Chemical Reactor Design-CHEM-E7135 Yongdan Li The field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place Professor of Industrial Chemistry Department of Chemical and Metallurgical Engineering School of Chemical Technology Aalto University Email: [email protected]Kemistintie 1, E404
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Chemical Reactor Design-CHEM-E7135
Yongdan Li
The field that studies the rates and mechanisms of chemical
reactions and the design of the reactors in which they take place
Professor of Industrial ChemistryDepartment of Chemical and Metallurgical EngineeringSchool of Chemical TechnologyAalto UniversityEmail: [email protected] 1, E404
Date/time Place Topic Lecturers
Mon 7th of Jan 10:15-12:00 Ke 5 D 311 Lecture 1: Introduction to the course and basic
kinetics
Yongdan Li
Mon 21th of Jan 10:15-12:00 Ke 5 D 311 Lecture 2: Ideal reactor design Yongdan Li
Mon 28th of Jan 10:15-12:00 Ke 5 D 311 Lecture 3: Non-ideal flow patterns Yongdan Li
Mon 4th of Feb 10:15-12:00 Ke 5 D 311 Assignment 1: Lecture 1-2
Assign the project
Reetta Karinen/Tiia
Viinikainen
Yingnan Zhao/Yongdan Li
Mon 11th of Feb 10:15-12:00 Ke 5 D 311 Lecture 4: Typical catalytic reactors Yongdan Li
Mon 25th of Feb 10:15-12:00 Ke 5 D 311 Assignment 2: Lecture 3-4 Reetta Karinen/Tiia
Viinikainen
Fri 1th of Mar 10:15-12:00 Ke 5 D 311 Lecture 5: Typical non-catalytic reactors Yongdan Li
Mon 4th of March 10:15-12:00 Ke 5 D 311 Lecture 6: Micro-structured reactors Yongdan Li
Fri 8th of March 10:15-12:00 Undetermined Feedback of project Yingnan Zhao/Yongdan Li
Mon 11th of March 10:15-12:00 Ke 5 D 311 Lecture 7: Biochemical reaction systems Yongdan Li
Fri 15th of March 10:15-12:00 Ke 5 D 311 Lecture 8: Reactors with ion transfer through
interfaces
Zhengze Pan/Yongdan LI
Mon 18th of March 10:15-12:00 Ke 5 D 311 Assignment 3: Lecture 5-7 Reetta Karinen/Tiia
Viinikainen
Course Timetable
8 Lectures, 3 Assignments and 1 Project are contained
Professor Yongdan Li
– Office hours whenever office door is open, room E404
Note: The reacted amounts of A and B at any time t are equal, i.e., CA0XA= CB0XB,
Let M = CB0/CA0 be the initial molar ratio of reactants,
After separation and integration it becomes
Lecture 1.2 Constant-Volume Batch Reactor
41
After breakdown into partial fractions, integration, and rearrangement, the final result in
a number of different forms is
(24)
Fig 1.3 Test for the bimolecular mechanism A + B → R with CA0 ≠ CB0
CA0 CB0
Lecture 1.2 Constant-Volume Batch Reactor
42
Reactants are introduced in their stoichiometric ratio
go back to the original diff-
erential rate expression
For a second-order reaction with equal initial CA0 and CB0 or for the reaction
the defining second-order differential equation becomes
(25)
On integration it yields
(26)
Lecture 1.2 Constant-Volume Batch Reactor
43
Rate Equations of nth Order reaction
When the mechanism of reaction is not known
(27)
On separation and integration it yields
(28)
Trial-and-error solution select a value for n and calculate k. The value of n which minimizes
the variation in k is the desired value of n
Curious features
the reaction never goes to completion
the reactant concentration will fall to zero and
then become negative
n > 1
n < 1
Lecture 1.2 Constant-Volume Batch Reactor
44
Zero-Order Reactions high
concentration
(29)
Integrating and noting that CA can never become negative
(30)
concentration
independent
radiation intensity,
available surface
Fig 1.4 Test for a zero-order reaction
Lecture 1.2 Constant-Volume Batch Reactor
30
30
45
Overall Order of Irreversible Reactions from the Half-Life t1/2
If CB0/CA0 = β/α…, at any time CB/CA = β/α…
(31)
Integrating for n ≠ 1 gives
Half-Life t1/2 (Time needed for CA /CA0 =1/2) is
(32a)
Lecture 1.2 Constant-Volume Batch Reactor
32a
46
Irreversible Reactions in Parallel
(33)
(34)
(35)
Eq. 33, which is of simple first order, is integrated to give
(36)
dividing Eq. 34 by Eq. 35 we obtain the following
(37)
Lecture 1.2 Constant-Volume Batch Reactor
47
Fig 1.6 Plotting for Eqs. 36, 37 Fig 1.7 Concentration-time curves for Parallel reactions
Lecture 1.2 Constant-Volume Batch Reactor
3637
48
Irreversible Reactions in Series
First consider consecutive unimolecular type first-order reactions
(38)
(39)
(40)
Start with a concentration CA0 of A, no R or S present. Integrate Eq. 38,
(41)
Substitute CA in Eq. 39
(42) (43)
Lecture 1.2 Constant-Volume Batch Reactor
49
Because there is no change in total number of moles,
(44)
In general, for any number of reactions in series it is the slowest
step that has the greatest influence on the overall reaction rate
Differentiate Eq. 43 and set dCR/dt = 0, CR, max occurs
(45) (46)
Lecture 1.2 Constant-Volume Batch Reactor
50
Fig 1.8 Typical concentration-time curves for consecutive first-order reactions
Evaluate k1 and k2
Lecture 1.2 Constant-Volume Batch Reactor
43
41
44
46
45
51
First-Order Reversible Reactions
Irreversible reactions can be considered as reversible ones with large equilibrium constants.
(47)
Starting with M = CR0/CA0
equilibrium constant
(48)
Now at equilibrium dCA/dt = 0, Hence
and
Combining the above three equations (48, 49, 50)
Lecture 1.2 Constant-Volume Batch Reactor
(49) (50)
(51)
52
(51)
(21)
Reversible
Irreversible
(22)
special case CAe=0 or
XAe=1 or
KC= ∞
i
ii
Fig 1.9 Test for the unimolecular type reversible (i) and irreversible (ii) reactions
Lecture 1.2 Constant-Volume Batch Reactor
51
21-22
53
Second-Order Reversible Reactions
For the bimolecular-type second-order reactions
(52a)
(52b)
(52c)
(52d)
When CA0=CB0 and CR0=CS0=0
(53)
Fig 1.10 Test for the reversible bimolecular reactions
Lecture 1.2 Constant-Volume Batch Reactor
53
54
Lecture 1.3 Varying-Volume Batch Reactor
Fig 1.11 A varying-volume batch reactor
The progress of the reaction is followed
by noting the movement of the bead with
time
Isothermal constant
pressure operations
Volume is linearly related
to the conversion (54)
(55)Fractional change in volume of the system between no
conversion and complete conversion of reactant A
Examplepure A 50% A
50% Ar
55
Noting that (56)
On combining with Eq. 54
(57)
(isothermal varying-volume systems)
In general
Replace V (Eq. 54) and NA (Eq. 56)
in terms of volume (Eq. 54)
(58)
(59)
Lecture 1.3 Varying-Volume Batch Reactor
56
Zero-Order Reactions
(60)
Lecture 1.3 Varying-Volume Batch Reactor
First-Order Reactions
Replace XA by V from Eq. 54 and integrate it gives
(61)
Second-Order Reactions
or
(62)
Yongdan LiProfessor of Industrial ChemistryDepartment of Chemical and Metallurgical EngineeringSchool of Chemical TechnologyAalto UniversityEmail: [email protected] 1, E404
Chemical Reactor Design
The field that studies the rates and mechanisms of chemical
reactions and the design of the reactors in which they take place