![25 - 02/16/19
DepartmentofChemicalEngineering
Reaction Rate
Consider species j:
1.rj is the rate of formation of species j per unit
volume [e.g. mol/dm3
s]
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 = kCA
2
)
25](https://image.slidesharecdn.com/lecture1-190216170825/85/Lecture-1-25-320.jpg)
Lecture 1
- 1. 1 - 02/16/19 DepartmentofChemicalEngineering Professor De Chen Institutt for kjemisk prosessteknologi, NTNU Gruppe for katalyse og petrokjemi Kjemiblokk V, rom 407 chen@nt.ntnu.no
- 2. 2 - 02/16/19 DepartmentofChemicalEngineering Kjemisk reaksjonsteknikk Chemical 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: 11:15:13:00 Problem solving: Tuseday:16:15-17:00
- 4. 4 - 02/16/19 DepartmentofChemicalEngineering 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 reaksjonsteknikk Chemical Reaction Engineering
- 5. 5 - 02/16/19 DepartmentofChemicalEngineering Lecture notes will be published on It’s learning after the lecture (Pensumliste ligger på It’s learning Deles ut på de første forelesningene) Øvingsopplegget ligger på It’s learning Deles ut på de første forelesningene
- 6. 6 - 02/16/19 DepartmentofChemicalEngineering Felleslaboratorium Faglærer: Professor Heinz Preisig For information: It’s learning Introduction lecture: Place : in PFI-50001, the lecture room on the top of the building Date: Tuesday 21 of August Time: 12:15 - 14:00
- 7. 7 - 02/16/19 DepartmentofChemicalEngineering 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 Øyvind Juvkam Eraker: oyvindju@stud.ntnu.no Emily Ann Melsæther: melsathe@stud.ntnu.no
- 8. 8 - 02/16/19 DepartmentofChemicalEngineering Lecture 1 Kjemisk reaksjonsteknikk Chemical Reaction Engineering 1.Industrial reactors 2.Reaction engineering 3.Mass balance 4.Ideal reactors
- 9. 9 - 02/16/19 DepartmentofChemicalEngineering Steam Cracking (Rafnes)
- 10. 10 - 02/16/19 DepartmentofChemicalEngineering Batch reactor
- 11. 11 - 02/16/19 DepartmentofChemicalEngineering Fixed bed reactor
- 12. 12 - 02/16/19 DepartmentofChemicalEngineering CSTR bioreactor
- 13. 13 - 02/16/19 DepartmentofChemicalEngineering Artificial leaf, photochemical reactor
- 14. 14 - 02/16/19 DepartmentofChemicalEngineering Chemical Engineering Reaction engineering Mass transfer Heat transfer Momentum transfer
- 16. 16 - 02/16/19 DepartmentofChemicalEngineering Reaction Engineering Mole Balance Rate Laws Stoichiometry These topics build upon one another 16
- 17. 17 - 02/16/19 DepartmentofChemicalEngineering Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 17 No-ideal flow
- 18. 18 - 02/16/19 DepartmentofChemicalEngineering 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
- 19. 19 - 02/16/19 DepartmentofChemicalEngineering Reaction Engineering 1. Week 34, Aug. 21, chapter 1, Introduction, mole balance, and ideal 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
- 20. 20 - 02/16/19 DepartmentofChemicalEngineering 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.
- 21. 21 - 02/16/19 DepartmentofChemicalEngineering 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 21
- 22. 22 - 02/16/19 DepartmentofChemicalEngineering 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 as The rate of Formation (Generation) of product: rP 22
- 23. 23 - 02/16/19 DepartmentofChemicalEngineering 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 23
- 24. 24 - 02/16/19 DepartmentofChemicalEngineering 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 24
- 25. 25 - 02/16/19 DepartmentofChemicalEngineering Reaction Rate Consider species j: 1.rj is the rate of formation of species j per unit volume [e.g. mol/dm3 s] 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 = kCA 2 ) 25
- 26. 26 - 02/16/19 DepartmentofChemicalEngineering General Mole Balance = + − =+− = + − time mole time mole time mole time mole dt dN GFF jSpeciesof onAccumulati RateMolar jSpeciesof Generation RateMolar outjSpecies ofRate FlowMolar injSpecies ofRate FlowMolar j jjj0 Fj0 FjGj System Volume, V 26
- 27. 27 - 02/16/19 DepartmentofChemicalEngineering General Mole Balance If spatially uniform Gj =rjV If NOT spatially uniform 2V∆ rj2 Gj1=rj1∆V1 Gj2=rj2∆V2 1V∆ rj1 27
- 28. 28 - 02/16/19 DepartmentofChemicalEngineering General Mole Balance Gj = rji∆Vi i=1 W ∑ Gj = lim∆V→0 n→∞ rji∆Vi i=1 n ∑ = rjdV∫ Take limit 28
- 29. 29 - 02/16/19 DepartmentofChemicalEngineering General Mole Balance General Mole Balance on System Volume V In −Out + Generation = Accumulation FA0−FA + rA∫ dV = dNA dt FA0 FAGA System Volume, V 29
- 30. 30 - 02/16/19 DepartmentofChemicalEngineering Batch Reactor Mole Balance FA0 −FA + rA∫ dV= dNA dt FA0 =FA =0 dNA dt =rAV Batch VrdVr AA =∫Well Mixed 30
- 31. 31 - 02/16/19 DepartmentofChemicalEngineering Batch Reactor Mole Balance dt = dNA rAV Integrating 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 dN t 0 31
- 32. 32 - 02/16/19 DepartmentofChemicalEngineering Batch Reactor Mole Balance ∫ − = A A N N A A Vr dN t 0 NA t32
- 33. 33 - 02/16/19 DepartmentofChemicalEngineering CSTR Mole Balance FA0−FA + rA∫ dV= dNA dt dNA dt =0Steady State CSTR 33
- 34. 34 - 02/16/19 DepartmentofChemicalEngineering FA0−FA+rAV=0 V= FA0 −FA −rA VrdVr AA =∫Well Mixed CSTR volume necessary to reduce the molar flow rate from FA0 to FA. CSTR Mole Balance 34
- 35. 35 - 02/16/19 DepartmentofChemicalEngineering Plug Flow Reactor Mole Balance ∆V V VV ∆+ FA FA 0 0 =∆+− = ∆ + ∆+ − ∆+ VrFF Vin Generation VVat Out Vat In AVVAVA 35
- 36. 36 - 02/16/19 DepartmentofChemicalEngineering lim ∆V→0 FAV+∆V −FAV ∆V =rA Rearrange and take limit as VΔ 0 dFA dV =rA 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.
- 37. 37 - 02/16/19 DepartmentofChemicalEngineering Alternative Derivation – Plug Flow Reactor Mole Balance 00 =+− ∫ dVrFF AAA 0= dt dNA Steady State dt dN dVrFF A AAA0 =+− ∫ PFR 37
- 38. 38 - 02/16/19 DepartmentofChemicalEngineering dFA dV =rA 0− dFA dV =−rA Differientiate with respect to V ∫= A A F F A A r dF V 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 38
- 39. 39 - 02/16/19 DepartmentofChemicalEngineering ( ) ( ) dt dN WrWWFWF A AAA =∆′+∆+− A WAWWA W r W FF ′= ∆ −∆+ →∆ 0 lim 0= dt dNASteady State PBR Packed Bed Reactor Mole Balance 39
- 40. 40 - 02/16/19 DepartmentofChemicalEngineering Packed Bed Reactor Mole Balance dFA dW = ′rA 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 dF W 0 The integral form to find the catalyst weight is: 40
- 41. 41 - 02/16/19 DepartmentofChemicalEngineering Reactor Mole Balance Summary Reactor Differential Algebraic Integral V= FA0 −FA −rA CSTR Vr dt dN A A = 0 ∫= A A N N A A Vr dN tBatch NA t dFA dV =rA ∫= A A F F A A dr dF V 0 PFR FA V 41