Note: Descriptions are shown in the official language in which they were submitted.
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This is a divisional of Canadian ap~lication 405,038
filed 11 June 1982.
This invention relates to a special form of fluid
cyclone in which the velocity energy in the exit fluid is
converted into exit pressure thus permitting the device to
discharge to atmospheric pressure or a higher pressure while
a vacuum may exist in the central core of the vortex.
This invention also relates to a special arrangement
for multiple fluid cyclones which operate with less energy due
to recovery of the energy in the fluid as it leaves the device.
~he principles of the invention may be applicable,
where the ~luid is a liquid or a gas and permits removal of
solid or liquid particles of highex density than the main fluid.
Fluid cyclones and Hydroclones have been in use for
~ome time by the paper industry and metallurgical industry.
These devices are described in the textbook "Hydroclones"
written by D. Bradley and pu~lished by the Pergamon Press.
The most common form of Hydroclone i5 the straight
conical design. Fluid enters by a tangential inle into a
short cylindrical section. A vortex is created in the cylindrical
section and a conical section below the cylindrical section as fluid
23 spirals in a path moving downward and inward, then upward in a
helical path to an exit pipe co-axial with the cy~indrical section.
The centrifugal accelerationldue to rapid rotationof the ~luid,
causes dense particles to be forced outward to the wall of
the cylinder and cone.
The dense particles are transported in the slower moving
boundary layer downward towards the apex of the cone where they leave
ac a hollow cone spray. ~he high centrifugal force near the
centre opens up a liquid free space which is referred to as a
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vortex core. In the conical cylone,with free discharge o
rejects to the abmosphere~this core is filled with air and a
back pressure at the exit of the hydroclone is required to
prevent air insuction.
In some designs the cylindrical section is much longer
than in others. One design having a longer cylindrical
~ection is sold under the trade mark "Vorvac" which was d~si~ned to
remove both dirt and gas ~imultaneously.' The general flow pattern
is similar to that described for conical designs, but there is
, 10 an additional dswnward moviny helical flow next to the core
carrying froth or light ma,terial. This extra flow is obtained
because of the use of a device at the exit which will be
discu~sed later and referred ~o as a core trap. The reject flow
from the Vorvac i~ usually to a vacuum tank and the entire
fluid in the device is b~low atmospheric pres~ur~ in order to
expand gas bubble~ so they can be taken out more readily.
Anothex known device sold under the trade mark "Vo~ject"
has a conventional type of fluid flow pattern, but the conical
reduction at the bottom is used to turn back the main downward
~low toward~ the main fluid exit~ but not to limit discharge
of reject flow. The boundary layex fluid containing the reject
material is separated from the rest of the fluid nearer the
centre by use of a core trap and it i~sues forth from a tangential
exit under pressure. The rejection of material and prevention
of air insuction in this type of design is not affected by
outlet pressure. Rejection of material may be controlled by
throttling of the reject stream and may also be limited by
injectiOn of water to carry back fine material while removing
coarser material.
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Various desiqns ~f fluid cyclones and other vortex
separators are disolosed in the following United States Patents:
2,982,409 2,835,387 3,421,622
2,849,930 3,7B5,489 3,543,932
2,816,490 3,734,288 3,861,532
2,757,581 3,716,13~' 3,057,476
2,920,761 3,696,927 3,353,673
2,757,5~2 3,612,276 3,288,286
2,92~,693 3,101,313
The fluid leaving a fluid cyclone ha~ a very high
tangential velocity about the central axis and quite a high
axial velocity. In most designs this velocity energy becomes
dissipated as turbulence in the exit piping.
A principal object of the present invention is to
provide a modified design for the recovery of energy in the fluid
which in previous designs was lost.
Where multiple small units are used they are usually
assembled into some form of bank. The pa~t method used headers
with individual connectors and more recent arrangements
involve placing multlple units in~ank like systems. In both
these systems nozzles or slots provide a throttling means to
ensure distribution of the flow and a tangential entry velocity
to the individual units.
A further object of the present invention is to provide
a special arrangement for multiple cyclones which operate
with less energy due to re~overy of the energy in fluid as
it leaves the device.
A further object of the pre~ent invention is to provide
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a special arrangement for multiple cyclones which leads to
reduced energy loss in creating the tan~ential velocity upon
entering the fluid cyclones, thereby leaving more energy to
be recovered on exit from each individual cyclone. In addition,
the same special arrangement at the exit leads to more complete
recovery of vel~city energy in fluid leaving the individual
cyclones.
In keeping with the foregoing there is provided in accord-
ance with one aspect of the present invention a fluid cyclone
having an upper cylindrical end portion with inlet and outlet
pa~sage~ tangential thereto, said outlat passage having an
annular inlet in the cylindrical portion and coaxial therewith
followed by an inner passage that gradually increases in
area and diameter to the tangential outlet passage and a lower
portion with a reject outlet in the lower end thereof.
In accordance with a further aspect of the present
invention there is provided a header for a plurality of
cyclones, said header having a passageway with a first inlet
thereto and a plurality o outlets therefroM, said outlets
being ~paced apart from one another downstream from said first
inlet and providing inlets to respective ones of the plurality
of cyclones; and deflector means in said passag~way to create
vortices of flowing fluid at each of said plurality of outlets.
In accordance with a further aspect of the present
invention t where a plurality of cylones are to be supplied
with fluid, their tangential velocity may be pxovided by a
multiple vortex pattern established between two plates with the
centre of the multiple vortices centered on the axis of the
cyclones. In a similar manner a reverse flow of vortices may
be obtained in a separate space between two plates. This is
best done witll an equal number of fluid cyclones half of which
rotate clockwise and with inflow to the vortices between the
parallel plates, and exit from the parallel plate on one
side of the bank of cyclones whereas the other half of the
fluid cyclones rotate in a counterclockwise direction and
receive and discharge their flows to vortices between the plates
from and to a channel on the other side of the bank of cyclones.
A set of deflector plates may be used on the inlet channels
to the vortex space to insure proper formation of the vortex
pattern by directing flow at the proper orientation towards
the vortex about each cyclone~
The invention is illustrated by way of example in the
accompanying drawings wherein:
Figure 1 is a~ elevational view of a typical cone
type fluid cyclone;
Figure 2 is a similar view of a fluid cyclone provided
i~ accordance with the present invention for recovery of
velocity energy;
Figure 3 is a cross-sectional view taken along line 3 3
of Figure 2;
; ~igure 4 is a partial elevational sectional view illus-
trating an alternate reject system;
Figure 5 is a horizontal sectional view taken along
essentially 5-5 of Figure 6 of fl~id cyclones of conventional
: type mounted in a special arrangement in accordance with the
present invention;
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Pigure 6 is a vertical section~l view of th multiple
cyclone of Figure 5 taken along line 6-6 of Figure 5;
Figure 7 is a view similar to Figure 6 illustrating a
raject system with cyclones of the type illustrated in Figure 2;
Figure 8 is an elevational view of a multi-cyclone
provided in accordance with the present invention;
Figure 9 is an elevational view of the upper header
for the multi-cyclone of Figure 8;
Figure 10 is a sectional view taken along a ~tepped
sectional line 10-10 of Figure 11;
Figure 11 is a cross-sectional view taken along
stepped sectional line 11-11 i~ Figure 9:
Fi~ure 12 is a cross-sectional view taken along
stepped sectional line 12-12 in Figure 9;
Figure 13 is a cro~s-sectional view taken along
sectional l~ne~ 13~13 in Figures 9 and 11; and
Figure 14 is an enlarged cross-sectional view showing
in detail one of the cyclones of the multi-cyclone unit.
Referring now i~ detail to the drawings, there i~
illu~trated in Figuxe 1 the mosk common fonm of hydrocyclone
which is a straight conical design. Fluid enters by a tangential
inlet 1~ into a short cyclindrical section 2. A vortex is
created in the cylindrical section and a conical section 3
below the cylindrical section as fluid spir ls in a path moving
downward and inward, then upward in a helical path to an exit
pipe 4 co-axial with the cylindrical section. The centrifugal
aoceleration due to rapid rotation of the fluid cau es dense
particle~ to be forced outward to the wall of the cylinder and
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cone. The dense particles are transported in a slower movin~
boundary layer downward toward the apex 5 of the cone where they
leave as a hollow cone spray. The high centrifugal force near
the center opens up a fluid ~ree space which is referred to as
the vortex core when the fluid is a liquid. In the conical cyclone,
with free discharge of rejects to atmosphere, this cone i5 filled
with air and a back pressure at the exi~ of the hydrocy¢lone
is re~uired to prevent air insuction.
The present invention is directed to reducing energy
lo~ses caused by friction in fluid cyclones. In considering
energy states in a fluid cyclone, at the inlet to the fluid
cyclone the hydraulic ~nergy in the fluid is mostly pressure
with some as velocity.
In the descending path, as the fluid spirals inward
towards the smaller radius 9f exit, velocity increa~es roughly
according to the relationship V~- krn~ If there were no friction
n would have a value of 1, but because of friction n lies
~omewhere between -0.4 and -0.9 depending on design. In this
region pres~ure energy goes down as velocity energy rises so
that near the exit a major foxm of the energy is as velocity.
In a normal fluid cyclone this velocity energy is lost and the
outl~t pressure i5 almost entirely ~rom the mean pressure energy
in the outlet area.
If the velocity energy were to be completely converted
into pre~sure energy at the exit and friction losses were zero
in the cyclone it could operate at any flow theoreti~ally with
no pressure drop. The velocity possible would be limited by
the fact that the pressure could not fall below a vacuum of
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;2yr
about 25 inche~ of mercury without having the space filled
with water vapor. In practice, there are however lo~ses of
hydraulic energy by fluid friction which means less recovery of
energy than that applied.
The tangential velocity and hence centrifuge force in
the vortex of a cyclone is related to the pressure differential
between the inlet pressure and the average pressure s the fluid
leave~ the central exit from the separating region. In the case
of the conventional centrifuge with an air core, thi~ average
pre~sure on exit of accepted fluid is somewhere between the core
pre~sure and the exit pressure which hs to be above atmospheric
pre~sure, whereas with a pressure recovery design, which ha~ a
vacuum at the core, the average pre3sure will again be somewhere
between the core pressure and that of the outlet, but much
nearer the core pres~ure. Thus, the operation of the
conventional and velocity reco~ery unit~ ~hown in the table
below will have the same separation performance with inlet and
outlet pressure ~hown compared in the table below.
PRESSURE ~P.S~I.
PRESSURE CONVENTIONAL _ VELOCITY RECOVERY
DIFFERENCE INLET OUTLET CORE INLET OUTLET CORE
High 50 5 0 40 10 -15
Low SO 5 0 ¦ 40 10 -15
A fluid cyclone with recovery of velocity energy is
illustrated in Figure 2 wherein fluid to be treated enter~ by a
tangential nozzle inlet 10 into a cyclindrical section 11. Here
it mixes with fluid which has come up from below, but not
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left the central exit opening 12. The mixture then follows
a helical form of path downward to the cone 13 which is shown
as a preferred curved form although a straight form would
also function.
Any dense material is deposited by centrifugal force
in the slower moving outer boundary layer. This layer travels
quickly down the cone due to the differential pressure between
differing radii resulting from centrifugal forces on the high
speed fluid in the interior. The boundary layer material can
be allowed to leave without the inner fluid by blocking the
vortex with a blunt cone plate 14 while permitting the boundary
layer fluid with its content o~ heavy material to leak away
through a gap between the end 15 of the cone 13 and ~he blunt
cone plate 14.
The main flow inside the boundary layer i5 turned back
upward by the restriction of cone 13 and may either rejoin
the downward stream in the cylindrical section 11 or leave by
the central exit 12. The exit channel i~ anannular passage 16 be-
tween an innercone 17 andan outercone 17A providing a space which leads
gently outward and expand~ in area. In the design shown this
passage curve~ outward however, although this is the preferred
design as the expansion of the path is gentlest where velocity
is highest, straight cones would also serve ~ome useful purpose.
The fluid leaves by tangential outlet 18.
The gradual expansio~ in the exit passage and gradual
increase in its radius leads to a conversion of both the axial
and tangential velocity into pressure energy. Thus the unit can
di4charge to a much higher pressure than either at the core of
_ g _
the vortex or the mean pressure in ~he exit stream. With
discharge to atmospheric pressure there will be a partial vacuum
at the core yet the design shown will permit the flow out of the
reject end to occur to atmospheric pressure.
The blunk cone plate 14 blocks the vortex at the bottom
and a central depre~sion 14A in the blunt cone plate 14 stabilize~
the core. The rejected fluid escaping from the gap 19 between
cones 13 ~nd 14 entexs a cylindrical ~pace 20 the~ passe~
downward past the edge of the blunt cone plate 14 and spaced
ap~rt support rods 21 into a space 22 between the bottom of the
blunt con¢ plate 14 and a bottom plate 23. At thi~ point the
reject fluid will have considerabl0 tangential velocity and
pre~sure. As it pas~es the smaller radius towards a central
exit 24 in plate 23, t~e tangential velocity will increase
~uch that a vortex will exist between plate 23 and the undex-
side of the cone plate 14. The reject fluid will emerge finally
through th~ central hole 24 as a hollow cone sprayO The pressure
drop across the vortex on plate 23 will limit the rejection rate
in selective fashion.
The pre~sure drop acros~ a vortex occur~ because of the
centrifugal acceleration which acts on the mass of khe fluid.
The tangential velocity which causes this is dependent upon
the initial tangential velocity of fluid enterinq the periphery
of the vortex. If this fluid is a boundaxy layer fluid only,
the velocity and hence throttling effect of the vortex will
be low. If thi~ fluid contains higher velocity liquid from the
inner portion in cone 13, then the velocity and throttling
effect of the reject vortex will be high.
-- 10 --
The design is hence selective in rejecting the
boundary layer fluid only. The depth of the boundary layer will
depend upon it~ viscosity and will increa~e it it contains a
high content of dense solids. The pressure differential in the
exit vortex is due to centrifugal force~ from the tangential
velocity. Thus an increa~e in viscosity which will cause
reduction in tangential velocity due to friction will thereby
reduce the throttling effect of the vortex permitting a larger
flow. This furthers the action of the reject sy~tem making it
react automatically to varying loads of undesirable material in
the fluid being treated.
Other arrangement~ may be made for removal of reject
material. An extension of the cone, such a~ shown in Figure 4
a~ 25, will throttle re~ect material and limit discharge. if
this is left open to the atmo~phere the pressure at the core of
the cyclone must be also at atmospheric pressure. This may
permit the fluid cyclone with velocity energy recovery to
discharge to a pressure which may be useful in certain
installat~ons. Where this is not the case it may be preferable
for this type of reject control to discharge rejects to a vacuum
receiver 26.
In instances where the quantity of unde~irable ~olids
is extremely low they may be collected in a closed receiver.
Thus the space between the orifice plate 23 (Figure 2) and the
bottom of the cone plate 14 may be replaced with a receiving
chamber having a suitable mechanism for dumping the collected
solids.
It is a known fact that smaller cyclones can remove
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finer particles than larger units. Experiments conducted by
the applicant ~avealso revealed that a smaller unit for the
same design capacity has less loss of hydraulic energy by
friction and hence more recoverable hydraulic energy. The
applicant has also established through experiments that the
simple tangential entry into a cylinder results in a great deal
of loss of hydraulic energy and generation of turbulence.
These studies have resulted in multiple arrangements of cyclone
units by the applicant and which are illustrated in Figures 5
to 14. In the multiple units, multiple vortices are created
directly in a header system in a stable arrangement. The
arrangement may be considered identical to that of the stable
pattern of vortex eddies which are created when a stream of
~luid passes a fixed object and is known as a vortex trail.
Vortices of opposite rotational sense progress in two lines.
The ~pacing of the two lines normally would be 0.2806 times
the spacing of individual vortices at each trail.
Referring to Figures 5 and 6 there i8 illustrated six
cyclone units 4OA, 40B, 40C, 4OD, 4OE and 4OF (only three
appear in Figure 6~ that are of conventional design but provided
with a novel inlet and outlet means. The inflow fluid to the
- cyclone units is from a common chamber 42 and the outflow into
a common chamber 44. Chambers 42 and 44 are separate from
one another and provided by spaced apart flat parallel plates
45, 46 and 47 interconnected by side walls and ena walls. The
chambers have respective opposite end walls 48 and 49, each of
whicA have curved wall portions 50 and 51 interiorly of the
chambers, such portions being preferably of spiral shape.
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2~ 24.~.
Cyclone units 40A, 40C and 40G are spaced apart from one
another in a first row and cyclone units 40B, 40D and 40F are
spaced apart from one another in the second row. The first
and second rows are spaced apart from another and the
cyclone units are staggered as best seen from Figure 5.
Cyclone units 40A, 40C and 40G have fluid rotation which appear
from top view to rotate clockwise as indicated by arrows 53,
54 and 55 whereas units 40B, 40D and 40F have fluid rotation
which appears from the top view to rotate coun$erclockwise
as indicated by arrows 56, 57 and 58. The row of counter-
rotating units is displaced by half the distance between units
in the row direction and by approximately ~28 times the
distance between units sideways, thus placing the unitæ in
the pattern normally observed in a vortex trail. In this
pattern, counter-rotating vortices are closest to each other
and there is no frictional shear between them. The individual
cyclone units acquire their fluid flow, not from individual
tangential inlets, but by a general pattern of multiple vortices
which i~ established in the space 42 between the parallel plates
45 and 46. The pattern of flow is established by two streams
of con~tant velocity admitted by two chann~ls 59, one to feed
~ fluid into clockwise vortices 53, 54 and 55 and the other into
counterclockwi~e vortices 56, 57 and 58. Fluid is diverted
from the channels 59 at the appropriate angle and po~ition
to form the proper spiral vortex pattern by deflection plate~
60 and the spiral containment end walls 50 and 51. The two
feed channels 59 are joined by a passage 61 having an inlet
62 thereto through which the entering fluid is fed.
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3~'~
Fluid which enters the barrel of the cyclones leaves
the cyclones by respective exit pipes 63 with a high rotational
velocity into the space 44 between the plates 46 and 47.
Although much of the rotational velocity is lost with the abrupt
corner as shown, there will be reverse vortex flow in the space
44 in the tangential matrix in a similar sense to that in
space 42 but with outward fluid flow movement. The fluid from
the space 44 flows by way of two channels 64 interconnected
by a passage 65 and is discharqed throuqh a cor~on outlet
similar to inlet 62 illustrated in Fi~ure 5.
The heavy material rejected at the bottom exit of the
fluid cyclones i~ ~hown a~ being collected in a pan 66 and
discharged through an exit passage 67.
The ambodiment illustrated in Figure 7 is simila~ to
that illustrated in Figure~ 5 and 6 and consists of a
plurality of cyclone units 70 which are of the energy recovery
type of Figure 2. The energy recovery cyclones are arranged
in the t~pe of arrangement of Figure 5 with the pattern of
spiral vortices of a similar type created in the ~pace between
2D flat plates definin~ the chambers. The cyclones have conical
and bottom end design 71 which is similar to that shown in
Figure 2 and an annular opening 72 fsr outflow of material
from the cyclone. The annular outlet 72 leads to an expanding
annular space 73 which in turn leads to space between the plates
defining chamber 74. In this latter space the reverse spiral
flow pattern described above with reference to Figures 5 and 6
occurs with fluid being collected by a pair of channels 75,
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only one of which is shown and which are interconnected by a
pas~age 76 having an outlet there~rom ~not shown) similar to
inlet 62 illustrated and described with reference to Figure 5.
Reject materials are collected in a pan 77 and taken away
by a pipe or other passage means 78.
Material to the respertive cyclone units 70 is from a
chamber 79 common to all of the units and having a pair of
inlet passage means ~0 (only one of which ;.s shown) similar
to the pas~a~es 59 described and illustrated with reference
to Figure 5. The pair of pa~sages 80 are interconnected by
a passage 8l. having an inlet thereto (not shown) corresponding
to inlet 62 illustrated and described with reference to
F.igure 5.
Referring to Figures 8 to 14 inclusive, there is
illu~trated in more detail a practical embodiment of a multi-
cy d one unit consi~ting of a plurality of individual cyclone
units 100 having an inlet and outlet header system 200 on the
upper end and a reject box 300 on the lower end, all of which
are mounted on a supporting structure 400O The suppor~ing fxame
2~ consists of four vertical posts 401 rigidly connected by
way of coupling members 402 to a horizontally disposed support
plate 403. The reject box 300 is al50 rigidly connected to
the legs 401 by way of bracket members 301~ further rigidifying
the entire structure.
The header 200 has an inlet 201 for fluids to he treated
and an outlet 20~ Details of the header 200 are illus rated
in Figures 9 to 13 inclusive and reference will now be made
thereto. The header 200 is a rigid assembly having four
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sockets 203 for receiving the upper ends of the frame posts 401,
thereby mounting the header on the rame. Suitable locking
means, for example set screws or the like, may be utilizea in
anchoring the headex to the posts. The header 200 has a
chamber 204 in which there is established a pattern of vortex
flow Ruch that the chamber serves as a common inlet for all
of the cyclone units. Similarly there is a chamber 205
common to all of the individual cyclone units for the outflow
o~ fluid from the cyclones. The inlet chamber 204 is defined
by a central plate 206 and a lower plate 207 together with
side plates 208 and 209. The outlet chamber is defined by
the central plate 206 and upper plate 210 spaced therefrom
and the side plates 208 and 209.
In referring to Figure 11 thexe is located in ~he inlet
chamber 204, a partition wall 212 that divides the inflowing
fluid into two passages designated respectively 213 and 21~.
In the respective passages are diverter plates 215 and 216
secured to the central plate 206 and projecting downwardly
therefrom toward the lower wall of the inlet manifold but
spaced thersfrom. The diverter plates 215 and 216 direct the
inflowing fluid to form spiral vortices about the inlets of
respective individual cyclone units lOOA and lOOB. Fluid
flowing below the diverter plates 215 and 216 is directed to
form spiral vortices about the respective individual cyclone
unit~ lOOC and lOOD. The curvedend wall portions 221, 222,
223 and 224 serve as containment walls for the vortices
at respective cyclone units lOOA, lOOB, lOOC and lOOD
and as previously mentioned are preferably spirally shaped.
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The passages in outlet chamber 205 are shown in Figure 12 which
is a section taken along stepped line 12-12 in Figure 9. The
outlet from the individual cyclone units lOOA, lOOB, lOOC
and lOOD i9 into chamber 205 and fluid flow therefrom is
divided by partition wall 217 into passages 218 and 219
connected by way of passage 220 to the outlet 202.
A cross-section of an individual cyclone unit is illus-
trated in Figure 14 and includes an upper cylindrical portion
101 followed by a lower tapered conical sectionlO2. Inflow of
fluid to be treated through chamber 204 enters the cyclone from
the centre of the spiral vortex in said manifold by annular
inlet passage 1030 Outflow from the cyclone is through an
annular pa~sage 104, gradually increasing in size to the outlet
chamber 205 where lt spirals outward. The passage 104 is
provided by truncated conical member 105 mounted on the inter-
mediate plate 206 and a further conical member 106 projecting
thereinto and mounted on the upper plate 210 by a plurali~y
of bolt~ 107. The cylindrical portion 101 and tapered lower
end portion 102 may be a single unit or, alternatively, separate
units as illustrated, the cylindrical portion being provided
by a short length of sleeve abutting at one end the lower mani-
fold plate 207 and at the other end a flange on the tapered
cone 102. A plurality of screws lU8 r threaded in the frame
plate 403, press against an annular bearing ring 109 abutting
the flange on member 102 and presses the cylindrical sleeve 101
against the manifold~ O-ring seals 110 are provided to seal
the joints.
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2~J~
The reject box 300 i~ mounted on the ~rame posts 401
at the lower reject outlet end of the cyclone. Between the
reject box and mounted on the lower end of th~ conical portion
are upper and lower plates 120 and 121 interconnected by a
plurality of bolt and nut units 122 and held in ~paced apart
relation by a short sleeve 1230 The lower end of the cone 102
is open as indicated at 112 and spaced therebelow is a cone
plate 125. The cone plate 125 is mounted on the plate 120 by
a plurality of machine screws 126 spaced apart from one
another circumferentially around the cone plate. The cone
plate i~ held in suitable spaced relation from plate 120 by
spacer~ 127. Rejects from the cyclone follow the path in-
dicated by ~he arrow A and discharge into the reject header
box 300 by way of an aperture 128 in the lower plate 121.
Cyclone~ of the foregoing design are basically intended
for use with water as the working fluido The present design,
however, is also deemed applicable when using gas as the work-
ing fluid; for example, treating gases from furnaces to
remove fly ash and smoke.
There would, of course, be no pha~e discontinuity with
ga~ in the cyclone, but the core pre~sure could al~o become
~u~atmospheric with a de~ign with pressure recovery. If the
core pressure was low enough the gas near the core would expand
thus increa~ing the velocity and become cold because of
adiabatic expansion. The velocity of gases and hence the
centrifugal force will be very much hiyher due to it~ low~r
density with an upper limit at the velocity of sound or approx-
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imately 1000 ft/~econdO ~his compares to a maximum theoretical
pos~ible velocity with water as the fluid, with 10 p.s.i. inlet
and vacuum core of 60 ft. per second. The cantrifugal accel-
eration3 at a radius of 1/2 inch with these tangential velocities
would be 2683 time~ that of gravi~y for the water and 745,341
times that of gravity for the ~as at the velocity of sound.
In practice neither of these maximum velocities will be
achieved because of friction in both devices. Gas cyclones
are usually employed with only a few inches water gauge as
a pressure differential. The velocity of sound can be achieved
with 10 p.s.i. o~ air pressure. Atmospheric pressure is in
excess of this so that very low friction loss and complete
pressure recovery could achieve close to the velocity of sound
in the gas near the core with a very low pres~ure differential
across the unit.
A small multi-cyclone unit as described in the foregoing
has been teste~ by the applicant for comparison in operability
with air as opposed to water as the working fluid. In testing
the unit to txeat air, a fan was used to suck the air
through the unit. The comparison makes the assumption that
friction losses are proportional to velocity head whether one
is dealing with air or water which is approximately true at
very high Reynold~ number. The following table shows comparative
operation of the ~ystem on water and air
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~f~
CONPAP.ISON 3" MULTICYLONE 4 UNITS
Water Air
Inlet Pressure 10 p.s.i. Atmospheric
Outlet Pre~sure 0 p.~ 1" Water Gauge
F1GW150 US gallon/min 62 cubic ft/min
Mean Gravities 315 97 5
Mean Pressure at Outlet 6" Hg Vacuum -1.2" Water gauge
Core Pressure28" ~ligh Vacuum10" Hg Vacuum?
In practice one would use much larger and more numerous
cyclones to handle air at the l~w fan pressures used
~/ in the test. ~ydraulic capacities are roughly proportional
to the square root of the applied pressure differential. Mean
gravities will be roughly proportional to the pressure
differential. The mean pressure shown is in the fluid leaving
the interior of the unit. ~he very center of the vortex will
have a much lower pressure which in the case o~ water is filled
with wa.ter vapour. The core condition with air is difficult
to estimate due to expansion of the gas resulting in reduced
d~nsity and temperature. The tests conducted, however, do
establish applicability in the use of the multiple arrangement
20 for not only liquids but gases.
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