A tank with an efficient rotor in the bottom used to repulp bales of pulp and mix the pulp fibers with water prior to making paper.
Non-integrated paper mills must purchase pulp in the form of dried one-ton bales. These bales go into the repulper, which is a tank with a mixer in the bottom. A horizontal drive motor is connected by shaft to a right-angle gearbox with the output shaft driving the repulper rotor. Bales are added to water in the repulper tank and the rotor blades draw the dried pulp below the water surface, defiber the pulp bales, and mix the fibers with water before the pulp is used to make paper.
Energy-efficient repulper rotors are available and can reduce annual repulper energy use. The most efficient rotor design may depend on pulp characteristics such as fiber length (freeness) and percentage of hardwood versus softwood. It is crucial that the rotor does not degrade product (paper) quality.
The Wisconsin Focus on Energy conducted tests at Wausau Paper to determine the energy savings due to using an efficient Voith HM instead of the baseline HOG rotor. They investigated energy savings, defibering time, freeness and final product attributes. The efficient rotor defibered the pulp furnish to the same degree as the conventional rotor with no effect on product quality. Metering established a 23% reduction in energy use. Most rotors run continuously, but while operating only 60% of the time, the 500-horsepower motor-driven rotor at the Wausau Paper plant produced savings of 560,000 kWh/year. Because repulper rotors are rebuilt or replaced periodically, facility staff have the opportunity to upgrade with new efficient rotors.
Status:
Baseline Description: HOG Repulper Rotor Baseline Energy Use: 2434780 kWh per year per unit
Wisconsin Focus on Energy conducted tests at Wausau Paper to determine the energy savings due to using an energy-efficient Voith HM repulper rotor instead of using the baseline HOG rotor. Metering established a 23% reduction in energy use after the new repulping rotor was installed. The 500 hp motor-driven rotor at the Wausau Paper plant operated an estimated 74% of the time (many operate continuously). Baseline energy use was 2,434,780 kWh/year with energy savings exceeding 560,000 kWh/year.
"Typical" Savings: 23% Energy Savings Reliability: 3 - Limited Assessment
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Jerry Aue, 06/15/2009. Voith Hight Efficiency HM Rotor Energy Data: A Repulper Rotor DEsign Case Study Proceedings of the 27th Industrial Energy Technology Conference
Klaas Kramer, 01/01/2009. Energy efficiency Opportunities in the U.S. Pulp and Paper Industry Lawrence Berkeley National Laboratory
Bill Fineran, 06/01/2006. Energy-Efficient Repulper Rotor Blade: Case Study at Wausau Paper – Rhinelander, WI 2006 Forum on Energy
Wisconsin Focus on Energy, 07/08/2010. Energy-Efficient Repulper Rotor – Best Practices Wisconsin Focus on Energy