Axisymmetric acoustophoresis for paper pulp concentration

Area of Science:

• Fluid dynamics
• Acoustic engineering
• Chemical engineering

Background:

• Mechanical screening and washing are standard in pulp and paper mills for pulp concentration.
• Environmental and production optimization necessitate alternative methods for pulp concentration (3-6% consistency).
• Acoustic levitation (acoustophoresis) shows promise for efficient pulp concentration and water recirculation.

Purpose of the Study:

• To present a numerical model for acoustophoresis in pulp flow concentration within a pipe.
• To analyze the sensitivity of pulp concentration to various physical and ultrasound parameters.
• To assess the industrial feasibility of acoustophoresis for paper pulp concentration.

Main Methods:

• Modeling pulp flow as a pseudo-homogenous fluid using turbulent Low Re k-ε formalism.
• Simulating spherical pulp particles subjected to acoustic radiation force and Stokes drag force.
• Analyzing parameter influences (particle size, fluid properties, ultrasound parameters) via a parametric study.

Main Results:

• Acoustophoresis effectively concentrates pulp particles at the pipe's center.
• Parametric study identifies optimal conditions for particle deflection and pulp concentration.
• Demonstrated concentration gain up to 15% with potential for industrial application.

Conclusions:

• Numerical modeling validates acoustophoresis as a viable technique for paper pulp concentration.
• The study provides insights into parameter optimization for enhanced efficiency.
• Acoustophoresis presents a promising, environmentally friendly alternative to traditional mechanical methods.