General Separation Process 22 Jan 2013

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



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SEPARATION BY PHASE



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SEPARATION BY PHASE



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SEPARATION BY SOLID AGENT

Solid

Feed

Phase 1

Phase 2

Examples

Adsorption Ion

exchange


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Based on differences in species adsorbability

Most commonly, the solid agent = porous

particles high surface area


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Phase 1

Phase 2

Feed Barrier

SEPARATION BY BARRIER

Example Membrane processing


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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
http://www.beilstein-journals.org/bjoc/content/figures/1860-5397-6-86-1.png?scale=3.0&max-width=1024&background=FFFFFF


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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


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 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 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.

General Separation Process 22 Jan 2013

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