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### Lecture 2

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 – Tuesday 1/15/2013

- Review of Lecture 1
- Definition of Conversion, X
- Develop the Design Equations in terms of X
- Size CSTRs and PFRs given –rA= f(X)
- Conversion for Reactors in Series
- Review the Fall of the Tower of CRE

ReactorMole Balances Summary

NA

FA

FA

The GMBE applied to the four major reactortypes

(and the general reaction AB)

t

W

V

Batch

CSTR

PFR

PBR

Define conversion, X

Consider the generic reaction:

Chose limiting reactant A as basis of calculation:

Define conversion, X

CSTR

Consider the generic reaction:

Chose limiting reactant A as basis of calculation:

Define conversion, X

CSTR

CSTR volumenecessary to achieveconversion X.

PFR

Steady State

Levenspiel Plots

ReactorSizing

Given –rA as a function of conversion, -rA= f(X), one can size any type of reactor. Wedo this by constructing a Levenspielplot. Here we ploteither (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:

Levenspiel Plots

LevenspielPlots

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

Reactors in Series

Given: rA as a function of conversion, one can also design any sequence of reactors in series by defining X:

Only valid ifthere are no sidestreams.

Molar Flow rate of species A at point i:

Reactors in Series

Space time τ is the time necessary to process 1 reactor volume of fluid at entrance conditions.

KEEPING UP

- The tower of CRE, is it stable?

Mole Balance

Be careful not to cut corners on any of the

CRE building blocks while learning this material!

Heat Effects

Rate Laws

Stoichiometry

Mole Balance

Otherwise, your Algorithm becomes unstable.

End of Lecture 2

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