design of karr extractor

Term Project: Design of Karr Extractor

Group # 04

Subject:

Separation Processes (Ch.E-309)

Instructor:

Sir Saqib Javed

Members:

M Fahad (UW-13-CHE-BSC-052)

Waleed Shahid (UW-13-CHE-BSC-010)

Mohsin Raza (UW-13-CHE-BSC-018)

Haseeb Iqbal (UW-13-CHE-BSC-021)

Saeed Akhtar (UW-13-CHE-BSC-023)

Ali Hassan (UW-13-CHE-BSC-031)

M Fahad (UW-13-CHE-BSC-052)

Date of Submission:

30th May, 2016

Term Project Separation Processes (Ch.E-309)

Design of Karr Extractor i Group No. 4

Acknowledgement

This report is dedicated to GOD Almighty and to all those special individuals who have played

an important role in our life and contributed towards our success.

My deepest gratitude to Sir Saqib Javed for his assistance, advice and guidance throughout the

duration of our term project without his assistance, the compilation of this project would not

be feasible.


Design of Karr Extractor ii Group No. 4

Summary

Karr Reciprocating-Plate Extractor was designed as a term project for “Separation Processes”.

The extractor was designed to separate a solution of methylene chloride and methanol with the

input mass flow rates of 2185 lb/h (991 kg/h) and 33 lb/h (15.0 kg/h) respectively, using water

as selective solvent with a mass flow rate of 2218 lb/h (995 kg/h) to recover 95% methanol.

The calculated diameter and height of extractor is 10.42 inch and 7 ft.


Design of Karr Extractor iii Group No. 4

Nomenclature

1x = Mass Fraction of Solute in Feed

2x = Mass Fraction of Solute in Raffinate

1y = Mass Fraction of Solute in Extract

2y = Mass Fraction of Solute in Selective Solvent

Sm = Mass Flow Rate of Solvent

SMm = Minimum Mass Flow Rate of Solvent

Fm = Mass Flow Rate of Feed

C = Concentration Mass per Unit Volume

K = Liquid Vapor or Liquid-Liquid Equilibrium Ratio

AE = Extraction Factor

NE = Number of Equilibrium Stages

Fρ = Density of Feed

Sρ = Density of Solvent

A = Cross Sectional Area

D = Diameter of Column of System

D1 = Diameter of Column taken as Standard

1

HETS = Height Equivalent of Transfer Unit of Column taken as Standard

HETS = Height Equivalent of Transfer Unit of Column of System

EZ = Height of Extractor

SZ = Height of Settler

Z = Height of Column


Design of Karr Extractor iv Group No. 4

Table of Contents Introduction to Liquid-Liquid Extraction: ................................................................................. 1

Definition: .............................................................................................................................. 3

Advantages of Liquid-Liquid Extraction: .............................................................................. 3

Disadvantages of Liquid-Liquid Extraction: ......................................................................... 3

Liquid-Liquid Extraction Equipment:........................................................................................ 4

Selection of Equipment:............................................................................................................. 4

Karr Reciprocating-Plate Column:......................................................................................... 4

Uses:....................................................................................................................................... 5

Industrial Application: ............................................................................................................... 6

1. Extraction of Fermentation Broth by using Karr Reciprocating-Plate Extractor: .......... 6

2. Extraction of Penicillin in Karr Reciprocating-Plate Extractor: ..................................... 6

3. Use of Ionic Liquid in a Karr Reciprocating-Plate Extractor: ........................................ 6

Design of Karr Reciprocating Extractor: ................................................................................... 7

Step 1: Mass Fraction in Raffinate......................................................................................... 7

Step 2: Minimum Solvent Flow Rate..................................................................................... 7

Step 3: Minimum Solvent Rate and Operating Rate.............................................................. 8

Step 4: Mass Fraction of Solute in Extract ............................................................................ 8

Step 5: Calculation of Extraction Factor AE .......................................................................... 8

Step 6: Calculate the Number of Equilibrium Stages ............................................................ 8

Step 7: Extractor Diameter..................................................................................................... 9

Effect of Concentration on Height: .......................................................................................... 12

Effect of Percentage Recovery on Height:............................................................................... 12

Effect Solvent Rate in Feed on Diameter: ............................................................................... 13

Attachments: ............................................................................................................................ 14

Bibliography: ........................................................................................................................... 15


Design of Karr Extractor v Group No. 4

List of Figures

Figure 1: Counter Current Extraction. ...................................................................................... 2

Figure 2: Karr Reciprocating-Plate Column (RPC).................................................................. 5

Figure 3: Concentration vs. Height ......................................................................................... 12

Figure 4: Percentage Recovery vs. Height.............................................................................. 13

Figure 5: Solvent Rate in Feed vs. Diameter .......................................................................... 13


Design of Karr Extractor vi Group No. 4

List of Tables

Table 1: Terminology that may be used to describe the extraction system. ............................. 2

Table 2: Minimum NETS and Volumetric Efficiency for the Karr, RPC .............................. 11


Design of Karr Extractor vii Group No. 4

List of Equations

2 1

1 2F SM

1 2

x =(1-ε)x ..........................................................................................................................Equation(1)

K(x -y )m m = ....................................

(x -x )

F S F SM

............................................................Equation(2)

m m =C( m m )..........................................................................................................Equation(3

1 2 F S 1 2

E F S

)

y =y +( m m )( x -x ).....................................................................................................Equation(4)

A = ( m m ) K..........................................................

1 2

E E E E

2 2

SP P S

......................................................Equation(5)

x - y KN = log 1-A +A log(1 A ) ...............................................................Equation(6)

x - y K

m ρ + m ρA = ........

J

0.38

11

....................................................................................................Equation(7)

DHETS= HETS ..................................................................

D

E E

................................Equation(8)

Z =N HETS ...................................................................... ...........................................Equation(9)


Design of Karr Extractor 1 Group No. 4

Introduction to Liquid-Liquid Extraction:

Liquid-liquid extraction is a mass transfer technique in which a solution (feed: mixture of solute

and carrier liquid) is brought into intimate contact with an immiscible or slightly miscible liquid

(selective solvent) in order to achieve transfer of the solute from the feed to the solvent. The

two liquid phases that have different densities are then separated. The solute-rich phase is called

the extract; the residual feed stream that may have a little amount of the solute left in it is called

the raffinate.

If the carrier in the feed and the solvent are partly miscible, the raffinate will also have a little

amount of solvent dissolved in it, and the extract phase will contain a little amount of dissolved

carrier. The solute is separated from the extract phase in an acceptably pure form, and the

solvent dissolved in the raffinate is recovered. An extraction process generally involves four

major steps.

1) Bringing the feed and the solvent into intimate contact by dispersing one phase into the

other as droplets.

2) Separation of the extract and the raffinate phases that have different densities.

3) Removal and recovery of the solute from the extract phase in relatively pure form (by

evaporation, crystallization, etc.).

4) Removal and recovery of the solvent from each phase, usually by distillation.

Separation of a liquid mixture or solution by distillation is operationally simpler than

extraction. For the extraction method to be categorized as simple, it involves:

a) Solute, which is a substance that needs to be extracted.

b) Carrier

c) Solvent, which is the substance that is used to extract solute from the carrier.

Figure 1 describes the counter current extraction process and Table 1 provides the terminology.

For a highly efficient contact between the solvent and the feed, a large interfacial area is

required. An increase in vibrating levels can increase the interfacial area and also enhance the

mass transfer. The phase with the largest volume is commonly selected as a continuous phase.

However, each of the phases can be dispersed by setting the interface level in either the top or

the bottom section.



Figure 1: Counter Current Extraction.

Table 1: Terminology that may be used to describe the extraction system.

Terminology Definition

Feed The substance that contains a carrier and the solute that needs

to be extracted.

Carrier The non-solute portion of the mixture (portion that remains

after extraction takes places).

Solute The substance that needs to be extracted.

Solvent The fluid that is used to influence the extraction.

Extract phase/stream The output stream that contain high amount of solutes.

Light phase/stream The input stream that has lower density and flows up the

column and then accumulates at the top.

Heavy phase/stream The input stream that has higher density which flows down the

column and then accumulates at the bottom.

Dispersed phase/stream The input stream that is distributed in a drop form through the

distributor pores.

Continuous

phase/stream

The input stream that flows in bulk and does not form drops.

Raffinate phase/stream The output stream that contains small or zero amounts of

solute.



Definition:

Separation of components of a liquid mixture by treatment with solvent in which desired

component is soluble. Liquid-Liquid Extraction (LLE) is a useful method to separate

components of a liquid mixture having two or more components. Removal of acetic acid from

water can be achieved using distillation and LLE. [iv. (Seader, 2011)]

Advantages of Liquid-Liquid Extraction:

In comparison to distillation, liquid- liquid extraction can be used in the separation of

azeotropes as well as for components that have close boiling points. It is usually operated at a

lower cost, and can be operated at low to moderate temperature for recovery of heat sensitive

products in the petroleum, food and pharmaceutical industries.

In selecting a separation process the relative cost is significant. Even though the extraction

process may involve other separation units beside the extractor, the relative cost may be lower.

In case of more dilute solutions, where water needs to be vaporized in the distillation for

separation, extraction is more economical due to the facts that the heat of vaporization of most

organic solvents is substantially lesser than that of water.

LLE is cheaper and can be used instead of using the chemical methods because chemica l

methods use reagents that result in expensive disposal for chemical by-products. It has rapid

and very selective separations that are usually highly efficient.

Disadvantages of Liquid-Liquid Extraction:

Normally, the extraction system consists of one distillation to recover the solvents. However,

if the solvent is soluble in the carrier, multiple extractions might be required to recover the

solvent from the raffinate, thereby increasing time, consumption of materials, and generation

of waste. Other disadvantages mentioned by the authors are as follows:

Can be time consuming, especially if attainment of equilibrium is slow.

Can be affected by small impurities in the solvent(s).

Cumbersome for a large number of samples or for large samples.

Formation of emulsions can interfere with the phase-separation process.

Counter-current process can be complicated and can require complicated equipment.

Alteration of the chemical form can occur, going from one phase to the other, thereby

altering the distribution coefficient and effectiveness of the extraction.



Liquid-Liquid Extraction Equipment:

The equipment used to carry out the LLE are called Liquid-Liquid Extractors. Common

extractors are divided into following classes:

1. Mixer-Settlers

2. Spray Columns

3. Packed Columns

4. Plate Columns

5. Mechanically Agitated Columns

Selection of Equipment:

We are designing a Karr Reciprocating-Plate Column which is included in the class of

mechanically agitated columns. We selected this specific equipment for the given system,

because it is suitable for the systems having intermediate to low interfacial tension, as in the

given system.

Karr Reciprocating-Plate Column:

The Karr Reciprocating-Plate column as shown in Figure 1 is a descendent of the pulsed sieve-

tray column. It has a reciprocating shaft with perforated plates mounted thereon. In this column

plates move up and down approximately 2–7 times per second with a 6.5–25 mm stroke, using

less energy than for pulsing the entire volume of liquid. Also, the close spacing of the plates

(25–50 mm) promotes high turbulence and minimizes axial mixing, thus giving high mass-

transfer rates and low HETS. The annular baffle plates in Figure 1 are provided periodically in

the plate stack to minimize axial mixing. The perforated plates use large holes (typically 9/16-

inch diameter) and a high percentage hole area (typically 58%). The central shaft, which

supports both sets of plates, is reciprocated by a drive at the top of the column.



Figure 2: Karr Reciprocating-Plate Column (RPC).

Uses:

Karr columns are particularly useful for bio-separations because residence time is reduced, and

they can handle systems that tend to emulsify and feeds that contain particulates. Biologica l ly

produced chemicals and fuels, like algae often required LLE. This is also used for the systems

having intermediate to low interfacial tension. [i. (Dutta, 2010)]



Industrial Application:

There are many industrial applications of Karr Reciprocating-Plate Column. Three of which

from different industries are mentioned as follows:

1. Extraction of Fermentation Broth by using Karr Reciprocating-Plate Extractor:

The apparatus employed in the pharmaceutical industry for extracting fermenta t ion

broths is the centrifugal extractor. However, a recent research indicates that the Karr

Reciprocating Plate Extractor Column could be considered for such applications .A

pharmaceutical company have been using a centrifugal extractor to extract a whole

fermentation broth. However, they could not feed the broth to the extractor unless they

pretreated the broth by a “hand wash” or a preliminary batch extraction. It required

three passes through the centrifugal machine to achieve the desired degree of extraction.

On the other hand, with one pass through the Karr Column, essentially complete

extraction was achieved. The advantages evident included a 55% reduction in solvent

requirements, and substantially less capital, utilities, maintenance cost & solvent losses.

[ii. (Jameson, 1980)]

2. Extraction of Penicillin in Karr Reciprocating-Plate Extractor:

The suitability of Penicillin recovery by reactive extraction at room temperature in a

Karr reciprocating plate extractor is determined when PH values are kept between 5 to

6, the extraction and re-extraction losses of Penicillin are less than 0.3% as opposed to

losses larger than 10% in the industrial process using a centrifugal extractor at pH

values 2 – 2.5 and 5 °C with short contact. [iii. (M. Reschke, 1985)]

3. Use of Ionic Liquid in a Karr Reciprocating-Plate Extractor:

Ionic liquids offer different way to volatile organic solvents for extraction of wide range

of materials. That work observes that the mass transfer performance of a Karr

reciprocating plate extractor with an ionic liquid as a different solvent for the extraction

of phenol from water. The product indicate that ionic liquids can be used in existing

solvent extraction apparatus and that existing correlations and models can be used to

predict mass transfer operations.



Design of Karr Reciprocating Extractor:

The extractor is designed to separate a solution of methylene chloride and methanol with the

input mass flow rates of 2185 lb/h (991 kg/h) and 33 lb/h (15.0 kg/h) respectively, using water

as selective solvent with a mass flow rate of 2218 lb/h (995 kg/h) to recover 95% methanol.

Calculate the diameter and height of the given system.

Given data:

Feed:

Methylene chloride = 2185 lb hr

Methanol = 33 lb hr

Total Fm = 2218 lb hr

Recovery coefficient = K = 2

Methanol recovery % = = 0.95

Concentration mass unit = C = 0.5

Densities

Methylene chloride=82.41 3lb ft

Methanol = 48.7 3lb ft

Water = 62.43 3lb ft

1x = mass fraction = 33

2218=0.0148

Solution:

Step 1: Mass Fraction in Raffinate

For finding the mass fraction in raffinate, we use the following equation

2 1x = ( 1- ε ) x

2x 0.000744

Step 2: Minimum Solvent Flow Rate



F 1 2

SM 1 2

m Kx - y=

m (x - x )

2(0.01488)-0

= = 2.105(0.01488-0.000744)

Step 3: Minimum Solvent Rate and Operating Rate

F F

S SM

m m= C

m m

=0.5×2.105

F

S

m = 1.053

m , F

SM

m = 2.105

m

Fm = 2218 lb hr

s

2218m = = 2106 lb hr

1.063

Step 4: Mass Fraction of Solute in Extract

F1 2 1 2

S

my = y + x -x

m

=0+(1.053)(0.01488-0.00074)

1 0.014885y

Step 5: Calculation of Extraction Factor AE

F S

E

m /mA =

K

Step 6: Calculate the Number of Equilibrium Stages

1 2

E E E E

2 2

x - y KN = log 1-A + A log (1 A )

x - y K

E

1.063 =

2

A = 0.5265



E

0.014878-0N = log 1-0.5265 +0.5265 log(1 0.5265)

0.000744

EN =3.587

EN 4

Step 7: Extractor Diameter

For calculating the column cross-sectional area we require the volumetric flow rates of both

Feed and Selective solvent.

Feed = 3F

F

m 2185 33= + = 27.19 ft hr

ρ 82.41 48.7

= 27.19×7.48 = 203.4188 gal hr

Selective Solvent 3S

S

m 2106= = = 33.7514 ft hr = 252.4942 gal hr

ρ 62.43

SP P Sm ρ + m ρA =

J

To calculate the extraction height from first calculate HETS. HETS is correlated with

interfacial Tension. The interfacial tension does not appear to be available for this system. We

will use the data given in Table 2. Table 2 gives data for several extractor diameters. Select the

12 in (0.305 m) diameter extractor, which is expected to be close to the calculated diameter.

For the 12 in (0.3048 m) extractor there are several values of HETS at varying agitator speeds

and throughputs. Select the extractor that gives the maximum volumetric efficiency. The

minimum HETS is 5.6 in (0.142 m), and the total volumetric throughput is 1193 gal/hr ft2.

1

1

D = 12 inches

HETS = 5.6

Volumetric throughput 2

gal= J = 1193

hr.ft

We have supposed these values because interfacial tension data is not given to us so we are

actually scaling by making one plant our standard.

SP P Sm ρ + m ρA =

J



2203.418+262.4942= = 0.3812 ft

1193

So for our system

Diameter

0.5 0.5A 0.38067

= 4× = 4× = 0.6975ftπ 3.14

So this calculated Diameter is less than 30 inch and we have standard pipe size of diameter

10.42 inch, so we use 10.42 inch pipe.

Now

HETS

0.38 0.38

1

1

D 10.42=(HETS) =5.6 =5.307in

D 12

For our design we increase value of HETS by 20% to avoid flooding.

E E

Corrected HETS=5.307×1.20=6.368 in

Z =N (HETS)=4(6.368)=25.47

Rounding off ZE to nearest 3

EZ =27

On both top and bottom we have installed settlers which have the diameter 50% greater than

the extractor diameter and also height of each settler is equal to settler diameter.

Diameter of settler=1.5×10.42=15.63 inch

Height of both settler= 2×15.63=31.26 inch

To join Extractor with settler we require reducers which are a foot long.

Now reduces height= 2 12 24

E SZ=Z +Z +Reducers height

=27+31.26+24=82.26inch

Z=6.86ft

Approximated height is

Z=7ft



Table 2: Minimum NETS and Volumetric Efficiency for the Karr, RPC

[v. (Sila, 2003)]



Effect of Concentration on Height:

To study the effect of concentration on the height of Karr Reciprocating-Plate Column, by

using dummy values of Concentration and plotting them against Height as shown in Figure 3.

Figure 3: Concentration vs. Height

As the Figure 3 shows that the trend is increasing i.e. when we increase the concentration, a

prominent increase in the height occur, so we can say that the concentration is directly related

with the height of the Karr column.

Effect of Percentage Recovery on Height:

Figure 4 illustrates the effect of increase in percentage recovery on the height of Karr

Reciprocating-Plate column. In the respective figure the values of percentage recovery are

varying from (10-95) % but the height undergoes slight changes from (5-7) ft approximate ly,

but one can say that height of column is directly proportional the percentage recovery of the

key component.

So, the more the percentage yield of the Karr column the more height of the Karr column is

required.

7

8 8

10

12

5

6

7

8

9

10

11

12

13

0.4 0.5 0.6 0.7 0.8 0.9 1

Hei

ght

(ft)

Concentration (lb/ft3)



Figure 4: Percentage Recovery vs. Height

Effect Solvent Rate in Feed on Diameter:

The solvent rate in feed vs. diameter plot is shown in Figure 5 which describes that the increase

in solvent rate in feed causes an increase in the diameter of the Karr Reciprocating-P late

column but as one can notice that a large increase (in hundreds of lb/hr) in solvent rate results

a small change (in decimals of inches i.e. 0.2-0.4 inches in each increment approximately) in

diameter of the column.

Figure 5: Solvent Rate in Feed vs. Diameter

6.772

6.272

5.6885.6885.688

5.1885.1885.1885.1885.188

5

5.5

6

6.5

7

0 20 40 60 80 100

Hei

ght

(ft)

Recovery (%)

8.48.58.8

99.2

9.49.7

9.910.1

10.310.5

10.710.9 11

11.211.4

11.611.8

1212.12

8

8.5

9

9.5

10

10.5

11

11.5

12

12.5

0 500 1000 1500 2000

Dia

met

er (

in)

Solvent Rate in Feed (lb/hr)



Attachments:

The copies of MS Excel sheet and hand written calculations for the design of Karr

Reciprocating-Plate Column are attached at the end of the report for the ease of understanding

the design.



Bibliography:

i. Dutta, B. K. (2010). Liquid liquid Extraction. In B. K. Dutta, Principles of mass

transfere and separation processes (pp. 422-423). Abu Dabhi , UAE: PHI learning

private limited.

ii. Jameson, G. (1980). Extraction of whole fermentation broth with karr reciprocating

plate extraction column. The Canadian Journal of Chemical Engineering, 249–252.

iii. M. Reschke, K. S. (1985). Continuous reactive extraction of Penicillin G in a Karr

column. The Chemical Engineering Journal, B19-B26.

iv. Seader, H. R. (2011). Liquid-Liquid Extraction. In H. R. Seader, Separation Process

Principles Chemical and Biochemical Operations (pp. 302-306). United States of

America: John Wiley & Sons, Inc.

v. Sila, H. (2003). Karr Extractor. In H. Sila, Chemical process engineering Design and

Economics (pp. 357-366). New York.Basel: Marcel Dekker,INC.

0

lb/hr kg/hr Methanol Recovery Coefficient K 2

33 14.9685 Methanol Recovery ε 0.95

2185 991.099 Concentration Mass Per Unit Volume 0.5

mF 2218 1006.07 Densities lb/ft3

kg/m3

Water (Selective Solvent) mS 2107.1 955.764 Methanol 48.7 780.101

Step 1: Mass Balance Methyline Chloride82.41 1320.08

Mass Fraction x1 0.01488 Water 62.43 1000.03

Mass Fraction of Solute in Raffinate x2 0.00074 Using Equation 1 For Pure Water y2 0

Step 2: For Extract Mass Fraction and Minimum Solvent Rate

2.10526 Using Equation 2

Step 3: Minimum Solvent Rate and Operating Rate

1.05263 Using Equation 3

mS 2107.1

Step 4: Mass Fraction of Solute in Extract

Mass Fraction (S) y1 0.01488Using Equation 4

Step 5: Calculation of Extraction Factor AE

AE 0.52632 Using Equation 5 Volumetric Flowrates For Step 7 ft3/hr gal/h m

3/hr

Step 6: Calculate the Number of Equilibrium Stages Methanol 0.67762 203.419 0.76997

NE 3.587 Using Equation 6 Methyline Chloride 26.5138 5.06926 0.01919

Corrected NE 4.000 Total Feed Rate 27.1914 198.35 0.75078

Step 7: Extractor Diameter and Height Water (Selective Solvent) 33.7514 252.494 0.95573

Area 0.38216 ft2

Using equation 7 Volumetric Throughput 1193 gal/hr.ft2

Calculated Diameter 0.69755 ft 8.37061 inch 0.21267 m

From Table 1 we select 12" diameter extractor and at this diameter we select HETS 5.6 and Volumetric Throughput is 1193 gal/hr.ft2

Diameter of Standard Column 12 inch HETS of Standard Column 5.6 inch

Diameter of System 0.86833 ft 10.42 inch 0.26474 m

Now HETS for our System HETS 5.30749 inch

Feed Composition Useful Data

Methanol

Methyline Chloride

Total Feed Rate

As our calculated dia is less then 30 inch therfor we have selected 10.42 inch diameter pipe