Unit 29. Multiple Reactor Networks

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.

Unit 29 considers systems where two or more reactors are somehow connected and function together in the processing of a feed stream. There are two reasons for considering these types of reactor networks. First, one might be called upon to perform reaction engineering tasks on a real system that uses such a network of reactors. One common example is a reactor network wherein multiple CSTRs are connected in series. This configuration is sometimes referred to as a cascade of CSTRs, and the greater the number of CSTRs in series, the more the cascade as a whole behaves like a PFR. A less obvious reason for considering reactor networks is that one might attempt to model a single real world (non-ideal) reactor using a network of ideal reactors. The resulting model would be empirical in nature, but nonetheless it would be useful if it proved to accurately predict the performance of the real world reactor.

Learning Resources

• Archive (.zip) - Contains all learning resources listed below for this unit
• Documents to Read:
  • Unit 29 Informational Reading (.pdf)
  • Example 29.1 (.pdf)
  • Example 29.2 (.pdf)
  • Example 29.3 (.pdf)
• Videos to Watch (please right-click and save, then play back locally on your computer):
  • Unit 29 Informational Video (.mov)
  • Example 29.1 Video (.mov)
  • Example 29.2 Video (.mov)
  • Example 29.3 Video (.mov)
• Reference Files:
  • Unit 29 Definitions, Nomenclature and Equations (.pdf)
• Other Files:
  • Example_29_1_a.m - MATLAB file used in the solution of the single CSTR case in Example 29.1
  • Example_29_1_b.m - MATLAB file used in the solution of the CSTR cascade case in Example 29.1
  • Example_29_2.m - MATLAB file used to model the reactor networks in Example 29.2
  • Example_29_2_cstr.m - MATLAB file used to model each CSTR in Example 29.2
  • Example_29_2_pfr.m - MATLAB file used to model each PFR in Example 29.2
  • Example_29_3.m - MATLAB file used to model the reactor networks in Example 29.3
  • Example_29_3_pfr.m - MATLAB file used to model each PFR in Example 29.3

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
• Alternative Questions (.pdf) that could be used in a pre-class quiz

Practice Problems

1. An aqueous solution at 30 °C containing A and B at concentrations of 1.0 and 1.2 M, respectively, is to be fed to two CSTRs in series at a flow rate of 75 L min^-1. Reaction (1a) will occur in the adiabatic reactors with a rate of reaction that is accurately described by equation (1b). The heat of reaction (1a) is -10,700 cal mol^-1 and may be assumed to be constant. The heat capacity of the solution and the density of the solution may be taken to be constant and equal to those of water (1.0 cal g^-1 K^-1 and 1.0 g cm^-3). If 90% of the A needs to be converted, what is the minimum total volume required, and how is it divided between the two reactors?

(Problem Statement as .pdf file)