Dewatering

Question 1

• decrease the weight to reduce handling and shipping cost
• many operations such as furnace smelting require a semi-dry charge
or there is danger of explosion from the steam generated
• plant water can be recovered and reused as a conservative step

Answer 1

Dewatering

Question 2

What are the three classifications under dewatering?

Answer 2

 Sedimentation
 Filtration
 Thermal drying

Question 3

rapid settling of solid particles in a liquid produces a clarified liquid
which can be decanted, leaving a thickened slurry, which may require
further dewatering by filtration

Answer 3

Sedimentation

Question 4

very fine particles settle extremely slowly by gravity alone, and
centrifugal sedimentation may be performed or may be agglomerated

Answer 4

Sedimentation

Question 5

Sedimentation:
- minerals have inherent
surface charges

Answer 5

Coagulation

Question 6

are electrolytes
having opposite charge to the
particle

Answer 6

Coagulants

Question 7

Sedimentation:
they carry multiple monomers w/ attached
electrolytes that adsorbs to the oppositely-charged particles

Answer 7

Flocculation

Question 8

Many inter-particle bridges get linked together, forming a _________ a mass of
particles linked together by flocculants)

Answer 8

floc

Question 9

What are the two types of sedimentation?

Answer 9

 Gravity sedimentation or thickening

 Centrifugal sedimentation

Question 10

 most widely applied dewatering technique in mineral processing
 relatively cheap and high-capacity process

Answer 10

gravity sedimentation or thickening

Question 11

 can be regarded as an extension of gravity separation, as settling
rates of particles are increased under the influence of centrifugal
force

Answer 11

centrifugal sedimentation

Question 12

 The thickened underflow solids move continually downward to an
annular trench at the center
 The clarified liquid moves upward and radially outwards
 The arms “rake” the solids

Answer 12

gravity sedimentation

Question 13

 can be performed either by hydrocyclones or centrifuges
 more costly and complex, but have a much greater clarifying power
and are generally more flexible

Answer 13

centrifugal sedimentation

Question 14

 process of separating solids from liquid by means of a porous medium
which retains the solid but allows the liquid to pass

Answer 14

filtration

Question 15

Filtration:

These are the most common type of medium due to their low initial cost and availability in a wide variety of weaves

Answer 15

cotton fabrics

Question 16

What are the 4 types of filters?

Answer 16

1. pressure filters
2. vacuum filters
3. rotary drum filters
4. disc filters

Question 17

 consists of alternately arranged plates
and frames pressed by screw or
hydraulic piston
 filter cloth is fitted in between plates

Answer 17

Pressure filters

Question 18

 slurry is fed by a continuous channel at the
corners of the plates; clarified liquid is
removed the same way as the other end
 cake is washed when the filter is full, prior to discharge

Answer 18

Pressure filters

Question 19

are the most frequently

used type of pressure filter

Answer 19

filter press

Question 20

 incorporate filter media suitably supported
on drainage system, beneath which the
pressure is reduced by connection to a
vacuum

Answer 20

vacuum filters

Question 21

 a filter drum rotates horizontally while
partially submerged in slurry
 suction is delivered from the inside of the
drum, discharge is at the tail end of rotation

Answer 21

rotary drum filters

Question 22

 similar to drum filters, but discs are used
 the perforated discs rotate through a
through of slurry
 discharge is by pulsating air blow w/ scraper

Answer 22

disc filters

Question 23

 long sloping cylindrical shell

 hot gases or air is fed either parallel flow or counter-current

Answer 23

thermal drying

Question 24

often used thermal drying equipment

Answer 24

rotary thermal dryers