Isothermal Batch Reactors: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • Material balances on individual components are most useful for reactor design:
    Accumulation(+ or -) = In(+) – Out(+) + Generation by reaction(+ or -)
  • Batch reactors (BR) are usually liquid phase. The contents are spatially uniform in concentration and temperature, but both concentration and temperature change with time.
  • The best approach to solve batch reactor problems is to write a mass balance for each component and then solve the differential equations simultaneously. Since most reactors involve multiple reactions and are not isothermal (see other modules), the differential equations should be solved numerically.
  • Batch are reactors used for processes that:
    • Are new and untried.
    • Have multiple grades.
    • Require long reaction times.
    • Have varying demands.
    • Make smaller amounts of products (drugs, dyes, specialties).
    • Make high priced materials.
    • Require a reaction to be slowed until a test is performed.
    • Can be contaminated (fermentation).
    • Can rapidly foul.
  • The same batch reactor can be used to make the desired amount of one product and then cleaned and a different reaction can be carried out.
  • The amount of reaction for a first-order, isothermal reaction depends on the total number of moles. Diluting a batch reactor does not change the conversion for an isothermal, first-order reaction.
From studying this module, you should now be able to:
  • Determine the time for a single reaction in an isothermal batch reactor to reach a desired conversion, given a rate constant, order of reaction for each reactant, and starting reactant concentrations.
  • Determine the size of an isothermal batch reactor to produce a desired amount of product per hour, given reaction time to reach a certain conversion.


Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder