Professor De Chen Institutt for kjemisk prosessteknologi, NTNU Gruppe for katalyse og petrokjemi

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Departm

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Professor De Chen

Institutt for kjemisk prosessteknologi, NTNU

Gruppe for katalyse og petrokjemi

Kjemiblokk V, rom 407

chen@nt.ntnu.no

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Departm

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Kjemisk reaksjonsteknikkChemical Reaction Engineering

H. Scott Fogler: Elements of Chemical Engineering

www.engin.umich.edu/~cre

University of Michigan, USA

Time plan: Week 34-47, Tuesday: 08:15-10:00

Thursday: 11:15:13:00Problem solving: Tuseday:16:15-17:00

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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.

Kjemisk reaksjonsteknikkChemical Reaction Engineering

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Lecture notes will be published on It’s learning after the lecture

(Pensumliste ligger på It’s learningDeles ut på de første forelesningene)

Øvingsopplegget ligger på It’s learningDeles ut på de første forelesningene

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Felleslaboratorium

Faglærer: Professor Heinz Preisig

For information: It’s learning

Introduction lecture:

Place :  in PFI-50001, the lecture room on the top of the buildingDate:    Tuesday 21 of AugustTime:    12:15 - 14:00

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TKP4110 Chemical Reaction Engineering

Øvingene starter onsdag 26 august kl 1615i K5.Lillebø, Andreas Helland: andreas.lillebo@chemeng.ntnu.no

Stud.ass.:Kristian Selvåg : krisse@stud.ntnu.no

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

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

Reaction engineering

Mass transfer

Heat transfer

Momentum transfer

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Reaction Engineering

Mole Balance Rate Laws Stoichiometry

These topics build upon one another

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ngineering Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

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No-ideal flow

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Chemical kinetics and reactor design

are at the heart of

producing almost all industrial chemicals

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 reactors,

2. Week 34, Aug. 23, chapter2, Conversion and reactor size3. Week 35, Aug. 28, chapter 3, Reaction rates4. Week 35, Aug. 30, chapter 3, Stoichometric numbers5. 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) Reaktorberegninger for ikke-isoterme systemer. 42 (16/10, 18/10) 8.3 – 8.5 (JPA) Energibalanser, stasjonær drift. Omsetning ved

likevekt. Optimal fødetemperatur. 43 (23/10, 25/10) 8.6 - 8.7 (JPA) CSTR med varmeeffekter og flere løsninger ved

stasjonær drift, ustabilitet. 44 (30/10, 1/11) 11 (JPA) Masseoverføring, ytre diffusjonseffekter i

heterogene systemer. 45 (6/11, 8/11) 11 (JPA) Fylte reaktorer (packed beds). Kjernemodellen

(shrinking core). Oppløsning av partikler og regenerering av katalysator.

46 (13/11, 15/11) 12.1-12.4 (JPA) Diffusjon og reaksjon i katalysatorpartikler, Thieles modul, effektivitetsfaktor.

47 (20/11,22/11) 12.5-12.8 (JPA) Masseoverføring og reaksjon i flerfasereaktorer. Oppsummering.

50 (Mandag 13/12) 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:

1. Decomposition CH3CH3 H2 + H2C=CH2

2. Combination N2 + O2 2 NO

3. Isomerization C2H5CH=CH2 CH2=C(CH3)2

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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:

The rate of Disappearance of reactant: -rA

or asThe rate of Formation (Generation) of product: rP

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Reaction Rate

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 RateConsider 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

time

mole

time

mole

time

mole

time

moledt

dNGFF

jSpeciesof

onAccumulati

RateMolar

jSpeciesof

Generation

RateMolar

outjSpecies

ofRate

FlowMolar

injSpecies

ofRate

FlowMolar

jjjj

0

Fj0 FjGj

System Volume, V

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General Mole Balance

If spatially uniform

G j rjV

If NOT spatially uniform

2V

rj 2

G j1 rj1V1

G j 2 rj 2V2

1V

rj1

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General Mole Balance

G j rjiVii1

W

G j lim V 0 n

rjiVii1

n

rjdV

Take limit

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General Mole Balance

General Mole Balance on System Volume V

In Out Generation Accumulation

FA 0 FA rA dV dNA

dt

FA

0

FAGA

System Volume, V

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Batch Reactor Mole Balance

FA 0 FA rA dV dNA

dtFA 0 FA 0

dNA

dtrAV

Batch

VrdVr AA Well Mixed

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Batch Reactor Mole Balance

dt dNA

rAVIntegrating

Time necessary to reduce number of moles of A from NA0 to NA.

when t = 0 NA=NA0

t = t NA=NA

A

A

N

N A

A

Vr

dNt

0

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Batch Reactor Mole Balance

A

A

N

N A

A

Vr

dNt

0

NA

t32

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CSTR Mole Balance

FA 0 FA rA dV dNA

dt

dNA

dt0Steady State

CSTR

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FA 0 FA rAV 0

V FA 0 FA

rA

VrdVr AA Well Mixed

CSTR volume necessary to reduce the molar flow rate from FA0 to FA.

CSTR Mole Balance

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Plug Flow Reactor Mole Balance

V

V VV

FA

FA

0

0

VrFF

Vin

Generation

VVat

Out

Vat

In

AVVAVA35

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limV 0

FA V V FA V

VrA

Rearrange and take limit as ΔV0

dFA

dVrA

Plug Flow Reactor Mole Balance

36

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

0 0 dVrFF AAA

0dt

dN ASteady State

dt

dNdVrFF A

AAA 0

PFR

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dFA

dVrA

0 dFA

dV rA

Differientiate with respect to V

A

A

F

F A

A

r

dFV

0

The integral form is:

This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA0 to the exit molar flow rate of FA.

Alternative Derivation –Plug Flow Reactor Mole Balance

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dt

dNWrWWFWF A

AAA

AWAWWA

Wr

W

FF

0lim

0dt

dN ASteady State

PBR

Packed Bed Reactor Mole Balance

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Packed Bed Reactor Mole Balance

dFA

dW r A

Rearrange:

PBR catalyst weight necessary to reduce the entering molar flow rate FA0 to molar flow rate FA.

A

A

F

F A

A

r

dFW

0

The integral form to find the catalyst weight is:

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Reactor Mole Balance Summary

Reactor Differential Algebraic Integral

V FA 0 FA

rA

CSTR

Vrdt

dNA

A 0

A

A

N

N A

A

Vr

dNtBatch

NA

t

dFA

dVrA

A

A

F

F A

A

dr

dFV

0

PFR

FA

V41