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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