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. Lecture 2 1
Today’s lecture Review of Lecture 1 Solution to P1-6 Definition of Conversion, X Develop the Design Equations in Terms of X Size CSTRs and PFRs given –r A = f(X) Conversion for Reactors in Series Review the Fall of the Tower of CRE 2
Reactor Mole Balance Summary ReactorDifferentialAlgebraicIntegral CSTR Batch NANA t PFR FAFA V 3
Homework Problem Solution 4 Liquid phase Given the following information, Find V
(1) Mole Balance: (2) Rate Law: (3) Stoichiometry: 5
(4) Combine: (5) Evaluate: 6
Consider the generic reaction 7
Batch 8
Integrating The necessary t to achieve conversion X. 9
CSTR Steady State 10
Well Mixed CSTR CSTR volume necessary to achieve conversion X. 11
Steady State PFR 12
This is the PFR volume necessary to achieve conversion X. PFR Integrating 13
Reactor Mole Balances in terms of conversion ReactorDifferentialAlgebraicIntegral CSTR PFR Batch X t PBR X W 14
Levenspiel Plots Reactor Sizing Given –r A as a function of conversion, -r A = f(X), one can size any type of reactor. We do this by constructing a Levenspiel plot. Here we plot either (F A0 /-r A ) or (1/-r A ) as a function of X. For (F A0 /-r A ) 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: 15
Levenspiel Plots 16
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 17
Reactors in Series Given: r A 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: 18
Reactors in Series 19
Reactors in Series Reactor 1: 20 V1V1
Reactors in Series Reactor 2: 21 V2V2
Reactors in Series Reactor 3: 22 V3V3
Reactors in Series 23
Reactors in Series Space time τ is the time necessary to process 1 reactor volume of fluid at entrance conditions. 24
KEEPING UP The tower of CRE, is it stable? 25
Reaction Engineering These topics build upon one another Mole BalanceRate LawsStoichiometry 26
Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 27
Mole Balance Rate Laws 28
Mole Balance Rate Laws Stoichiometry Isothermal Design Heat Effects 29
End of Lecture 2 30