Note: Descriptions are shown in the official language in which they were submitted.
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NONCXRCU~AR REJECTS OUTLET
FOR CYCLONE SEPARATOR
Background of the Invention
The present invention relates to apparatus
5 for separating suspensions of solid particles in
fluids, including both gases and liquids/ into light
and heavy fractions, and in particular to the
separation of undesired particles from paper pulp
slurries.
The use of vortex or cyclone cleaners for
separating sand, grit, bark particles, and shives
~rom cellulose fibers in a paper pulp slurry is now
well known~ In general, such cleaners include an
elongated chamber of circular cross-section, either
15 cy1indrically shaped or somewhat tapered. The pulp
slurry to be cleaned is introduced under pressure
into one end of the chamber through a restricted
tangential inlet so that ~ high velocity vortex is
developed along the length of the chamberO The
20 vortex is typically of a velocity high enough to
form a centrally-located axial gas core in the
chamber. The end of the chamber opposite the inlet
is tapered and forms a relatively small diameter
apex discharge outlet for the denser and larger
25 particle rejects portion of the pulp slurry.
Acceptable Eibers, which are of a relatively lower
density and are located near the inner portion of
the vortex, reverse their direction of flow adjacent
the tapered end of the chamber and flow upwardly to
30 be withdrawn through an axial outlet at the larger
diameter end oE the chamber.
Generally, a cyclone separator system
includes several stages coupled in series, with each
stage including several separators connected in
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parallel~ having common inlet and outlet chambers.
The second stage ~reats ~he rejects of the first,
the third stage treats the rejects o~ the second,
and so on, in an effort to minimize the amount of
5 discarded good fibers while concentrating the
impurities. Such a system is utilized to separate
the original highly diluted pulp suspension into a
usable paper making fiber portion (a lower density
accepts portion) and a thickened large and denser
10 impurities portion (rejects). An increase in the
rejects flow from a cyclone separator system can
result in the more complete removal of contaminants
and impurities rom the pulp suspension. However,
increased rejects flows result in greater power
15 requirements for the system to handle and transport
greater volumes of material. Additionally,
increased rejects flows increase the amount of good
fiber which is discarded from the system.
However, the smaller the diameter o~ the
20 rejects outlet of a separator, the more susceptible
it becomes to plugging and clogging with
impuritiesc Many attempts have been made to solve
the problems of con~rolling fiber loss and plugging
of rejects discharge outlets. Some have supplied
25 water under pressure to dilute the heavy rejects
fraction and wash out good paper making fibers.
Other~ have utilized special valving arrangements to
control the flow of rejects through the discharge
outlet. Examples of this type of attempted solution
30 include Jakobsson et al, W~S. Patent No. 3,696~927
and Skardal, U.S. Patent No. 3,277,926. Still
others have utili~ed grooves, ledges, and guide bars
positioned in the tapered portion o~ cyclone
chambers to control the ~low of rejects. Examples
35 of this type of attempted solution include Reid,
U.S. Patent No. 3,971,718, Frykhult, U.S. Patent No.
~3~
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4,153,558, Skardal, U.S. Patent No~ 4,156,485, and
Skardal, U.S. Patent NoO 4,224,145.
These attempts have at best been only
partially successful in solving plugging problems
5 and reducing fiber losses. Accordingly, the need
still exist~ in the art for a cyclone separation
device which is efficient, not subject to plugging
problems, and which minimizes good
paper-making fiber losses through the rejects
10 discharge outlet.
According to one aspect of the present
invention, a cyclone separator is provided having a
separation chamber, a first end thereof having a
generally circular cross-section with a tangential
15 inlet and a central outlet and the opposite end
thereof tapering toward an outlet of smaller flow
area then the chamber in which the internal wall
defining the outlet is of a noncircular
cross-section.
In a preferred embodiment9 the internal
wall o the device gradually transforms from a
circular cross-section into a rejects discharge
outlet which is noncircular in cross-section. It
has been discovered that by varying the shape of the
25 rejects outlet of a cyclone separator, the rejects
rate, the thickening factor, and the feed pressure
- to t~e device can also be varied while maintaining
substantially the same cleaning e~ficiency without
plugging problems. The modified rejects outlet of
30 the present invention may be incorporated or formed
as an integral part of a conventional cyclone
separation device or may be fabricated as a
replaceable tip. Additionally, the present
invention may be utilized in both single separator
35 devices as well as in clusters o such devices. The
modified rejects outlet of the present invention may
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also be used in conjunction with reverse centrifugal
cleaning devices such as the device taught in
Seifert et al, U.S. Patent No~ 4,155,839. Finally,
the present invention may also be utilized in the
5 separation of solids from gases.
By modifying the rejects outlet into a
noncircular configuration, a number of operational
advantages may be achieved. These include:
1. Significantly reduced rejects rates,
lQ i.e~, the percentage of fiber in the rejects
compared with the feed stock, without plugging,
minim~zing the loss of good fibers from the cleaner;
2~ A gxeater accepts consistency as com-
pared with a standard circular outlet, when a square
15 configuration is used;
3. Greater thickening factor, i.e., the
ratio rejects ¢onsistency to feed consistency, when
an oval or oblong outlet configuration is used;
4. Satisfactory operation at lower feed
20 pressures than with standard circular outlets
5. Ability to handle more volumetric
feedstock flow; and
6. Ability to utilize substantially larger
outlet openings, which are less likely to plug, and
25 still maintain substantially the same rejects rate
as conventional circular rejects outlets.
Surprisingly~ the cleaning efficiency of
cyclone separators using the present invention is
substantially unaffected by the noncircular rejects
30 outlets. This provides flexibility in the design of
such cyclone separator systems to achieve one or
more of the above operational advantages at no
sacrifice in cleaning efficiency.
Accordingly, it is an object o~ the present
35 lnvention to provide a cyclone separator device
having a modified rejects outlet which is efficient,
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not sub3ect to plugging problems, and which
minimizes the losses of good paper making fibers
from the rejects discharge outlet. This, and other
objects and advantages of the invention will be
5 apparent from the following description, the
accompanyin~ drawings, and the appended claims.
Brief Description of the Drawings
~ ig. 1 is a sectional view of a typical
cyclone separator having a rejects outlet;
Figs. 2, 3, 4 and 5 are top elevational
views looking down into cyclone separator rejects
outlets;
Figs. 2a, 3a, 4a, and Sa are sectional side
views of the respective rejects outlets; and
lS Fig. 2b is a sectional view taken along
line 2b--~b in Fig. 2a.
Description of the Preferred Embodiments
Referring to Fig. 1, a typical cyclone
separation device is illustrated. Of course, the
2Q invention is not limited to single devices including
reverse centrifugal cleaning devices but is equally
applicable to cluster arrangements. The apparatus
includes a hollow cyclone member 10 orming a
separation chamber having a cylindrical portion 12,
25 a tapering portion 14; and a hollow apex cone or tip
portion 16 which has an outlet port 17. The
cylindrical and tapering portions of the cyclone
body may be formed of a polymeric resin material
such as polypropylene, polystyrene, nylon, or the
30 like. The apex tip portion 16 is preferably ormed
of a ceramic material which resists abrasion,
although it may also be formed as a unitary
structure with the cyclone body out of the same
material as the body is ~ormed.
The cylindrical portion 12 o~ the cyclone
has a tangentially extendin~ slot-like inlet 18
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through which a fluid suspension of material, such
as paper stock, will enter the appara~us. The end
of cylindrical portion 12 of the cyclone body is
provided with a closure cover 20 which may be
S fabricated of the same polymeric resin material as
other portions of cyclone member 10. Closure cover
2n and the end of cylindrical portion 12 may be
threaded for sealing engagement. Closure cover 20
is also provided with a centrally located vortex
10 finder or overflow nozzle tube 22 through which the
accepts portion o the suspension flows and which
extends inwardly into the center of cylindrical
portion 12.
Cyclone member 10 includes an apex tip
15 portion 16 which is preferably formed of an abrasion
resistant cast ceramic material. The tapering tip
portion 16 forms an extension of tapering portion
14, and can be formed with an outwardly projecting
threaded portion 26 as an original part thereof for
20 receiving an annular internally threaded coupling
nut 28 to seal tip portion 16 to tapering portion
14. Alternativelyr the threaded portion may be
cemented in place on the tip portion 16 in a known
manner.
Figs. 2t 2a and 2b illustrate an embodiment
of the invention in whic~ apex tip portion 116 has
an outlet port 117 having a square cross-section.
As shown, apex tip 116 is designed to be a
replaceable element which can ~e joined to a cyclone
30 separator body using threads 126.
As shown in Figs. 2, 2a, and 2b, the inner
wall 101 of the hollow tapering body portion of apex
tip 116 gradually transforms from circular to square
cross-section a portion of the distance along the
35 length of the tip. Tapering wall portions 102, 104,
106, and 108, which together form a tapered
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passageway having a square cross-section, may be
~ntegrally molded into apex tip 116 during its
fabrication (as illustrated) or may be secured in
position after formation o the apex tip by suitable
5 means. It has been found that the performance of
the tip, which is improved by the use of an outlet
of noncircular cross-section, is even further
enhanced when at least a portion of the inner wall
of the tip leading to the outlet gradually assumes
10 the same cross-sectional configuration as the
outlet, as best shown in Fig. 2b, where opening 117b
has started to assume a square cross-section. The
exact amount and angle of taper will depend on many
factors including the initial size and diameter of
15 the cyclone separator and the desired
cross-sectional area of the outlet opening.
It will of course be recognized that
different portions of inner wall 101 will have
differing angles o taper. ~hat is, as the
20 cross-section of the separator is gradually
~ransformed from circular to noncircular, certain
wall portions will form lesser angles with the
longitudinal axis of separator than other wall
portions~ For example~ as illustrated in Figs. 2,
25 2a, and 2b, tapering wall portions 102, 104, 106,
108 will form lesser angles with the longitudinal
axls of the separator than the wall portions 103,
105, 107 and 109 which are located between the
tapering wall portions.
On the other hand, if a different
manufacturing process is utilized and certain
portions of the inner wall of the separator are
removed, for example, to produce a nominal 5/16"
square outlet from the same diameter circular
35 outlet, then the inner wall portions located along
lines ending at each oE the four corners of the
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finished outlet will form greater angles with the
longitudinal axis o~ the separator than other wall
portions since portions of the inner wall will be
removed. When it is stated in this specification
5 that the internal wall of the separator gradually
transforms from a circular to a noncircular
configuration, that expression is meant to cover
both of the situations described above.
In another embodiment of the invention
10 illustrated in Figs. 3 and 3a, apex tip portion 216
has an outlet portion 217 having a triangular
cross-section. Tip 216, as shown, is designed to be
joined to a cyclone body using threads 226. Inner
wall 201 of tip 216 changes from a circular to a
15 trianyular cross-section a portion of the distance
along the length o the tip. Tapering wall portions
202, 204, and 206 are provided which together form a
tapering passageway having a triangular
cross-section.
The embodiment of the invention shown in
Figs. 4 and 4a illu~trates the use of an oblong or
elliptical outlet port 317 in apex tip 316. The
elliptically~shaped outlet results from the
formation of the end of tip 316 at an angle ~ from
25 the axis normal to the long axis o~ the tip. The
angle a may be varied from 1 to 89 to vary
the extent that outlet portion 317 deviates from a
circular cross section. Alternatively, the tip 316
may be formed with an elliptically-shaped outlet
30 having an end normal to the long axis of the tip.
As before, tip 316 may include threads 326 to secure
it to a cyclone body.
The embodiment o~ the invention shown in
Figs. 5 and 5a illustrates the use of a polygonal or
3S saw-too-thed shaped outlet portion 417 in an apex tip
416 designed to be joined to a cyclone body using
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g
threads 426~ Inner wall 401 of tip 416 changes from
a circular to a polygonal cross-section a portion of
the distance along the length of the tip. Tapering
wall portions 40~, 403, 404, 405, 406, 407, 408,
5 409, 410, ~11, 412, 413, 414, 415, 419 and 420
together form a tapering passageway having a
polygonal cross-section and giving a saw-toothed
effect to the outlet 417.
In order that the invention may be better
10 understood, reference is made to the following
~onlimiting examples.
~xample 1
Several tests werP run using as the
feedstock a deink stock from the third stage rejects
15 of a cyclone separator system. A 3" diameter
Cellu-Clone cyclone cleaner, available from The
B~ack Clawson Company, Middletown, Ohio, was used
for the tests. Four diferent rejects tips were
tested as follows:
~0 1. Standard tip-circular cross-section,
0.36" diameter (0~103 sq. in. open
area)
2, Tip A - circular cross-section, 0.25"
diameter (0.049 sq. in. open area)
3. Tip B - square cross-section, 0.25"
~ides, tapered (0.063 sq. in. open
area)
4. Tip C - oblong cross-section, 0.173" x
0.365" (0.063 sq. in. open area).
The results are reported in Table I below.
In Runs 1-4, reject flow was controlled by a reject
valve present in the cyclone separator device. Runs
5-8 were per~ormed with the reject valve wide open
to eliminate any possibility of plugging of the
35 valve. An arrangement to provide free discharge was
set up so that the rejects from the device dis-
~v~ ~
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charged into an open pipe located approximately 8
feet above the device. This arrangement provided
approximately 3.5 psi back pressure on the reject
stock, The pressure drop measured through the
5 device was 20 psi for all runs.
Tabl e
Consis~ency Flow Rates, GP~ Pulp Flow, O.D. T/D -Reject
Re~t Pressure Rate TempO Thickenin~
~unTip Feed Accept Reject Feed Ac~ept Reject Feed AcceptReject Drop g~ BOP F Fac o~
(Calc . ?
STD 0~ 71 0~61 3~29 44~0 42~4 1 o6 1~87 1~55 ~32 2017~1~6 88 4~63
A 0~56 0~51 2~88 44~0 43~L ~9 1~48 1~32 - ~16 2010.8~6 99 5~14
3 B 0.59 0~56 2~38 43~0 42~3Js ~66 1~51 1~42 ~09 20 6~0~ 100 4~03
4 C 0~55 0~47 3~28 44~0 4207 1~3 1~46 1~20 ~26 2017~8% 1L5 5~g6
STD 0~62 0~52 2~99 42~0 40~3 ~7 1~57 1~26 ~31 2019~8!?6 76 4~82
6 A 0~59 0~55 2~85 42~0 41~8 ~62 1~48 1~37 ~11 207~4% 84 4~83
7 B O ~ 59 0 ~ 57 2 ~ 30 44 ~ 0 43 ~ 56 ~ 4 21 ~ ~5 1 ~ 49 ~ 06 20 3 ~ 9% 86 3 ~ 90
8 C 0~55 0~5~ 3~10 43~0 42~4~i ~54 1~D53 1~33 ~10 20 7~0% 87 5~64
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As can be seen, Runs 3 and 7 performed with
square tip B resulted in significantly lower reject
rates and thickening factors than the standard
circular tip (Runs 1 and 5) or tip A (Runs 2 and
5 6)o Visual observation indicated that cleaning
efflciency was substantially the same for all tips.
No plugging of any tips occurred. Oblong tip C
~Runs 4 and 8) exhibited a significantly greater
thickening factor indicating its utility in
10 situations where a higher consistency rejects stream
is desired.
Example 2
The same arrangement as in Example 1 was
used to test the tips except that the feedstock
15 utilized was a mixture of Kraft corrugated furnish,
clippings, and pieces. The results are reported in
Table II kelow. ~yain, the pressure drop through
the device was measured to be 20 psi for all runs.
Table II
Consistency Flow Rates, GPM Pulp Flow~ O.O. T/I) Pressure Re~ect Temp. Thicken~ng
~T~pCt ~eed Accept Re~ect FeedAccept Reject Feed Accept Reject ~rop % ~PP F Factor
(Calc . )
9 ST!) 0.53 0.50 l.52 46 44.6 1.4 1.47 1.34 .13 20 8.9% 80 2.87
B 0.55 0.54 1.60 48 47.5 .5 1.59 l.54 .05 2Q 3,2~ 87 2.9û
} C 0.51 0.49 1.70 48 47.3 .7 1.46 1.39 .07 20 4.9~ 92 3.33
~ ~a
~ 3LZ(137~9
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Again, square tip B (Run 10) operated at
significantly lower reject rate than the standard
circular tip (Run 9~. No plugging occurred~ and
cleaning efficiencies for all tips appeared to be
S substantially the same. As before, oblong tip C
(Run ll) exhibited a significantly higher thickening
factor than the standard circular tip.
Example 3
Further test runs were made using the
lO eedstock of Example l at a higher consistency
(i.e., approximately 1.0%). The results are
reported in Table III below. The pressure drop
measured through the device was 20 psi, for all runs.
~able III
Consistency Flow Rate~,~ GPM Pulp Flow7 OoD~ TjO Reject
Re7ec'c Pressure Rate Temp. Thickening
~unTip Feed Accept Reject Feed Accept Rejec'c Feed AcceptRe~ect Drop % BOP F Factor
(Calc.)
1 2 ~ 0.93 C.92 2.32 42 41.7 .3 2.34 2.30 .04 20 1.8% 64 ~.~0
13STD 0.86 0.8~ 2.88 43 42.06 .94 2023 2.07 .1~ 20 7. % 7Q 3.35
~ ~ C O . 99 0 . 96 3 . 08 42 41 ~, 4 . 6 2 . 49 2 . 38 . 11 20 4 . 5% 66 3 . 1~.
_ 15STD 0.93 0~89 2.95 42 41.16 .84 2.35 2.20 .15 20 6.3% 70 3.17
~,
~Z037'7~9
16-
Again, even at higher feed consistencies,
the square tip B (Run 12) exhibited a significantly
lower reject rate as well as a lower thickening
factor. Again, no plugging was observed.
5 Example 4
Further test runs were made using the
feedstock of Example 1. A new tip was also tested
as follows
Tip D - square cross-section, 0.25" sides,
no taper (0.063 sq. in. open area)
By "no taper" it is meant that the walls of the tip
were parallel, rather than tapering inwardly. In
later runs (Runs 19 and 22), tip D was modified to
give i~ tapered walls much like tip B. The results
15 of the tests are reported in Table IV below. The
pressure drop through the device was measured to be
20 psi for all runs.
Table IV
Consistency Flow Rates, GP~ Pulp Flow, O.D~ T/~ Reject
Reject Pres~ure Rate Temp~ Thickening
~un Tip Feed Accept Re~ect Feed Accept Reject Feed Accept Re3ect Drop % BOP F Factor
(Calc.~
16 D 0.55 0.45 3.75 4442.75 1.251.43 1.15 .28 20 19.5% 96 6.8
17 B 0.55 0.50 3.08 4443.23 .771.44 1.30 .14 20 9.7~ 96 So6
18 B 0~56 0.53 2.98 4443.42 .581.48 1.38 .10 20 7.0% 103 5.3
19 D 0.56 0.52 2.21 4442.9 1.10~.49 1~34 ,15 20 9.8~ 80 3.95
( (mo~ified)
20 B 0.52 0.49 2.50 44 43.3.7 1.38 1.27 .11 20 7.5% 95 4.81
21 STD 0.48 0.35 2.95 44 , 41.82.2 1.27 .B8 .39 20 30.7% 106 ~.15
22 D 0.50 0.46 2.43 44 43.1.9 1.32 1.19 .13 20 9.8% 115 4.86
~modified)
377.~
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rrhe tests show the improved operating
performance when using tapered sides in a square tip
(Runs 17, 18, 19, 20 and 22) versus no taper (Run
16). However, the no taper tip D (Run 16) still
5 operated at a lower reject rate than the standard
circular tip (Run 21). Thickening factors were
again lower for square versus circular tips. No
plugging occurred.
Thus, by utilizing a rejects outlet of
10 noncircular cross-section in a ~yclone separator as
taught by the present invention, the rejects rate,
thickening factor, and feed pressure to the device
can also be varied to yield improved performance of
the device while maintaining substantially the same
15 cleaning efficiency and without plugging problems.
For example, a lower rejects rate can be obtained
using the same open area for a square tip versus
prior art circular tips. If plugging is a problem,
larger open area square tips can be used at
20 substantially the same reject rates as prior art
circular tips. Other modifications of tip geometry
will be readily apparént to the skilled practitioner
to achieve optimum performance under varying
conditions of feed, pressure, consistency, and the
25 like.
While the apparatus herein described
constitutes preferred embodiments of the invention,
it is to be understood that the invention is not
limited to this precise apparatus, and that changes
3a may be made without departing from the scope of the
invention, which is defined in the appended claims.
.. .
