Tag Archive: Defoamers

1. Don’t Passover Our Antifoams

   February 22, 2021 9:00 am Leave a Comment

   Many types of foods and ingredients foam during the production process. If foaming is permitted, it can alter the product’s appearance, manufacturing time, quality or performance. Food-grade antifoams and defoamers are used to prevent, control, remove or mitigate foam to ensure high-quality, consistent production.

   Not only do these antifoams have to meet food safety regulations to ensure they’re safe for consumption, but they must also be certified kosher if they’re going to be used in kosher food products. This is especially important for Passover-certified products.

   Meeting Kosher Requirements in Chemical Manufacturing

   Some Jewish people follow precise Biblical laws regarding what they eat. These kosher guidelines are applied to the food itself, the materials and other food items that make contact with the food, and how the food is processed or prepared. There are three categories of kosher food:

   • Dairy: Dairy products must come from a kosher animal, be processed on kosher equipment, and include only kosher ingredients. It cannot be consumed with meat products or produced on equipment that processes meat.
   • Meat: Only meat from kosher animals (those that chew their cuds and have split hooves, such as cows, sheep, and goats, as well as certain domesticated fowl) can be eaten, as long as they are slaughtered and prepared in a kosher environment according to kosher guidelines. It cannot be consumed with dairy or processed on the same equipment.
   • Pareve: These are neutral foods, like fruit and vegetables, fish, eggs, coffee, and more, that can be eaten with meat or dairy. Pareve foods cannot be processed on equipment that also processes meat or dairy, or it is no longer pareve. If it makes contact with dairy, for example, it would be classified as such, and you would not be able to eat that item with meat.

   Food-grade defoamers, antifoams, and treated silicas are usually considered pareve, which allows them to be included in kosher food products.

   Why Kosher?

   Even though only a small percentage of Jewish people in the United States follow kosher laws, it is a top label claim from a consumer standpoint. Even people who don’t follow Jewish dietary practices trust and like to see the kosher label, which is why more than 40% of packaged foods in the country are certified kosher. Many food producers benefit from using kosher materials and ingredients, and manufacturers that serve all aspects of the food industry—including packaging, additives, and more—strive to become kosher certified to meet consumer demand.

   Passover-Certified Antifoams

   Passover, the eight-day Jewish holiday honoring liberation from subjugation in Ancient Egypt, comes with specific dietary requirements that go beyond regular kosher guidelines. For those eight days, leavened products and any food made with spelt, oats, barley, wheat, and rye cannot be consumed—and that includes emulsifiers and additives derived from these grains.

   At AMS, we offer Passover-certified food-grade antifoams. In concert with stringent rabbinical supervision, AMS manufactures kosher products that can be consumed during Passover and throughout the rest of the year. These include:

   • TRANS-10PK: a water-based 10% silicone antifoam
   • TRANS-100PK: a non-aqueous 100% active silicone antifoam compound

   AMS manufactures silicone, non-silicone, and powdered food-grade antifoams and defoamers for use in fermentation, grain processing, fruit and vegetable washing, beverage manufacture, and more. Our kosher- and Passover-certified products meet the strict requirements mandated by Jewish dietary law, and we’re proud to offer these antifoams to our customers.

   Contact us to learn more about how our food-grade antifoams can be a solution to your foaming problem.

2. What to Look for in a Foam Control Supplier

   January 11, 2021 8:07 am Leave a Comment

   Antifoams and defoamers are vital for the safe, efficient operation of processes in a multitude of industries. Finding an experienced foam control supplier can save a great deal of hassle, as they are able to provide expert solutions catered to the unique needs of your project. Here are a few of the key factors to take into consideration when choosing a foam control supplier.

   Industry Experience

   The best foam control supplier will have experience working in your industry, as this ensures that they can meet the needs of the project and provide accurate guidance. Foam control products serve several important roles in the following industries:

   • Chemical Manufacture. Used to stabilize chemical formulations and maintain production rates.
   • Ethanol Production. Aids the fermentation process.
   • Industrial Process Water. Increases efficiency and protects against hazardous conditions.
   • Paints, Inks, Coatings, and Adhesives. Speeds up production and prevents defects in paint and coating, craters in adhesives, and promotes even ink flow.
   • Landfill Leachate. Enables wastewater to be properly filtered or distilled.
   • Metalworking Fluids. Controlling foam allows for better lubrication and cooling.
   • Pulp and Paper Processing. Improved production flow and rates, allows for better chemical recovery, allows for better sheet formation and lower entrained air on paper machines.
   • Water Treatments. Prevent hazardous and slippery conditions, prevent cross-contamination and improve the overall treatment of water.
   • Food Processing. Prevents excessive foaming in processing, blending and bottling applications.

   Wide Variety of Antifoams & Defoamers

   Antifoams and defoamers are not “one size fits all” products. It is ideal to work with a supplier who provides a wide array of antifoam and defoamer options so that they can adapt to meet the needs of any type of application. A good selection will include the following:

   Silicone Antifoams

   This option will include products such as water-based antifoam emulsions, specialty silicone antifoams, and non-aqueous silicone antifoam compounds.

   Non-Silicone Antifoams

   There are a wide range of non-silicone antifoam options. These types of antifoams can be based on water, surfactants, organic solvents, or oils, including mineral and vegetable oils. Non-silicone antifoams may also include polymers and esters of various types.

   Powdered Defoamers

   Powdered defoamers are available in both food-grade and tech-grade options.

   Food-Grade & Tech-Grade Options

   Antifoams and defoamers intended for use in the food industry or in certain industrial settings must follow stringent regulations. Depending on the final application, these products may be organic, kosher and halal certified, or FDA and/or BfR compliant.

   Knowledge of Considerations for Proper Use

   In order to get the full benefit of antifoams and defoamers, the supplier must have an in-depth understanding of proper usage. Even something as simple as adding slightly too much antifoam may result in frustrating and time-consuming issues. Additionally, the supplier must be familiar with the regulations within a range of industries in order to ensure that they provide safe antifoams and defoamers appropriate to the desired application. 

   The following are some other key considerations a supplier should be aware of.

   Chemical and Processing Compatibility

   A reliable foam control supplier will be able to help choose the optimal antifoam or defoamer for your project, including providing samples for testing. This makes it possible to test for compatibility, as different products will vary in their performance depending on the specifics of the application.

   Proper Application

   The proper application technique will vary depending on the process. Foam control products will be most effective when they are added during a point that allows them to best disperse into the foaming liquid. In some cases it may be beneficial to add them at multiple points. Knowledgeable suppliers can provide guidance on when and how to add antifoams or defoamers for the best results.

   Acceptable Levels of Foam

   Not all processes require complete elimination of foam. Your supplier should be able to help you understand how much foam is acceptable within your process, so that you don’t spend more than you need to on foam control products.

   Partner with Applied Material Solutions

   Choosing the right foam control supplier ensures smooth operation for your business. At Applied Material Solutions, we are dedicated to providing high quality foam control solutions to resolve a range of processing challenges. To learn more about our capabilities, or to partner with us for your foam control needs, contact our experts today.

3. How Do Antifoaming Agents Work

   December 15, 2020 8:00 am Leave a Comment

   For most fluid systems, foam control is a challenge to overcome. Pure liquids do not foam. In an aqueous system, contaminants such as surfactants, proteins, small solid particulates will form a stable foam in water. Foam will significantly reduce system efficiency where foam or entrained air is undesirable. To prevent foam problems and keep the process running smoothly, many applications will use an antifoam or defoamer.

   What Is an Antifoam?

   

   The chemistry of defoamers and antifoams are often similar, their main difference being timing of application. Defoamers are used to control existing foam while antifoams are used to prevent the formation of foam.

   Typically, antifoams and defoamers are inert chemicals. They are comprised of a liquid, such as mineral oil, silicone, and/or hydrophobic polyol, and a hydrophobic solid, such as hydrophobic silica, ethylene-bis-stearamide, fatty acid, and/or fatty alcohol. An effective antifoam must be insoluble in the medium it is defoaming or it will not work. However, the antifoam must not be so incompatible as to cause deposition issues.

   How Do Antifoaming Agents Work?

   Two things are necessary for an antifoam or defoamer to work:

   1. An Entry Coefficient greater than zero
   2. A Spreading Coefficient greater than zero

   These are expressed in the simple algebraic expressions below:

   1. E = 𝑦w/a +  𝑦w/o +  𝑦o/a
   2. S =  𝑦w/a –  𝑦w/o –  𝑦o/a

   Where:

   • 𝑦w/a = surface tension of the foaming liquid
   • 𝑦w/o = interfacial tension between the defoamer and the foaming liquid
   • 𝑦o/a = surface tension of the defoamer

   The antifoam enters the interface between the air and the lamella, the bubble wall. The antifoam enters the bubble wall which is bridged by the antifoam droplet. This is called “bridging of the film,” and as the antifoam spreads the bubble wall is thinned. Once the antifoam has entered the lamella, a lens is formed by the antifoam on the lamella and begins to spread. The progressive spreading process reduces the thickness of the lens, the shape of which is altered by movements in the foam. Stresses occur until the lens breaks and the foam lamella ruptures. The resultant film is considerably less elastic than the surfactant film, which previously stabilized the lamella. This destabilization facilitates rupture of the lamella.

   

   Antifoam Benefits

   Foam can be highly damaging to fluid system functions and other industrial processes. It leads to operational impacts like:

   • Inconsistencies in product density
   • Damage to machinery or equipment used in production
   • Interference with separation or coating processes, diminishing product quality
   • Pump cavitation

   Foam can cause problems across the entire production workflow due to downtime needed for foam related issues. Antifoams work to minimize the operational consequences of foam by preventing foam before it becomes a problem, thus saving time and money. 

   Antifoam Applications

   Antifoams are used in a variety of applications.

   Food Processing and Agribusiness

   Food and agribusiness are susceptible to foam problems due to the levels of organic material processed, pressure, mixing, chemical reactions, and other process-related factors. Typical applications include:

   • Grain separation and processing
   • Fermentation
   • Fruit and vegetable washing and processing
   • Meat and poultry processing
   • Dairy products, beverages, brine systems, and more

   Water Treatment

   Foam control is critical in maintaining the safety and efficiency of municipal and industrial water treatment facilities. Antifoams prevent air or waterborne foam from developing during numerous steps of the treatment process. Antifoams are used in applications such as:

   • Aeration basins
   • Boiler water treatment
   • Clarifiers
   • Cooling towers
   • Equalization tanks
   • Evaporative water treatment
   • Final effluent
   • Landfill leachate
   • Manure pits
   • Membrane Bioreactors
   • Moving Bed Biofilm Reactors
   • Sequencing Batch Reactors

   Paint, Inks, Coatings, & Adhesives (PICA)

   Foam is formed due to the rigorous mixing, grinding, and chemical reactions involved in the production of PICA materials. Unmanaged foam leads to increased production times, reduced operational efficiency, and physical product defects like craters, fisheyes, and pinholes. To prevent these setbacks, antifoam is used in applications including:

   • Polymer/pigment grinding
   • Package filling
   • Shearing or spraying

   Chemical Manufacturing

   Antifoams and other foam control agents are used extensively throughout all stages of the chemical manufacturing process to regulate foam production. 

   Cleaning Compounds & Processes

   Foam control products play a critical role in the efficacy of both the production of cleaning products and the products themselves. They are applied in different capacities in manufacturing and use of:

   • Laundry detergents
   • Carpet cleaners
   • Personal care products
   • Soap and detergent

   

   Applied Material Solutions Antifoaming Agent

   Applied Material Solutions offers silicone and non-silicone antifoam solutions for a variety of applications. Our team is here to optimize the timing, location, and frequency of adding antifoam to your process. For more information on foam formation, associated problems, and preventative measures, download our eBook now. If you need help selecting an antifoam for your process or to see samples, contact us today.

4. What Is a Defoamer?

   December 1, 2020 9:02 am Leave a Comment

   For most fluid systems, foam control is an interesting challenge to overcome. Pure liquids do not foam or will not form a stable foam. In an aqueous system, contaminants such as surfactants, proteins, small solid particulates will form a stable foam in water. Foam will significantly reduce the efficiency of a given system where foam or entrained air is undesirable. To prevent these problems with foam, many applications will use defoamers to keep the process running smoothly.

   What Is a Defoamer? How Does It Work?

   Defoamers are one of two categories of foam control agents, the other category being antifoams. The chemistry of defoamers and antifoams are often similar. The main difference is the intended use: defoamers are used to control existing foam and antifoams are used to prevent the formation of foam.

   Typically, defoamers are inert chemicals. Defoamers are comprised of a liquid, such as mineral oil or silicone, and a hydrophobic solid, such as hydrophobic silica, ethylene-bis-stearamide, fatty acid, and/or fatty alcohol. An effective defoamer must be insoluble in the medium it is defoaming.

   Two things are necessary for a defoamer to work: (1) an Entry Coefficient greater than zero, and (2) a Spreading Coefficient greater than zero. These are expressed in the simple algebraic expressions below:

   • E = 𝑦w/a+𝑦w/o-𝑦o/a
   • S = 𝑦w/a-𝑦w/o-𝑦o/a

   Where:

   • 𝑦w/a = surface tension of the foaming liquid
   • 𝑦w/o = interfacial tensions between the defoamer and the foaming liquid
   • 𝑦o/a = surface tension of the defoamer

   The defoamer enters the interface between the air and the lamella, the bubble wall. Once the defoamer has entered the lamella, a lens is formed by the defoamer on the lamella and begins to spread. The progressive spreading process reduces the thickness of the lens, the shape of which is altered by movements in the foam. Stresses occur until the lens breaks and the foam lamella ruptures. The resultant film is considerably less elastic than the surfactant film which previously stabilized the lamella. This destabilization facilitates rupture of the lamella. It is important to note the bubble wall is bridged by the defoamer droplet. This is called “bridging of the film.” As the defoamer spreads, the bubble wall is thinned.

   Defoamer Benefits

   Defoamers are necessary in many industries because of the issues created by foam. Stable foam makes it harder for a fluid system to function as intended and causes product loss and potentially unsafe conditions in a facility. Other issues caused by foam include:

   • Variations in density that make it difficult to generate consistent package weights
   • Direct damage to equipment, resulting in the need for repairs and downtime
   • Interference with certain separation or coating processes, diminishing the quality of the product
   • Pump cavitation

   The defoamer type varies depending on the application and the materials used to make the defoamer. Defoamers can be mineral oil based, silicone based, glycol based, and polyol based. Once the appropriate tests are done to determine which type of defoamer best suits the needs of a given application, foam will no longer impede production.

   Defoamer Applications

   Many industrial processes have turned to defoamers to solve their problems. These foam control products are used in industries such as:

   • Food Processing and Agribusiness. Fermentations, fruit and vegetable washing and processing, and meat and poultry processing all use defoamer to fight foam caused by organic compounds present in these facilities.
   • Water treatment. Defoamers are used in multiple water treatment applications to remove air or waterborne foam.
   • Pulp & paper. Defoamer aids in eliminating foam caused by the chemical processes involved in pulp and paper production.
   • Paint & coatings. Defoamer eliminates foam caused by mixing, grinding, and chemical reactions involved in producing paint and coatings. 
   • Chemical manufacture and cleaning compounds. Defoamer is used regularly in the chemical and cleaning compound manufacturing processes to remove foam.

   Applied Material Solutions’ Defoaming Agent

   Applied Material Solutions specializes in effective foam control technologies tailored specifically to fit your process. Our antifoams and defoamers are created with individual industrial applications in mind, taking into account the unique conditions and contaminants present in each. To learn more about our comprehensive foam control plans, read our ebook or contact us today.

5. Top 4 Tips for Proper Antifoam Use

   September 16, 2020 3:24 pm Leave a Comment

   The formation of foam in aqueous processes and products—such as flume water for the transport of vegetables—can hinder or halt many industrial processing operations. Antifoams are chemicals which prevent the formation of foam, whereas defoamers control existing foam. The right antifoam must be applied properly to prevent foam formation and avoid additional problems in the production process.

   The following article provides Applied Material Solution’s top tips regarding the proper use of antifoam products.

   Survey the System

   Before applying an antifoam to your operation, it’s important to thoroughly survey system processes to determine where and when the antifoam would serve most effectively.

   • Is it an aqueous or non-aqueous system?
   • What is causing the foam?
     • Protein
     •  Starch
     • Soap formation
     • Is the foam solid stabilized?
   • Get water flow diagrams and process flow diagrams when available, or draw your own. You must understand the process and what is being made. You need to know:
     • Where the water came from.
     • Where the water is going.
   • For batch operations, what are the batch sizes? For continuous operations, what is the production rate?
   • What is the pH of the system? Take note of any pH changes throughout the production process.
   • Are there any chemical restrictions to the system?
   • What is the temperature of the system? Take note of any temperature changes throughout the production process.
   • What are the points of high and low tabulation?
   • Locate the points where air may be released.
   • Locate the points where air can be introduced.
   • Are there any filtration membranes used in the process?
   • Are there any regulatory requirements involved?

   Evaluate the Point of Addition

   

   The place and time at which antifoams should be added depends on the specifics of the process. However, as a general rule, antifoams should be applied at the point that allows for maximum dispersion through the foaming liquid and often prior to the onset of foaming. To obtain the best results, some processes may necessitate the addition of antifoam at multiple points.

   Peristaltic and low-flow metering pumps are effective tools for automating the dispensing operation. Facility workers and/or vendors can set up pumps to add a predetermined concentration of antifoam/defoamer per minute, thus optimizing the performance of the foam control agent.

   Test the Antifoaming Agent in Advance

   Antifoams are available in multiple types of formulations of varying chemistries, each of which performs differently. When choosing a new antifoam product, it is important to understand the process and where foam poses an issue. It is critical, as previously stated, to survey the system.

   While the answers to the Survey questions can help ensure the appropriate selection of the antifoam, thorough testing is also essential for determining the antifoam’s compatibility and performance within a particular application. When testing the antifoaming agent, simulate the expected operating conditions, especially the temperature, by using a medium that is similar—if not identical—to the actual foaming medium. When possible, the actual foaming medium is best.

   Determine How Much Foam Is Okay

   While some processing operations can handle a small amount of foam, others require complete foam elimination. In either case, the end user must determine whether a potential antifoaming agent can successfully control foam without undermining the quality of the product or process. As long as operation continues as expected, some foam in the process would just be an appearance issue, yet present no real issue or problem to the production operation.

   Quality Antifoam Products from Applied Material Solutions

   At Applied Material Solutions (AMS), we offer an extensive selection of antifoams and defoamers across a range of silicone and non-silicone formulations.

   Our silicone antifoam products include:

   • Non-aqueous silicone antifoam compounds
   • Specialty silicone antifoams
   • Water-based antifoam emulsions

   Our non-silicone antifoam products include:

   • Oil-based antifoams
   • Surfactant-based and polymer-based antifoams
   • Ester-based antifoams
   • Water-based antifoams

   AMS can assist customers with the selection of an optimal antifoam for their unique process. Once an antifoam solution is chosen, we can also help optimize the location, frequency, and antifoam dosage to ensure the best results.

   For more information about our antifoaming products and services, contact us today.

    

6. Defoamers for the Pulp & Paper Industry

   June 9, 2020 8:13 am Leave a Comment

   Foam in the Pulp & Paper Industry

   Lignin, rosin and fatty acid soaps, and hemicellulose are commonly formed during the pulping process, resulting in high levels of foam. Excess foam will negatively impact process and equipment efficiency, leading to inferior or rejected paper. Defoamers and antifoams are a necessity to the entire paper making process.

   Why Are Defoamers Necessary in Pulp Mills?

   The black liquor formed during pulp production has a strong tendency to foam. The foaming tendency is due to the fact that 12% to 15% of black liquor solids are comprised of NaOH, Na2S, tall oil soap, rosin soap, lignin, hemicellulose and other organic compounds. Defoamers are necessary for pulp washing, screening, and bleaching. Foam problems cause safety issues and poor housekeeping along with the mentioned production problems.

   Why Are Defoamers Necessary for Paper Machines?

   

   Foam is often generated through chemical interactions on the paper machine combined with the rapid motions involved in the paper making process. Some of these interactions may involve chemistries from:

   • Retention aids
   • Fillers
   • Sizing
   • Fines
   • Dry strength
   • Wet strength

   When paper machines generate foam and entrained air, it adversely affects production rates and paper quality. Defoamers facilitate the process of paper making and help to prevent the following issues:

   • Bacteria buildup
   • Poor sheet formation
   • Drainage issues
   • Pump cavitation
   • Poor housekeeping
   • Safety problems
   • Pulp consistency

   Slower production rates and inferior or rejected pulp and paper aren’t the only problems caused by foam. For both pulping and papermaking, other foaming issues can create costly outcomes. Foam is detrimental to the environment and can increase effluent COD, BOD, and color levels in the effluent. An excess of foam also creates workplace safety hazards and raises production costs. A few ways foam can increase operational costs:

   • Slower production rates
   • Increased deposits
   • Higher energy costs
   • Increasing makeup chemical costs
   • Increasing chemical demands on the paper machines

   Using defoamers makes the pulp and paper production process safer, more environmentally friendly, and increases overall production efficiency, all while reducing production costs.

   Defoamer Applications

   A variety of defoamer types serve different defoamer applications. Common applications include:

   • Brown stock washing and washing in general
   • Bleaching
   • Papermaking
   • Coatings
   • Effluent treatment

   Pulp Mill

   Utilized in brown stock washing, screen rooms, and bleach plants, pulp mill defoamers are effective at high temperatures and withstand high acid and alkaline conditions of the pulp mill process. Most mills use water-based silicone defoamers.

   However, pulping processes involving finished products, such as acetate dissolving pulp, will not tolerate silicone and/or silica. These processes use oil-based defoamers.

   Brown stock washing and pulp mill defoamers in general increase production rates by increasing washing efficiency. Increased washing efficiency is accomplished by improved drainage on the washer. Better washing reduces the pulp mill carry-over to the paper machine and will prevent deposits by washing the deposit forming compounds out of the pulp. This way, the deposit-causing compounds leave with the washed out liquor.

   Water-based and glycol-based defoamers may be used to control foam in both the screen room and bleach plant. Simultaneously, these defoamers improve drainage and bleaching efficiency by reducing entrained air.

   Papermaking

   

   Paper machine defoamers are typically either water-based fatty alcohols or glycol-based products.

   Paper machine defoamers are necessary in order to run at or above the designed capacity of the machine. A good paper machine defoamer program will reduce entrained air in the head box and on the formation wire which further increases the drainage on the paper machine. It will also help reduce steam cost on the dryers over and above the capacity of retention and drainage aide programs.

   Coating

   In small amounts, defoamers are added to coating to prevent fish eyes, give an even coating film, and avoid streaks and holes. In addition to defoamers, other coating additives may include:

   • Wetting agents
   • Lubricants
   • Dispersants
   • Water-resistant agents
   • Water-retention and rheology modifiers

   Effluent Treatment

   Defoamers control the foam in effluent systems. Better foam control results in better-treated water before it is released into the environment. Foam control in the effluent system also prevents dried foam from forming on top of the effluent pond, which can be blown into the environment. Water based defoamers are typically used in this application to avoid oil slicks on the waterway the effluent is discharged into.

   Applied Material Solutions Defoamers for Pulp & Paper

   As paper products have the potential to become indirect food additives, defoamers intended for this application must meet a number of regulatory requirements. At AMS, all our defoamers meet one or more sections of the FDA regulation 21 CFR 176.170, 176.180, 176.200, 176.210.  AMS also has defoamers which meet global regulations such as Chinese GB 9685 and German BfR. Our experts are well-versed in federal and international regulations and can help ensure you meet the highest standards, no matter your location.

   AMS defoamers provide a significant reduction of foam and entrained air, and when properly applied, there is little impact on paper machine sizing. They’re an excellent choice for resellers looking for an economical, high-quality defoamer with a low environmental impact. Contact us today to find your ideal defoamer solution.

7. What You Need to Know About Brown Stock Washing Defoamers

   April 1, 2020 12:47 pm Leave a Comment

   Brown stock washing is a complex, dynamic process in which dirty wash water or weak black liquor (dissolved organic and inorganic material obtained from the pulp cooking process) is separated from the pulp fibers¹. The organic materials are recovered for their fuel value and the inorganic material is recovered for the sodium content to regenerate NaOH.

   Under-designed capital equipment can be augmented using chemical enhancements. In the case of brownstock washers, the application of defoamer is required to improve mat drainage and to control foam to enable overloaded washers to wash efficiently; this also allows pulp from the digesters to flow continuously to the bleach plant and/or the paper machine.²

   Washing efficiency directly correlates to pulp cleanliness. Cleaner pulp results in better chemical recovery, lower bleaching costs, fewer deposition issues, and more consistent pulp is sent to the paper machine.

   The following article provides an overview of brown stock washing deformers, outlining how they work, key benefits, and the types available.

   How Do Brown Stock Washing Defoamers Work?

   Brown stock washing defoamers have two purposes. First is to control the foam and prevent vats from overflowing onto the floor causing loss of product (the pulp) and housekeeping issues, while providing drainage on the washers which provides cleaner pulp and improves washing efficiency.

   Second is to recover valuable spent liquor. The black liquor is recovered for the fuel value and to regenerate NaOH by recovering sodium from the washing process.

   The foam level in the vat is not an indication of how well the defoamer is performing. If the foam is not spilling over on to the floor it is then purely cosmetic. The real indication of the defoamer’s performance is how well the foam is being released from the fiber. When the foam is released from the fiber it allows drainage.

   It is important to understand the defoamer must have a positive Entry Coefficient and a positive Spreading Coefficient. These are expressed in the following equations:

   (Entry Coefficient) E = γw/a + γw/o – γo/a

   Where γ is the surface tension or interfacial tension in dynes/cm²

   (Spreading Coefficient) S = γw/a – γw/o – γo/a

   Where “w” is water, “o” is oil, and “a” is air

   

   The equations briefly explained:

   The Entry Coefficient is equal to the surface tension of the black liquor + the interfacial tension between liquor and oil (i.e. the defoamer), minus the surface tension of the oil. This allows the defoamer droplet to enter the monolayer at the air/water interface.

   The same is true for the Spreading Coefficient: black liquor – the interfacial tension between liquor and oil, minus the surface tension of the oil. This causes the defoamer droplet to spread along the air/water interface forming a defoamer “lens.”

   Hydrophobic particles within the defoamer facilitate the entering of the oil droplet into the surfactant monolayer at the air/water interface. With a positive Entry Coefficient, the defoamer droplet enters the surfactant monolayer at the air/water interface. Once the droplet is there, the positive Spreading Coefficient allows the defoamer droplet to spread across the monolayer forming a lens. The shape of the lens is altered by the movements in the foam. Stress occurs until the lens breaks and the foam lamella ruptures. This results in foam control throughout the pulp mill.

   On fiber, larger and larger bubbles are formed until the buoyancy of the bubble overcomes its adherence to the fiber and floats away from the fiber. The foam on the fiber causes an apparent increase in the fiber’s size. As the foam is removed from the fiber the apparent fiber size decreases creating a shorter path for the water to travel through the mat. The shorter path for the water results in improved drainage.

   It should be noted, when using defoamers in brown stock washing operations, it is important to understand that the defoamer must perform a balancing act, where the defoamer is sufficiently compatible in the black liquor to not cause deposition, yet incompatible (insoluble) enough to perform efficiently on the washer. A defoamer is never soluble in the medium it is defoaming.

   Benefits of Brown Stock Washing Defoamers

   A good defoamer program should facilitate production of the pulp, and add economic value to the pulp mill process by addressing the following:

   • Housekeeping issues
   • Increased chemical recovery
   • Reduced energy costs
   • Lower bleaching costs
   • The reduction of the environmental impact of the mill
   • Fewer safety hazards
   • Increased production rates
   • Increased quality of the end product
   • Lower reject rates³

   Types of Defoamers for Brown Stock Washing Operations

   Brown stock washing defoamers come in a variety of formulas and strengths to suit the needs of different pulp and paper processes. The types available include:

   • Oil-based defoamers
   • Water-extended, oil-based defoamers
   • Concentrated or water-based silicone defoamers
   • Polymer-based defoamers

   Oil-based and water-extended oil-based defoamers are less common than they were 15 to 20 years ago. They are used primarily in mills where silicone and/or silicates are not allowed.

   Brown Stock Washing Defoamer Solutions From AMS

   Brown stock washing defoamers are essential to both product and process quality. As a leading manufacturer and supplier of foam control products, Applied Materials Solutions has an extensive range of products suitable for use in these pulping applications. Our product offerings include:

   • Water-based silicone defoamers: (e.g. TRANS-2994 and TRANS-2931)
   • Oil-based defoamers: (e.g. TRANS-7285 and TRANS-7115)

   For additional information about our brown stock washing defoamers and other product solutions, contact us today.

    

   References

   Brownstock washing – A review of the literature, TAPPI Journal January 2014, Ricardo B. Santos and Peter W. Hart; page 9

   Brownstock Washing – Practices and Fundamentals. TAPPI Press, Peter Hart and Michael Brown, Chapter 15, page 545

   Brownstock Washing – Practices and Fundamentals. TAPPI Press, Peter Hart and Michael Brown, Chapter 15, page 562

    

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