nozzle ring bypass system
(%) 100 90 80 70 60 50 40 30 20 10 0
Mill arrangement This schematic illustrates a typical grinding installation. The arrangement is very simple and the operation is correspondingly flexible and reliable. To maintain the appropriate temperature in the mill circuit – for example to ensure adequate dehydration of the gypsum when grinding cement – the layout is prepared with provisions for recirculation of hot exit gas to the mill inlet. In case the mill feed is wet slag or includes a significant portion of wet additives, additional heat must be provided, for instance from a heat generator. Otherwise, if the mill feed is very hot, the mill exit temperature controls a damper for cold air intake.
Clinker
One mill, many products The OK mill efficiently grinds blended cements, with a wide range of additives such as slag, puzzolana, limestone and fly ash. Its versatility is demonstrated by the ability to switch between a wide variety of mixes, and to vary the particle size to meet individual needs.
Gypsum Pozzolana Limestone PFA Slag
A+B
C
D
D
E Plant
OK mill feed composition
E
F
F
F
Particle size distribution Examples of adjustments of particle size distribution when grinding to the same Blaine surface. The required steepness of the particle size distribution curve is attained by adjustment of the separator rotor speed, the mill airflow rate and the grinding pressure, in combination with the appropriate height of the dam ring.
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Wear liners The wear liners of the grinding table and the rollers are of the segmented type and are therefore easy to replace when worn out. For mills grinding very abrasive materials, like slag, hardfacing is an interesting and viable means of achieving a high availability of the grinding system, optimising the grinding process and saving refurbishment costs.
0.1 1 5 10 20 30 40 50 60 Residue (%)
Optimisation of operation Adjustment of mill airflow and grinding pressure for optimisation of the operation, including adjustment of particle size distribution, can be made imme diately. Adjustment of the dam ring, however, requires a mill stop, but only for a few hours. Switching between different types of products, for example from portland cement to slag, only requires easily made operating adjustments. Adjustment of the dam ring is not required. However, if the mill is to operate for a long time with one specific product only it may be expedient to adjust the dam ring to optimise the mill for operation with this specific product.
70 80
90
95 96 97 98
99 1
10
100
Particle size (µm)
OK mill steep PSD
Typical ball mill PSD
Hardfacing is an economical alternative to changing wear parts and is very suitable for the high chrome cast iron grinding parts used in the OK mill. Being of the segmented type the wear liners can be hardfaced numerous times throughout their life.
Seal between housing and roller.
Hardfaced segments
OK mill flat PSD
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Performance and experience Typical specific energy consumption (kWh/t) motor input
Portland cement
Slag*
Blaine (cm2/g) 3,300 4,000 4,000 5,000
OK mill
Mill
Ball mill
OK mill
Ball mill
OK mill
Ball mill
OK mill
Ball mill
17.6 34.2 21.3 44.9 25.7 51.8 32.2 71.1
Fan etc.
6.9 3.2 8.3 4.9 9.4 7.6 13.0 12.3
Total
24.5 37.4 29.6 49.8 35.1 59.4 45.2 83.4
*Slag with 8% moisture
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Examples of compressive strength (kgf/cm )
Portland cement
Blaine (cm2/g)
3,300 OK mill
Ball mill
Blended cement
Slag cement*
3,700 4,000 OK mill
Ball mill
3,800
OK mill
Ball mill
3 days
155 145 225 220 115 110
7 days
255 245 275 260 195 190
28 days
430 420 350 330 425 425
*50/50 clinker and slag mixture
Typical wear rates (g/t cement) of wear parts
Portland cement
Without hardfacing
1 1 5 6
With hardfacing
0.5 0.5 2.5 3.0
*50/50 clinker and slag mixture
Twin mill installation
Slag*
Roller Table Roller Table
OK 30-4 Installation
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Dimensions and characteristics The capacity range depends on fineness, grindability and additives (types and proportion of mill feed) OK mill
size
25-3 27-4 30-4 33-4 36-4 39-4 42-4 45-4
Mill motor, installed
kW
1350 1800 2350 3000 3750 4600 5500 6500
3
120 145 Airflow, approx., mill outlet Nm /s 30 40 50 65 80 100 t/h
45-90 60-125 80-165 105-210 130-260 160-315 190-380 225-450
Gear
kW
1544 2161 2829 3590 4446 5412 6488 7763
Output
t/h
51 72 94 119 148 180 216 258
size
25-3 27-4 30-4 33-4 36-4 39-4 42-4 45-4
Cement, capacity range Slag at 420 m2/kg
Dimensions OK mill A
m
13.7 13.9 15.5 17.3 19.0 20.6 23.7 26.7
B
m
12.1 12.2 13.5 15.3 16.8 18.4 21.2 23.1
C
m
5.2 6.0 6.7 7.6 8.4 9.2 11.0 12.1
D
m
8.2 7.0 7.8 8.5 9.4 10.2 10.9 11.7
OK 33-4 for slag
OK mill number represents mean grinding track diameter
C
B
27-4 30-4 33-4 36-4 39-4 42-4 45-4
25-3
D
D
A
- Proven technology - Flexible operation - Designed for grinding blended cements or slag - Excellent drying capacity - Easy maintenance and optimum utilisation of wear parts
View of rollers inside an OK mill.
The OK mill is manufactured by FLSmidth under patent & license from Earthtechnica Co., Ltd & Taiheiyo Cement Corp. 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.
Project Centre Denmark FLSmidth A/S Vigerslev Allé 77 DK-2500 Valby Copenhagen Tel: +45 3618 1000 Fax: +45 3630 1820 E-mail:
[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:
[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:
[email protected]
www.flsmidth.com
C 12-10 300-2-ENG V2
Slag mill inspection.
