Two Approximate Methods to Estimate Conversion and Yield in Mixed Chemical Reactors


In many cases, quick methods are needed to evaluate the conversion and yield that may occur in a given reactor with a desired chemical reaction and necessary product. Full experimentation and/or full numerical simulation to evaluate the situation is neither warranted nor needed. In many cases, methods even quicker than computational fluid dynamics (CFD) with closure are needed to approximate yield results for various versions of a reactor. This paper reviews two methods that might be used beyond assuming perfect mixing or perfect plug flow to determine the likely conversion and yield for reactions in tubular reactors with mixing effects and in stirred vessel reactors. These methods can typically be implemented using a simple numerical integration program (such as POLYMATH) and/or a math program (such as MATLAB). In most cases, the results will not perfectly duplicate actual laboratory or pilot results, but simulated comparisons of various reactor setups can be made which are likely to be valid, because they can give the trends that occur for given changes. Such simplified calculations should always be made before more costly laboratory and simulation efforts are made. The approximate methods reviewed and compared are plug-flow mixing in a pipe with or without static mixing elements and several segment mixing in a stirred vessel. Closures for the extent of mixing in the pipes or segments are paired-interaction (P-I) and random coalescence and dispersion (C−D) mixing, both of which have shown good correspondence with the experimental results when used in CFD simulations.


Chemical and Biochemical Engineering

Keywords and Phrases

Computational Fluid Dynamics; Simultaneous Partial Differential Equations; Stirred Vessels with Semi-batch or Continuous Flow Operation; Tubular Turbulent Flow Reactors

Document Type

Article - Journal

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