Pulp & Paper

Foam Control in the Pulp & Paper Industry

When manufacturing pulp, chemicals such as lignin, rosin fatty acids, tall oil fatty acid, and hemicellulose are released in the pulp mill. Chemical additives on the paper machine such as wet strength, dry strength, sizing, carry over from the pulp mill, and other chemical additives are used to make paper. As a result, the chemicals released in the pulp mill and used on the paper machine cause foam throughout the pulp and paper making process. Defoamers are critical to the pulp and paper manufacturing process.

Foam causes:

• Slower production rates
• Poor pulp and paper quality
• Loss of crucial sodium in the pulp mill
• Health and safety problems
• Poor housekeeping
• Plant shutdowns when the foam is too excessive

It is important that an effective defoamer and defoamer program be used throughout the pulp and paper making process.

Pulp Mills

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

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

In general, brown stock washing and pulp mill defoamers 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 to be burned in the recovery boiler.

AMS manufactures an array of defoamers for the pulp mill, which includes brown stock washers, the screen room, and the bleach plant.

Why is Foam Control 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 aforementioned production problems.

Pulp Mill Foam Control Options

Modern brown stock washing defoamers are predominantly fully formulated water-based silicone products, although some oil-based defoamers are still used for special applications that will not tolerate silicone or silicates, such as acetate dissolving pulp.

Brown Stock Washing Defoamers

Defoamers for brown stock are designed to control foam, enhance drainage, and minimize soda loss, and reduce anionic trash carry-over to the paper machine.

Some examples of AMS water-based silicone defoamers specifically designed for brown stock washing include:

• TRANS-2994
• TRANS-2931

AMS also supplies oil-based defoamers for the pulp mill. Some examples include:

• TRANS-7285
• TRANS-7115

Screen Room and Bleach Plant Defoamers

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. AMS has a number of products that are effective in this application.

Examples of AMS screen room and bleach plant defoamers include:

• TRANS-7565 A
• TRANS-7566
• TRANS-7665 C
• TRANS-7668 B
• TRANS-7944

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Paper Machines

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

Controlling paper machine foam allows for smooth operation of the paper making process. Defoamers keep foam in the wire pit and silos, help to maintain good sheet formation, allow the paper machine to run at designed capacity or higher, and help to improve drainage on the paper machine by keeping the entrained air typically at or below 1%.

Why is Foam Control 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 and antifoams 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

Slower production rates and inferior or rejected pulp and paper aren’t the only problems caused by foam. Outside of the pulp and paper mills, other foaming issues can create costly outcomes. Foam is detrimental to the environment and can increase COD (carbon oxygen demand), BOD (biological oxygen demand), and color levels in the effluent.

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

Paper Machine Foam Control Options

Paper machine defoamers are typically water-based or glycol-based products but may include other chemistries. AMS designs its defoamers to have a minimal impact on sizing and a maximum reduction of entrained air.

TRANS-7664 is a water-based defoamer developed as a high-solids concentrate to minimize the shipping of water, which ultimately maximizes its economic benefit. It was designed to be received, or diluted with water prior to use (e.g. in-line dilution), and it requires minimal production equipment to dilute to lower concentrations. This makes it a great choice for resellers looking to add a high-performance, economical paper machine defoamer to their product line.

Effective to use in paper machines, in screen rooms, in effluent systems, or any application requiring a water-based defoamer, TRANS-7664 performs over a wide range of temperatures up to 160 °F (71 °C) so it is effective in high-temperature applications that would prove too challenging for “run of the mill” water-based defoamers.

TRANS-3983 is an ester-based defoamer effective during wet strength runs and for fine paper, liner board, and corrugated media, and can often be utilized at significantly lower dosages compared to other defoamer chemistries.

Paper Machine Colloidal Silica Options

AMS also provides colloidal silica—nano-silica molecules suspended in water. This liquid sol helps direct or enhance the movement of substances in certain processes. For example, colloidal silica can be used in paper manufacturing to extract liquid from the finished paper product more rapidly, letting the paper dry faster while retaining the paper’s strengthening starch content. Other applications include adding anti-slip properties to finished paper products or fines retention during the paper manufacturing processes.

Our colloidal silica products for the paper manufacturing industry include the following:

• AMSol^™ 8 SMX
  • Pulp and paper adhesives
  • Retention aid for fines in paper
• AMSol^™ 30
  • Paper, inkjet, and photo
  • Paper fines retention
• AMSol^™ 50
  • Pulp and paper
    • Anti-slip surface coating

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Paper Coatings

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

Paper Coating Foam Control Options

AMS coatings defoamers comply with 21 CFR 176.200. Examples of these defoamers include:

• AC-24
• TRANS-785

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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 that the effluent is discharged into, and to minimize the chemical impact on the aquatic life in the environment.

Effluent Treatment Foam Control Options

Examples of AMS water-based effluent defoamers:

• AC-WWT-3
• TRANS-7565 A
• TRANS-7665 C

Defoamers for the Paper Industry from Applied Material Solutions

Because paper products have the potential to directly or indirectly come into contact with food, defoamers intended for this application must meet a number of regulatory requirements. At AMS, all of our defoamers meet one or more sections of the FDA paper regulations, including 21 CFR 176.170, 176.180, 176.200 and 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 your finished product meets the highest standards, no matter your location.

Applied Material Solutions (AMS) provides a wide selection of defoamer products to meet your specific needs. Contact us today to learn how we can help with your facility’s defoamer challenges.