Impellers

Impellers

Impellers are most widely used Agitatiors, among all types, Straight Blade and
InterMig Impellers are discussed in this post.

Straight Blade Impeller

Cleveland Eastern offers a wide range of mixing impeller designs for laboratory,
pilot plant and production blending. Sizes range from 3″ diameter propellers to
10′ diameter special purpose impellers. We can provide four bladed axial,
radial, or custom turbine designs along with high efficiency hydrofoils. All are
available with either welded or bolted blade construction. Shaft sizes from 1/2″
to 4″ diameter can be accommodated. Materials of construction include 304 or 316
L grade stainless steel, carbon steel, Carpenter 20, and Hastelloy C. PVC,
rubber, and Teflon coatings are also offered.

D/d = 3 – 5

Rpm = 200 – 250

Rpm of the stirrer = (Motor’s pulley*Motor’s rpm)/ (Gear’s pulley*Gear Ratio )

Limitation

For high viscous liquid this type of the agitator not used.

If this type of the stirrer is used for high viscous liquid, more power
consumption will required.

Applications

A cost effective impeller for operation very near the floor of a tank for
agitating the heel in solids suspension applications
Also an effective impeller in laminar flow applications, especially when
impeller Reynolds numbers drop below 50.

INTER-MIG IMPELLER

Tank with Impeller

Nomenclature

D = Impeller Diameter

C = Impeller off Bottom Clearance

N = Impeller speed Z = liquid Depth

T = Vessel Diameter

B = Baffle Width

What is mixing?

Mixing is the random distribution, into and through one another, of two of more
initially separate phases. Information Required for Mixer Selection :
Viscosity

Density

Pressure & Temperature

Blend Time

Volume

Inter-mig Impeller, How it works?

Intensive mixing of the vessel content and the liquid surface due to a complex
up and down movement of the fluid, due to the opposite pitches of the inner
outer blades.

Structure of Impellerler

The Ekato Company developed two-blade axial flow impellers, the mig and the
intermig, mainly for high viscosity liquids. However, they can be effective for
low to medium viscosity liquids as well. These impellers are designed at high
impeller/tank diameter ratio [D/T] and have two sections of blades at opposite
angles. If the inner blade pumps down, the outer blade pumps up to enhance the
liquid circulation.

Blade shapes

The outer blade section of interning has to staggered sections designed for
minimizing local form drag losses, which results in more distinct axial flow and
a lower power number.

Limitations with Advantage

These agitators are commonly used for processes that require thorough axial
mixing with minimal shear such as fermentations that use cells that are easily
destroyed by intense agitation or crystallization of shear-sensitive crystals.
High local forces lead to coagulation of E-polymer sates and therefore to bad
qualities. A uniform blending is achieved with the two-stage EKATO-INTERMIG.

This ensures short residence times at the liquid surface.
Homogeneous dissipation of introduced energy,
High axial flow velocities, therefore increased heat transfer and reduced
scaling at vessel wall,
Low shear mixing Further design conditions are:

High viscosities up to 130,000 cP

Diameter ratio d/D = 0.7 ( Turbulent Flow – Baffle Required )

d/D > 0.7 (Laminar Flow – Baffle not Required)

Short batch cycles

High heat transfer coefficients

Application

Plastics, food, paint, biotechnology, energy and waste-water treatment
industries.

Polybutadienlatex: (PBL)  Styrene-Acrylnitril-Copolymerisates (SAN)
Styrene-Butadiene-Rubber (SBR) and Styrene Crystallization Operation

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