lec 2 part 2 multi-reactors arrangementseacademic.ju.edu.jo/z.hamamre/material/chemical... ·...
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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
4
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be used when the feed stream only enters the first reactor in the series and there are no side streams either fed or withdrawn.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
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CSTRs in Series
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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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.
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Example Cont.
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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
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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
Tel. +962 6 535 5000 | 22888
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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.
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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
15
Combinations of CSTRs and PFRs in Series
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Combinations of CSTRs and PFRs in Series
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
17
Example
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Example Cont.
Construct the table
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Example Cont.
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Example Cont.
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Example Cont.
and
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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:
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24
Space Velocity
Calculate the space time and space velocities for each of the reactors shown previously