Engineering Integrity Blog

Scale of Agitation for Blending

March 27, 2017

In our daily interactions with customers, we are often asked “how do I know it is mixed?” Alternatively we ask, “can you describe the level of mixing or how the amount of fluid motion the process requires?”

In general, the table below helps to quantify or at least describe the mixing intensity for a given scale of mixing. While not exhaustive in explaining the ‘degree of mixedness’, or how to achieve the desired process goal, it does provide a basis for communication.

The concept and achieved result of Mixing Intensity is based on many different factors that would include at least:

HP Investment/Per Volume

Torque Investment/Per Volume

Impeller Pumping Rate/Batch Volume

Impeller Tip Speed

Turbulent Energy Disipation Rate

Ratio of impeller diameter to tank diameter.

TABLE 1

SCALE OF AGITATION FOR BLENDING

 

Agitation Scale Bulk Velocity Description Typical Applications
1
2
6
12
No dead spots; flat surface, long blend times. Storage tanks – Mild blending of miscible liquids. Mixing foamers. Holding tanks with long retention times.
3
4
5
6
18
24
30
36
Levels 3-6 are characteristic of most CPI applications. Surface rippling at low viscosity. Shorter blend times. Mild to moderate agitation. Most blending jobs. Holding & neutralization tanks w/ average retention times. Easy heat transfer applications. Non-critical reactors.
7
8
9
10
42
48
54
60
Levels 7-10 are characteristic of applications requiring high fluid vel. Short blend times. Surging surface at low viscosity. Critical reactors. Neutralization and flash mixers with short retention time. Good heat transfer.

For more information on this topic, feel free to contact us directly at 860-669-1199.

 

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