Home » Ball Mills » Cylindrical Ball Mill

Cylindrical Ball Mill


Ball mill is an efficient tool for grinding materials like ores, chemicals, ceramic raw materials, paints etc. into fine powder or fine paste by grinding in a wet way. The Ball Mill operates by rotating a cylinder with grinding balls like steel, CI, ceramic and pebble balls as grinding media.

Material fed through the mill is crushed by impact and grounded by attrition between the balls and also the internal cascading effect reduces the material in to a fine powder.

Ball Mills usually have liners inside which are replaceable when they wear. Liners will be of wave shape which key the ball charge in to the shell and prevent the slippage.
The rotation of the powder mixer is usually between 4 to 20 revolutions per minute, depending upon the diameter of the mill. The larger the diameter is, the slower the rotation will be. Ball Mills are generally used to grind material ¼" and finer, down to the particle size of 20 - 75 microns. To achieve reasonable efficiency, the ball mills are to be operated in a closed system, with oversize particles continuously being re-circulated back to the mill and to be reduced.

Types :
Cylindrical Single / Multi compartment with classifier and without classifier.
Single / Multiple Compartments Cylindrical Ball Mill

Single compartment Mill is a conventional type of batch mill, consists of cylindrical steel shell with flat steel ends welded to shell. Ball Mill rotates around a horizontal axis partially filled with raw materials to be ground plus the grinding medium. The material and the grinding medium are fed and discharged through an opening manhole on the cylinder shell. Ball Mills usually have replaceable liners inside and replaced when they wear out. Material fed through the mill is crushed by impact and grounded through attrition between the balls.

Design Features
The horizontal cylinder of the ball mill, which is fabricated out of mild steel plates, is rotated using a side drive system at one end of the mill. The drive comprises of a girth gear, generally made from alloy steel casting, bolted onto the mill which is driven by its pinion, generally made out of alloy steel forging, through a gear reducer and motor coupled together.

The two ends of the cylinder are covered with mill headers one placed at each end, the inlet and at the discharge. The mill headers have a central inlet and discharge opening from where the material enters the mill and exits the mill. These mill headers are generally made out of alloy steel casting. The mill headers are rested on fabricated trunions at both ends on which the headers rotate on a special self lubricating white metal lining. External lubrication system is also provided to keep the mill headers properly lubricated at all times. Other accessories include a set of low pressure and high pressure pumps which help to pre-jack the mill during startup.
Grinding Media
A ball mill is partly filled with steel balls (some are cylindrical shaped cylpebs) that impart a tumbling and cascading action when the mill rotates around its horizontal axis. Material fed through the mill is crushed by impact and ground by attrition between the balls. The grinding media are usually made of high-chromium steel or manganese steel. The smaller grades are generally cylpebs.


Mill Liners
Mill liners are generally of high chromium steel or manganese steel. The liners are selected based on the type and hardness of the material to be ground. The grinding media is also selected with the same principal and suitable to the material of the liners. The thickness and design of the liners largely effect the grinding efficiency of the mill and hence various improvements in the designs have been made from time to time.


Technical Data

Size Dia x L, ft Max. Ball Load lb. Motor HP Normal RPM Cement clinker
From 97%
<200 - m To
95% < 325 -
m bbl / hr. (a)
LimeStone
from
<12.m to 95%
< 100m t.p.h. (b)
Calcined
Gypsum to 95%,
100m t.p.h. (c)
4 x 10 8.500 50 28 to 30 9 2 2
4 x 18 15.300 100 28 to 30 17 5 4
5 x 22 36.000 200 25 to 27 37 10 9
6 x 24 70.000 350 22 to 24 65 17 16
7 x 26 102.000 500 20 to 22 95 25 23
8 x 30 180.000 900 18 to 20 170 45 42
9 x 30 223.000 1200 16 to 18 235 65 60
10 x 30 278.000 1500 15 to 17 280 80 74

  • Closed-circuit with air classifier. Product size equivalent to 1.750 to 1.800 cm²/gm
  • Open circuit ; moisture less than 0.5%, average grind ability
  • Feed temperature , 200° to 300°F - Open circuit operation