An article that begins on page 14 (and is featured on the cover of this issue) takes an in-depth look at kneading technology as a promising new approach for deinking wastepaper to be used in making various grades of tissue and toweling. Kneading is not really a new technology. It has been around for years and is in limited commercial use globally, though not so much if at all in North America – at least not yet.
Printing and writing (P&W) papers have been and still are the main source of quality wastepaper for making tissue. But with the rise of digital communications in recent years, P&W production has declined significantly, and quantities of graphic papers have fallen in the recycling stream, creating the first stages of a potential tissue fiber crunch that could impact certain away-from-home markets in the not too distant future, especially in North America where most AfH tissue grades are made with recycled P&W paper fiber.
In addition to improving both the quality and yield of recycled furnishes, the kneading process, especially when combined with advanced “vertical washing” technology as described in the article, also has a particularly attractive environmental/sustainability side. With the type of kneader-based recycling operation that Hiroki Nanko of Insight Technology International LLC has set up in his pilot plant operation in Macon, Ga., wastepaper can be very effectively deinked without any chemistry at all, and with attractive yield increases.
In Nanko’s Taizen (Japan) kneader pilot plant, recycled fibers go through a gentle but intensive rubbing motion for a long time (about 10 min), without the use of any deinking chemicals. Friction between the fibers breaks almost all of the fiber-ink bonds, resulting in very small ink particles that are more easily removed in the subsequent vertical washer stage. The flotation deinking process, by comparison, is only efficient for ink particles larger than 10μm.
In the subsequent washing stage, not only the detached ink, but also the ash (fillers and coatings) and fines must be removed. For tissue grades, low ash content is a basic requirement since it interferes with fiber-to-fiber bonding and slows drainage. Fines also need to be removed to improve drainage on the tissue machine. Other technologies such as the DNT washer can achieve this, but cause significant fiber loss in the process. The vertical washer can remove ink, ash and fines without losing long fibers, according to Nanko,
Kneader-based technologies can also be used to pulp non-wood, alternative fibers for tissue production. At the TAPPI Tissue Forum at PaperCon, May 16-18, 2016, in Cincinnati, Ohio, USA, Nanko will examine kneader technologies for processing alternative fibers for tissue and towel production. His presentation is set for Session TF2 from 3:30-5:00 p.m. on May 16.
In his presentation, Nanko looks at a new Alkaline Peroxide Mechanical Pulping (APMP) system based on kneader technology that is proving to be highly effective with non-wood fibers. A wide variety of non-wood plant materials can be pulped with the APMA process, including wheat straw, rice straw, bagasse, bamboo, kenaf, Arundo donax, Miscanthus, switch grass, flax, oil palm EFB, etc.
Non-wood fiber is pulped in the Taizen kneader, in the presence of frictional heat, that softens the lamella lignin between fibers. Chemicals, typically 3 percent NaOH, are added in the kneader, allowing the fibers to be very effectively separated. H2O2 also can be added to make the pulp whiter when it exits the kneader. Gentle chemi-mechanical treatment of the Taizen system keeps the fibers long with no “cutting,” so that the pulp produced is suitable for making tissue.
Editorial Director/Associate Publisher, Tissue360o.
KEN PATRICK, Editorial Director/Associate Publisher
LARRY N. MONTAGUE, President & CEO, TAPPI
ERIC FLETTY, VP Operations, TAPPI
JAN BOTTIGLIERI, Editorial Director, Paper360o
MONICA SHAW, Editorial Director, TAPPI Journal