What is the working principle of ball mill?
3.6. A ball mill is a type of grinder used to grind and blend bulk material into QDs/nanosize using different sized balls. The working principle is simple; impact and attrition size reduction take place as the ball drops from near the top of a rotating hollow cylindrical shell.
How is ball mill diameter calculated?
Based on his work, this formula can be derived for ball diameter sizing and selection: Dm <= 6 (log dk) * d^0.5 where Dm = the diameter of the single-sized balls in mm. d = the diameter of the largest chunks of ore in the mill feed in mm.
How do you calculate ball mill power?
The grinding-product size, P, in a Bond ball mill, which is given by the aperture size which passes 80% of the grinding product as a function of the aperture size of the test screen Pk, can be expressed by the formula P= P k K 2 .
Which are the modes observed in ball mill?
Mixed mode – the rolling the grinding balls when part of the grinding balls move in a circular trajectory with further fall. Waterfall – the grinding balls move along a circular trajectory and change it further under gravity. Supercritical mode – centrifuging of the total grinding media volume.
What is the size reduction?
Size reduction is a process in which the particle size of a solid is made smaller. The term size reduction is applied to ways in which particles of solids are cut or broken into smaller pieces. Size reduction is necessary if the starting material is too coarse, and the final product needs to be a fine powder.
What is the size of balls used in ball mills?
3.5. Ball mills give a controlled final grind and produce flotation feed of a uniform size. Ball mills tumble iron or steel balls with the ore. The balls are initially 5–10 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.
What is ball mill reduction ratio?
Ball Mill Design For primary grinding, the ratio could vary between 1:1and 1.8:1. For fine regrinding in open circuit, the ratio ranges from 1.3:1 to 1.5:1. Some ball mills are separated in to compartments by grates. The grates hold back particles above a certain size for additional grinding.
What is the critical speed of ball mill?
A Ball Mill Critical Speed (actually ball, rod, AG or SAG) is the speed at which the centrifugal forces equal gravitational forces at the mill shell’s inside surface and no balls will fall from its position onto the shell. The imagery below helps explain what goes on inside a mill as speed varies.
What is cascading in ball mill?
Cascade mode motion of grinding balls carried out at low drum speed. At start-up of a mill, the grinding material rotated by a certain angle and grinding balls start to move by closed path. In cascade mode grinding occurs as a result of crushing and abrasive actions by grinding balls.
Why mills are used in size reduction?
Generally, size reduction and size separation are combined to obtain powder with the desired particle size distribution (PSD) for acceptable flow and compressibility for downstream processing . The mechanical process of reducing the particle size of a solid is also called milling.
What is the working principle of a ball mill?
The ball mill consists of a metal cylinder and a ball. The working principle is that when the cylinder is rotated, the grinding body (ball) and the object to be polished (material) installed in the cylinder are rotated by the cylinder under the action of friction and centrifugal force.
How are ball mills used in grinding plants?
Ball mills Ball mills are used for dry and wet grinding of different materials such as cement materials, cement, lime, and ceramic materials. PSP Engineering has continuously refi ned the design of its ball mills. Horizontal ball mills have become a reliable part of grinding plants
What are the factors that affect ball mill efficiency?
Factors affecting ball milling efficiency, in addition to the structure of the ball mill. Mainly the rotation speed of the ball mill, the size and number of the grinding body, the volume of the object to be polished, the grinding medium and the grinding time.
How are fines produced in a ball mill?
If a ball mill contained only coarse particles, then 100% of the millgrinding volume and power draw would be applied to the grinding ofcoarse particles. In reality, the mill always contains fines: these finesare present in the ball mill feed and are produced as the particlespass through the mill.