Overview of applications of ultrasonics in the pulp and paper industry

The pulp and paper industry encompasses a broad range of processes from wood harvesting to debarking, pulping, bleaching, papermaking, and converting operations. In relation to these processes and others, several uses of ultrasonics have been investigated. One generally distinguishes two main categories: (a) use of ultrasonic energy in process-related applications, and (b) ultrasonic measurement of pulp and paper materials. Examples of applications in the first category include recycled pulp deinking, pulp refining, and water stream clarification. The second category considers applications such as measurement of pulp consistency and evaluation of paper elastic stiffness properties. The paper proposes an overview of applications in both categories and an analysis of the status of ultrasound in the pulp and paper industry. Also, the use of acoustic radiation pressure to manipulate liquid-suspended particles and laser ultrasonics techniques to probe paper stiffness properties on moving paper are discussed