Energy Efficient Paper Recycling contaminants, form bubbles that float to A Novel Unit the surface, and the foam containing the Operation particles can be selectively removed. to Remove Benefits for Our Industry Hydrophobic and Our Nation Broad use of the BNP in U.S. paper mills Contaminants could significantly improve papermaking machine productivity and product quality. Bubble Nucleation Process separates Key benefits include the following: and removes stickies and pitch in pa- permaking operations • Stickies and pitch-related problems result in paper machine downtime, lost production, and product quality issues. Recovered paper entering paper recycling BNP use could significantly reduce the mills contain hydrophobic contaminants costs of papermaking from recovered called “stickies” that significantly paper. hinder paper making productivity. These • The potential energy savings is contaminants are pressure sensitive estimated to be 7 Trillion Btu per year adhesives (PSA), wax, polyvinyl acetate, if all U.S. recycling mills implement and plastics found in recycled paper. The the BNP. sources of these contaminants include ad- dress labels, postage stamps, envelopes, • BNP could eliminate the use of book bindings, and binders used in inks polluting chemical solvents and high and coatings. pressure showers used to clean deposits from wires and felts in papermaking Hydrophobic contaminants from a brown Stickies and pitch (resins from wood) stock mill water sample floating near the machines. Other environmental benefits accumulate in the pulp white water surface of the Bubble Nucleation Process include a reduction in water consump- and eventually agglomerate and form Tube. Photograph courtesy of Doshi & tion and sludge production. deposits on papermaking machine rolls, Associates, Inc. and the USDA Forest Products Laboratory wires, felts and dryer surfaces. Expensive • An economical means to remove stick- chemicals to coagulate particles, screens, ies could lead to increased recovery of white water and provide a visual online and other processes used today are not paper by U.S. paper mills. It could also very effective at removing particles less warning of the build of hydrophobic reduce the volume of rejected contami- particles. A commercial VAF unit could than 100 microns in size. Periodically, nated paper products. the paper machine has to be shut down to be useful to many paper mills, increasing remove the deposits with toxic cleaning the efficiency and competitiveness of the solvents. In addition, residual stickies Applications in Our U.S. paper industry. cause holes in paper boards and tissue, Nation’s Industry reduced paper quality, and problems in BNP could offer significant advan- Project Description the machines that print on the paper. tages over other methods and flotation Project partners will develop a novel unit processes used commercially today to operation, BNP, to selectively agglomer- This project will develop a new unit remove hydrophobic contaminants (e.g., ate pitch and stickies particles without the operation called Bubble Nucleation dissolved air flotation (DAF), dispersed use of any toxic chemicals (thus reducing Process (BNP) to remove hydrophobic air flotation or froth flotation, cavitation costs and the environmental footprint of contaminants from paper mill process air flotation, electro-flotation, centrifugal this process). Researchers will design streams without the use of expensive flotation). BNP does not have many mov- and build both a batch and a continuous chemicals. When the pressure is reduced ing parts so it should be relatively easy unit for laboratory testing and mill trials. to the slurry containing fibers, water, to install and operate. A small scale unit Diverse parameters will be evaluated to and hydrophobic contaminants, dis- could be used to monitor paper machine calibrate the magnitude and duration of solved gas nucleate on the hydrophobic ADVANCED MANUFACTURING OFFICE ADVANCED MANUFACTURING OFFICE vacuum, retention time in the vessel, and dissolved gases (air, carbon dioxide and Project Partners the flow rate to maximize agglomeration others), and fiber content. Doshi & Associates, Inc. and removal of hydrophobic particles. Appleton, WI Results will be used to design a com- Results will be used to design and Principal Investigator: Mahendra Doshi mercial unit that will be useful for many operate a continuous laboratory-scale Email: [email protected] paper mills as well as other manufactur- unit. Removal efficiency will be tested extensively on standardized synthetic ing processes requiring the removal of USDA Forest Products Laboratory process water samples and mill samples. hydrophobic contaminants. Outcomes Madison, WI will be characterized in terms of stick- A pilot-scale unit with proper process controls will be constructed and installed ies removal efficiency (SRE) and paper For additional information, reject ratio. The removal target is 80% at a mill to automate the unit to the of hydrophobic particles in the synthetic extent possible and verify performance, please contact process water and 60% in the industrial including maximizing agglomeration and David R. Forrest process water. separation of micro stickies and other U.S. Department of Energy hydrophobic contaminants. A commercial Advanced Manufacturing Office Phone: Barriers unit will be designed to demonstrate (202) 586-5725 • Many different types of hydrophobic performance at scale Email: [email protected] contaminants exist and the concentra- Milestones tion in the pulp white water entering the papermaking machine varies. This two-year project began in April 2015. • Dissolved air and carbon dioxide in • Construct a laboratory-scale batch the process water hinders paper quality BNP unit and complete testing of by interfering with good fiber-fiber mill samples at optimized conditions bonding and may also lead to pin holes (Completed). in the finished sheet of paper. • Design, construct, and test a • The presence of fibers in the process laboratory-scale continuous BNP unit water complicates the measurement of (Completed). stickies. • Design, construct, and test a pilot- • Determining the amount of process wa- scale continuous BNP unit achieving ter that needs to be treated to enable the contaminant removal targets (2016). smooth operation of a paper machine. Commercialization • The amount of acceptable stickies The continuous pilot-scale unit will be in the paper depends on the type of built and operated at the USDA Forest product. Products Laboratory in compliance Pathways with U.S. mill regulations and needs. Commercial vendors will be invited to A batch BNP unit will be built to the mill to observe the operating BNP demonstrate the vacuum design, stick- unit. Results will be used to design a ies removal in the float separator, and full-scale commercial unit that is ap- the remaining water. To determine the plicable to many paper mills as well as specifications for optimal performance, other manufacturing processes requiring experiments and statistical analysis will the removal of hydrophobic contaminants be conducted to evaluate the effect and from water streams. interaction of the following parameters: temperature, magnitude of vacuum, time, pH, filler (clay and calcium carbonate), bicarbonate concentration, turbidity, For more information, visit: manufacturing.energy.gov DOE/EE-1264 • April 2016.