Unit 28. Choosing a Reactor Type

This website provides learning and teaching tools for a first course on kinetics and reaction engineering. Here, in Part III of the course, the focus is on the modeling of chemical reactors. In particular, it describes reaction engineering using the three ideal reactor types: perfectly mixed batch reactors, continuous flow stirred tank reactors and plug flow reactors. After considering each of the ideal reactor types in isolation, the focus shifts to ideal reactors that are combined with other reactors or equipment to better match the characteristics of the reactor to the reactions running within it.

The preceding sections of Part III examined reaction engineering using one of the three ideal reactor types in isolation. Section E considers the important topic of matching the reactions being run to the reactor that is best-suited to those reactions. It examines ways in which the ideal reactors can be modified or augmented so that their performance is further improved. In all cases considered in this section, each reactor is still one of the three ideal types, and it is still modeled as described in the preceding sections. The things that differ from prior analyses are the external connections to the reactor or reactors. These changes lead to improved performance for a selected class of reaction, but they can also affect the mathematical approach used to solve the reactor model equations.

Reaction engineering with each of the three types of ideal reactors was considered in the preceding sections of Part III of A First Course on Kinetics and Reaction Engineering. The advantages and disadvantages of each reactor type have been considered. However, in all of the reaction engineering tasks that have been considered, the type of reactor to be analyzed has always been specified. Suppose a different type of engineering task was assigned wherein a reaction was specified and the assignment was to design a reactor system for that reaction (or set of reactions). Unit 28 considers the situation where deciding which type of reactor to use is part of the engineering analysis.

Learning Resources

• Archive (.zip) - Contains all learning resources listed below for this unit
• Documents to Read:
  • Unit 28 Informational Reading (.pdf)
  • Example 28.1 (.pdf)
  • Example 28.2 (.pdf)
  • Example 28.3 (.pdf)
• Videos to Watch (please right-click and save, then play back locally on your computer):
  • Unit 28 Informational Video (.mov)
  • Example 28.1 Video (.mov)
  • Example 28.2 Video (.mov)
  • Example 28.3 Video (.mov)
• Reference Files:
  • Unit 28 Definitions, Nomenclature and Equations (.pdf)

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
  • Class Lesson Plan (.pdf)
  • Complete slides to make available to students after class
    • Keynote 09
    • PowerPoint
  • Other files
    • Activity_28_1.m, Activity_28_1_cstr.m and Activity_28_1_pfr.m - MATLAB file used to produce the plot for Activity 28.1

Practice Problems

1. Consider the irreversible, liquid phase reaction A → Z, equation (1a) which occurs at constant density. Reactant A is supplied at a rate of 4 L min^-1 in a concentration of 2 mol L^-1 and at a temperature of 43 °C. The heat capacity of the fluid is 0.87 cal mL^-1 K^-1 and the heat of reaction is -27.2 kcal mol^-1. The reaction is second order in the concentration of A, equation (2), and the rate coefficient obeys Arrhenius' law with a pre-exponential factor of 6.37 x 10⁹ L mol^-1 min^-1 and an activation energy of 14.3 kcal mol^-1. (a) Using a qualitative analysis, predict whether the required reactor volume of an adiabatic PFR or of an adiabatic CSTR would be larger assuming the conversion to be 50%, then perform a quantitative analysis to check your prediction. (b) Repeat part (a) assuming the conversion to be 95%.

(Problem Statement as .pdf file)