A strong thin Steatite ceramic lining brick increases the working volume in a mill than thick natural stone lining blocks. In a 1800 mm Ø x 1800 mm L ball mill, a 65 mm thick Steatite brick lining will increase mill working volume by 25%, than the 125 mm thick conventional natural stone lining blocks.
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Steatite is a magnesium meta silicate composite formulated from selected quality soapstone, china clay, barium carbonate and other chemicals in its residual. The raw mix composite is wet milled to micro fine particle size. The composite slurry is spray dried in micro processor controlled spray dryer to form homogeneous free flowing spherical granules. Such granules are pressed at high pressure compaction in T.C. moulding tools in uniaxial or isostatic automatic compacting presses.
The pressed mill lining blocks and grinding media are sintered at around 1350°C in gas fired high temperature kilns in natural oxidising atmosphere to form an impervious, vitrified, tough, non porous, dense hard material. Due to its mechanical strength and other relative features steatite ceramic is found most suitable ceramic composite for ball mill linings and grinding media.
The true value of mill lining and grinding media is measured by length of trouble free service in relation to mill production output. Our steatite ceramic grinding Balls are well known for its excellent quality, optimum milling results and long service life.
Jyoti Ceramic’s Steatite grade HF 82 Ceramic composite corresponds to German Steatite ceramic grade KER 221. It is a low loss, alkali free, tough, hard and dense ceramic.
| Physical Properties | ||
|---|---|---|
| Colour | -- | Off White |
| Density | g/cm3 | 2.70 ± 0.05 |
| Bulk Density | kg/ltr | 1.60 ± 0.05 |
| Water absorption | % | 0.00 |
| Flexural strength | Mpa | 130 |
| Compressive strength | Mpa | 850 |
| Vicker’s hardness | Hv5 (kg/mm2) | 520 - 550 |
| Hardness on Moh’s scale | -- | 7 |
| Co-efficient of linear thermal expansion (20 ℃ – 1000 ℃) | X 10-6 / ℃ | 8.5 |
| Safe operating temperature (No load) | ℃ | 1050 |
| Volume resistivity (20 ℃) | Ω - cm | 1013 |
| Cumulative Wear loss / hr after 120 hrs of wear test | % | 0.025 |
| Chemical Properties | ||
|---|---|---|
| SiO2 | 61.5% | |
| MgO | 27.4% | |
| BaO | 3.2% | |
| Al2O3 | 6.8% | |
| Fe2O3 | 0.5% | |
| Na2O | 0.1% | |
| CaO | 0.5% | |
*Steatite ceramic is resistant to all acids and alkalis except Hydrofluoric Acid.
Versatile Industrial Applications of Steatite Grinding media
Steatite Ceramic tapered & flat mill lining bricks
Steatite ceramic mill lining bricks protect the steel ball mill shell & provide high purity grinding. They come with a tongue & groove design to form an interlocking pattern during installation. This ensures bricks are fixed firmly in a mill shell and in end flanges with a minimum quantity of fixing adhesive / cement. Interlock fixing of bricks prevent them from giving way from installation, chipping off and spalling off edges. Steatite mill lining bricks are available in a wide range of sizes and thickness to suit small and large size ball mills.
Features and benefits
- Chemically inert and will not react when exposed to chemicals except Hydrofluoric Acid.
- Lower in cost as compared to alumina ceramic.
- Wear rate of the Lining is negligible and more constant as compared to traditional ceramic lining materials.
- Dimensional stability : Steatite ceramic mill lining bricks are uniform and stable in dimensions.
- Easy to machine, chip or grind: any skilled or semiskilled mason can easily and speedily carry out the installation of lining in the ball mill under the supervision of a civil / mechanical engineer.
- Hard and tough, resists high impact, high abrasion, and corrosion wear.
- Has higher temperature resistance than steel, rubber, polyurethane, natural stone, and other conventional mill lining materials.
- Substantial increase in mill volume due to lesser thickness as compared to traditional stone lining.
High production capacity
Recommended Staggered Lining Pattern
Mill Shell Lined with All Tapered Bricks
Ball Mill Lined with Bricks
Calculation for lining bricks
To calculate lining for cylindrical mill (flanges are lined first and feed door opening are not considered).
1. Straight bricks for flanges
| where | : N1 = Number of straight bricks |
| : a1 = Length of straight brick in cm | |
| : b1 = Width of straight brick in cm | |
| : D = Internal diameter of mill in cm |
2. Tapered bricks of cylindrical face
| where | : N2 = Number of tapered bricks |
| : a2 = Length of tapered brick in cm | |
| : b2 = Width of tapered brick in cm | |
| : D = Internal diameter of mill in cm | |
| : L = Internal length of the mill after lining in cm |
Example : To calculate the number of bricks required for Ø 6' X 6' Long (Ø 180cm X 180 cm Length) cylindrical ball mill (flanges are lined first)
Here: a1 = a2 = 150 mm = 15 cm
b1 = b2 = 50 mm = 5cm
D = 180 cm
L = 170 cm
Steatite Ceramic Ball Mill Lining Brick
Dimensional tolerances ±0.5 mm or 2.0% whichever is greater, Bow allowance maximum 0.5% of length.
Dimensions and weights of standard size mill lining blocks
| Block Number | Dimension in millimetres | Approximate weight in kgs | Suitable for ball mill size | |||
|---|---|---|---|---|---|---|
| Taper | A | B | C | D | ||
| C-32 | 40.0 | 47.0 | 32.0 | 100 | 0.465 | Ø 457 mm to 762 mm (18” Ø to 30” Ø) |
| C-51 | 59.5 | 65.0 | 51.5 | 150 | 1.400 | 900 mm Ø (3’ Ø) |
| C-53 | 59.5 | 65.0 | 53.5 | 150 | 1.450 | 1200 mm Ø (4' Ø) |
| C-54 | 59.5 | 65.0 | 54.5 | 150 | 1.470 | 1524 mm Ø (5' Ø) |
| C-55 | 59.5 | 65.0 | 55.5 | 150 | 1.450 | 1830 mm Ø (6' Ø) |
| Straight | ||||||
| B-30 | 50.0 | 30.0 | -- | 100 | 0.400 | For mill end lining: Ø457 mm to 762 mm (18" Ø to 30" Ø) |
| B-32 | 32.0 | 47.0 | -- | 100 | 0.400 | -- |
| B-42 | 65.0 | 42.0 | -- | 150 | 1.070 | For mill end lining: Ø900 mm to 2133 mm (3' Ø to 7' Ø) |
| B-53 | 53.3 | 65.0 | - | 150 | 1.360 | -- |
Steatite Ceramic Grinding Media
Types Of Steatite Grinding Media
Steatite ceramic balls and mill lining bricks are manufactured from the same fine-grained composite and are ideal performance partner. Thus, they retain their shape better and last longer than flint / river pebbles, natural stones, porcelain etc. Due to their higher density, hardness, toughness and a higher degree of sphericity, Steatite ceramic grinding media saves over 20-25% milling time than river pebbles. (Steatite ceramic grinding media generate low heat in the milling process, They are ideal for milling where radiantes are sensitive to temperature, such as paints, phosphorous material, chemical solvents etc.)
Advantages of Steatite Ceramic Grinding Media
- Higher density, hardness & sphericity : As compared to flint river pebbles and natural stone.
- Longer milling life : As Steatite grinding media have dense homogeneous internal microstructures, it offers superior wear resistance as compared to other conventional media.
- Wide range of sizes : Steatite satellite type grinding media is available in 8 assorted sizes Ø 6, 8, 10, 12.5, 15, 20, 25, 30 and Isostatic (ISO) pressed media 40, 50 & 60 mm diameter to meet the most demanding applications for dispersion and particle size reduction.
- Easy to use : Steatite grinding media is fully vitrified, non-porous and satin smooth in surface finish, allowing easy and thorough cleaning while changing the charge from one colour shade to another.
- Low contamination : With high levels of homogeneity wear rate of our Steatite grinding media is so insignificant, that it has no effect on the colour & composition of the end milled product.
- Uniform quality : Steatite grinding media is produced in the most modern plant under stringent quality control checks at various stages of manufacturing to ensure consistency in quality and elevate the grinding media to the highest quality level.
Steatite Ceramic spherical & cylindrical grinding media for various types of mills.
Ball mills : Ball mills are the most commonly used mills to accomplish particle size reduction. A revolving vessel, the ‘drum’, lined with ceramic bricks contains grinding media and the raw material to be ground.
Ball mills are classified into :-
Batch type & Continuous type : Batch type ball mills are versatile and most widely used. Particle size reduction takes place by impact on the material with the tumbling grinding media and by abrasion between the media and the mill wall.
Recommended size are:
25mm, 30mm, 40mm, 50mm, & 60mm
Batch Type Ball Mill
Selection of grinding Media
For a fresh charge, it is the most general practice to use three different ball sizes: 25% of large size, 50% of medium size & 25% small size. There might be cases where using 2 to 4 different size of grinding balls may be necessary. This will require a change in the proportions of each size used. For topping of the mill, we suggest a selection of the largest dia balls.
Recommended charge of material to be ground and grinding media.
Charge of material to be ground :
There are no hard and fast rules about charging of mills; some general rules are adopted from experiences of operators which helps in achieving optimum milling efficiency at economical cost. In most cases, the quality of material to be ground should be 25-30% of mill’s useful volume. Non-obersvance of these limits can lead to high wear rate of grinding media and the mill lining or to a considerably longer grinding time.
Recommended quantities of grinding media :-
To obtain optimum grinding effciency, we recommend.
1) For batch type mill: Grinding media should fill 55% of mill's useful volume
2) For continuous type mill : Grinding media should fill 35% of mill’s useful volume.
To calculate media charge for cylindrical mill. Formula is given below :
| Where | : M = Weight of the grinding media charge in kgs |
| : D = Mill internal dia in cms after lining | |
| : L = internal length of the mill in cms after lining |
For batch type ball mill:
M = 0.000691 X D2 X L
Example : To calculate grinding media charge for a Steatite brick lined batch type mill size : Ø 6’ x 6’ Long (Ø 180 cms x 180 cms L ) (Mill openings are not considered).
Thickness of tapered brick = 6.5 cm
Thickness of straight brick = 4.2 cm
| Therefore | : D = 180 – 13 = 167 cm |
| : L = 180 – 8.4 = 171.6 cm | |
| : M = 0.000691 x 1672 x 171.6 | |
| Grinding media quantity = 3307 kg |
Ball Mill volume, media charge & RPM
| No. | Mill I. D. | Lining thickness | Usable volume of mill |
Media qty @ 55% vol |
Media quantity % and size | Speed | |
|---|---|---|---|---|---|---|---|
| mm | Inch | mm | Ltr | kg | mm | rpm | |
| 1 | 450 | 18 | Taper : 47 Straight : 30 | 38.8 | 34 | 50% Ø 20 mm + 50% Ø 25 mm | 37 – 38 |
| 2 | 600 | 24 | “ | 108.6 | 95 | 50% Ø 25 mm + 50% Ø 30 mm | 32 – 33 |
| 3 | 750 | 30 | “ | 233.3 | 205 | 50% Ø 25 mm + 50% 30 mm | 30 – 31 |
| 4 | 900 | 36 | Taper : 65 Straight : 42 | 380.2 | 334 | 25% Ø 25 mm + 50% Ø 30 mm & 25% Ø 40 mm | 27 – 28 |
| 5 | 1050 | 42 | “ | 642.4 | 565 | 25% Ø 25 mm + 50% Ø 30 mm & 25% Ø 40 mm | 25 – 26 |
| 6 | 1200 | 48 | “ | 1004 | 883 | 25% Ø 25 mm + 50% Ø 30 mm & 25% Ø 40mm | 23 – 24 |
| 7 | 1350 | 54 | “ | 1480.6 | 1303 | 25% Ø 30 mm + 50% Ø 40 mm & 25% Ø 50 mm | 21 - 22 |
| 8 | 1500 | 60 | “ | 2088.3 | 1837 | 25% Ø 30 mm + 50% Ø 40 mm & 25% Ø 50 mm | 20 – 21 |
| 9 | 1800 | 72 | “ | 3760.4 | 3309 | 25% Ø 30 mm + 50% Ø 40 mm & 25% Ø 50 mm | 18 - 19 |
Recommended mill rotation speed:
- Mill rotating speed is an important parameter for optimizing grinding efficiency.
- Using proper speed has a cascading effect where the charge and grinding balls roll over one another, thus developing maximum milling action with minimum wear of grinding media and lining.
- If the ball mill rotates at an excessive speed, there will be centrifugal effect and no particle size reduction will take place.
- If the speed is too slow it results in purring effect where the charge is lifted to small angle and balls tend to slide back on the lining hence the grinding action is poor.
Calculations for mill motor power & mill speed
Considering the weight of mill lining and grinding media, work out the motor power required in consultation with the mill manufacturer.
To calculate the motor power required for a cylindrical type ball mill, the following formula can be applied:
W = 0.04116 x D3 x L x n x (0.6d + 0.4d1)| Where | : W = Required motor power in HP |
| : D = Internal Ø of the mill in mtrs | |
| : L = Internal length of the mill in mtrs | |
| : d = Specific gravity of grinding media | |
| : d1 = Specific gravity of Substance | |
| : n = Speed of ball mill in rpm |
Example : Let the internal Ø of the mill be 1.8 mtrs and internal length be 1.8 mtrs. If Steatite grinding media is used then density d=2.7. If milling substance is Steatite in slurry form with around 70% solids, then density d1 = 1.6.
d = 2.7 and d1 = 1.6 then
W = 0.04116 x (1.8)4 x 19 x (2.7 x 0.6 + 1.6 x 0.4) = 18.5 hp
To calculate the speed of the mill, use the following formula :
| Where | : Nc = Critical speed. |
| : D = Internal Ø in ft. |
Actual speed of the mill should be approximately 62% of the Nc for wet milling and 75% of Nc for dry milling
Table indicating the optimum mill speed and motor power of ball mill
| Inside | Inside | Dry grinding with Steatite media | Wet grinding with Steatite media | ||
|---|---|---|---|---|---|
| Dia (mm) | Length (mm) | Speed (rpm) | Motor Power (hp) | Speed (rpm) | Motor power (hp) |
| 300 | 300 | 60 | ½ | 46 | ½ |
| 450 | 450 | 50 | ½ | 37 | ½ |
| 600 | 600 | 43 | 1 | 33 | 1 |
| 750 | 750 | 39 | 1½ | 29 | 1 ½ |
| 900 | 900 | 35 | 2 ½ | 27 | 2 ½ |
| 1050 | 1050 | 33 | 5 | 25 | 4 ½ |
| 1200 | 1200 | 31 | 7 ½ | 23 | 6 ½ |
| 1350 | 1350 | 29 | 12 | 22 | 8 |
| 1500 | 1500 | 27 | 15 | 21 | 12 |
| 1800 | 1800 | 25 | 25 | 19 | 20 |
| 2100 | 2100 | 23 | 37 | 17 | 30 |
| 2400 | 2400 | 22 | 55 | 16 | 45 |
| 2700 | 2700 | 20 | 90 | 15 | 75 |
| 3000 | 3000 | 19 | 125 | 15 | 100 |
Jar mills : Particle size reduction takes place by impact over the material with the tumbling grinding media and by abrasion between the media and the mill wall. It works on the same principle as batch type ball mills.
Recommended grinding media : Balls of Ø 12.5mm to 20mm.
Attritor mills : Particle size reduction takes place by wet milling. In this process, the media is agitated with a series of stirring arms or disc mounted on vertical axial shaft.
Recommended grinding media : Ball of Ø 6mm / 8 mm / 10 mm & 12.5 mm.
Recommended media charge : 70 - 75% of mill’s useful vol.
Calculation of media load :
Example :
Attritor mill net volume is 50 Ltr charging with Ø 8 mm balls. 70% of mill’s vol = 35 Ltr x 1.6 kg/Ltr (bulk density of Steatite media).
That is 56 kg of Steatite grinding media is required for 50 Ltr capacity attritor mill.
Vibro mills : For grinding and producing fine particle size less than 1 micron in a cost effective manner. Since high impact like conventional costly ball mills are not required in vibro mills. Instead a large number of low energy impacts are necessary using small grinding media with high vibration or rotation rate.
Recommended grinding media : Cylinders of Ø 6.0 mm to Ø 20.0 mm.
Recommended media charge : 60 - 70% of mill’s useful vol.
Calculation of media load
Example :
Vibro mill net volume is 350 Ltr charging with Ø 12.5 mm cylinders.
60% mill’s vol = 210 Ltr x 1.6 kg/Ltr (Bulk density of Steatite media)
That is 336kg of Steatite grinding media required for 350 ltr capacity vibro mill
Wear rate test procedure
| Jar Mill | 20 Ltr capacity rubber lined |
| Speed | 30 rpm |
| Grinding media charge | Steatite ceramic grinding media Ø 25 mm and quantity 50% of jar mill’s useful volume. |
| Material charge | 5 kg silica sand of 0.3 mm size |
| Water | 5 Ltr |
Grinding media is weighed on an electronic balance of 10 mg resolution & milled for 24 hrs after being loaded into the jar with material, charge, and water. After milling, grinding media is unloaded, washed, dried thoroughly and weighed again and weight loss percentage per hour is calculated. This process is repeated every 24 hrs for a total of 120 hrs. Graph of wear rate versus time is drawn. It is inferred from the graph that the wear rate reduces with time upto 0.025% per hour for Steatite grinding media and then remains almost constant.
Mode of packaging :
- • Ceramic macro grinding media are packed in strong double lined HDPE plastic bags.
- • Each bag contains grinding media of net weight 25 kg / 50 kg.
- • For exports, these HDPE plastic bags are re-packed in strong, sea-worthy wooden pallet type crates.
