Dave Dickey Forum Moderator 292 Posts
Re: What is the suggested rpm and motor speed for an anchor impeller?26 April 2012 at 1:29pm
The answer to this question comes with some serious misgivings. The batch volume seems very large for the vessel diameter. For a 1500 mm diameter vessel to hold 6660 liters, the straight-side (height) of the tank needs to be 4500 mm. A 3:1 height to diameter is like trying to mix a vertical pipe. An anchor operating at any speed would take a long time to obtain batch uniformity.
For the sake of answering the question, if the anchor impeller operates at 45 rpm, the motor would have to be 20 KW. Because of the extreme height to diameter ratio for the vessel, a helical impeller is strongly recommended. An anchor impeller does not to a good job of mixing when the liquid level is approximately equal to the tank diameter, because it creates very little top to bottom motion. With this tall tank, a helical impeller might work. A helical impeller would also require 20KW at 45 rpm, but provide much better mixing than the anchor
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I am planning to have a mixer with an anchor impeller that has the following specifications for blending a viscous liquid (different lots of same material for the purpose of achieving homogeneity): Mixing vessel volume: 7000 liter; Batch volume of the liquid: 6660 liter (6 t); Tank diameter: 1500 mm; Density of the liquid: 900 kg/m3; viscosity of the liquid: 5000 - 7000 cp; liquid type: Viscous polymer For the above application, kindly suggest the impeller rpm and motor power required. It would be of immense help to me if you can provide me the corresponding thumb rules. Also, what is the suitability of other impellers (helical, etc.) for the above application?
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