Defoamer Series Part 2 – The Proper Set-Up of a Defoamer Application: A Few Topics Worthy of Consideration

Foam, while appearing innocuous, can significantly disrupt industrial processes, impacting efficiency, product quality, and equipment lifespan. The selection and application of a defoamer is not merely a “set it and forget” operation. Instead, it is a critical process that requires the careful consideration of several technical parameters.  If not given the proper consideration, a poorly configured defoamer application can lead to excessive chemical usage, increased operational costs, environmental issues, and, fundamentally, a failure to control foam.  To ensure a high probability of success, the following provides a high-level summary of some of the key considerations that are taken into account when setting up and optimizing a defoamer application.

Defoamer Selection (Matching the Chemistry to the System)

The foundation of any effective defoamer application starts with selecting the right chemical additive.  Defoamers are broadly classified by their chemical composition (ex. silicone-based, oil-based, water-based, fatty ester-based, etc.) and have specific properties that can provide enhanced performance over another or simply be more conducive to the operating conditions in which it is being applied.

• Product Compatibility – The chosen defoamer must be chemically compatible with the environmental process conditions (pH, temperature, shear forces) and the finished goods being produced. For example, silicone-based defoamers are often frowned upon in the auto industry because of they tend to inhibit paint adhesion on metal surfaces. Similarly, the pulp and paper industry has a tendency to migrate towards the application of fatty esters as they are more compatible in the presence of organics and highly effective in brownstock washing.
• Overall Performance – Defoamer products should be evaluated based on the speed at which they eliminate the foam (“initial knockdown”) and persistence or time taken to maintain its control (“hold down”). Some processes require rapid knock down at a specific point, while others demand continuous suppression over an extended period of time.  Bench-scale testing using water from foam generating sections of the process is an indispensable means of determining if a particular product can meet either of those requirements.
• Oil or Water-Based Formulations – Sometimes the decision to use an oil-based additive or water-based material can be significant. For example, oil-based defoamers are known for being relatively cheap, readily dispersible and highly successful when applied to highly agitated systems.  That being said, under the right conditions, they also have a tendency to leave behind undesirable product residues.  Under these circumstances, a water-based additive, because of its enhanced compatibility and solubility, may be the better choice.
• Regulatory Considerations – Depending on the application, certain defoaming additives are only approved for use as long as their concentration does not exceed a certain threshold. For example, within the food processing industry, silicone-based defoamer additives must be limited to 10 ppm within or as a residue, on any “ready-for-consumption” products.  In some cases, like in the dairy industry, no silicones are allowed at all.

Injection Point (Location, Location, Location)

The physical location of where a defoamer additive is introduced is paramount to its performance.  Contrary to popular demand, these additives are not magic bullets and must be injected into a location that will give them sufficient time and opportunity to work.

• Optimal Location – The ideal injection point is often a location of high shear or agitation immediately upstream of where foam generation is most problematic. Proper dispersion and mixing will ensure the defoamer additive can do its job.
• Avoid Dead Zones – Introducing a defoamer into a static tank or a “dead zone” within a piping array can promote poor dispersion/mixing and an unnecessary increase in product consumption to achieve the desired result.
• Multiple Points: For complex systems with several foam generation points, multiple injection locations may be necessary. For example, in production of potato chip, foam generation is observed at many locations as potatoes proceed from bulk washing, skin removal, slicing and secondary washing to the friers. As the addition of a defoamer additive at the front end of the process will not carry through, multiple injection points are required.

Injection Equipment and Dosing Strategy (Ensuring Reliability, Precision and Control)

It goes without saying, the injection equipment used to feed defoamer products must be robust and reliable.  This is because many of defoamer additives in use today are highly viscous and will not get injected into a process unless the right equipment is used.

• Pump Selection – Peristaltic or high-viscosity diaphragm pumps are a good choice when looking to deliver precise and consistent volumes. Having the ability to proportionally feed chemistry based on flow or some other process/operating variable should also be considered.  Being able to tie a pump (or injection system) it into a PLC/DCS would be beneficial in the long run.
• Control Methods – As noted above, consider some form of automation as a means of control. A simple manual setup is often a good starting point, but integrating foam sensors (conductivity or optical probes) that trigger a dosing pump on demand can optimize usage and ensure consistent foam levels. This kind of “feedback loop” or “proportional feed integration” will often result in significant cost savings.
• Product Dilution or the use of Carrier Streams – Depending on the product used, there may be a need to either dilute (make-down) the product or provide a carrier stream. Some defoamers perform better when pre-diluted with clean, compatible water, while others can be applied neat.  Dilution should always be performed carefully and within a short timeframe before use to prevent emulsion instability or microbial growth in the diluted product.  Always check the manufacturer’s recommendations regarding how the defoamer additive should be applied.
• Suction and Discharge Lines – Keep suction lines as large as possible (diameter), piped with short runs and as few bends as possible. This will ensure adequate flow with minimal restrictions on the suction side.  If a diaphragm pump is used, consider the installation of a backpressure valve.  This will ensure proper function of the check valves within the liquid end of the pump and ensure dosing accuracy.

Storage and Handling (Maintaining Product Integrity)

A defoamer’s performance can degrade if stored improperly. The physical integrity of the chemical must be maintained right up to the point of application.

• Temperature – Store products within the manufacturer’s recommended temperature range. Extreme cold can cause crystallization or separation of components (ex. fatty ester emulsions), while extreme heat can break and emulsion or cause chemical degradation. Where applicable storage containers and injection tubing at the application site should also be protected from excessive heat or freezing.
• Agitation – Certain defoamers, particularly emulsions, will benefit from gentle mixing if they have been stored for extended periods. This will ensure the product is homogenous and ready for use when placed in service.

As one can appreciate, setting up an effective defoamer application requires a holistic approach that goes well beyond simply acquiring a pump and injecting the chemical.   Paying attention to details like proper chemical selection, selecting strategic injection points, using the right equipment and proper product handling will go a long way in helping you achieve success.  Luckily, Aquasan is available to support your needs with a product portfolio and the technical expertise that is needed to conduct the necessary audits and ensure all factors critical to your success are considered.

At Aquasan, your success is how we measure ours!