3- Conversion and Reactor Sizing_stu

Today’s Lecture

• Solution to Homework

• Definition of Conversion, X

• Size CSTRs and PFRs given –rA=f(X)

• Review the Fall of the Tower of CRE

Solution to homework

Solution to homework (Cont.)

Solution to homework (Cont.)

Solution to homework (Cont.)

Solution to homework (Cont.)

Review of Mole Balances

Definition of Conversion

A general reaction:

fedA moles

reactedA moles X

D a

d C

a

c B

a

b A

ncalculatio of basis asA reactant limiting Choose

D d C c B b A a

Batch Reactor Design Equations

Design Equations for Flow Reactors

Levenspiel Plots (reactor sizing)

Numerical Evaluation of Integrals

CSTR Sizing

PFR Sizing

Numerical Evaluation of Integrals

Numerical Evaluation of Integrals (Cont.)

Numerical Evaluation of Integrals (Cont.)

Example 3-1

The reaction A B, described by the experimental data at 500 K and 830 kPa, is to be carried out in a CSTR. Species A enters the reactor at a molar flow rate of 0.4 mol/s.

Example 3-2

The reaction A B, described by the experimental data at 500 K and 830 kPa, is to be carried out in a PFR. Species A enters the reactor at a molar flow rate of 0.4 mol/s.

Comparing CSTR and PFR Sizes

Reactors in Series

Reactors in Series (Cont.)

Reactors in Series (Cont.)

Comparing Vohntes for CSTRs in Series

For the two CSTRs in series, 40% convenion is achieved in the first reactor. What is the volume of each of the two reactors necessary to achieve 80% overall conversion of the entering species A?

Approximating a PFR by a large number of CSTRs in series

Sizing Plug-Flow Reacfors in Series

Calculate the reactor voIumes V1 and V2 for the plug-flow sequence shown in Figure below when the intermediate conversion is 40% and the final conversion is 80%. The entering molar flow rate is the same as in the previous examples, 0.4 mol/s.

An Adiabatic Liquid-Phase Isomerization

The isomerization of butane was carried out adiabatically in the liquid phase and the data in Table below were obtained.

It is real data for a real reaction carried out adiabatically, and the reactor scheme shown in Figure below is used.

Some Further Definitions

• The space time, z. is obtained by dividing reactor volume by the volumetric flow rate entering the reactor:

• The space time is the time necessary to process one reactor volume of fluid based on entrance conditions. It is also called the holding time or mean residence time.

The two space velocities commonly used in industry are the liquid-hourly and gas-hourly space velocities, LHSV and GHSV, respectively.

Homework