Mixing

Mixing

Mixing can be divided in two parts, Micro and Macro mixing. There is a new trend
of computational fluid Mixing modeling with the help of computiational fluid
dynamics, all this things are discussed in this post.

Macro Level Mixing

Miacro level mixing covered here describe how the flow pattern generated by the
impeller or impellers affects the suspension or incorporation of and the
distribution of the particles within the vessel. Most often people think of
solids suspension from the bottom of the vessel because solids are usually
heavier than the displaced liquid, but the incorporation of floating solids is
also described here. Parameters that affect Liquid-Solid mixing are the shape of
solids, solid size distribution, solid concentration, solid density, and liquid
density and viscosity.

Micro level mixing

It deals almost entirely with liquid-solid (solid-liquid) mass transfer across a
phase boundary, in this case through the solids. This category deals more with
the rate of the mass transfer, and less with the physical distribution of the
solids. The solids can be porous catalysts for catalytic reactions, active
agents for adsorption, polymers and co-polymers for suspension polymerization,
or particles that need to be dissolved or coated. In the case of crystallization
and precipitation, the solids are the final product. In the special case of
dissolving, the solids are generally added to the surface. Although the solid
density is greater than the liquid density, the solids may initially float and
gel with each other. The gel creates a “protective layer” around the solids,
making it nearly impossible for the solids inside the gel to be wetted out. This
phenomena is particularly interesting in the polymer industry

Computational Fluid Mixing (CFM)

CFM is a powerful tool that is used to mathematically model fluid flows of
different agitator/impeller designs in mixing tanks. Other valuable analyses
include the mixing and reaction rates of chemicals and heat transfer. Mixing of
single and multi-phase fluids in stirred tank reactors is a common operation in
many industries.

Understanding the fluid flow in these tanks is critical for equipment design, scale-up,
process control and economic factors. CFM models allow you to see what is taking
place in the mixing vessel.

The results enable an engineer to select the best agitator design to obtain the
desired process performance. The flow patterns in stirred tanks are complex,
which makes traditional CFM a time-consuming process.

A CFM technician may need as long as three days to define all of the equations and run the
program. However, we have applied a variety of proprietary techniques to
expedite this process.

Chemical engineers can obtain a two-dimensional CFM analysis in as little as 10 minutes,
and a 3-D analysis in 3 to 4 hours. Our analytical capabilities are not limited
to just cylindrical stirred tanks. Rectangular and side-entering agitated tanks
as well as turbulent and laminar flow static mixers can all be successfully
evaluated using our CFM technology.

Chemineer CFM models receive extensive validation using advanced experimental
techniques. Chemineer is the first in the industry to use laser based Particle
Image Velocimetry (PIV) for mixing analysis. The unique data obtained with PIV
further improves our modeling capabilities and provides you with the most
accurate design for your agitation needs.

Facebook Comments

Leave a Reply