Professor De Chen
Institutt for kjemisk prosessteknologi, NTNU
Gruppe for katalyse og petrokjemi
Department of Chemical Engineering
Kjemiblokk V, rom 407
chen@nt.ntnu.no
1 - 13/04/2015
Kjemisk reaksjonsteknikk
Chemical Reaction Engineering
H. Scott Fogler: Elements of Chemical Engineering
www.engin.umich.edu/~cre
University of Michigan, USA
Department of Chemical Engineering
Time plan:
Week 34-47, Tuesday: 08:15-10:00
Thursday: 11:15:13:00
Problem solving: Tuseday:16:15-17:00
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Kjemisk reaksjonsteknikk
Chemical Reaction Engineering
 Chemical Reaction Engineering (CRE) is the field that
studies the rates and mechanisms of chemical reactions
and the design of the reactors in which they take place.
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Lecture notes will be published on It’s
learning after the lecture
(Pensumliste ligger på It’s learning
Deles ut på de første forelesningene)
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Øvingsopplegget ligger på It’s learning
Deles ut på de første forelesningene
5 - 13/04/2015
Felleslaboratorium
Faglærer: Professor Heinz Preisig
For information: It’s learning
Introduction lecture:
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Place : in PFI-50001, the lecture room on the
top of the building
Date: Tuesday 21 of August
Time: 12:15 - 14:00
6 - 13/04/2015
TKP4110 Chemical Reaction Engineering
Øvingene starter onsdag 26 august kl 1615
i K5.
Lillebø, Andreas Helland: andreas.lillebo@chemeng.ntnu.no
Stud.ass.:
Kristian Selvåg : krisse@stud.ntnu.no
Department of Chemical Engineering
Øyvind Juvkam Eraker: oyvindju@stud.ntnu.no
Emily Ann Melsæther: melsathe@stud.ntnu.no
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Lecture 1
Kjemisk reaksjonsteknikk
Chemical Reaction Engineering
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1.Industrial reactors
2.Reaction engineering
3.Mass balance
4.Ideal reactors
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Steam Cracking (Rafnes)
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Batch reactor
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Fixed bed reactor
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CSTR bioreactor
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Artificial leaf, photochemical reactor
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Chemical Engineering
Momentum
transfer
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Reaction
engineering
Mass
transfer
Heat
transfer
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Reaction Engineering
Mole Balance
Rate Laws
Stoichiometry
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These topics build upon one another
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No-ideal flow
Heat Effects
Isothermal Design
Stoichiometry
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Rate Laws
Mole Balance
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Chemical kinetics and reactor design
are at the heart of
producing almost all industrial chemicals
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It is primary a knowledge of
chemical kinetics and reactor design that
distinguishes
the chemical engineer from other engineers
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Reaction Engineering
1. Week 34, Aug. 21, chapter 1, Introduction, mole balance, and ideal
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reactors,
2. Week 34, Aug. 23, chapter2, Conversion and reactor size
3. Week 35, Aug. 28, chapter 3, Reaction rates
4. Week 35, Aug. 30, chapter 3, Stoichometric numbers
5. Week 36, Sept. 4, chapter 4, isothermal reactor design (1)
6. Week 36, Sept. 6, chapter 4, isothermal reactor design (2)
7. Week 37, Sept. 11, chapter 10, catalysis and kinetics (1)
8. Week 37, Sept. 13, chapter 10, catalysis and kinetics (2)
9. Week 38, Sept. 18, chapter 10, catalysis and kinetics (2)
10.Week 38, Sept. 20, chapter 5,7, kinetic modeling (1)
11.Week 39, Sept. 25, chapter 5,7, kinetic modeling (2)
12.Week 39, Sept. 28 chapter 6, multiple reactions (1)
13.Week 40, Oct. 2, chapter 6 multiple reactions (2)
14.Week 40, Oct. 4, summary of chapter 1-7, and 10
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Reaction Engineering
 41 (9/10, 11/10) 8.1 - 8.2 (JPA)
 42 (16/10, 18/10) 8.3 – 8.5 (JPA)
 43 (23/10, 25/10) 8.6 - 8.7 (JPA)

 44 (30/10, 1/11)

 45 (6/11, 8/11)
11 (JPA)
11 (JPA)
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 46 (13/11, 15/11) 12.1-12.4 (JPA)
 47 (20/11,22/11) 12.5-12.8 (JPA)
 50 (Mandag 13/12)
Reaktorberegninger for ikke-isoterme systemer.
Energibalanser, stasjonær drift. Omsetning ved
likevekt. Optimal fødetemperatur.
CSTR med varmeeffekter og flere løsninger ved
stasjonær drift, ustabilitet.
Masseoverføring, ytre diffusjonseffekter i
heterogene systemer.
Fylte reaktorer (packed beds). Kjernemodellen
(shrinking core). Oppløsning av partikler og
regenerering av katalysator.
Diffusjon og reaksjon i katalysatorpartikler,
Thieles modul, effektivitetsfaktor.
Masseoverføring og reaksjon i flerfasereaktorer.
Oppsummering.
Eksamen, kl 0900-1300.
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Chemical Identity and reaction
 A chemical species is said to have reacted
when it has lost its chemical identity. There are
three ways for a species to loose its identity:
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1. Decomposition
2. Combination
3. Isomerization
CH2=C(CH3)2
CH3CH3  H2 + H2C=CH2
N2 + O2  2 NO
C2H5CH=CH2 
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Reaction Rate
 The reaction rate is the rate at which a species
looses its chemical identity per unit volume.
 The rate of a reaction (mol/dm3/s) can be
expressed as either:
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 The rate of Disappearance of reactant:
-rA
or as
 The rate of Formation (Generation) of product:
rP
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Reaction Rate
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Consider the isomerization
AB
rA = the rate of formation of species A per unit
volume
-rA = the rate of a disappearance of species A per unit
volume
rB = the rate of formation of species B per unit
volume
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Reaction Rate
 For a catalytic reaction, we refer to -rA', which is
the rate of disappearance of species A on a per
mass of catalyst basis. (mol/gcat/s)
NOTE: dCA/dt is not the rate of reaction
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Reaction Rate
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Consider species j:
1.rj is the rate of formation of species j per unit
volume [e.g. mol/dm3s]
2.rj is a function of concentration, temperature,
pressure, and the type of catalyst (if any)
3. rj is independent of the type of reaction system
(batch, plug flow, etc.)
4.rj is an algebraic equation, not a differential
equation
(e.g. = -rA = kCA or -rA = kCA2)
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General Mole Balance
System
Volume, V
Fj0
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Gj
Fj
 Molar Flow  Molar Flow   Molar Rate   Molar Rate 
 Rate of
   Rate of
  Generation    Accum ulation

 
 
 

 Species j in   Species j out of Species j  of Species j 
dN j
Fj 0

Fj

Gj

dt
 m ole
 m ole
 m ole
 m ole











 tim e 
 tim e 
 tim e 
 tim e 
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General Mole Balance
If spatially uniform
G j  r jV
If NOT spatially uniform
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
V1
rj1
G j1  rj1V1


V2
rj 2
G j 2  rj 2 V2
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General Mole Balance
W
G j   rjiVi
i1
Take limit
n
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Gj  
rji Vi

 r dV
j
i1 lim V  0 n  
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General Mole Balance
System
Volume, V
FA0
GA
FA
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General Mole Balance on System Volume V
In
 Out  Generation
FA 0  FA

 r dV
A
 Accumulation
dN A

dt
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Batch Reactor Mole Balance
Batch
FA 0  FA 
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
dN A
rA dV 
dt
FA 0  FA  0
Well Mixed

r
A
dV  rAV
dNA
 rAV
dt
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Batch Reactor Mole Balance
dN A
dt 
rAV
Integrating
when t = 0 NA=NA0
t = t NA=NA

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t
NA

N A0
dN A
 rAV
Time necessary to reduce number of moles of A from NA0 to NA.
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Batch Reactor Mole Balance
t
NA

N A0
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dN A
 rAV
NA
t
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CSTR Mole Balance
CSTR
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dNA
FA 0  FA   rA dV 
dt
Steady State

dNA
0
dt
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CSTR Mole Balance
Well Mixed
 r dV  r V
A
A
FA 0  FA  rAV  0
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
FA 0  FA
V 
rA
CSTR volume necessary to reduce the molar flow rate from FA0 to
FA.
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Plug Flow Reactor Mole Balance
V
FA
FA


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V
V  V
 In  Out
 Generation

0
at V   



 at V  V  in V

FA V  FA V  V
 rA V
0
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Plug Flow Reactor Mole Balance
Rearrange and take limit as ΔV0
lim
V  0
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
FA V V  FA V
V
 rA
dFA
 rA
dV
This is the volume necessary to reduce the entering molar flow rate
(mol/s) from FA0 to the exit molar flow rate of FA.
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Alternative Derivation –
Plug Flow Reactor Mole Balance
PFR
dN A
FA0  FA   rA dV 
dt
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Steady State
dN A
0
dt
FA0  FA   rA dV  0
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Alternative Derivation –
Plug Flow Reactor Mole Balance
Differientiate with respect to V
dFA
0
 rA
dV

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The integral form is:
dFA
 rA
dV
V 
FA

FA 0
dFA
rA

This is the volume necessary to reduce the entering molar flow rate
(mol/s) from FA0 to the exit molar flow rate of FA.
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Packed Bed Reactor Mole Balance
PBR
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dN A
FA W   FA W  W   rA W 
dt
dN A
Steady State
0
dt
lim
W 0
FA W  W  FA W
W
 rA
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Packed Bed Reactor Mole Balance
Rearrange:
dFA
 rA
dW
The integral form to find the catalyst weight is:
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
W 
FA

FA 0
dFA
rA
PBR catalyst weight necessary to reduce the entering molar flow
rate FA0 to molar flow rate FA.
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Reactor Mole Balance Summary
Reactor
Batch
Differential
Integral
t
dN A
 rAV
dt
NA

N A0
dN A
rAV
NA
t
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FA 0  FA
V 
rA
CSTR
PFR
Algebraic
dFA
 
rA
dV
V 
FA

FA 0
FA
dFA
drA
V
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