Separation System

7/28/2019 Separation System

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1

Separation System

Synthesis of Separation System

Distillation Systems for Separating Azeotropes

(a). Not Adding third component

- Pressure-swing distillation (THF-H2O)

- Binary heterogeneous azeotropic distillation (n-butanol-H2O)

- Hybrid distillation with pervaporation (membrane)

- Hybrid distillation with adsorbent (molecular sieve)

(b). Adding third component

- Review of residue curve maps

- Extractive distillation (IPA-H2O+DMSO)

- Heterogeneous azeotropic distillation (IPA and HAc dehydration)

- Salt distillation (Saline extractive distillation)


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Design of Separation System

Liquid Exit Stream


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Reactor Exit is Vapor and Liquid


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Vapor Exit Stream


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Vapor Recovery System Location


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Types of Vapor Recovery System

Condensation high pressure or low temperature, or both

e.g. recovering of acetone from an air stream

Absorption

e.g. using water as a solvent to recover acetone from a air stream

Adsorption

e.g. design procedure is available.

Membrane separation process

Design procedure and cost correlation from vendors.

Reaction systems

e. g. to remove CO2 from gas stream, or H2S is recovered with amines.


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Design Vapor Recovery System First(usually generates a liquid stream or a new recycle loop)


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Liquid Separation SystemAlternatives for Light-Ends Removal

1. Drop P or increase T, and remove it in a phase splitter.

or by the following options:


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Group the components with relative volatility < 1.1


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Column Sequencing Simple Columns

For sharp splits of a ternary mixture(much more alternatives for more components)


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General Heuristics for Column Sequencing

1. Remove corrosive components as soon as possible.- material of construction much more expensive than carbon steel.

2. Remove reactive components or monomers as soon as

possible.- reactive components change the separation problem, monomers foul

reboiler so needs to run at vacuum to decrease column temperature.

3. Remove recycle streams as distillate, particularly if they are

recycled to a packed bed reactor.- avoid contamination with heavy materials, rust, etc., which always

accumulate in a process.


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Select sequence to minimize # of columns in recycle loop


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Column Sequence Example HDA Process

(After light-ends, lightest and plentiful first)


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Complex Column Sequence (Designs 3-7)

- Design guidelines available


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Other choices with relative volatility < 1.1

Extractive Distillation (will study later)


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Azeotropic Distillation (will study later)


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Reactive Distillation (reaction reverse in second column)


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Crystallization


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Introduction of AzeotropeMinimum-boiling Azeotrope (e.g. IPA-H2O)

IPA

XF1

Azeotrope

Azeotrope @ 31 mol%

H2O and 80.0 C

Water

XF2

Azeotrope

xF1 xF2


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Maximum-boiling Azeotrope (e.g. Acetone-Chloroform)

Chloroform

XF1

Azeotrope

Acetone

XF2

Azeotrope

Azeotrope @ 34 mol%

Acetone and 64.5 C

xF1 xF2


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Thermodynamic Model

Extremely important for any design studyCheck your application and select the proper class of

property method

Use Aspen Plus built-in model parameters or the

parameters from literature to predict VLE (Txy, yx),LLE, and azeotropic compositions and azeotropictemperatures

Verify from data in DECHEMA, Azeotropic Data III

(Horsely, 1973), Azeotropic Data (Gmehling, 2004),and also from literatures

You may need to re-fit model parameters usingparameter estimation capability in Aspen Plus


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Pressure-Swing Distillation Can be used in systems where there is significant change

in the azeotropic composition with pressure. Azeotrope: @1.01 bar 82.3 mol% THF, 64 C

@7.9 bar 63.9 mol% THF, 137 C Minimum-boiling homogeneous azeotrope varies with

pressure.

63.9 mol% THFAt 7.9 bar

82.3 mol% THFAt 1.01 bar


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Remarks about the Design Flowsheet

Two pressures are design variables to be optimized, as well asthe number of trays in each column and feed-tray locations.

The larger the difference in the two pressures, further apart theazeotropic compositions, less recycle is required and thelower of the energy consumption.

However, the lower the pressure in the low-pressure column,the larger the diameter and the coolant required in thecondenser. The higher the pressure in the high-pressurecolumn, the higher the pressure of the steam that must be

used in the reboiler and other problems with high temperatureat reboiler.

Possible heat integration of the condenser (HPCOL) and thereboiler (LPCOL).


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Total Annualized Cost (TAC) Analysis

The design variables can be determined by minimizingTAC of the overall system.

TAC includes: stream costs, annualized capital costs,and utility costs.

If feed stream and product streams are with fixed flowrates and compositions, the stream costs can beneglected.

Annualized capital costs for the above system include:LPCOL column, LPCOL column trays, reboiler for LPCOL,

condenser for LPCOL, and another four terms forHPCOL column. (payback period is assumed to be 3 yrs)

Utility costs include: steam costs for the two reboilers andcooling water costs for the two condensers


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Cost Data for Column


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Cost Data for Reboiler and Condenser


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Information on Estimation of U in Calculating A


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Information on Utility Costs

Control Strategy for this System


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Control Strategy for this System


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Isobaric Phase Diagrams forBinary Azeotropic Mixtures

Homogeneous Azeotrope Heterogeneous Azeotrope


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Separation of a Binary HeterogeneousAzeotropic Mixture (excerpt from Doherty and Malone, 2001)


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Design when Feed Composition is inmiscible Region (e.g. 20% water)


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Examples of Binary Mixture Systems

No need to add entrainer.

Examples include: purifying water-hydrocarbonmixtures (e.g., water with any one of the

following components: C4-C10, benzene,toluene, xylene, etc.).

Water-alcohol mixtures (e.g. butanol, pentanol,

etc.) as another example.

C5s and methanol separation.


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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Vapory(m

olefractioniC5)

Liquid x (mole fraction iC5)

Another Example: iC5/methanol binary system

1 atm

5 atm

2.6 atm

10 atm


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1

7

1

5

Feed

1126 kmol/hr320 K0.4446 iC50.0783 nC50.03371-Pentene0.1431 2-Pentene0.2814 MeOH0.0037 2M1b0.0149 2m2B

0.0003 H2O

Light1301 kmol/hr

Heavy418 kmol/hr

320 K

391 K

10.02 atm

328 K

2.6 atm

375 K

10 atm

7.213 MW

4.30 MW

1.187 MW

C1ID 0.751 m

C2ID 2.785 m

2.4 atm

B1

314 kmol/hr0.999 MeOH0.001 H2O

Ovhd1

104 kmol/hr0.4633 iC50.0750 nC50.0382 1-Pentene0.1622 2-Pentene0.2407 MeOH0.0045 2M1B0.0160 2m2B0.0001 H2O

365 K

2.64 atm

0.778MW

B2

812 kmol/hr0.6166 iC50.1086 nC50.0467 1-Pentene

0.1984 2-Pentene0.0039 MeOH0.0051 2M1B0.0207 2m2B

Ovhd2

489 kmol/hr0.4627 iC50.0605 nC50.0264 1-Pentene

0.1121 2-Pentene0.3235 MeOH0.0037 2M1B0.0109 2m2B0.0001 H2O

Decanter


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1

7

1

5

Feed

LightHeavy

320 K

2.4 atm

391 K

10.02 atm

328 K2.6 atm

375 K

10atm

7.21 MW

4.30MW

1.19 MW

ID 0.751 m

VLEID 2.78 m

VLLE

B1

0.999 MeOH

365 K

2.64 atm

0.778 MW

B20.0039 MeOH

FCLC

LC

LC

LCPC PC

TC TC

320 K

2.4 atm

TC TC

0.17 MW

320 K

2.4 atm


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Review of Residue Curve Maps

d

d

)yx(H

V

dt

dx

Vydt

)Hx(d

Vdt

dH

iii

ii


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Simple Distillation Residue Curves


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RCM for Ternary Mixture without Azeotrope


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RCM for Ternary Mixture with one BinaryMinimum-Boiling Azeotrope

True Systems for Above Cases


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True Systems for Above Cases

Selected RCMs for Ternary Mixtures


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Selected RCMs for Ternary Mixtureswith Multiple Azeotropes


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RCM vs. Distillation Lines

columnstagedassamethe1hAssumeh

ratcolumnpackedfortionrepresentaEuler

x:columnstagedFor

x)0h(dh

d:columnpackedForrWhen

xx1r

1

1r

r:ColumnStaged

x)0h(r

x

r

1r

dh

d:ColumnPacked

n1n

1n1n

n1n

D0n1n

D

D0Dn1n

DD


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Example of RCM vs. Distillation Lines

Total Reflux vs. Finite Reflux Ratio


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Total Reflux vs. Finite Reflux Ratio(Notice also the mass balance line)


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Summary of RCM

Easily sketched with the help of Aspen Plus.

The residue curve through any given liquidcomposition point is tangent to the vapor-liquid tie-linethrough the same point.

The structure of the RCM is the underlying

thermodynamic principle that governs the shape ofcomposition profiles and consequently the productsthat can be obtained from a distillation.

The composition of the desired products from each

column should lie in the same distillation region (notnecessary including F). If the distillation boundariesare linear, the products from the entire sequence mustlie in the same distillation region.

Exception for Curved Distillation Boundary


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Exception for Curved Distillation Boundary


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Extractive Distillation

Separating minimum-boiling binary azeotrope by usingheavy entrainer.

Two-column sequence with first extractive distillationcolumn separating out one product and second entrainer

recovery column separating out entrainer and anotherproduct.

Most widely used form of homogeneous azeotropicdistillation in industries

Examples include: n-butane-butadiene using furfural;dehydration of ethanol using ethylene glycol; acetone-methanol using water; pyridine-water using bisphenol.

C t l D i Fl h t


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Conceptual Design Flowsheet

Qr1

Extractive

distillation columnEntrainer

recovery column

Qc1

F2

D1

IPA-water feed (FF)

Entrainer feed (FE)

Entrainer recycle

Entrainer makeup

D2

Qc2

Qr2

B2

NFE

NFF

NF2

N1 =.?

NFE =.?

NFF =

.?

N2 =.?

NF2 =.?

Which will be the D1 product?


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Which will be the D1 product?

Isovolatility curve

Adding entrainer

causing

1Acetone

Methanol

Using Different Entrainer


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Using Different Entrainer

Isovolatility curve

Adding entrainer

causing

1Acetone

Methanol

Case Study of an Extractive Distillation


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Case Study of an Extractive DistillationColumn System

Isopropyl Alcohol (IPA) is widely used in semi-conductorindustry as a cleaning agent, thus the recovery of IPAfrom waste solvent stream is an important issue worthyof study.

Dehydration of IPA using Dimethyl Sulfoxide (DMSO) asentrainer.

Minimum-boiling azeotrope with heavy entrainer, thus anextractive distillation system.

Two-column system with an extractive distillation columnand an entrainer recovery column.

Optimum design and control of the overall system.

Compare of Candidate Entrainers


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Co pa e o Ca d date t a e s(adding DMSO keeps IPA toward the top of the column)

WATER

(100.02 oC)

DMSO

(190.74 oC)

IPA (82.35 oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.6

0.

7

0.

8

0.

9

80.00 oC

1

1.5

2

3

4

5

6

78

XE = 0.15

Isovolatility curve

Equalvolatility curve

with =2.0

Compare to EG as Entrainer


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Compare to EG as Entrainer(enhancement of is less)

WATER

(100.02 oC)

EG

(197.08 oC)

IPA (82.35 oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.

6

0.

7

0.

8

0.

9

80.00 oC

1

1.5

2

3

4

56

78

xE = 0.20

Counterexample by only Observing


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Counterexample by only ObservingIsovolatility Curve

DMC(90.22 C)

EG(197.08 C)

MeOH (64.53 C)

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95

0.

05

0.

1

0.

15

0.2

0.

25

0.

3

0.

35

0.

4

0.

45

0.

5

0.

55

0.

6

0.6

5

0.

7

0.

75

0.

8

0.

85

0.

9

0.

95

63.60 C

1.5

2

3

4

5

Appeared better?

More effective in

changing

Entrainer #1 Entrainer #2(183.88 C)0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95

0.

05

0.

1

0

.15

0.

2

0.

25

0.

3

0.

35

0.

4

0.

45

0.

5

0.

55

0.

6

0.

65

0.

7

0.

75

0.

8

0.

85

0.

9

0.

95

MeOH (64.53 C)

DMC(90.22 C)

Aniline

63.60 C


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Check VLE of IPA-DMSO


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Check VLE of H2O-DMSO


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Optimum Design of the Flowsheet

The design variables include: total stages for extractivecolumn and recovery column; feed location for extractivecolumn, recycled entrainer location, and feed location forrecovery column; ratio of recycled entrainer and freshfeed; andrecycled entrainer feed temperature.

Equal molar fresh feed composition of IPA and water.

IPA product spec. at 99.9999 mol% for semi-conductorindustry usage, bottom spec. of extractive column set atx

IPA

/(xIPA

+xH2O

)=0.001, and Water spec. at 99.9 mol%.

Do optimization for the extractive distillation column firstand then for the overall flowsheet.

Material Balance Lines for the System


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Material Balance Lines for the System

WATER(100.02 oC)

DMSO(190.74 oC)

IPA (82.35 oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.1

0

.2

0.

3

0.

4

0.5

0.6

0.7

0.

8

0.9

80.00 oC

D1

FF

D2B2

DMSO makeup

F2

FF + B2 + DMSO makeup

B2 + DMSO makeup

Liquid Composition Profiles for the two Columns


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q p

Pure IPA

Water diminished

Pure DMSOPure water

DMSO maintained in

extractive section

Overall Control Strategy


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Overall Control Strategy

C-2

C-1

IPA product Water product

IPA-Water

Reflux

drumLC

PC

LC

PC

LC

38 TC1

TC212

Reflux

drum

FC

DMSO

makeup

FC

FC

TC

LCLC

RC

RCFCFC

RC

Conclusions for Extractive Distillation Study


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Conclusions for Extractive Distillation Study

Isovolatility curve can be used to determine D1 product. Iso- and equalvolatility curves to find more effective

entrainer. Check VLE of the other two pairs to confirm easy

separation in rectifying section of the extractive columnand also in entrainer recovery column.

Extractive agent (DMSO) was added to alter the relativevolatility between IPA and H2O.

IPA goes toward top of the extractive column and watergoes toward bottom of this column.

Two-column design to obtain pure IPA and H2O.

A pre-concentrator column is needed for diluted freshfeed. Simple control strategy is developed with only one tray

temperature control loop in each column to handle feedvariations.

Same Separation Using Heterogeneous


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p g gAzeotropic Distillation

Minimum Temp

Distillation Boundary

Three-Column Design with a


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Three Column Design with aPre-concentrator Column

NF2

Decanter

C-3C-2

IPA Water

IPA-Water

Cyclohexane makeup

Organic reflux

Aqueous outlet flow

Water

C-1

NF1

D1 D3NF3

WATER(100.02 oC)

CyH(80.78 oC)

IPA (82.35 oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.2

0.

3

0.4

0.5

0.6

0.7

0.

8

0.9

69.44oC

63.77oC

80.00oC

69.34oC

D1

FFD3

Organic reflux

Aqueous outlet flow

B1 and B3

D1 + D3

B2

Total liquid in decanter

Two-Column Design


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g(with larger top vapor rate)

NF

Decanter

C-2C-1

IPA Water

IPA-Water

Cyclohexane make up

Organic reflux

Aqueous outlet flow

D2

NF

WATER(100.02

oC)

CyH(80.78

oC)

IPA (82.35oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.6

0.

7

0.

8

0.

9

69.44oC

63.77

o

C

80.00oC

69.34oC

D2

FF+D2

B1

B2

FF

Aqueous outlet flow

Organic reflux


Proposed Two-Column Design: One column served


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p gas pre-concentrator and also recovery column

WATER(100.02 oC)

CyH(80.78 oC)

IPA (82.35o

C)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.

6

0.

7

0.

8

0.

9

69.44oC

63.77oC

80.00oC

69.34oC

D2

B2

FF + Aqueous outlet flow

FF

Organic reflux

Aqueous outlet flow

B1


Decanter

C-2C-1

B1 B2

IPA-Water mixture

Cyclohexane makeup

Organic reflux

Aqueous outlet

D2

Heterogeneous Azeotropic Column Pre-concentrator/Recovery Column

FF

V1

Overall Control Strategy for the Proposed Design


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gy p g

Decanter

C-2C-1

IPA product Water product

IPA-Water

Cyclohexane makeup

Organic reflux

Aqueous outlet flow

Reflux

drum

TC

FC

FC

LC

PC

LC

TC

LCLC

PC

FC

LC

7 TC1TC2

9

RC

RC

Deficiency of Using this RCM type


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y g yp

WATER

(100.02 oC)

CyH

(80.78 oC)

IPA

(82.35 oC)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0

.6

0.

7

0.

8

0.

9

69.44 oC

63.77 oC

80.00 oC

69.34 oC

V1

FF

Aqueous outlet

Organic refluxB2

B1

FF + Aqueous outlet

D2

b

a

V1 flowrate = B1 flowrate

a

b

Using Benzene as Entrainer


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g

BENZENE

(80.13 C)0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0

.6

0.

7

0.

8

0.

9

(100.02 oC)

Aqueous outlet

FF + Aqueous outlet

FF

80.00 oC

D2

WATER

IPA

(82.35 oC)

B1

V1

65.38oC

Organic reflux

69.35oC

71.74oC

b

a


a

b

B2

Even Better Entrainer


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Even Better Entrainer

Entrainer0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.

6

0.

7

0.8

0.9

Minimun-boiling

azotrope

80.00 oC

D1

FF

B1 Organic reflux

IPA

(82.35oC)

WATER

(100.02 oC)

b

a

V2

Aqueous outlet

B2


a

b

Other System using Heterogeneous Azeotropic


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Distillation (PM-water Separation)

Other System using Heterogeneous Azeotropic


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Distillation (Pyridine-water Separation)

Better Design for the Pyridine-water Separation


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Conclusions for Heterogeneous Azeotropic


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g pDistillation Study (I)

Heterogeneous Azeotropic Distillation able to crossdistillation boundary and obtain products at differentdistillation regions.

Combined pre-concentrator/recovery column design

reduce TAC and operating cost for the IPA dehydrationsystem, save equipments and instrumentations, and alsodampen disturbances from fresh feed.

Illustration of using heterogeneous azeotropic distillation

for various RCM type. The most competitive design is to find an entrainer with

only one additional binary heterogeneous azeotropewhich is also minimum-boiling.

Case study (II): Acetic Acid Dehydration


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Case study (II): Acetic Acid Dehydration

No azeotrope exists for the acetic aciddehydration system.

VLE exhibits tangent pinch near pure water end.

Needing many trays if using simple distillation.

Adding entrainer via heterogeneous azeotropic

distillation to help the separation.

Study the entrainer selection, design, andcontrol of this system.

Thermodynamic model


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Thermodynamic model

Nonideal vapor phase with vapor association ofHAc is described via Hayden-OConnellssecond virial coefficient method

Liquid phase using NRTL activity coefficientmodel

Consider three acetates (ethyl acetate, iso-butylacetate, n-butyl acetate) as candidates ofentrainer

Using DECHEMA VLE, LLE data and azeotropicdata to obtain NRTL model parameters

yx and Txy plots of HAc-water system


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y y p y

Tangent Pinch


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Important factors for the selection of entrainer


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p

Azeotropic composition containing more water

organic phase composition containing moreentrainer

Azeotropic temperature the lower the better

Aqueous phase composition containing as

little entrainer as possible

Entrainer pricing the lower the better

Using ethyl acetate as entrainer


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g y

WATER(100.02 C)

EtAc(77.20 C)

HAC (118.01 C)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.

6

0.

7

0.

8

0.

9

69.99 C

Highest temp in

ternary system

Outer Material

Balance Line

Outer Material

Balance Line

Inner Material

Balance Lines

Using iso-butyl acetate as entrainer


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iBuAc(116.40 C)0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0.

3

0.

4

0.

5

0.

6

0.

7

0.

8

0.

9

87.72 C

HAC (118.01 C)

WATER(100.02 C)

Highest temp in

ternary system

Possible Steady-

State Cases with

Aqueous Reflux

Using n-butyl acetate as entrainer


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85

g y

nBuAc(126.01 C)0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.

1

0.

2

0

.3

0.

4

0.

5

0.

6

0.

7

0.

8

0.

9

90.51 C

HAC (118.01 C)

WATER(100.02 C)

Highest temp in

ternary system

Possible Steady-

State Cases with

Aqueous Reflux

Important factors for the selection of entrainer


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p

Azeotropic composition (NBA-best, EA-worst)

organic phase composition (IBA-best, EA-worst)

Azeotropic temperature (EA-best, NBA-worst) Aqueous phase composition (IBA-best, EA-worst)

Entrainer pricing (EA-best, IBA-worst)

Optimum design for the individual system


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Feed flow rate of 500 kg/h with equal molar of HAc andH2O

Minimizing total annual cost (TAC)

TAC including annualized capital costs, utility costs, andmake-up entrainer cost

Column bottom HAc composition is fixed at 99.9 mol%by varying reboiler duty

Column top aqueous outlet composition is fixed at 0.1mol% HAc loss by varying entrainer make-up flow rate

Aqueous reflux (if any) is varied to obtain lowest reboilerduty

Varying total column stages and feed location tominimize TAC

Comparison of TAC for the alternative systems


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Entrainer Optimum

TotalStages

Optimum

FeedStage

Capital

Cost ($)

Utility

Cost ($)

Entrainer

Cost ($)

TAC

($)

EA 16 2 6.84104 4.20104 5.40104 1.64105

IBA 30 9 6.81104 1.80104 1.70104 1.03105

NBA31

118.44104 2.78104 6.08104 1.73105

Noentrainer

50 37 1.42105 4.37104 0 1.86105

Optimum Operating Condition


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89

p p g

Entrainer EntrainerMake-up

OrganicReflux

AqueousReflux

Ethyl

Acetate

2.24

mol/min

574

mol/min

0.0

mol/min

i-ButylAcetate

0.16mol/min

92.7mol/min

33.4mol/min

n-ButylAcetate

0.70mol/min

102.3mol/min

98.8mol/min

Vapor and liquid profiles for the optimum system HAc-iBuAc-H2O


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Difficult Region

for the Separation

is Avoided

Minimum aqueous reflux fraction under various feed compositions


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Feed Water Composition

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

AqueousRefluxFraction

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Proposed overall control strategy


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IBA Makeup

Organic

RefluxFeed

(HAC+H2O mixture)

Steam

Distillate

(H2O Rich)

FC

FC

Bottom Product(HAC)

Reboiler

FC

LCLC

LC

FC

Decanter

TC

6

RC

FC

FC

RC

Summary of control strategy


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Simple control strategy with only one tray temperaturecontrol loop in the system manipulating the aqueous

reflux flow

The temperature control point is selected from open-loopsensitivity test

Organic level organic reflux flow

Aqueous level aqueous outlet flowBottom level bottom flow

Reboiler duty and entrainer makeup both are ratioed tothe feed flow

Both bottom and top products are maintained at highpurity despite 10% changes in the feed H2Ocomposition or in the feed flow rate

Conclusions


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Using acetate as entrainer can help in the separation ofHAc and H2O via heterogeneous azeotropic distillation

Optimum design of three candidate entrainers arecompared using TAC as objective function

TAC with i-butyl acetate as entrainer is only about 55%of the TAC for no entrainer system

Simple control strategy is developed with only one traytemperature control loop

This control strategy is able to hold both bottom HAcproduct and top aqueous product at high-purity despitefeed composition or feed flow rate disturbances

Process flowsheet of an industrial unit


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AqueousReflux

Condenser

F1

F2

F3

F4

F5

SidedrawAqueousOutlet

IBA Makeup

OrganicReflux

Decanter

Steam

Reboiler

BottomProduct

Design and Operation of

this Side Stream

Paper References


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96

1. Chien, I-Lung; Zeng, K. L.; Chao, H. Y. Design and Control of a CompleteHeterogeneous Azeotropic Distillation Column System. Ind. Eng. Chem. Res.2004, 43 (9), 2160-2174.

2. Arifin, Saiful; Chien, I-Lung Combined Preconcentrator/Recovery Column Designfor Isopropyl Alcohol Dehydration Process. Ind. Eng. Chem. Res.2007, 46 (8),2535-2543.

3. Arifin, Saiful; Chien, I-Lung Design and Control of an Isopropyl AlcoholDehydration Process via Extractive Distillation Using Dimethyl Sulfoxide as anEntrainer. Ind. Eng. Chem. Res.2008, 47 (3), 790-803.

4. Chien, I-Lung; Zeng, K. L.; Chao, H. Y.; Liu, J. H. Design and Control of AceticAcid Dehydration System via Heterogeneous Azeotropic Distillation Column.

Chem. Eng. Sci. 2004, 59 (21), 4547-4567.5. Chien, I-Lung and Kuo, Chien-Lin Investigating the Need of a Pre-Concentrator

Column for Acetic Acid Dehydration System via Heterogeneous AzeotropicDistillation. Chem. Eng. Sci. 2006, 61 (2), 569-585.

6. Chien, I-Lung; Huang, Hsiao-Ping; Gau, Tang-Kai; Wang, Chun-Hui. Influence ofFeed Impurity on the Design and Operation of an Industrial Acetic AcidDehydration Column. Ind. Eng. Chem. Res.2005, 44 (10), 3510-3521.

7. Huang, Hsiao-Ping; Lee, Hao-Yeh; Gau, Tang-Kai; Chien, I-Lung Design andControl of Acetic Acid Dehydration Column with p-Xylene or m-Xylene FeedImpurity. 1. Importance of Feed Tray Location on the Process Design. Ind. Eng.Chem. Res.2007, 46 (2), 505-517.

8. Huang, Hsiao-Ping; Lee, Hao-Yeh; Chien, I-Lung Design and Control of AceticAcid Dehydration Column with p-Xylene or m-Xylene Feed Impurity. 2. BifurcationAnalysis and Control. Ind. Eng. Chem. Res.2008, 47 (9), 3046-3059.

Book References


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97

oo e e e ces

Doherty, M. F. and M. F. Malone, Conceptual Design ofDistillation Systems, McGraw-Hill, 2001.

Douglas, J. M., Conceptual Design of ChemicalProcesses, McGraw-Hill, 1988.

Turton, R., R. C. Bailie, W. B. Whiting, and J. A.Shaeiwitz,Analysis, Synthesis, and Design of ChemicalProcesses, Prentice Hall, 1998.

Luyben, W. L., Plantwide Dynamic Simulators inChemical Processing and Control, Marcel Dekker, 2002.

Upcoming New Book to be Published


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Upcoming New Book to be PublishedEnd of 2009

Williams L. Luyben and I-Lung Chien, Design and

Control of Distillation Systems for SeparatingAzeotropes, John Wiley & Sons, Inc., 2009.

Fourteen chapters of real examples using variousseparation methods

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