The document discusses the process of ore dressing, which involves separating valuable minerals from waste rock through various methods. Ore dressing begins with comminution to break ore into smaller pieces through crushing and grinding. This is followed by classification to separate particles based on size and density using equipment like air classifiers, rake classifiers, and hydrocyclones. The goal of ore dressing is to extract and concentrate valuable minerals from raw ore in an economically viable way while addressing environmental factors.

1. ORE DRESSING
By
Saguna Sharadbhai Oza
Paper GEL 501
Roll no. 09
M.Sc. Sem III

2. Table of contents
• Definitions
• What is ore dressing ?
• Methods of ore dressing
• Conclusion
• References

3. Definitions
Mineral
- A mineral is a naturally occurring, inorganic solid substance with a specific
chemical composition and a highly ordered atomic structure.
Ore
- Ore is a naturally occurring mineral or rock that contains valuable
substances, typically metals or minerals, that can be extracted and
processed for economic gain.
Gangue
- Gangue refers to the non-valuable, or waste, material that is closely
associated with an ore or mineral deposit.

4. What is ore dressing ?
• Ore dressing, also known as mineral processing or mineral
beneficiation, is the process of separating valuable minerals
from their ores.
• The goal of ore dressing is to extract and concentrate these
valuable minerals, making them suitable for further refining or
use.
• The process of ore dressing involves several stages, which may
vary depending on the nature of the ore and the desired end
product.

5. Methods of ore dressing
• Generally, mineral processing begins when an ore is delivered from a
mine, to a processing facility. At this point, the ore is called run-of-
mine material because there has been no treatment performed on
it.
• The choice of ore dressing methods depends on the type of ore, its
mineral composition, and the desired product specifications.
• The main steps typically include:
A. Comminution
B. Classifiers

6. A. Comminution
• Comminution involves the breaking down of larger chunks of raw ore
into smaller particles to prepare them for further processing and
extraction of valuable minerals.
• The process typically consists of two main stages,
- Primary comminution
- Secondary comminution

7. Primary comminution
• Primary comminution is the initial stage of particle size reduction,
typically involving the coarse crushing or breaking down of larger
chunks of raw material into smaller pieces.
• The primary goal of this stage is to prepare the material for further
processing and make it suitable for subsequent processes.
• Primary comminution is often carried out using such crushers,
1) Jaw crusher
2) Gyratory crusher
3) Impact crusher

8. 1) Jaw crusher
- A jaw crusher has a fixed jaw and a movable jaw.
- The crushing chamber is formed by the two jaws,
and it's where the rock or ore is placed and crushed.
- The movable jaw is attached to an eccentric shaft
that's driven by a motor.
- When the motor is powered, the eccentric shaft
rotates, and the movable jaw moves back and forth.
- As the movable jaw moves closer to the fixed jaw,
the material between them is crushed and reduced
in size.

9. 2) Gyratory crusher
• The crushing action is created by the
closing the gap between the hard
crushing surface attached to the
spindle and the concave liners (fixed)
mounted on the main frame of the
crusher.
• The gap is opened and closed by an
eccentric drive on the bottom of the
spindle that causes the central
vertical spindle to gyrate.

10. 3) Impact crusher
• Material to be crushed is fed into the
crusher from the top via a feed
chute or conveyor.
• Inside the impact crusher, there is a
rapidly rotating rotor with hammers
or bars attached to it.
• As the material enters the crushing
chamber, it collides with the
hammers or bars, shattering and
breaking it into smaller pieces.

11. Secondary comminution
• After primary comminution, the ore is still not at the desired particle
size for effective separation processes.
• Secondary comminution further reduces the particle size to enhance
liberation.
• This is typically done using grinding mills, such as
1) Ball mills
2) Rod mills
3) SAG (semi autogenous grinding) mills

12. 1) Ball mills
• The ore or material to be ground is fed
into the cylinder, which is partially filled
with grinding media, such as steel balls.
• Once the mill is loaded and the ore and
grinding media are in place, the mill is
rotated on its longitudinal axis.
• As the mill rotates, the grinding media
cascade within the mill, lifting and falling,
which causes impact between the media
and the ore particles.
• The impact and friction between the
grinding media and the particles break the
ore into smaller fragments.

13. 2) Rod mills
• Rod mills are similar to ball mills
but use long rods as the grinding
media instead of steel balls.
• The rods grind the ore by tumbling
within the mill, similar to the
grinding action of ball mills.
• Rod mills are particularly useful for
breaking up larger particles,
especially when a finer product size
is desired.

14. 3) SAG mills
• In a SAG mill, a portion of the ore
itself serves as grinding media.
• As the mill rotates, the ore
particles and grinding media
collide and impact each other,
breaking down the ore particles
through impact and abrasion.
• The autogenous grinding action is
particularly effective for breaking
down larger particles.

15. B. Classifiers
• In ore dressing and, a classifier is a machine that separates particles
based on various specific gravities and sizes, often used in
conjunction with other equipment like crushers, and grinding mills.
• Classifiers are commonly used to separate and classify particles into
different size fractions and to remove undesired materials (gangue)
from valuable minerals.
• Classifiers such as,
1) Air classifier
2) Rake and spiral classifier
3) hydrocyclone

16. 1) Air classifier
• Air classifiers use airflow to separate
particles based on their size and
density.
• Particles are introduced into an air
stream, and centrifugal forces and
airflow cause larger particles to be
thrown outward and finer particles to
be carried upward and collected as
overflow.
• Air classifiers are often used in dry
processing operations.

17. 2) Rake and spiral classifier
• These classifiers operate similarly
to spiral classifiers but use
mechanical devices like rakes to
remove the settled particles from
the bottom of the tank.
• Rake and spiral classifiers are used
for large particles or materials that
settle quickly.

18. 3) Hydrocyclone
• A hydrocyclone, or cyclone, is a classifier
that utilizes centrifugal force to separate
particles based on their size and density.
• The slurry containing particles enters the
hydrocyclone tangentially, causing the
particles to spin within the cyclone.
• The centrifugal force causes larger and
denser particles to move to the outer
wall and be collected as underflow, while
lighter particles are carried toward the
center and exit as overflow.

19. Summury
In essence, ore dressing is a
fundamental and multidisciplinary field
that encompasses a range of processes
and techniques. It plays a pivotal role
in extracting valuable minerals and
metals from their natural ores,
supporting various industries and
contributing to economic development
while addressing environmental
considerations.

20. References
• https://chat.openai.com/c/997dcee8-c596-41ca-b6a1-f975200d7727
• https://www.kau.edu.sa/Files/0052737/Subjects/(8)%20Ore%20proc
essing%20(beneficiation).pdf
• Notes of dressing and beneficiation provided by Dr. P. M. Solanki

21. THANK YOU