Dave Dickey Forum Moderator 292 Posts
Re: Can I estimate how much I need blend using the recirculation loop?13 April 2010 at 1:29pm
Using a recirculation loop for mixing is unpredictable in all cases.
1) For mixing a small batch, recirculation may work or may not, depending on the degree of mixing required. Mixing with a recirculation loop may work if minimal or poor mixing is adequate. Vigorous mixing with a high degree of uniformity is probably not possible with a recirculation loop. The flow location and velocity returning to the vessel will dictate the degree of uniformity possible and is unpredictable. In all cases, bulk uniformity will be more difficult to achieve with a recirculation loop than with a well designed mixer.
2) If impeller mixing if not desired because of high shear, then a recirculation loop is even less desirable. A typical centrifugal pump used in a recirculation loop will create five to ten times the shear of an impeller mixer.
The simple answer concerning the use of a recirculation loop is try it and if it works, use it. If it does not work for the required mixing, don't be surprised. Mixing is too general to describe simply, even just for blending as both time and uniformity are involved. A recirculation loop tends to create uniformity in some locations and not in others.
The answers by this expert are based on the best available interpretation of the information provided. The consequences of the application of this information are the responsibility of the user. If clarification is needed, please submit a further question.
I had previously asked regarding the use of recirculation loop for mixing. Here are couple scenarios to use recirculation loop for mixing: 1) The batch size smaller than minimum batch size to use agitator in the existing vessel 2) Impeller mixing not desired (I am guessing due to high shear from the existing impeller) Yes, the recirculation loop will be inefficient, but for the products that may not be made ever again, upgrading the existing resources is not an option. If I can use the Betty Crocker equation or the data from various studies to estimate the max volume or the time for the blending using the agitator, can I estimate how much I need to scale down or how much longer I need to blend using just recirculation loop? I can't find any study on the role of recirculation loop in mixing. Neither did I get any insights from "Handbook of industrial mixing: science and practice."
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