Elements of
Chemical Reaction Engineering
6th Edition



Home

Essentials of
Chemical Reaction Engineering
Second Edition

  Select  Chapter  >>     TOC     Preface     1     2     3     4     5     6     7     8     9     10     11     12     13     14     15     16     17     18     Appendices  
›

By Chapter Hide

  • Objectives
  • Living Example Problems
  • Extra Help
  • - Summary Notes
  • - LearnChemE Screencasts
  • - FAQs
  • - Interactive Computer Modules
  • Additional Material
  • Self Test
  • i>Clicker Questions
  • Professional Reference Shelf

By Concept Hide

  • Interactive Modules
  • -Web Modules
  • -Interactive Computer Games
  • Living Example Problems

U of M Hide

  • Asynchronous Learning
  • ChE 344
  • ChE 528

Chapter 17: Distributions of Residence Times for Chemical Reactors

Example: Calculate Xmm and Xseg

Calculate the conversion in a real reactor using the segregation and the maximum mixedness model.  The reaction A -> B is carried out in a real reactor that has the following F-curve. The entering concentration of A is 8 mol/dm3. The following F(t) was determined from a trace test

 


For 10<t<20

For 20<t<30

The reaction rate also varies with time as per below equation

For 10<t<20 -rA = k * CA0.6

For 20<t<30 -rA = k * CA2.7

Where, k=0.1

Calculate the conversion using

1)   the segregation model

2)   the maximum mixedness model

Also explain the difference in conversions between the two models.









 

Solution

1)   X seg = 0.796 [Polymath code]

2)   X mm = 0.796 [Polymath code]

 

Both models predict the same conversion!

The reason is: for reaction order 0 < n < 1, max mixedness predicts higher conversion and for n > 1, segregation predicts higher “X”. In this case, the reaction goes from 0.6 to 2.7 as CA decreases. Thus, the predictions of the two models average out.

 

 

Back to Chapter