Refining recycled fiber comes with its own
set of challenges. One must look at the contaminants inherent in the
furnish and the intricacies of developing already refined fiber. If not,
over-refined fiber, short plate life and slower paper machine speeds can
By choosing the correct refiner plate design, refining can maximize
fiber strength development, make the fiber more flexible by hydrating
the fiber, and minimize the freeness drop. The trick is to refine the
fiber to develop strength while limiting the amount of power applied and
not cause a reduction of fiber length and unwanted freeness drop.
What happens when you refine the “already refined” fiber again? The
answer comes from understanding how the recycled fiber was treated in
the past. What was the specific energy applied, refining intensity, and
how much potential the fiber has for developing additional strength.
Various contaminants are found in recycled fiber that complicate the
ability to refine recycled fiber at low intensity. Possible contaminants
are tramp metal, stones, plastic, baling wire and sand, each is a
potential cause of reduced plate life. Excessive bar breakage can be
caused by tramp metal and stone, plastic and baling wire can lend itself
to plugging, and sand/grit can cause accelerated bar wear.
In order to combat these issues, it is
necessary to look at the refiner plate design. Selecting the right
pattern is essential to addressing stock contaminants. Choosing the
correct alloy can determine the best balance between the risk of bar
breakage and wear resistance. For example, J&L’s Reverse Flare™
patterns minimize plate plugging by eliminating the potential to wedge a
contaminant into a groove that narrows toward the outer diameter of the
plate. J&L’s Powercast™ designs allow the use of lower intensity plates
for improved quality and offers improved hydraulic capacity and longer
life through zero-degree draft angle technology.
In addition to the challenges of contaminants, already refined fiber
characteristics are often less than desirable. The recycled fiber’s
strength is reduced due to previous fiber length reduction and
fibrillation. The usual range of applied energy (HPD/T) is less than for
the same fiber in a virgin state. It is necessary to minimize the
refining SEL intensity (W-sec/m) in order to utilize the energy applied
and not generate further fines, fiber cutting, or freeness reduction.
J&L’s Six-Step System Analysis combines the understanding of recycled
fiber with the needs of the paper machine to find the best plate design
that will meet all the specific guidelines for your recycled fiber.
Specific energy must be minimized while still developing the full
potential of the fiber. Intensity also must be minimized as low as
possible to achieve proper fiber characteristics. Contaminants will
dictate the pattern design used to minimize intensity. Consistency
should be considered, and specific freeness drop should be calculated
and compared to objectives for recycled fiber.
When setting the plate parameters, information gathered using the
analysis process is essential. The result will be a plate design
optimized for recycled fiber that has low intensity, doesn’t plug, and
has a long life. The optimum pattern will have the proper groove width,
low Km/rev (Intensity), ReverseFlare design, PowerCast technology and
one of J&L’s low carbon stainless steel alloys. The ReverseFlare design
and PowerCast technology are great solutions for addressing stock
contaminants. J&L’s C90, C91 or C96/C97 alloys provide good wear
resistance and are virtually unbreakable… a great defense against
Click the following link to view J&L’s Six
Step System Analysis process,
Take the challenge out of refining recycled fiber and optimize your
process today. Contact your local J&L representative or
Shawn Berg to set up a free analysis.
J&L Fiber Services, Inc.
809 Philip Drive
Waukesha, Wisconsin 53186
2008 J&L Fiber Services, Inc.