1. Kjemisk reaksjonsteknikk Chemical Reaction Engineering
Lecture 2
Kjemisk reaksjonsteknikk
Chemical Reaction Engineering
Review of Lecture 1
Definition of Conversion, X
Design Equations in Terms of X
Size CSTRs and PFRs given –rA= f(X)
Conversion for Reactors in Series

2. General Mole Balance General Mole Balance on System Volume V FA0 FA GA2

3. Reactor Mole Balance Summary
Differential
Algebraic
Integral
Batch NA t
CSTR
PFR FA V 3 3

4. Consider the generic reaction4

5. Batch 5

6. Reactor Mole Balances in terms of conversion
Differential
Algebraic
Integral
Batch X t
CSTR
PFR
PBR X W 6 6

7. Batch reactor

8. Continuous stirred tank reactor (CSTR)

9. Continuous stirred tank reactor (CSTR)

10. Plug flow reactor (PFR)

11. Plug flow reactor (PFR)

12. Levenspiel Plots
Reactor Sizing Given –rA as a function of conversion, -rA= f(X), one can size any type of reactor. We do this by constructing a Levenspiel plot. Here we plot either (FA0/-rA) or (1/-rA) as a function of X. For (FA0/-rA) vs. X, the volume of a CSTR and the volume of a PFR can be represented as the shaded areas in the Levenspiel Plots shown as: 12

13. Levenspiel Plots 13

14. Numerical Evaluations of Integrals
The integral to calculate the PFR volume can be evaluated using method as Simpson’s One-Third Rule: (See Appendix A.4)
Other numerical methods are:
Trapezoidal Rule (uses two data points)
Simpson’s Three-Eight’s Rule (uses four data points)
Five-Point Quadrature Formula 14

15. Reactors in Series Only valid if there are no side streams.
Given: rA as a function of conversion, one can also design any sequence of reactors:
Only valid if there are no side streams.
Molecule Flow rate of species A at point i: 15

16. Reactors in Series 16

17. Reactors in Series
Reactor 1: V1 17

18. Reactors in Series
Reactor 2: V2 18

19. Reactors in Series
Reactor 3: V3 19

20. Reactors in Series 20

21. Important Definitions
Space time  is the time necessary to process one reactor volume of fluid at entrance conditions.
S-1
Space velocity:
SV = v0/V (s-1)=1/ 
Space velocity is normally given at the standard conditions (STP).
Liquid hourly space velocity (LHSV= v0,liquid/V)
Gas hourly space velocity (GHSV) = v0,gas/V
Reciprocal of the space time. But it is different on the condiitons