Unit 37. Overview of Multi-Phase Reactors

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.

Unit 37 presents an introduction to the modeling of reactors containing two-phases. In Part III of the course, packed bed tubular reactors and semi-batch reactors were the only systems considered that involved two phases. For packed bed reactors assumptions were made that allowed the design equations to be formulated as if the solid phase was not even present. Often, the assumptions that allowed that simplification are not valid and it becomes necessary to explicitly account for the presence of two phases. This was done in the case of a semi-batch reactor where one product evaporated from the liquid phase, but again using some assumptions (no concentration or temperature gradients in either phase) that will not always be valid. This unit shows that to properly model such systems, it is necessary to write design equations separately for each phase. It is additionally necessary to model the exchange of material and energy between the two phases in that model, which will be considered in Section B of Part IV. This unit concludes with a brief overview of different kinds of process equipment for multi-phase reactions.

Learning Resources

• Archive (.zip) - Contains all learning resources listed below for this unit
• Documents to Read:
  • Unit 37 Informational Reading (.pdf)
  • Example 37.1 (.pdf)
• Videos to Watch (please right-click and save, then play back locally on your computer):
  • Unit 37 Informational Video (.mov)
  • Example 37.1 Video (.mov)

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 37.1
  • Class Lesson Plan (.pdf)
  • Complete slides to make available to students after class
    • Keynote 09
    • PowerPoint
• Alternative Questions (.pdf) that could be used in a pre-class quiz

Practice Problems