Ultrasound In Paper Manufacturing

Power ultrasound has emerged as a versatile and energy-efficient process technology in modern paper mills. By introducing high-intensity ultrasonic waves into liquid or slurry systems, mills can harness cavitation effects–microscopic bubble formation and collapse – to improve mixing, mass transfer, fiber modification, and contaminant removal. As both virgin fiber production and recycled paper processing face increasing pressure to reduce energy use, water consumption, and chemical demand, ultrasonic technology offers a compelling set of inline, retrofit-ready solutions.

Ultrasound in Paper Manufacturing

In paper manufacturing, ultrasonic systems are primarily applied to improve stock quality, fiber performance, and process stability. One important application is degassing of pulp suspensions. Entrained air in stock can cause watermarks, streaks, and formation defects that directly reduce paper quality. Ultrasonic degassing efficiently removes dissolved and entrained gases from pulp slurries, stabilizing the wet end and helping to prevent visual defects without additional chemicals.
Another major application is the enhancement of fiber fibrillation. Power ultrasound promotes external and internal fibrillation of pulp fibers by generating intense localized shear forces through cavitation. This can partially replace or enhance conventional beating and refining stages. Compared to mechanical refining alone, ultrasonic treatment can achieve similar or improved fiber development while consuming less energy. Importantly, fiber strength is maintained, and in some cases improved, because ultrasound promotes controlled fibrillation rather than excessive fiber cutting. Ultrasonic energy can also assist chemical reactions associated with fiber modification, such as oxidative or bleaching processes, improving reaction efficiency and uniformity.

Ultrasound can further support pulp disintegration, either during the breakdown of wood chips into pulp or during repulping of recovered paper. Cavitation accelerates fiber separation and loosens bonding between fibers, fillers, inks, and coatings, improving pulping efficiency and reducing processing time.

Sonication in the Wet End

Papermaking operations are increasingly recognizing that improvements in wet end performance are driven more by chemical utilization efficiency than by higher additive dosages. As a result, ultrasonic dispersion is gaining attention as an advanced process technology for the controlled activation and homogenization of wet end additives prior to stock addition. High-power ultrasound generates cavitation-induced shear forces that deagglomerate particles and promote uniform dispersion of polymers, fillers, and emulsions in inline process streams. This enhanced dispersion leads to more predictable chemical–fiber interactions, improved retention and sheet formation, and increased process stability, while simultaneously reducing overall chemical demand and energy consumption. Owing to its linear scalability and the availability of industrial-grade sonicator systems from Hielscher Ultrasonics, ultrasonic dispersion has progressed from laboratory-scale studies to full-scale implementation as a technically robust and economically viable wet end optimization strategy.

Read more about the advantages of ultrasonic dispersion in the wet end of paper mills!

Ultrasound in Paper Recycling

In recycling applications, power ultrasound addresses some of the most persistent challenges in recovered fiber processing. One key use is fiber cleaning and contaminant removal. Ultrasonic cavitation helps detach dirt, oils, printing inks, colorants, and lacquer residues from fiber surfaces. In de-inking operations, ultrasound enhances ink particle detachment and dispersion, improving flotation or washing efficiency and enabling higher brightness levels with reduced chemical input.
Ultrasound also contributes to microbial reduction in whitewater systems. By mechanically disrupting microbial cells and biofilms, ultrasonic treatment can lower microbial loads without relying solely on biocides. This supports cleaner process water loops and can reduce odor, slime formation, and biofouling risks.
Another important recycling-related application is dewatering. Ultrasonic energy can improve drainage characteristics of fiber suspensions by modifying fiber networks and reducing bound water. Enhanced dewatering can increase press and wire efficiency, lowering thermal energy demand in subsequent drying stages.
 

Sonication energy vs draining time (in minutes) for nanopaper preparation (corresponding to CNF(1)LA sample).
100 J/ml of sonication energy corresponds to 100 seconds of sonication, etc.
(Study and image: ©Sethi et al., 2018)

Additional Process Applications

Beyond fiber and water treatment, power ultrasound is used for homogenizing and dispersing paper slurries and additives. Ultrasonic homogenization ensures uniform distribution of fillers, pigments, polymers, and functional additives, improving chemical efficiency and product consistency. Ultrasound is also applied in spraying and coating processes, where ultrasonic nozzles generate fine, uniform droplets for precise application of coatings, sizing agents, or functional layers onto paper surfaces.

Inline Integration and Industrial Implementation

A key advantage of ultrasonic technology is that most applications can be implemented inline, allowing mills to retrofit ultrasonic reactors into existing process loops without major redesign. Flow-through ultrasonic systems can be scaled linearly and adapted to specific consistencies, flow rates, and process objectives.
With proper system selection and integration, power ultrasound becomes a flexible process intensification tool rather than a standalone treatment. Equipment suppliers such as Hielscher Ultrasonics support mills in selecting and configuring industrial-grade ultrasonic systems tailored to specific paper manufacturing or recycling challenges.

Improve Paper Quality and Reduce Costs

From improving fiber development and dispersion to enabling cleaner recycling and more stable wet end operation, power ultrasound offers a broad range of applications in paper mills. Its ability to enhance physical and chemical processes while reducing energy, water, and chemical consumption makes ultrasound an increasingly attractive technology for both new installations and retrofits. As sustainability and efficiency continue to shape the paper industry, ultrasonic processing is positioned as a practical and scalable solution for modern papermaking.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

Design, Manufacturing and Consulting – Quality Made in Germany

Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.

Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.