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Ball Mill
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Group No. 3
Contents
Introduction
Types and Process
Principle of workPrinciple of work
Description of Ball mill
Design and Cost
Introduction
�It is a device used for size reduction, It can reduce sizes up to a tenth of a micron.
�Cylindrical in shape.�Rotates on a horizontal axis.
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�Rotates on a horizontal axis.�Partially filled with the material to be ground and the grinding medium.
Types and Process
Types and process
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There are two Processes
1. Wet Process2. Dry Process
There are two Types
1. Continuous2. Batch
Principle of ball mill
�The rpm of mill
�The difference in speed between balls
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BB
AAInlet
Drive
Description
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DD
CC
Drive
Outlet
Mill Internals
A. Inlet
�INLET TUBE
mostly for wet mills
� INLET CHUTE � INLET CHUTE
with fresh air flap for mill
ventilation
�INLET SCREW
for problematic feed materials
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Types of inlet
1- TUBE 2- CHUTE B.3- SCREW
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B. Drivers
1- CENTRAL 2- GEAR RIM/PINION
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Types of drives
�CENTRAL DRIVE
�GEAR RIM / PINION�GEAR RIM / PINION
with one pinion or double pinion
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C. Outlet
�OVERFLOW MILLS WITH/WITHOUT
SCREEN CAGE
for wet mills
�DISCHARGE DIAPHRAGM
for wet and dry mill
�CENTRAL DISCHARGE
for dry mills
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Types of Outlet
1- OVERFLOW 2- DISCHARGE DIAP. 3- CENTRAL
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D. Mill Internals
�STEEL LINING
for wet and dry mills
� RUBBER LINING� RUBBER LINING
for wet mills
� CERAMIC LINING
for iron-free grinding
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Types of Mill Internals
STEEL RUBBER CERAMIC
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Fastening systems
Bolted version
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Bolted version
Semi-bolted version
Boltless version
ERECTION of COMPACT LINING
Design
IMPORTANT DATA TO DESIGN A Ball IMPORTANT DATA TO DESIGN A Ball IMPORTANT DATA TO DESIGN A Ball IMPORTANT DATA TO DESIGN A Ball
MILLMILLMILLMILL
Feed materialFeed materialFeed materialFeed material:Temperature [°C]:
Grain size [80% < x µm]:
EnvironmentEnvironmentEnvironmentEnvironment:
Altitude [m a.s.l.]Ambient temperature [°C]
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Grain size [80% < x µm]:Work Index acc. Bond [kWh/t]:
Feed quantity [kg/h]:
Ambient temperature [°C]
ProductProductProductProduct:
max. temperature [°C]:Grain size [80% < x µm]:
ProcessProcessProcessProcess:
Dry / wet grindingOpen / closed circuitGrinding media
Calculation
� Feed capacity → Mill dimensions
� Filling ratio (30-45%), Mill dimensions → Bulk volume of the balls
� ball size : D2 = k * Dp
(where k ranges from 0.9 to 1.4)(where k ranges from 0.9 to 1.4)
� Speed of the shell
Ncritical = (30*f)/√(R-r), where f =0.65-0.75
� Mass of balls = Bulk volume * Bulk density
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Cost
Cost Ball mills, Ball charge are $315 S/ton
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Cost Ball mills dry grinding
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Cost Ball mills for wet grinding
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To get the price of the ball mill for 2007
�Cost 2007
=(Cost 1990)*(Cost index 2007)/(cost index 1990)
Cost index 2007=533.1Cost index 2007=533.1
Cost index 1990=357.6
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