Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

1 

Dr.-Eng. Zayed Al-Hamamre

Chemical Reaction Engineering

Multi-Reactors Arrangements

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

2 

Content

Reactors in Series

o CSTRs in Series

o PFRs in Series

o Combinations of CSTRs and PFRs in Series

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

3 

FA 0

rA

Area = Volume of PFR

V 0

X1FA 0

rA

dX

X 1

FA 0

rA

X

Area = Volume of CSTR

X1

V FA 0

rA

X1

X1

Review

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

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Reactors are connected in series so that the exit stream of one reactor is the feed stream for

another reactor

Reactors in Series

Only be used when the feed stream only enters the first reactor in the series and there are no side streams either fed or withdrawn.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

5 

CSTRs in Series the rate of disappearance

of A

But

the rate of disappearance

of A

But

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

6 

CSTRs in Series

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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7 

Example

For the two CSTRs in series, 40% conversion is achieved in the first reactor. What is the volume

of each of the two reactors necessary to achieve 80% overall conversion of the entering species

A?

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

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Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Approximating a PFR by a large number of CSTRs in series

PFR can be approximated with a number of small

equal-volume CSTRs of Vi in series

The total volume to achieve 80% conversion

for five CSTRs of equal volume in series is

roughly the same as the volume of a PFR.

As the volume of each CSTR is made

smaller and by increasing the number of

CSTRs, the total volume of the CSTRs in

series and the volume of the PFR will

become identical

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

11 

PFRs in Series

The overall conversion of two PRFs in series is

the same as one PRF with the same total volume.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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For the two PFRs in series, 40% conversion is achieved in the first reactor. What is the volume of

each of the two reactors necessary to achieve 80% overall conversion of the entering species A?

Example

Using Simpson's rule (APP. A.4)

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

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Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

14 

Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

15 

Combinations of CSTRs and PFRs in Series

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

16 

Combinations of CSTRs and PFRs in Series

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

Tel. +962 6 535 5000 | 22888

17 

Example

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Example Cont.

Construct the table

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Example Cont.

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Example Cont.

and

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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22 

Example Cont.

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Space Time The space time or residence time (τ) is the time necessary to process one reactor volume of

fluid based on entrance conditions

The space time is obtained by dividing reactor volume by the volumetric flow rate entering

the reactor:

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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24 

Space Velocity

Calculate the space time and space velocities for each of the reactors shown previously