Search results
Results from the WOW.Com Content Network
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.
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.
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.
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.
Cross-sectional diagram of stirred tank reactor. Baffles are flow-directing or obstructing vanes or panels used to direct a flow of liquid or gas. It is used in some household stoves [1] and in some industrial process vessels (tanks), such as shell and tube heat exchangers, chemical reactors, and static mixers.
In its most commonly used form, the first Damköhler number (Da I) relates particles' characteristic residence time scale in a fluid region to the reaction timescale. 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 ...
The volume of a CSTR necessary to achieve a certain conversion at a given flow rate is equal to the area of the rectangle with height equal to and width equal to . The volume of a PFR necessary to achieve a certain conversion at a given flow rate is equal to the area under the curve of F A o − r A {\displaystyle F_{Ao} \over -r_{A}} plotted ...