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The influence of mixing on liquid phase reaction can be modeled
using Fluent CFD. Hydrolysis, crystallization, neutralization, and
other reactions can be modeled either directly or indirectly by
addition sub-models that include effects of micromixing.
Product plume forming as a result of reactant injection
through the dip tube.
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In contrast to CSTR models in simulators that assume perfect mixing,
CFD predictions incorporate the effect of mixing on the reaction.
The model can incorporate the effect of tank style, impeller choice
and location, impeller RPM, feed location, and feed rate. In the
example considered here, the agitator system consists of a axial
impeller in a baffled dish-bottomed tank.
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Influence of agitation on liquid phase reactions
Consider a reactor system consisting of the following homogeneous
liquid-phase chemical reaction scheme:
A + B -> R (fast kinetics)
B + R -> S (slow kinetics)
B + C -> Q (slow kinetics)
When mixing is rapid, formation of R is favored. When mixing is
very slow, formation of Q is favored. At intermediate levels of
mixing, formation of S is favored. All reactions compete for B.
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The FLUENT results depend on key equipment design choices,
such as impeller RPM or feed location. The exit concentrations
of S and Q are displayed for different choices of impeller speed
and feed stream location.
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