Docsity
Log inSign up
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search Store documents

The best documents sold by students who completed their studies

Search through all study resources
Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

University Rankings

Discover the best universities in your country according to Docsity users

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Exams and Study
Go to the blog

e201201-1401.pdf, Study notes of Chemical Processes

Canterbury Christ Church University (CCCU)Chemical Processes

Underwood Equation for Minimum. Reflux (1). V. D. Material balance over all stages ... Based on the Fenske equation (at total reflux conditions).

Typology: Study notes

2021/2022

Uploaded on 09/27/2022

mancity4ever
mancity4ever 🇬🇧

4.5

(15)

251 documents

1 / 8

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Lecture Lecture 14. 14.
ApproximateApproximate
MulticomponentMulticomponent
Approximate
Approximate
MulticomponentMulticomponent
Methods (2)Methods (2)
[Ch. 9][Ch. 9]
•Minimum Reflux
- In binary systems
- In multicomponent systems
- Underwood equationUnderwood equation
•• Gilliland CorrelationGilliland Correlation for Actual Reflux Ratio and
Theoretical Stages
•Feed-Stage Location
•
Distribution of
Nonkey
Components at Actual Reflux
•
Distribution
of
Nonkey
Components
at
Actual
Reflux
pf3
pf4
pf5
pf8

Partial preview of the text

Download e201201-1401.pdf and more Study notes Chemical Processes in PDF only on Docsity!

LectureLecture 14.

ApproximateApproximate Multicomponent

Multicomponent

ApproximateApproximate Multicomponent

Multicomponent

Methods (2)Methods (2)

[Ch. 9][Ch. 9]

  • Minimum Reflux
    • In binary systems - In multicomponent systems- Underwood equation

Underwood equation

  • • Gilliland Correlation

Gilliland Correlation for Actual Reflux Ratio andTheoretical Stages

  • Feed-Stage Location• Distribution of Nonkey Components at Actual Reflux• Distribution of Nonkey Components at Actual Reflux

Minimum Reflux in Binary SystemsMinimum Reflux in Binary Systems

  • Minimum reflux
    • Infinite stages- Pinch point (or point of infinitude)- Most of the stages are crowded into a constant-composition zone

Most of the stages are crowded into a constant

composition zone

Binary system, ideal conditions

Binary system, nonideal conditions

Feed

Feed

: location of pinch-point zone

Underwood Equation for MinimumUnderwood Equation for Minimum

Reflux (1)Reflux (1)Reflux (1)Reflux (1)

V^

D

Material balance over all stages

,^

,^

,

i^

i^

i D

y^

V

x

L

x^

D

^

^

^

V
L
D

^

 

,^

,^

,

j^

j^

j D

y^

V

x

L

x^

D

^

^

^

L

Phase equilibrium relation

(phase compositions do not change in the pinch zone)

,^

,^

,

i^

i^

i

y^

K

x

^

^

,^

,^

,

j^

j^

j

y^

K

x

^

^

(^
/^
)^
(^
/^
^
^

Pinch-point

zone

,^

,^

,^

,^

,

,

(^
/^
)^
(^
/^
(^
)^

i D

i^

i j

j D

j

i j

x

x

x

x

L D

^

^

^
^

V∞

L∞

For Class 1 separation, flashed feed- and pinch-zonecompositions are identical

^

,^

,

(^

i^

i F

x^

x

^

,^

,^

,^

,^

,

min

,

(^
/^
/^
)^
(^
)^
(^
/^
(^
(^
)^

F^

LK D

F^

LK F

LK HK

F^

HK D

F^

HK F

LK HK

F

L
F

Dx

L x

Dx

L x

L
F

^

^
^

Underwood Equation for MinimumUnderwood Equation for Minimum

Reflux (2)Reflux (2)Reflux (2)Reflux (2)

-^

Distribution of nonkey components

,^

,^

,^

,^

,

min

(^
/^
/^
)^
(^
)^
(^
/^
(^
(^
)^

F^

LK D

F^

LK F

LK HK

F^

HK D

F^

HK F

L
F

Dx

L x

Dx

L x

L
F

^

^
^

,

(^

)^

LK HK

F

F

Replace

LK

with component

i

,^

,^

,^

,^

,

min

(^
/^
/^
)^
(^
)^
(^
/^
(^
(^
)^

F^

i D

F^

i F

i HK

F^

HK D

F^

HK F

L
F

Dx

L x

Dx

L x

L
F

^

^
^

, (^

)^

i HK

F

F

,^

,^

,^

,^

,^

,

(^
)^
(^
)^
(^

i D

i HK

F^

LK D

LK HK

F^

i HK

F^

HK D

Dx

Dx

Dx

^
^
^
^
^
^
^
^
^
^
^
^

,^

,^

,^

,^

,

(^
)^
(^

F^

i F

LK HK

F^

F^

LK F

LK HK

F^

F^

HK F

L x

L x

L x

^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^

, ,

i D i F Dx Fx ^

^
^
^

For all nonkey componentsin a Class 1 separation

FeedFeed-

-Stage Location

Stage Location

-^

Suggestion of Brown and Martin (1939)- Based on the Fenske equation (at total reflux conditions)- Not reliable except for fairly symmetrical feeds and separations

min min

(^

(^

R^

R

S^

S

N

N

N

N

min

/

,^

,^

,^

,

/

(^

log (

/^

/^

) log[(

)^

]

log (

/^

/^

) log[(

)^

]

1 2 1 2

S^

S

LK D

LK F

HK F

HK D

B^

F

x

z^

z^

x

z^

x

x

z

  

^

^

^

^

,^

,^

,^

,

log (

/^

/^

) log[(

)^

]

LK F

LK B

HK B

HK F

D

F

z^

x

x

z

 

^

^

-^

Empirical equation of Kirkbride

N

R

p

q

.

,^

,

0 206

2

HK F

LK B

R^

z^

x

N

B

^

^

^

^

^

Feed

N

R

,^

,

S^

LK F

HK D

N

z^

x

D

^

^

^

^

^

^

^

^

^

^

N

S

Distribution ofDistribution of Nonkey

Nonkey Components

Components

at Actual Refluxat Actual Refluxat Actual Refluxat Actual Reflux

-^

For multicomponent mixtures - Total reflux condition: all

components distribute to someextent between distillate andextent between distillate andbottoms

  • Minimum reflux condition: none

Minimum reflux condition

none

or only a few of the nonkeycomponents distribute

  • Reflux ratio near minimum: the

product distribution liesbetween the two limitsbetween the two limits

  • High reflux ratio: the product

distribution may lie outside thedistribution may lie outside thelimits

inferior separation