CERAMIC GRINDING MEDIA
Duralox ceramic grinding media and ball mill lining bricks are manufactured from the same fine grained composite and have proven to be ideal partners for high performance, since they retain their shape better and last longer than flint / river pebbles, natural stones, porcelain, steatite, etc.
Types of Duralox Grinding Media
Duralox 92W Ceramic Spherical Isostatically Pressed Grinding Media
Duralox 92W Ceramic Cylindrical Grinding Media
ADVANTAGES OF DURALOX® 92W CERAMIC GRINDING MEDIA
- Higher density hardness and sphericity - As compared to flint river pebbles, natural stones and Steatie. Due to their higher density, hardness, toughness and higher degree of sphericity, Duralox ceramic grinding media save over 35% milling time.
- Easy to use - Duralox grinding media are fully vitrified, non-porous and smooth as compared to other materials.
- Longer milling life - As Duralox grinding media has dense, homogeneous internal microstructure, it offers superior wear resistance as compared to other conventional media.
- Wide range of sizes - Duralox spherical isostatically pressed grinding media are available in 6 assorted sizes from Ø 20mm to Ø60mm to fulfill most demanding applications for dispersion and particle size reduction. Duralox cylinders with radius corners are available in 8 assorted sizes from Ø 6mm to Ø 30 x 30mm length
- Uniform quality - Duralox grinding media are manufactured in the most modern plant under stringent quality control checks at various stages to ensure that the final product is consistently of highest quality level.
Duralox® 92W Ceramic Spherical & Cylindrical Grinding Media for various types of 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.
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 quality of Grinding Media :
To obtain the optimum grinding efficiency, we recommend :
1) For batch type mill : Grinding media should fill 55% of the 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, the formulae are given as below :
1. For batch type ball mill :
M = 0.000929 x D2 x L
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.
Example : To calculate grinding media charge for a Duralox brick lined batch type mill size : Dia. 6' x 6' Long (Dia. 180 cms x 180 cms L) (Mill opening are not considered).
Thickness of tapered bricks = 5.0 cms.
Thickness of straight bricks = 5.0 cms.
D = 180 - 10 = 170 cms
L = 180 - 10 = 170 cms.
M = 0.000929 x (170)2 x 170.0
Grinding media quantity = 4564 kgs.
2. For continuous type ball mill :
M = 0.000503 x D2 x L
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 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)
W = Required motor power in HP
D = Internal dia. 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 dia. of the mill be 1.8 mtrs. and internal length be 1.8 mtrs. If Duralox grinding media is used density d = 3.7 gms/cc. If milling substance is alumina in slurry form with around 70% solids.
then d1 = 1.8
d = 3.7 and d1 = 1.8 then
W = 0.04116 x (1.8)3 x 1.8 x 1.9 x 19 x (0.6 x 3.7 + 0.4 x 1.8) = 24.13 HP
To calculate the speed of the mill use the following formula :
Nc = Critical speed
D = Internal dia. 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 mills
|Inside dia (mm)
||Inside length (mm)
||Dry grinding with Duralox Media
||Motor Power (HP)
||Motor Power (HP)