Unit 36. Segregated Flow Models

This website provides learning and teaching tools for a first course on kinetics and reaction engineering. In the preceding parts of the course, the reacting fluid was always treated as if it was homogeneous, and only ideal reactor types were considered. The knowledge gained to this point is sufficient for reaction engineering for many commercial processes. Nonetheless, there are situations where the reactor does not conform to one of the ideal types and/or the rates are affected by the kinetics of physical processes in addition to the chemical reaction rate. Part IV of the course surveys a few such situations. It does not provide an in-depth analysis of any of them, but the information provided should serve as a good foundation for further study.

The first section of Part IV considers reactors that do not satisfy the assumptions of any of the ideal reactor types. It touches upon three approaches to modeling such reactors. One approach is to increase the rigor of the ideal reactor models by changing one of more of the assumptions that define the ideal reactor, but retaining most of the original model. A second approach is to effectively abandon rigor in favor of a quantitatively accurate description of the reactor behavior. The last approach uses statistical methods to describe the performance of a reactor. Section A then concludes by considering changes that are necessary when modeling reactors wherein two phases are involved in the reaction(s) taking place, and presenting with an overview of reactors that are used when the reaction involves two or more phases.

Segregated flow models, the focus of Unit 36, are an alternative to the ideal reactor models that can be used in situations where the flow assumptions of the ideal models are not met. Segregated flow models effectively represent the reactor as a distribution of smaller reactors. The distribution is chosen so that the residence times of the smaller reactors match the residence time distribution of the real reactor being modeled.

Learning Resources

• Archive (.zip) - Contains all learning resources listed below for this unit
• Documents to Read:
  • Unit 36 Informational Reading (.pdf)
  • Example 36.1 (.pdf)
  • Example 36.2 (.pdf)
• Videos to Watch (please right-click and save, then play back locally on your computer):
  • Unit 36 Informational Video (.mov)
  • Example 36.1 Video (.mov)
  • Example 36.2 Video (.mov)
• Reference Files:
  • Unit 36 Definitions, Nomenclature and Equations (.pdf)
• Other Files:
  • Example_36_1.m - MATLAB file used to perform the calculations for Example 36.1
  • Example_36_2.m - MATLAB file used to perform the calculations for Example 36.2

Teaching Resources

• Archive (.zip) - Contains all teaching resources listed below for this unit
• Sample Class
  • Online Pre-class Quiz (.pdf file)
  • Redacted slides to make available to students before class
    • Keynote 09
    • PowerPoint
  • Other files to make available to students before class
    • Worksheet for Activity 36.1
  • Class Lesson Plan (.pdf)
  • Complete slides to make available to students after class
    • Keynote 09
    • PowerPoint
  • Other files to make available to students after class
    • Activity_36_1.m - MATLAB files used in the solution of Activity 36
• Alternative Questions (.pdf) that could be used in a pre-class quiz

Practice Problems

1. The stirred tank reactor from AFCoKaRE Practice Problem 11.5 is going to be used to convert A to Z isothermally. The reaction is second order in A with a rate coefficient of 0.127 L mol^-1 min^-1. A liquid phase solution containing 2 mol L^-1 of A and no Z will be fed to the reactor at a rate of 1 gal min^-1. Use a (late mixing) segregated flow model to calculate the conversion of A that can be expected.

(Problem Statement as .pdf file)