lec 2 conversion and reactor sizing
TRANSCRIPT
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Dr.-Eng. Zayed Al-Hamamre
Chemical Reaction Engineering
Conversion and Reactor Sizing
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Content
Definition of Conversion
Design Equations
Batch Reactor
CSTR
PFR
Applications for Continuous-Flow Reactors
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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In defining conversion, we choose one of the reactants as the basis of calculation and then late
the other species involved in the reaction to this basis
Definition of Conversion
fedA moles reactedA moles
X
D ad
C ac
B ab
A
ncalculatio of basis asA reactant limiting Choose
Dd CcBb A a
For irreversible reactions, the maximum conversion is 1 .0, i.e., complete conversion.
For reversible reactions, the maximum conversion is the equilibrium conversion, Xe
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Batch Reactor Design Equations
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Batch Reactor Design Equations
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Batch Reactor Design Equations
The differential form of the
design equation for batch
reactor
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Batch Reactor Design Equations
and
At time equal zero where there is no conversion initially
The conversion increases with time spent in the reactor.
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Design Equations for Flow Reactors For continuous-flow systems, this time usually increases with increasing reactor volume
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Design Equations for Flow Reactors
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Design Equations for Flow Reactors
The size of the reactor will depend on the flow rate, reaction kinetics, reactor
conditions, and desired conversion
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Example
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Since pure A enters, the total pressure and partial pressure entering are the same
Example Cont.
Design Equations for CSTR
For species A in the reaction
and
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Because the reactor is perfectly mixed, the exit composition from the reactor is identical to the
composition inside the reactor, and the rate of reaction is evaluated at the exit conditions.
Design Equations for PFR
No radial gradients in concentration, temperature, or reaction rate.
As the reactants enter and flow axially down the reactor, they are consumed and the conversion increases along the length of the reactor
Design Equations for CSTR
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Design Equations for PFR
The volume necessary to achieve
a specified conversion X
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Design Equations for Packed-Bed Reactor
Packed-bed reactors are tubular reactors filled with catalyst particles
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
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Applications of the Design Equations for Continuous-Flow Reactors
is almost always a function of the concentrations of
the various species present.
L
For a 1st order reaction
In CSTR
Or
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Since then
Applications of the Design Equations for Continuous-Flow Reactors
Rate of reaction as a function of the XA
Size Row reactors for
different entering molar
flow rates.
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Applications of the Design Equations for Continuous-Flow Reactors
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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Applications of the Design Equations for Continuous-Flow Reactors
Chemical Engineering Department | University of Jordan | Amman 11942, Jordan
Tel. +962 6 535 5000 | 22888
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For all irreversible reactions of greater than zero order
Applications of the Design Equations for Continuous-Flow Reactors
a
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a. Calculate the volume necessary to achieve 80% conversion in a CSTR
b. Show this in plotted diagram
Example
and
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Example Cont.
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Example
The reaction is carried out in PFR,
a. Find out the volume necessary to achieve 80% conversion in a CSTR
b. Show this in plotted diagram
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Example Cont.
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For the five-point formula with a final conversion of 0.8,
Example Cont.
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Example Cont.
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Example Cont.
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