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In this way, a higher efficiency may be obtained, or the size and cost of the PFR may be reduced. A PFR has a higher theoretical efficiency than a CSTR of the same volume. That is, given the same space-time (or residence time), a reaction will proceed to a higher percentage completion in a PFR than in a CSTR.
There are four main groups of chemical reactors - CSTR, PFR, semi-batch, and catalytic - with variations on each. Depending on the nature of the chemicals involved in the reaction, as well as the operating conditions (e.g. temperature and pressure), certain materials will perform better over others.
A CSTR often refers to a model used to estimate the key unit operation variables when using a continuous agitated-tank reactor to reach a specified output. The mathematical model works for all fluids: liquids, gases, and slurries. The behavior of a CSTR is often approximated or modeled by that of an ideal CSTR, which assumes perfect mixing. In ...
The key assumption is that as a plug flows through a PFR, the fluid is perfectly mixed in the radial direction but not in the axial direction (forwards or backwards). Each plug of differential volume is considered as a separate entity, effectively an infinitesimally small continuous stirred tank reactor , limiting to zero volume.
The residence time scale can take the form of a convection time scale, such as volumetric flow rate through the reactor for continuous (plug flow or stirred tank) or semibatch chemical processes: D a I = reaction rate convective mass transport rate {\displaystyle \mathrm {Da_{\mathrm {I} }} ={\frac {\text{reaction rate}}{\text{convective mass ...
Where is the molar rate of addition of the reactant A. Note that the presence of these addition terms, which could be negative in case of products removal (e.g. by fractional distillation) are the ones marking the difference of the semi batch reactor cases from the simpler batch cases. For standard batch reactors (no addition terms) the ...
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As a result, the dispersity of the reactor lies between that of a batch and that of a homogeneous CSTR. [9] Step growth polymerization is most affected by reactor type. To achieve any high molecular weight polymer, the fractional conversion must exceed 0.99, and the dispersity of this reaction mechanism in a batch or PFR is 2.0.