Foaming and Air Entrainment: A Common Mixing Issue

While foaming and air entrainment may occasionally serve a purpose, they are more often undesirable side effects of laboratory mixing that can hamper production efficiency and compromise the quality of your final product. In this article, we will dive into the problems associated with foaming and air entrainment while using an overhead stirrer, dispel the misconception surrounding the necessity of a vortex during mixing, and explore strategies to prevent these issues from arising.

Why is Foaming and Air Entrainment a Problem?

Foaming and air entrainment can wreak havoc on production processes. Handling foamy mixtures can be challenging, as they tend to be unstable and difficult to control, resulting in potential spills, product loss, and extensive clean-up operations. This prolonged cycle time directly translates to reduced productivity and increased costs. Moreover, these unwanted air bubbles can inhibit chemical reactions, degrade sensitive ingredients, and hinder mass transfer, affecting the desired outcome of the process.

Once foaming and air entrainment occur, they become challenging to eliminate from the final product. The presence of bubbles within the product compromises its quality and aesthetics, rendering it less desirable to consumers. Depending on the specific characteristics of the product, foaming can also impact its functionality and performance, making it unfit for its intended purpose.

The Vortex: A Misunderstanding

There is a common misconception that a vortex at the surface of a mixture is necessary for achieving thorough mixing. However, the reality is often quite the opposite. While a modest vortex can aid in some mixing processes, a deep and strong vortex is more likely to exacerbate foaming and air entrainment issues. The intense agitation generated by a vigorous vortex leads to increased air incorporation and creates conditions for the formation and persistence of foam.

How to Prevent Foaming and Air Entrainment

The most effective way to tackle the issue of bubble formation and air entrainment is by minimizing or preventing their occurrence altogether. Here are some strategies that can help mitigate such undesired outcomes:

Adjusting the position of the impeller within the vessel: An easy first step is to confirm the impeller blades are never above the liquid level during the mixing process. Positioning the stirrer off-centre from the vessel, or tilting the stirrer for the impeller to be at an angle in the batch, if space and equipment allows, lessens the likelihood of vortex formation and subsequent air incorporation. Caframo’s A120 Fastening Clamp is fully adjustable and easily allows for dynamic adjustments in angle and height.

Utilizing Bidirectional Mixing: Harness the power of a specially designed overhead stirrer like Caframo’s BDC2010 Reversing Digital. Its unique ability to oscillate between clockwise and counterclockwise rotations curtails vortexing and air entrainment, greatly reducing foaming.

Baffles: By redirecting the flow of the mixture, baffles act as barriers that disrupt the formation of a strong vortex and allow for more controlled mixing.

Optimizing mixing speed: This is a balance of reducing speed to address the foaming but maintaining sufficient shear and tank movement to achieve mixing objectives. The additional time required with this option may determine if this is a solution.

Vacuum: Mixing in a system which can apply a vacuum can minimize the introduction of air into the mixture while allowing full-speed mixing.

Chemical defoamers: These additives are specifically designed to suppress foam formation. However, the suitability of chemical defoamers varies depending on the product being manufactured, as they can be considered contaminants in certain applications and can be quite costly.

It is important to note that no single solution may be sufficient to completely eradicate foaming and air entrainment. However, by implementing a combination of these techniques, you can significantly reduce the occurrence of these issues and optimize your mixing processes.

Get Expert Advice for Your Application

So, whether air entrainment or foam are necessary to your process or an unwanted consequence, the Caframo Lab Solutions team has technical knowledge to help you achieve the mixing results you need. Contact us today to discuss your application solution.

References:

Reduce Foaming and Air Entrapment During Mixing (n.d.). Retrieved May 2023, from https://www.mixers.com/resources/mixing-technology-reports/reduce-foaming-and-air-entrapment-during-mixing/

A Simpler Way to Control and Reduce Foams and Bubbles in Industrial Chemical Production (n.d.). Retrieved May 2023, from https://blog.agchemigroup.eu/a-simpler-way-to-control-and-reduce-foams-and-bubbles-in-industrial-chemical-production/#:~:text=To%20restrict%20or%20reduce%20bubbles,or%20glycols%2C%20to%20their%20mixtures

Bottom-Mounted Mag Mixer Vortex (n.d.). Retrieved May 2023, from https://www.metenova.com/blog/bottom-mounted-mag-mixer-vortex

How to Avoid Foaming in Your Mixing Process (n.d.). Retrieved May 2023, from https://www.jongia.com/industries/food-industry/how-to-avoid-foaming-in-your-mixing-process/

Foam Control in Industrial Processes (n.d.). Retrieved May 2023, from https://www.aiche.org/sites/default/files/cep/20150835.pdf

Foaming and Air Entrapment Common to Mixing Processes (n.d.). Retrieved May 2023, from https://www.jongia.com/industries/dairy-industry/foaming-and-air-entrapment-common-to-mixing-processes/

Producing Adhesives Under Vacuum (n.d.). Retrieved May 2023, from https://hockmeyer.com/blog/articles/producing-adhesives-under-vacuum/