Robert W. Gooding1,2
The screen rotor affects every aspect of pulp screen performance, including power consumption, capacity, fiber loss and debris removal efficiency. Fundamental studies have typically focused on the backflushing pulse induced by the rotor and, in particular, the pulse frequency and strength. More recently, small-scale turbulence and larger three-dimensional flow structures have been determined to be of at least equal significance. The present study reviews some of these fundamental studies and proposes a comprehensive model of the rotor action which embraces both pulsation and non-pulsation effects. Two novel rotor designs are discussed in the context of mill applications. One rotor is a solid-core design. As is typical, elements are attached to the periphery of the rotor to induce pressure pulsations. What is novel is that the leading edge of each element has a waveform to induce three-dimensional flow structures. With this waveform, the rotor is able to achieve higher capacities, or run at lower speeds to save energy, or operate with smaller slots for increased debris removal. A Brazilian mill used this novel rotor technology to achieve a 33% energy saving and reduce reject thickening factor from 3.0 to 1.6. A lower thickening factor reduces fiber loss and enhances runnability. The second rotor is based on foil-type design and has a thicker foil to increase wake turbulence. A dual foil-support design provides a very uniform rotor-cylinder gap and thus a more consistent and effective rotor action. Angled foils and supports ensure strings do not accumulate on the rotor. Mill case studies demonstrate the effectiveness of this rotor design in OCC headbox screen applications where there may be a high level of troublesome debris. The combination of theoretical studies and mill experiences supports a more comprehensive model of rotor performance as well as demonstrating the benefits of the advanced rotor designs.
Keywords: energy, power, pulp screen, rotor, runnability
1. Aikawa Fiber Technologies Inc., Canada.
2. Aikawa AFT do Brasil, Brazil.
Corresponding author:Mathieu Hamelin, Aikawa Fiber Technologies Inc., 5890 Monkland Avenue, Suite 400, Montreal, Quebec, Canada, H2A 1G2. Phone: +1 (514) 481-6111 ext. 298. E-mail: firstname.lastname@example.org
ARTICLE REFERENCES O PAPEL VOL 77 NUM 4 - PP 80-86 - APR 2016