Screening and Liberation (sa book)

Question 1

an operation used for the separation of particles according to their sizes.

Answer 1

Screening

Question 2

a batch process used
almost exclusively for test purposes

Answer 2

Sieving

Question 2

a continuous process and
is used mainly on an industrial scale.

Answer 2

Screening

Question 3

The material passing through the screen
aperture is called

Answer 3

Underflow

Question 4

material retained on the
screen surface is called

Answer 4

Overflow

Question 5

generally used for dry treatment of coarse material.

Answer 5

Screening

Question 6

the medium containing the apertures for the passage of the undersize
material.

Answer 6

Screen Surface

Question 6

Rod/Bar Cross sections

used for lumpy and coarser size particles

Answer 6

parallel rods or profile bars

Question 6

OPENINGS

• Circular, In-line and Staggered
  openings
• Square, In-line and Staggered
  openings

used for coarser and small sizes

Answer 6

Punched or perforated plates

Question 7

Slot-like, In-line and Staggered

openings

• Slot-like, In-line and Staggered
  openings
• slotted openings are
  sometimes used
  for fine particles

Answer 7

Punched or perforated plates

Question 8

OPENINGS

• square
• used for fairly coarse particles

Answer 8

woven wires

Question 9

OPENINGS

• rectangle
• used for fine particles

Answer 9

Woven wires

Question 10

The material is fed at ____ of the screen.

Answer 10

One end

Question 10

Openings

• Triple shute elongated
• used for fine particles

Answer 10

Woven wires

Question 11

The screen surface can be ____ or ____

Answer 11

Fixed or Moveable

Question 12

STATIONARY SCREENS

Equally spaced parallel rods or bars running in flow direction. Sloped to allow gravity transport.

Answer 12

Grizzly

Question 13

Parallel rods running in flow direction. Fixed at one end. Gap increases from fixed to free end.

Answer 13

Divergator

Question 14

Stationary curved screen with horizontal wedge bars at right angles to slurry flow. Feed slurry enters tangentially. Imparts centrifugal action.

Answer 14

Sieve Bend

Question 15

REVOLVING SCREEN

Rotating, punched or woven wire. Slightly inclined cylindrical shell

Answer 15

Trommel

Question 16

VIBRATING SCREEN

Similar to stationary grizzly. Mechanical or electrical vibrations.

Answer 16

Vibrating Grizzly

Question 17

High speed motion to lift particles. Mechanical or electrical vibrations. Both horizontal and inclined types.

Answer 17

Vibrating Screen

Question 18

mounted either horizontally or with a gentle slope, has a slow linear motion essentially in the plane of the screen.

Answer 18

Shaking Screen

Question 19

The screen having one screening surface is called

Answer 19

Single-deck screen

Question 20

screen has two or more screen surfaces, it is called

Answer 20

Multi-deck Screen

Question 21

used to **prepare the feed** to any unit operation.

Answer 21

Feed Screen

Question 22

used to remove the trash material.

Answer 22

Trash Screen

Question 23

used to remove small amounts of either oversize or undersize.

Answer 23

Scalping Screen

Question 24

used to remove water from mixture of solids and water.

Answer 24

Dewatering Screen

Question 25

used to remove slimes from the coarse material.

Answer 25

Desliming Screen

Question 26

used to remove medium solids from coarse material

Answer 26

Medium Recovery Screen

Question 27

(often called the effectiveness of a screen) is a measure of the success of a screen in closely separating oversize and undersize materials. There is no standard method for defining the screen efficiency.

Answer 27

Screen Efficiency

Question 28

The ____ is defined as the product of the recovery of oversize mate rial into the screen overflow and the recovery of undersize material into the screen underflow.

Answer 28

Overall Efficiency

Question 29

The ____ is defined as the quantity of material screened per unit time per unit surface area of the screen and is expressed as tons/hr/m2.

Answer 29

Capacity of an Industrial Screen

Question 30

the first and the most important step in Mineral Beneficiation.

Answer 30

Liberation

Question 30

The second step,____, is impracticable if the first step, liberation, is not accomplished successfully

Answer 30

Separation

Question 30

It can be defined as the freeing or detachment of dissimilar mineral grains.

Answer 30

Liberation

Question 30

The operation employed to liberate the dissimilar mineral grains is ____ or ____

Answer 30

Size Reduction or Comminution

Question 31

If the particles of ore consist of a single mineral, they are termed as ____.

Answer 31

Free Particles

Question 32

If the particles of ore consist of two or more minerals, they are termed as ____

Answer 32

Locked Particles

Question 33

If the locked particles contain valuable minerals at considerable quantity, they are termed as ____

Answer 33

Middling Particles | double D na yot

Question 33

It is the size of a mineral as it occurs in the ore.

Answer 33

Grain Size

Question 34

It is the size of any particle whether free or locked particle.

Answer 34

Particle Size

Question 34

It is the size of a mineral particle at which that mineral is completely liberated. It is the size of a free particle of required (valuable) mineral.

Answer 34

Liberation Size

Question 35

results in true freeing or detachment of minerals

Answer 35

Comminution

Question 36

When the run-of-mine ore is reduced in size to grain size of valuable mineral, all the valuable mineral particles exist as ____, no matter whether remaining particles are free or locked particles of gangue minerals.

Answer 36

Free Particles

Question 36

This type of liberation is known as Liberation by size reduction or Transgranular liberation. Liberation of most of the ores comes under this category.

Answer 36

Equivalent to Freeing

Question 37

quantitatively referred to as percent liberation, of a certain mineral, is defined as the percent of that mineral liberated and occurring as free particles in relation to the total amount of the same mineral present in the ore

Answer 37

Degree of Liberation

Question 38

In these ores, reasonable amount of crushing makes the valuables liberated.

Answer 38

Massive Ores

Question 39

In these ores, valuables can be freed only partially by crushing and require certain amount of grinding to complete the liberation

Answer 39

Intergrown Ores

Question 40

In these ores, valuables are sparely distributed through a waste rock matrix and require fine grinding to liberate the valuables. Example: Gold ore

Answer 40

Disseminated ores