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8/13/2019 General Separation Process 22 Jan 2013
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PROSES
PEMISAHAN ICHE232
Nani Indraswati
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TEXTBOOKS C.J. Geankoplis, Transport
Processes and Separation
Principles, 4thed., 2003 McCabe, Unit Operations of
Chemical Engineering, 7thed., 2005
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OUTLINE General separation processes
Humidification
Drying
Evaporation
Crystallization
Membrane processes
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GENERALSEPARATION
PROCESSES
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INTRODUCTION Many chemical & biological substances
occur as mixturesof different
components in the gas, liquid or solidphase
To separate one or more of the
components from the mixture contacted with another phase
solute(s) diffuse between phases
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INTRODUCTION The 2 phases :
Gas - liquid
Gas - solid
Liquid liquid (immiscible)
Liquid - solid The solute redistribute themselves
between the 2 phases
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INTRODUCTION
The products differ in composition
and may differ in phase.
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INTRODUCTION In most instances, the separation is not perfect
If the feed contains > 2 specie 2 or more
separation operations may be required.
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INTRODUCTION
Separation processes are used for 3
primary functions
Purification
Concentration
Fractionation.
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INTRODUCTION Purification
the removal of undesired components in a feed
mixture from the desired species.
Example: acid gases, such as SO2and nitrogen
oxides, must be removed from power-plant
combustion gas effluents before they are
discharged into the atmosphere
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INTRODUCTION
Concentration
to obtain a higher concentration of desired
components that are initially dilute in a feedstream.
Example: the concentration of metals
present in an electroplating process by
removal of water allows metals to berecycled back to the electroplating process
rather than discharged to the environment
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INTRODUCTION
Fractionation
a feed stream of 2 or more components is
segregated into product streams of differentcomponents, typically relatively pure streams
of each component.
Example: The separation of radioactive
wastes with short half-lives from thosehaving much longer half-lives facilitates
proper handling and storage.
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INTRODUCTION
Feed(s)Product 1
Product 2Processes(chemical, physical or biological
Unit
operation
Unit
operation
Unit
operation
Unit
operation
Unit
operation
Unit
operation Product 3
Product 4
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INTRODUCTION
The concept of a unit operation
Based on the same
design criteria and general analysis
scientific principles
regardless of the species and quantitiestobe processes
Allows us to scale-up orscale-downa processbased upon results obtained on a different-sizepiece of equipment
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INTRODUCTION
Laboratory scale bench or pilot-scale
equipment using the results for the
design of the full-scale process In separations, a unit operation is any
process that uses the same separation
mechanism
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INTRODUCTION
Unit operations
Examples
Distillation
used to purify or separate alcohol in the beverage industry
hydrocarbons in petroleum industry
Drying Drying of grains or other foods
Drying of lumber, filtered precipitates, wool
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INTRODUCTION
Absorption
Absorption of O2from air in a fermentation
process or in a sewage treatment plant Absorption of H2in oil hydrogenation process
Evaporation
Evaporation of salt in the chemical industry Evaporation of sugar solution or fruit juices in
the food industry
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INTRODUCTION
Settling and sedimentation of suspended
solids
In the sewage treatment plant In the mining industry
Liquid flow
Flow of liquid hydrocarbons in the petroleumrefinery
Flow of milk in a dairy plant
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BASIC SEPARATION METHODS
Separation by phase creation
Separation by phase addition
Separation by solid agent
Separation by barrier
Separation by force field or
gradient
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SEPARATION BY PHASE
CREATION
creates a second phase (immisciblewith the feed phase)
by :
1. Energy (heat) transfer or
2. Pressure reduction.
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Separationdevice
Feed
Energy
or pressure
reduction
Phase 1Phase 2
Examples:
Evaporation
Distillation Drying
SEPARATION BY PHASE
CREATION
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SEPARATION BY PHASE ADDITION
Separation device
Feed
Mass Separating Agent (MSA)
Phase 1
Phase 2
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SEPARATION BY PHASE
ADDITION
Separation
device
Feed
Mass SeparatingAgent
(MSA)
Phase 1
Phase2
Examples:
Absorption / Stripping
Humidification/dehumidification
Extraction
Leaching
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SEPARATION BY PHASE
ADDITION
Disadvantages of using an MSA are
need for an additional separator to recover the
MSA for recycle need for MSA makeup
possible MSA product contamination
more difficult design procedures
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SEPARATION BY PHASE
ADDITION OR CREATION
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SEPARATION BY PHASE
ADDITION OR CREATION
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SEPARATION BY PHASE
ADDITION OR CREATION
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SEPARATION BY PHASE
ADDITION OR CREATION
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SEPARATION BY SOLID AGENT
Solid
Feed
Phase 1
Phase 2
Examples
Adsorption Ion
exchange
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SEPARATION BY SOLID AGENT
Based on differences in species adsorbability
Most commonly, the solid agent = porous
particles high surface area
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SEPARATION BY SOLID AGENT
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Phase 1
Phase 2
Feed Barrier
SEPARATION BY BARRIER
Example Membrane processing
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SEPARATION BY BARRIER
The barrier is usually a polymer membrane
Feed: gas or liquid
Based on: differences in speciespermeabilities through the barrier
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MEMBRANE PROCESSING
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SEPARATION BY BARRIER
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Separation by force field or gradient
Phase 1
Phase 2
Feed
Use external fields (centrifugal, thermal,
electrical, etc.)
Force field or gradient
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Separation by force field or gradient
Examples
Centrifugation
Electrophoresis: for separating proteins basedon differences in electric charge and
diffusivity
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ABSORPTION
B
B
B
B
B
B
B
B
B
B
B
BA
A
A
AB
B
C
C
C
CC
C
CCC
C
C
C
C
C
C
A
A
A
C
C
A
A
Gas phase Liquid phase
Solute AGas B
Liquid C
interface
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DESORPTION / STRIPPING
B
B
B
B
B
B
B
B
B
B
B
B
A
A
A
AB
B
C
C
C
CC
C
CCC
C
C
C
C
C
C
A
A
A
C
C
A
A
Gas phase Liquid phase
Solute AGas B
Liquid C
interface
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HUMIDIFICATION
BB
B
B
B
B
B
B
B
B
B
B
B
B
C
C
C
CC
C
C
CC
C
C
C
C
CC
CC
Gas phase Liquid phase
Gas B
Liquid C vapor C
C
C
C
C
C CCC
C
C
interface
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DEHUMIDIFICATION
B
B
B
B
B
B
B
B
B
B
B
B
B
B
C
C
C
C C
C
C
CC
C
C
C
C
C
CCC
Gas phase Liquid phase
Gas B (inert)
Vapor C liquid C
C
C
C
C
C CCC
C
C
interface
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LIQUID-LIQUID EXTRACTION
B
B
B
B
B
B
B
B
B
B
B
BA
A
A
AB
B
C
C
C
CC
C
CCC
C
C
C
C
C
C
A
A
A
C
C
A
A
Liquid
phase 1
Liquid
phase 2Solute A
Liquid B
Liquid C
interface
AA
Example
antibiotics in aqueous
fermentation solution
removed with an organic
solvent
BB C
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LEACHING
Solute
SolventSolid
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MEMBRANE PROCESSING
B
B
B
B
B
B
B
B
B
B
B
B
B
B
C
C
C
CC
C
C
CC
C
C
C
C
C
CCC
Phase 1 Phase 2
C
C
C
C
C C
C
C
C
C
membrane
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CRYSTALLIZATION
Solute crystal
Solvent
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ADSORPTION
Solid adsorbent
solvent
Solute / adsorbate
Porous solid /
adsorbent
Surface area
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Example
Feasibility of a separation method
Explain why the operation will or will not be successful.
1. Separation of air into oxygen-rich and nitrogen-rich
products by distillation
2. Separation of m-xylene from p-xylene by distillation
3. Separation of penicillin from water in a fermentation
broth by evaporation of the water.
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1. Separation of air into oxygen-rich
and nitrogen-rich products
The normal boiling points of O2(183C) andN2(195.8C) are sufficiently different that theycan be separated by distillation,
but elevated pressure and cryogenictemperatures are required.
At moderate to low production rates, they are
usually separated at lower costby eitheradsorption or gas permeation through amembrane
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2. Separation of m-xylene from p-
xylene
The normal boiling points of m-xylene
(139.3C) ~ p-xylene (138.5C) separation
by distillation is impractical. Widely different melting points (47.4C for m-
xylene and 13.2C for p-xylene) separation
by crystallization
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3. Separation of penicillin from water
in a fermentation broth
Penicillin: melting point of 97C & decomposesbefore reaching the normal boiling point canpenicillin isolated from water by evaporation of thewater?
Penicillin and most other antibiotics are heat-sensitive must be maintained at room temperature
Water evaporation at room temperature needs highvacuum impractical
A practical separation method is liquidliquidextraction of the penicillin with n-butyl acetate or n-amyl acetate.
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