Note: Descriptions are shown in the official language in which they were submitted.
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R ~RSE CENTRIFUGAL CLEANING
OF PAPER MAKING STOCK
background of the Inventlon
Centrifugal cleaners have been employed for many
vears in the paper industry for removing small particles
of higher specific gravity than paper fibers from slurries
of paper making fiber, especially waste paper stocks.
In centrifugal cleaners used for that purpose, in
what is hereinafter referred to as "conventional
centrifugal cleaning teehnique," the discharge outlet at
the apex (tip) of the cylindrical-conical vessel is
relatively small in comparison with the inlet and accepts
outlet, e.g. 1/8 inch in diameter as compared with 5/8
inch diameters for the other two ports in a conventional
c]eaner 3 inches in diameter. In such conventional
c]eaning operations, therefore, the reject discharge
through the apex outlet is correspondingly small in
comparison with the aecepts flow, e.g. 3% and 97% by
vo]ume respeetively.
In comparatively reeent years, there has been an
ncreasing use of centrifugal cleaners to separate good
paper fibers from contaminants of closely similar or lower
specifie gravity such that they cannot be readily
separated by conventional centrifugal eleaning teehnique.
In general, cleaners for such "reverse"
centrifugal eleaning have been made by modifying the
construetion and/or operation of a conventional cleaner to
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provide operating conditions which cause the good fiber to
be discharged through the apex outlet as the accepts flow
while the lights are discharged as reject through the base
(top) outlet which is the accepts outlet in conventional
centrifugal cleaning. For an extended discussion of prior
and up dated reverse centrifugal cleaning developments,
reference is made to Seifert et al. U.S. Patent No.
4,155,839 wherein the present inventor was a joint
patentee.
Summary of the Invention
A primary object of this invention is to provide
an improved centrifugal cleaner particularly adapted for
reverse centrifugal cleaning wherein both of the discharge
ports, for the two fractions into which the cleaner
separates the feed flow, are located adjacent the apex end
of the cleaner, so that there is no reversal of flow
within the cleaner as in past practice for both
conventional and reverse cleaning.
More specifically, in a reverse centrifugal
cleaner in accordance with the invention, the apex outlet,
which heretofore has been used as the outlet for the
"heavy" fraction, whether it be reject in conventional
cleaning or accepts in reverse cleaning,
becomes the outlet for the light fraction which
constitutes rejects in reverse centrifugal cleaning.
The cleaner of the invention is provided with a second
discharge outlet in its side wall, and preferably at the
downstream end of the conical portion of the interior of
the cleaner, which is then the discharge outlet for the
heavy fraction constituting the accepts flow in reverse
centrifugal cleaning.
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Thus in the practice of the invention, there is a
through flow of the feed stock from the base end to the
apex end of the cleaner, with no reverse flow through the
central part of the cleaner as in both conventional and
reverse cleaning as heretofore practiced. This feature is
of particular value in the application of the invention to
cyclone assemblies or "canister" cleaners wherein multiple
individual centrifugal cleaners are assembled in parallel
relation within a common canister whose interior is
divided into feed, accepts and reject chambers which
connect respectively with the inlet and discharge ports of
all of the individual cleaners.
A specia' feature of the invention resides in the
construction and assembly of the outlet for the light
fraction, which comprises a tube releasably locked into
position within the cleaner in such manner that in the
event of blockage of the outlet for the heavy fraction
from the cleaner body, this tube can be temporarily
retracted to effect relief of the blockage.
Brief Description of the Drawings
Fig. 1 is a view in axial section of a reverse
cleaning unit in accordance with the invention;
Fig. 2 is a fragmentary view similar to Fig. 1
and showing a modified inlet port arrangement;
Fig. 3 is a fragmentary view illustrating the
application of the invention to a canister-type cyclone
assembly;
Fig. 4 is a view similar to Fig. 1 showing a
reverse cleaning unit incorporating a modified discharge
tube arrangement for the light fraction; and
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Fig. 5 is a fragmentary exploded isometric view
illustrative details of the mechanism for releasably
locking discharge tube of the cleaner in Fig. 4 in
operative position.
Description of the Preferred Embodiments
A typical reverse centrifugal cleaner indicated
generally at 10 is shown in Fig. 1 as housed in a casing
11 which has its interior divided by partitions 12 and 13
into a supply or feed chamber 15 at one end of the casing
11, a reject chamber 16 at the other end of the casing,
and an accepts chamber 17 located intermediate the
chambers 15 and 16, each of these chambers being provided
with its own port 20, 21 and 22, respectively.
The cleaner 10 comprises a main tubular vessel 25
the interior of which is cylindrical over a portion of its
length and frusto~conical throughout its remaining
portion. A housing 26 is threaded on the smaller end of
the vessel 25, and a tubular tip piece 27 is secured
within the housing 26 by a retainer nut 28 as shown. The
cylindrical bore 29 within the tip piece 27 forms a
continuation of the interior of housing 25 which leads to
the discharge port 30.
he housing 26 has one or more radially or
tangentially arranged ports 31 therethrough which provide
a total flow area larger than that of the port 30 leading
into the interior of the reject chamber 16. The lower end
of the housing 26 is closed by a threaded cap 33 which
extends through an opening în the end wall 34 of the
casing 11 and clamps the casing wall against the end of
housing 26 to the casing wall. The base end of the vessel
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25 is provided with a closure pluq 35 which is threaded
;nto the end OL the vessel 25 and also clamps the
parti.tion 12 ketween itse].f and the vessel 25.
A helical. groove A0 on the outer surface of the
plug 35 forms the inlet port to the interior of the
cleaner vessel 25, the spiral configuration of this groove
assuring that stocl; to he cleaned wlll be delivered from
the inter;.or of the feed chamber 15 to the interior of the
vesset 25 with a suhstantial circumferential flow
component. mhe plug 35 i.s otherwise solid, but it
includes a cylindrical extension 41 on its inner end which
acts in part as a vortex finder but more particularly as a
stabilizer for the air core which forms during operation
of the cleaner. the groove 40 may he duplicated around
the periphery of plug 35 to increase the effective inlet
port size as needed.
In addition to the outlet port 30 at its apex,
the cleaner ]0 is provided with one or more accepts outlet
ports 44 at the lower end of the frusto-conical portion of
vessel 25. the outlet ports 44 are preferably arranged
tangentially of the vessel 25, in the same direction as
the circulatory movement of stock wi.thin the vessel, and
these ports lead into the chamber 15 within the casing
11. Preferab~.y, the tip piece 27 includes a cylindrical
extension 45 which projects upstream therefrom into the
interior of the vessel 25 sufficiently far so that it at
least radially overlies the outlet port or ports 44 and
thus serves as a baffle preventing direct flow therefrom
to the i.nterior of tip piece 27 and the outlet port 30,
and the upstream end of the extension 45 thus effectively
ls the apex outlet port of the vessel 25.
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The inlet construction shown in Flg. 1 has
special advantage -n that it assures that all stock
entering the cleaner will contlnue to flow with a
substantial component lengthwise of the cleaner, rather
than having some heavy partic].es tend to orhit the inlet
end of the cleaner and thereby wear away its inner wall
surface. mhe invention can be practiced, llowever, with
the alternative inlet construction shown in Fig. 2, which
is essentially the same as i.n the above noted patent Mow
4,155,839.
It includes a plug 35' which differs from plug 35
only in having no groove 40 i.n lts outer surface.
Instead, an inlet port 40' of rectangular shape leads
tangentially through the wall of vessel 25 as shown in
patent No. 4,155,839. The position of the partition 12
wi.th relation to the vessel 25' therefore has to be
shifted so that the port 40' will be open to the feed
chamfer 15, so that partition 12 is to the left of port
40' in Fig. 2, and the partition 12 is therefore clamped.
between a shoulder 46 on the vessel 25' and a nut 47
threaded Oll the vessel 25' in opposed relation with the
shoul.der 46~
In the use of a cleaner of the construction
descrihed in connection with Figs. 1 and 2, the slurry to
he cleaned is delivered to the supply chamber 15 at the
appropriate pressure to cause it to enter the inlet port
40 or 40' at the desired flow rate-and velocity as
descried in patent No. 4,155,839, to develop within the
vessel 25 centrifugal force conditions causing vortical
separation of the slurry into an outer fraction containing
the large majority of the paper fibers, an inner fraction
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containing the large majority of light contaminant
particles, and commonly also an innermost air core.
The outer fraction will travel down the
frusto-coni.cal portlon of the interior of vessel 25 until
it reaches the accepts port or ports 44, and it will exit
through those ports to the accepts discharge chamber 17
anfl its outlet port 22. The inner fraction will enter the
upstream end of the extension 45 and travel therethrough
and through the interior of the zip piece 27 and the
outlet port 30 to the reject discharge chamber 16 and its
port 21.
Separati.on of the heavy and light fractions which
form within the cleaner as they discharge therefrom is
readily controlled hy regulating the respective discharge
flows from the chambers 16 and 17, by means such as valves
50 and 51 on the lines 52 and 53 leading from the ports 21
and 22. Determination of the proper flow splits from the
two discharge chambers will usually involve some
experimentation, depending upon the nature of the feed
stock, the feed flow rate and the feed pressure, and
satisfactory results have been obtained under test
conditions with this split varied from approximately equal
flows from both discharge chambers to approximately 90
from the accepts chamber 17 and 10% from the reject
chamher ~.6.
As a more specific example of the practice of the
invention, test runs were made with a cleaner constructed
as shown in Fig. 2 wherein the inlet port 40' had a flow
area of 0.625 sq. in., the minimum flow area of the apex
outlet port was 0.785 sq. in., and there were two outlet
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ports 44 each of a flow area of approximately 0.25 sq.
in. In a test run wherein the feed flow rate was 50
gallons/m-nute at 30 p.s.i.g., satisfactory results were
ohtained with flows from the discharge chambers 16 and 17
of approximately 26 and 24 gallons/minute. wetter results
were obtained with a feed flow rate of 68 g.p.m. at a feed
pressure of 40 p.s.i.g., and with the flows from the
discharge chamber 16 and 17 at the rate of 54.5 and 13.5
g.p.m. respectively.
mhe invention has also been tested with a cleaner
constructed as shown in Fig. l wherein the inlet port flow
area was 0.625 sq. in., the minimum flow area of the apex
port was 0.306 sq. in., and the accepts port 44 was
rectangular, similarly to the inlet port 40' in Fig. 2,
with dimensions of 1.5 inches x 3/8 in. and a flow area of
0.47 sq. in. Highly satisfactory results were obtained
with a Feed flow at 80 gallons/minute and a pressure of 45
p.s.i.g. with the flow from the chambers 16 and 17 at the
rates of 8.5 and 71.9 gallons/minute.
As pointed out hereinabove, the invention is
especially applicable to cleaner assemblies of the
canister type, as illustrated in Fig. 3, wherein the
canister 60 has lnternal wa ls 61 and 62 dividing its
interior into a central chamber 63 and opposite end
chambers 64 and 65. r~ultiple cleaners lO of the
construction described in connection with Fig. l are shown
as mounted within the canister 60, with the interior walls
ol and 62 and end wall 66 providing the same mounting and
partitlonlng functions as the partitions 12 and 13 and end
wall 34 in Fig. 1.
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The operation of a canister cleaner assembly of
the invention as shown in Fig. 3 is the same as already
described in connection with Fig. 1. The chamber 64
serves as the feed chamber and is provided with an
appropriately located port for receiving the inlet flow of
feed stock, and the chambers 63 and 65 become the reject
and accept chambers as described in connection with the
chambers 16 and 17 in Fig. 1. It should also be noted
that the canister cleaner of Fig. 3 can in effect can be
made double-ended by doubling the length of the canister,
installing a second set of partition walls and cleaners
opposite the set shown in Fig. 3, and then using chamber
64 as the feed chamber for both sets of cleaners.
The modified cleaner 100 in accordance with the
invention shown in Fig. is mounted in a canister casing
110 provided with an end head 111 and having its interior
divided by a partition 113 into a supply or feed chamber
115 and an accepts (heavies) chamber 117. Each of these
chambers is provided with its own port 120 and 121
respectively, but each cleaner 100 has its own outlet port
for reject tlights) from the casing 110 provided by a tube
123 as described in more detail hereinafter.
The cleaner 100 comprises a main tubular vessel
125 of essentially the same construction as the vessel 25
except that it is extended somewhat longer at its apex
end, and it has no outlet port in its side wall. The tip
housing 126 is threaded on the smaller end of the vessel
125 in clamping relation with the partition 113, and it
also serves as a mounting for the tube 123, the bore 130
of which forms the discharge port for lights from the
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cleaner. A guide member 131 within the housing 126 has an
axial bore 132 sized to receive the tube 123 freely
therein. The outer portion of the tube 123 passes through
a center bore in the threaded cap 133 which clamps the end
of the housing 126 to the end head 111 of the casing 110.
The bore 132 of the part 131 is provided with a
circumferential groove for receiving an O-ring 135 sized
to form a seal between the bore 132 and the tube 123. In
addition, releasable locking means are provided between
the tube 123 and the part 131, namely bayonet locking
means comprising radial projections 136 on the tube 123
which are sized to cooperate in locking relation with the
slotted and grooved portions at the outer end of the part
131. As shown, when the tube 123 is inserted in the part
131 with its projections 136 aligned with the slots 137 in
the end of part 131, the projections 136 will seat on the
bottoms of those slots, and then a quarter-turn of the
tube will effect locking engagement of the projections 136
in the grooves 138.
The feed inlet port to the interior of the vessel
125 is provided by one or more tangential slots 140 of
rectangular shape in the wall of the vessel adjacent its
base end, which is closed by a threaded plug 142. An
extension 141 on the plug 142 acts both as a vortex finder
and as a stabilizer for the air core which forms during
operation of the cleaner, and it may be solid as shown or
of the hollow cylindrical form shown in Figs. 1 and 3.
The lock.ing projections 136 on the tube 123 are
in predetermined spaced relation with the inner end of the
tube so that when they are locked in the grooves 138, the
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inner erd of the tube is located at or within the apex end
of the vessel 12S so that it defines an annular discharge
port 144 from the interior of the vessel 125 into the
annular chamber 145 surrounding the tube 123 on the
upstream side of the part 131. A plurality of ports 146
in the wall of the housing 126 lead from this chamber 145
into the accepts chamber 117 and then to the port 121.
The operation of the cleaner assembly shown in
Fig. 4 is essentially the same as described in connection
with Fig. 1, with the centrifugal force conditions
developed within the vessel 125 causing vortical
separation of the feed slurry into an outer fraction which
is discharged through the annular port 144 and an inner
fraction which is discharged through the tube 123. The
lS major advantage provided by this cleaner is that in the
event of plugging of the annular port 44 by solid
material, virtually immediate relief of the blocking can
be effected by manually retracting the tube 123 from
outside the casing 110 for a long enough interval for the
flow to clear the apex end of the vessel 125, and then
returning the tube 123 to its operating position
established by the locked relation of the parts 136-138.
In order to take advantage of this feature of the
invention, when multiple cleaners 100 are incorporated in
a single canister casing 110, all of the tubes 123 project
to the outside of the canister, and each is provided with
its own flexible tubing 150 for conducting the reject flow
therefrom to a common collection receiver. In order to
facilitate the use of the tubes 123 for relieving
blockage, each tube has its tubing 150 secured thereto by
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a clamp 151 which also acts as a handle by which the
associated tube 123 can be twisted to unlocked position,
temporari3.y retracte2, and then returned and locked in its
operative position.
In a typica], example of the cleaner shown in
Figs. 4-5 wherei.n the inner diameter of the cyl.indrical
portion of the vessel 125 is three inches, the inner
diameter of the apex end of the vessel is 1.1~ inches,
there are four ports 146 one inch in diameter, the tube
123 has an outer diameter of 0.625 inch and an inner
diameter of 0.500 inch, and it is preferahly beveled at
its upstream end to minimize turhulence in the flow
therepast. on addition, the space between the inner end
of the cap 133 and the downstream end of the member 131
lS provides for at least one inch of axial movement of the
tube ].23 to assure complete opening of the apex end of the
vessel, 125 ~7hen the tube is retracted. At the same time,
ahutting of the locking projections 136 against the end of
cap 133 limits retraction of tube 123 sufficiently so that
it is not retracted beyond the O-ring 135, and thus the
unit remains sealed against leakage past tube 123.
While the process and forms of apparatus herein
described constitute preferred embodiments of this
invention, it is to be understood that the invention is
not limited to this precise process and these forms of
apparatus, and that changes may he made therein without
departing from the scope of the invention.
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