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Mass Transfer Assignment 2

Libbis Sujessy

1106071681

Chemical Engineering, International Program

1. Define component A and B, calculate using analytical method and software if the mixture of themis flash vaporized.

Answer :

D (yd)

F

(xF)

W (xw)

Boiling point (760 mmHg) cyclohexane =80:C and toluene = 110.6:C with mass flow 100 kg/mol

hr. The equilibrium x-y* diagram between those two temperature is :

The mixture consists of 50% cyclohexane

and toluene at 40:C and it is subjected todistillation at a separator of 760 mmHg to

vaporize 52.5% of the feed. Then, the

composition of each of them :

Basis = 100 moles of feed

zF = 0.5

D = 0.525 x 100 = 52.5 moles

W = 100 52.5 = 47.5 moles

The operating line slop = -W/D = -

47.5/52.5 =- 0.903

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Based on the diagram, there are two equations :

y = -0.903x + 0.951

y = -0.838x2

+ 1.794x +0.025

y = y

-0.903x + 0.951 = -0.838x2

+ 1.794x +0.025

0.383x2 2.697x + 0.926 = 0

x1 = 6.68 x2 = 0.362

so, xA= 0.362 & xB = 0.638

and yA = 0.624 & yB = 0.376 (by substituting x-value into one of the equation of y)

yA = 0.362

yB = 0.638

xA = 0.5

xB = 0.5

xA = 0.624

xB = 0.376

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Mass Transfer Assignment 2

Below figure is the result based on Hysis using Antoine package

2. Similar to number 1, calculate for mixture A, B and C components.Composition : 35 mole% hexane, 35 mole% heptane and 30 mole% octane at 1 atm pressure.

Answer :

D (Vapour)

0.35 C6

F = 0.35 C7

0.30 C8

W (liquid)

First we have to find its bubble point and dew point by

guessing it.

Bubble point :

Guess temperature T = 98:C, at 1 atm.

Component Pi*,

atm

Ki =

Pi*/1

Xi Yi =

Ki.xi

Hexane 2.2 2.2 0.35 0.77

Heptane 1 1 0.35 0.35

Octane 0.44 0.44 0.30 0.132

1.252

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Mass Transfer Assignment 2

Since y is too large, try a lower temperature, T = 90:C.

Component Pi*,

atm

Ki =

Pi*/1

Xi Yi =

Ki.xi

Hexane 1.77 1.77 0.35 0.6195

Heptane 0.78 0.78 0.35 0.273Octane 0.34 0.34 0.30 0.102

0.9945

Since it is a little bit small, increase for a bit of the temperature into 91:C so that,

Component Pi*,

atm

Ki =

Pi*/1

Xi Yi =

Ki.xi

Hexane 1.79 1.79 0.35 0.6265

Heptane 0.78 0.78 0.35 0.273

Octane 0.345 0.345 0.30 0.1035

1.003

Yi is the composition of each components when it is at vapour phase.

Dew Point :

T = 98:C as a first guess, thus

Component Ki yi yi/Ki

Hexane 2.2 0.35 0.159

Heptane 1 0.35 0.35

Octane 0.44 0.3 0.682

1.191

Extrapolating it by using a lower number since the amount of y is more than one, the second

extrapolation T = 100:C

Component Ki yi yi/Ki

Hexane 2.4 0.35 0.146

Heptane 1.05 0.35 0.333

Octane 0.48 0.3 0.625

1.104

Third extrapolation T=103:C

Component Ki yi yi/Ki

Hexane 2.5 0.35 0.14

Heptane 1.12 0.35 0.31

Octane 0.53 0.3 0.56

1.01

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Mass Transfer Assignment 2

D, yC6 = 0.6265

yC7 = 0.273

0.35 C6 yC8 = 0.1035

F = 0.35 C70.30 C8

W, xC6 = 0.14

xC7 = 0.31

xC8 = 0.56

The next figure is the result by using Hysis with antoine packaging.

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Mass Transfer Assignment 2

3. Find a process production of chemical which uses distillation column, draw the flowsheetincluding information concerning to concentration of the component enter in and come out from

the column.

Answer :

One of many industries that use the distillation process is distillating and bleaching Glycerine. Inthis process, continue distillation is used (two level distillation) and then to batch distillation

process. The purpose of this process is to purify the glycerine until it gets the high purity (about

100% pure). The process flow diagram as we can see below:

Input & Output Specification :

1. Distillation Process IInput :

- Glycerine (evaporated)- Steam

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Mass Transfer Assignment 2

Output :

- Glycerine II, concentration : 90-95% (low grade distillate).- Water

2. Distillation Process IIInput :

- Glycerine, the product of distillation I- Steam

Output :

- Higrade Glycerine (glycerine with 99% concentration, to continue on the bleachingprocess in order to get higher quality).

- Low grade glycerine (to put into residue distillation process)- Steam

3. Residue Distillation (Batch distillation)Input :

- Steam- Low grade glycerineOutput :

- Glycerine II (low grade glycerine with the higher quality)- Residue

Brief Explanation of the Process:

As explained before, the objective on this process is to get the glycerine with the purity close to

100%. The input of this process is the glycerine with purity level only 80%. First, it is purified with

evaporation process. Evaporation goes on under vacuum condition (5 15 mbar) and with the

live steam to reduce the partial pressure of glycerine or the boiling temperature. After

evaporation process, the purity level of glycerine rises up into 88%. After that, it goes into

distillation process.

The vapour pressure of glycerine is about atmosphere pressure 760 mmHg at 270:C. The

distillation process needs to be kept on low pressure, since the glycerine will polymerized on 200:

C. The type of distillation used in thhe process is continue distillation (two level distillation), with

the product is higrade distillate I (99.9% precentage of concentration) and low grade distillate II

(90-95% percentage of concentration) with the amount about 8% from the first distillate. To

increase the purity of the low grade distillate produced from the previous continue distillation, it

is distillated by batching.

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Mass Transfer Assignment 2

References

Toluene from the NIST (National Institute of Standards and Technology)http://webbook.nist.gov/cgi/cbook.cgi?ID=C108883&Mask=4&Type=ANTOINE&Plot=on

Cyclohexene from the NIST (National Institute of Standards and Technology)http://webbook.nist.gov/cgi/cbook.cgi?ID=C110827&Mask=4&Type=ANTOINE&Plot=on

Glycerol distillation process from Google Patenthttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&so

urce=gbs_selected_pages&cad=4#v=onepage&q&f=false

http://webbook.nist.gov/cgi/cbook.cgi?ID=C108883&Mask=4&Type=ANTOINE&Plot=onhttp://webbook.nist.gov/cgi/cbook.cgi?ID=C108883&Mask=4&Type=ANTOINE&Plot=onhttp://webbook.nist.gov/cgi/cbook.cgi?ID=C110827&Mask=4&Type=ANTOINE&Plot=onhttp://webbook.nist.gov/cgi/cbook.cgi?ID=C110827&Mask=4&Type=ANTOINE&Plot=onhttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&source=gbs_selected_pages&cad=4#v=onepage&q&f=falsehttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&source=gbs_selected_pages&cad=4#v=onepage&q&f=falsehttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&source=gbs_selected_pages&cad=4#v=onepage&q&f=falsehttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&source=gbs_selected_pages&cad=4#v=onepage&q&f=falsehttp://www.google.com/patents?id=63cwAAAAEBAJ&pg=PA2&dq=distillation+glycerine&source=gbs_selected_pages&cad=4#v=onepage&q&f=falsehttp://webbook.nist.gov/cgi/cbook.cgi?ID=C110827&Mask=4&Type=ANTOINE&Plot=onhttp://webbook.nist.gov/cgi/cbook.cgi?ID=C108883&Mask=4&Type=ANTOINE&Plot=on