The document discusses different types of liquid-liquid extraction columns. It describes rotating disc columns, which use countercurrent flow and a rotating disc to agitate the two phases and facilitate mass transfer. Agitated columns are also discussed, using mechanical devices like impellers to create dispersion throughout the column. Various agitated column designs are explored, including baffled columns with mixing and settling zones. Pulse columns are also mentioned as a type of agitated column without internal mechanical parts.

1. :EXTRACTORS
Liquid-liquid extraction has only become popular
as a separations technique in the past thirty
years. In this time, liquid-liquid extractors have
become the separation equipment of choice for
.selected processes

2. :BASICS
The primary inlet and outlet streams of typical liquid-

liquid extractor are shown
Droplet formation is the most common method of mass transfer. The droplets
are formed in either the heavy phase or the light phase so as to maximize
surface area and solvent contact. Often LLE processes include a dispersioncoalescence cycle. Dispersion is the breaking up of the intact phase of liquid
into the droplets necessary for mass transfer. Coalescence is the coming
together of the droplets into one mass and the cycle is incorporated through a
series of multiple dispersion and coalescence stages to enhance mass transfer.
The picture below shows the dispersion of droplets that occurs in a liquid-liquid
.extraction column

3. Liquid – liquid extraction

4. :MIXER-SETTLERS

5. :GENERAL INFORMATION
Mixer-settler liquid-liquid extractors have two stages. In the
mixing stage the immiscible solvent and the solute-carrying
feed are brought into contact, droplets are formed by
mixing, and the desired solute(s) are extracted by the
solvent. To learn more about different
mixer designs
see the
Mixers section
of this
.encyclopedia
In the settler the two liquid components do just that, they
settle out into two phases. The heavier phase exits out the
bottom of the settler and the lighter phase is drawn off the
top. To learn more about different settler designs see the
.Gravity Separators section of this encyclopedia
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6. :EQUIPMENT DESIGN
For most processes one mixer and one settler will 
not be enough to achieve effective separation.
Often a system is designed with several mixersettler stages in series. Although the flow of the
two liquid phases can
be countercurrent, cocurrent or cross flow, solvent
use is most inefficient in cross flow. The
transportation of the liquids from one stage to the
next occurs either by gravity or using pumps. The
schematic below shows a countercurrent system
.with three mixers and settlers in series

7. Mixer-settler

8. :USAGE EXAMPLES
The mixer-settler system shown here is used in chemical
processing. Mixer-settler systems, became quite popular in
the metals industry for their ability to handle high
throughputs that required long residence times. They have
grown to find much use in several other processes, such as
aromatic extraction and nuclear fuel processing. Shown
below to the left is an example of a stainless steel 3-stage
mixer-settler liquid extractor. To the right is an example of
a mixer-settler with a tubular design used for glass,
enamelled steel and other metallic materials with high
.operational pressures
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9. :Examples

10. disadvantages
.Large amounts of floor space required 
. Only systems with a few stages are economical
Large amounts of valuable material, such as 
.the solvent, are tied up during the process
.Poor solvent conservation 

11. ADVANTAGES
.Reliable scale up techniques
.Can handle high flow rates
.Ideal for processes with slow mass transfer
Intense mixing, resulting in small droplets for
good mass transfer
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12. :Spray Column( 2
This set-up merely consists of an empty shell with 
provisions at the end for introducing and removing
the liquids. Its construction is the simplest but
suffers from low efficiency due to poor phase
contacting and excessive back-mixing in the
continuous phase. Because of their simple
construction, spray columns are still used in the
industry for simple operations such as washing
.and neutralization

13. SPRAY - COLUMNS
Spray column liquid-liquid extractors are the 
simplest of the column designs. The dispersed
phase is introduced via a nozzle either at the top
or the bottom of the column, depending on
whether the heavy phase or light phase is being
dispersed. The continuous phase enters the
opposite end of the column, resulting in mass
transfer through the vertical counter flow of the two
phases. There is no dispersion-coalescence cycle
inside the column, resulting in very low efficiency
for spray columns. Spray columns work best for
.fluids containing large suspended solids

14. :Packed column(3
liquid-liquid extractors are also similar to those 
seen in other separations sections of this
encyclopedia. The packing, which assists in
droplet formation, can either be structured in a
mesh net or randomly placed in the column.
Dispersion is accomplished with a nozzle at the
top or bottom of the column, depending on
whether the heavy or the light phase is being
dispersed. As in sieve tray columns, the internals
of the column need to be coated with the
.continuous phase

15. :USAGE EXAMPLES
Non-agitated liquid-liquid 
extractors have found their niche
in several different industries,
including the petrochemical and
water desalting and purification
.industries

16. PACKED – COLUMN

17. ADVANTAGES
.Spray columns are inexpensive
Sieve tray columns can handle a very sizeable
.throughput
Sieve tray columns have had good success
.with scale up procedures
Packed columns are highly efficient when only
.a few stages are needed
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18. DISADVANTAGES
.Spray columns are very inefficient
Sieve tray and packed columns can suffer from
.solids plugging
Packed columns have lower throughput due to
.the packing
Packed columns are hard to scale up
.accurately
The initial dispersion is a concern packed
columns, to avoid channeling
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19. :What is a baffle plate(4
Baffle plates have many design uses in general in different
applications. However, the name pretty much describes its
intended function for the biggest part. It baffles air to create
the pressurized conditions required within your systems
design for proper and distribution and flow rate through out
your system. Many baffles are adjustable and some are
fixed. There are various reasons for that too. Air noise is
also something that baffles are used to help alleviate noisy
.type situations that may exist or have a potential to do so
in your gas tank they dampen the movement of the fuel
when you accelerate or decelerate as an example
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20. What are the functions
?of baffle plates
Baffle plates are mainly used as 
a steam separator i.e the
mixture of steam of water gets
separated when the water
molecules struck the baffles and
due to gravity they fall down an

21. ?What is a baffle plate for
Baffle plates have many design 
uses in general in different
applications. However, the
name pretty much describes its
intended function for the
. biggest part. It baffles

22. how to remove a baffle plate from
?a wood heater
Open the door or doors of the wood heater to . 1 
locate the baffle plate near the top of the heater
interior. 2. Push up on the front edge of the
plate. 3. Tap the underside of the

23. What is the use af
?a baffle plate in the storage tank
To keep the liquid from sloshing around 

24. ROTATING DISC LIQUID-LIQUID(5
:EXTRACTION UNIT
HIS Rotating Disc Liquid-Liquid Extraction Unit has been
designed to demonstrate the
basic principles of a liquid-liquid extraction process. When
separation by distillation is ineffective or very
difficult, liquid-liquid extraction is one of the main alternatives to
consider. Close boiling mixtures or substances
that cannot withstand the temperature of distillation, even under
a vacuum, may often be separated from impurities by
extraction, which utilizes chemical differences instead of vapor
.pressure differences
Separation by liquid-liquid extraction can be defined as the
selective removal of one or more components either
from a homogeneous liquid mixture or from a solution, using a
second liquid or solvent, which is partially or wholly
.immiscible with the first
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25. :EXTRACTION UNIT
The normal mode of operation is that the light phase
and heavy phase liquids are pumped counter currently
into the extraction column. The heavy phase will enter
the top of the column and flow downwards while the
light phase will enter the bottom of the column and flow
upwards due to density differences. Countercurrent flow
in the column and agitation of the two phases by the
rotating disc will cause the transfer of solute component
from one phase (raffinate) to the other (extract). The
raffinate will emerge at the bottom while the extract will
emerge at the top of the extraction column. This liquid liquid
extraction process is done in numerous continuous
stages throughout the column to give a higher degree
.of separation
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27. EXPERIMENTAL CAPABILITIES
Demonstration of liquid / liquid extraction
.experiments using a rotating disc column
Determination of the height equivalent theoretical
plates (HETP) and extraction efficiency for the
.column
Investigatation on the effect of total feed flow rates
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to feed ratio on and solvent the column’s extraction

.efficiency 
Investigatation on the effect of rotating disc speeds 
.on the column’s extraction efficiency 

28. TECHNICAL SPECIFICATIONS
a) Rotating Disc Column
Column diameter : DN 50
Effective height : 2.0 m
No. of discs : 40
b) Stirrer Motor
.Variable speed motor with digital speed display
Speed range : 50 to 2000 rpm
Max. torque : 60 Ncm
Power : 130 W
.equipped with feed port, vent and drain valves
Capacity : 50 L
Graduations : 2 L
d) Dosing Pumps
.length and stroke frequency
Flow rate : up to 42 L/hr
.Power : 0.25 kW
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29. :AGITATED( 6
Many agitated column designs 
are used for liquid-liquid
extraction. Only a few of the
more popular designs will be
.explored in this section


30. AGITATED - COLUMN

31. :GENERAL INFORMATION
Agitated columns contain some type of 
mechanical device to agitate the liquids as they
pass through the column. Rotating and
reciprocating mechanisms are the most
common methods for creating and maintaining
dispersion throughout the column. The diagram
below to the right shows the interior of an
agitated column and the picture on the right is
.an agitator used in an extraction column

32. Examples

33. :EQUIPMENT DESIGN
Baffled mixing segments are common to all baffled 
column extractors. Turbine impellers rotate between a
set of baffles, creating several mixing zones along the
column length. The mixed liquids move to the outside
sets of stator baffles, where they can separate out and
move up or down to the next stage. The baffles help
reduce axial mixing, creating several mixing zones to
increase mass transfer. The Schreiber and the
Oldshue-Rushton columns are common baffled
.designs

34. Rotating disk

Rotating Disk Contactors (RDC) and Asymmetric Rotating Disk
Contactors (ARDC) are another type of agitated column
extractors. The ARDC seen in the animation is characterized by
.the off-center rotating shaft
The heavy phase enters the top of the extractor and mixes with
the light phase in the top mixing region, composed of a rotating
disk. The two phases then enter the external settling stage,
where they separate. The heavy phase then travels down to the
next mixing region. This mixing-settling action continues down
the length of the column. Individual mixing regions
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35. Rotating disk
are separated by baffles, and the 
mixing and settling regions by a stator.
A stator is a portion of a cylinder that
separates the two regions while
.allowing transport between the two
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36. USAGE EXAMPLES
Agitated column liquid-liquid extractors are 
used to purify water by extracting out impurities
.such as acetic acid and acetone
Agitated extractors are also used in 
biotechnical and environmental industries. The
picture below shows an extractor in a plant.
The column below has the ability to adjust the
cross-sectional area and the agitator speed,
which can optimize droplet size. This flexibility
.allows the column to maximize efficiency

37. AGITATED - COLUMN

38. DISADVANTAGES
Repair of internal mechanical 
.parts can cause process delays

39. ADVANTAGES
.Mechanical parts result in good dispersion 
Little axial mixing compared to non-agitated 
.columns
Karr column extractors can handle higher 
.throughputs than other agitated columns

40. Pulse - column

41. DISADVANTAGES
Packing in packed column hinders flow 
More expensive than non-agitated columns 

42. ADVANTAGES
Increases efficiency two fold 
No internal mechanical parts makes repairs 
easy