Note: Descriptions are shown in the official language in which they were submitted.
CA 02337419 2001-O1-15
WO 00/11264 PCT/US98/17162
REFINER PLATE WITH CHICANES
Background of the Invention
The present invention relates generally to disc refiners for
lignocellulosic material. More particularly, the present invention relates
to refiner plate segments for such an apparatus.
In high consistency mechanical pulp refiners, the wood fibers are
worked between two relatively rotating discs on which refiner plates are
mounted. The plates usually have radial bars and grooves. A large
volume of steam is produced between the plates as a result of this
refining work. For effective refining, the fibrous material must be
retained between the plates on the bar surfaces despite the high velocity
of the flowing steam, and the enormous centrifugal forces. Typically,
the steam is exhausted via the grooves, and dams are provided in the
grooves to interrupt material flow and thus improve the retention time
of the material in the refining region.
In a typical refiner plate with radial bars and grooves, the bars
provide impacts or pressure pulses which separate and fibrillate the
fibers. The grooves enable radially directed feeding of the fibers and
steam extraction. Near the perimeter of the plates, high radial steam
flow and high centrifugal force both act to sweep the fibers outwardly
from between the plates prematurely, thus reducing the refining
effectiveness. The flow restrictions due to a small gap between
opposed plates and fiber-filled grooves result in a steam pressure peak
between the plates, located radially inward from the perimeter. This
pressure peak is a major source of the refining thrust load, and can
induce control instability at high motor loads. It is thus desirable that
the steam generated during refining be discharged from the refining
region as quickly as possible, white retaining the pulp within the region
as long as possible.
CA 02337419 2004-04-07
68355-61
2
Summary of the Invention
Briefly stated, the invention includes a refiner
plate which is constituted from a plurality of refiner plate
segments, each of the segments formed with a pattern
including a refining zone having a plurality of radially
disposed rib segments. Each of the rib segments has
oppositely disposed radially inner and outer ends. A
chicane extends obliquely from the outer end of an inner rib
segment to the inner end of an outer rib segment to form a
zig-zag shaped bar. Adjacent bars define a plurality of
zig-zag shaped grooves alternating with the bars. The
chicanes define at least one substantially arcuate line
extending radially and laterally across at least the
refining zone.
In a preferred embodiment, the refiner has
relatively rotating opposed discs. Each of the discs has an
outer edge, a refining zone, and carries plates formed by
multiple plate segments. Each plate segment comprises
multiple radially disposed rib segments, each having
oppositely disposed radially inner and outer ends. A
chicane extends obliquely from the radially outer end of an
inner rib segment to the radially inner end of an outer rib
segment to form a zig-zag shaped bar. Multiple zig-zag
shaped grooves alternate with the bars, such that the
chicanes form multiple arcuate lines extending radially and
laterally across the refining zone.
The above-described refiner provides for
practicing a method for directing the flow of feed material
and steam, generated during refining of a lignocellulosic
material. In the method, feed material is directed up the
sloped leading face of the chicane to the refining gap with
a centrifugal force generated by rotating at least one of
CA 02337419 2004-04-07
68355-61
3
the refining discs for comminution of the lignocellulosic
material on the grinding surface of the bar. A first
portion of the steam is directed through the grooves to the
outer edge of the discs by centrifugal force, thereby
removing the first portion of the steam from between the
discs. A second portion of the steam is directed through
the refining gap intermediate adjacent lines of chicanes to
the outer edge of the discs by centrifugal force, thereby
removing the second portion of the steam from between the
discs.
It is an object of the present invention to
provide a refiner plate for the face of a refiner disc,
which facilitates the removal of steam while retaining the
pulp in the refiner region to achieve satisfactory pulp
quality.
This object is achieved by, in a preferred form,
by providing chicanes that form a zig-zag flow path for most
of the steam generated during the refining operation. A
sloping leading face on each chicane directs the flow of the
lignocellulosic material into the gap between the refiner
plates for comminution on the grinding surfaces of the bars.
Although the upwelling of lignocellulosic material into the
refining gap restricts flow of steam through the gap in the
vicinity of the chicanes, the chicanes are positioned to
form arcuate lines extending to the peripheral edge of the
disc. Consequently, steam may flow in the gap to the edge
of the disc in the arcuate corridors formed between the
lines of chicanes.
Accordingly, the object of achieving good fiber
quality with good steam management is accomplished by
CA 02337419 2004-04-27
'68355-61
3a
providing chicanea that direct the fiber into contact with
the grinding aur~aee while providing a plurality of floret
paths for directing steam through the xefining gap to the
peripheral edge of the disc. 2o the i.nventar~s knowledge,
no one previously provided chicanes that are distributed in
a manner that facilitates steam flow in the refining gap.
other objects and advantages of the invention will
become appar$nt from the drawings and specification.
Brief pescription of fife Drawings , ,
The present invention may be better unoterstood and its numerous
objects and advantages will become'apparent to those skilled in the art
by reference to the accompanying drawings in which:
Figure 1 is an elevation view of a refiner plate segment in
accordance with the invention;
' 15 Figure 2 is an enlarged section view along line 2-2 of Figure 1;
Figure 3 is an enlarged elevation view of Area 3 of Figure 1;
Figure 4 is an elevation view, partly broken away of a refiner plate
including a plurality of the refiner plate segments in accordance with the
invention;
Figure 5 is an elevation view o~# an alternate embodiment of the
refiner plate segment of Figure 1; and
Figure 6 is an enlarged elevation view of Area 6 of Figure 5.
Detailed Descriptiprr of the Preferred Embodiment
With reference to the drawings wherein like numerals represent
like parts throughout the several figures, a refiner plate in accordance
with the present invention comprises a plurality of refiner plate
segments 1 d which are securable to the franc face 12 of a substantially
circular refiner disc 14 (Figure 2). Although in the illustrated
embodiment each segment 10 has twa zones 16, 18 each having a
34 differently oriented set of patterns, each segment 10 could alternatively
have a single or three ar more zones having respective~sets of patterns
lFigure 1 ). '
CA 02337419 2001-O1-15
WO 00/11264 PCT/US98/17162
4
The plate segments 10 are attached to the disc face 12, in any
convenient or conventional manner, such as by bolts (not shown)
passing through bores 20. One end of the bolt engages the disc 14 and
at the other end has head structure bearing against a countersunk
surface. The disc 14, only a portion of which is shown, has a center
about which the disc rotates, and a substantially circular periphery. The
refiner plate segments 10 are arranged side-by-side on the face 12 of
the disc 14, to form a substantially annular refiner face, shown generally
at 22 (Figure 2). The face 22 forms a portion of a refiner region, when
confronting another refiner plate (not shown) carried by another disc.
With reference to Figure 1, each refiner plate segment 10 has an
inner edge 24 near the center of the disc, an outer edge 26 near the
periphery of the disc, and leading and trailing side edges 28, 30 which
abut the trailing and leading side edges 30, 28 of adjacent refiner plate
segments 10', respectively (Figure 4). The remainder of this description
will refer to a single plate segment 10, but it should be understood that
all the segments which define the annular plate, are preferably
substantially similar. The bars 32, 34 and grooves 36, 38 extend
substantially radially, i.e., radially, or parallel to a radius of the disc,
or
obliquely at an acute angle to such a radius. The plate segment 10 has,
on its face, at least one, and preferably two or three, distinct patterns
of bars and grooves between the bars, whereby material to be refined
can flow in the grooves in the general direction from the inner edge 24
to the outer edge 26 of the plate segment 10, 10' .
A first or inlet zone 16 has a multiplicity of bars 34 and grooves
38 between adjacent bars 34, all of which extend substantially in the
radial direction. This pattern is especially adapted for receiving wood
chips, wood pulp, or the like and performing an initial refining operation
thereon to reduce the size of the material and funnel it radially outward
into a second, refining zone 18. The refining zone 18 has a multiplicity
of bars 32 and grooves 36 between adjacent bars 32, which also extend
CA 02337419 2001-O1-15
WO 00/11264 PCT/US98/17162
in parallel, substantially radially. A third, outer zone (not shown) may
be provided between the refining zone 18 and the outer edge 26 of the
plate. As shown in Figure 1, each zone 16, 18 may comprise a plurality
of fields, where each field has a uniform pattern. In the embodiment
5 shown in Figure 1, the segment has two fields in each zone. The
patterns promote the flow of steam radially outward to the outer edge
26 of the disc 14 and radially inward to the inner edge 24 of the disc 14
for evacuation while retarding the flow of material to ensure that the
material is fully refined.
Since the disc 14 and plate rotate, the partially refined material
is directed, as a result of centrifugal force, radially outward. Substantial
quantities of steam are also generated in the refining zone 18 producing
a steam flow with high radial velocity. Especially with relatively large
discs, the centrifugal forces acting on the steam and partially refined
chips increase dramatically as the material moves farther and farther
radially outward. Although it is highly desirable that the steam be
quickly exhausted from the refining region, it is essential that the
partially refined fibers not be prematurely exhausted along with the
steam. This condition is influenced by the radial pressure profile along
the disc face 22 due to steam generated by the refining at high
consistency. Since the pressure peak is between the inner and outer
edges 24, 26 of the plate, the steam flows forward (radially outward)
from the outer side of the pressure peak and backward (radially inward)
inside the pressure peak, against the material feed.
In a first embodiment of the invention, the refining zone 18 of the
refiner plate segment 10 includes a plurality of radially extending first rib
segments 40. With reference to Figure 3, each first rib segment 40 is
connected at its radiaily outer end 42 to the radially inner end 44 of the
next outer first rib segment 40' by a chicane 46. Each chicane 46
comprises a second rib segment that extends obliquely in the direction
of disc rotation 48 from the inner first rib segment 40 to the outer first
CA 02337419 2001-O1-15
WO 00/11264 PCT/US98/17162
6
rib segment 40' to form a radially extending zig-zag bar 32. With
further reference to Figure 2, the inner side 50 of each chicane 46
slopes from the top 52 of the chicane 46 toward the adjacent chicane
46' to form a ramp face 54.
The grooves 36 formed between adjoining ribs 32 define a zig-zag
path substantially across the refining zone 18 for the movement of
fibers. The lignocellulosic material traveling in the groove 36 is drawn
into the corner of the chicane 46 and up the ramp face 54 of the
chicane 46 by centrifugal force. The lignocellulosic material is therefore
directed into the space or gap between the opposing refiner plates for
additional comminution. The zig-zag path therefore retards movement
of the lignocellulosic material, preventing material from exiting the
refiner without having being sufficiently refined. The majority of the
steam, which is less affected by the centrifugal force, continues
traveling in the groove 36 to the periphery of the plate where it exits the
refiner.
With reference to Figure 1, the chicanes 46 define a series of
substantially arcuate lines 56. In the embodiment shown in Figure 1,
the radially innermost end 58 of the lines 56 define an arc segment 60
positioned intermediate the outer edge 26 of the plate and the junction
of the inlet and refining zones 16, 18. Each of the lines 56 extends
from the arc segment 60 in the direction opposite to the direction of
rotation 48 of the disc to the outer edge 26 of the plate such that the
arc formed by the line of chicanes 46 has a substantially uniform radius
from a point P. The chicanes 46 of the present invention cause an
upwelling of feed material that constricts the plate gap in the vicinity of
the chicanes 46. However, steam generated during the refining
operation may flow radially through the corridor 82 between the lines
56, 56' of chicanes 46. Alternatively, the inner most end of the lines
of chicanes 46 may be positioned at the junction of the inlet and refining
zones 16, 18 and the lines may not extend to the outer edge 26.
CA 02337419 2001-O1-15
WO 00/11264 PCT/US98/17162
7
In the embodiment shown in Figures 5 and 6, interrupted bars 84
may be disposed intermediate pairs of zig-zag bars 86, 88. The
interrupted bars 84 are formed by providing a gap 90 between the
radially outer end 92 of an inner rib segment 94 and the radially inner
end 96 of an outer rib segment 98. The gaps 90 are disposed
intermediate the chicanes 100 of the zig-zag bar pair 86, 88 and
therefore extend obliquely in the direction of disc rotation 48.
With further reference to Figure 4, the radially outer end 62 of
each line 56 of chicanes 46 that terminate on the trailing side edge 30
of a refiner plate segment 10 is positioned adjacent the radially inner end
63 of a line 56 of chicanes 46 on the leading side edge 28 of the
adjacent refiner plate segment 10'. Consequently, the line of chicanes
56 may extend across two refiner plate segments 10, 10' to provide a
continuous line from the arc segment to the outer edge 26 of the plate.
While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. For example, the
present invention may also advantageously implemented on a three zone
segment. Accordingly, it is to be understood that the present invention
has been described by way of illustration and not limitation.
