Note: Descriptions are shown in the official language in which they were submitted.
CA 02228340 1998-O1-30
TITLE : SOLID-LIOUID SEPARATOR AND FILTER
FIELD OF THE INVENTION
The present invention relates to a centrifugal apparatus for separating solids
from liquids in a solid-liquid mixture. A specific application of the
apparatus is to separate
solids from the liquid in pig manure.
BACKGROUND OF THE INVENTION
Several types of centrifugal machines are known in which a fiusto-conical,
upwardly flaring, filter rotates about a vertical axis. The solid-liquid
mixture is discharged
at the bottom of the filter, the liquid is filtered out and the solids move
upwardly under
centrifizg~~l force to be discharged at the top larger diameter rim of the
filter; examples of such
a system are described in U.S. patent 2,802,574, dated August 13, 1957,
inventor E.
1 S Schwepf~e, entitled "Centrifizgal machine for extracting solids from
liquids", in U. S. patent
3,283,911), dated November 8, 1966, entitled "Centrifugal basket", inventors,
W. Grieselhuber
& al. In l:he above machines and others known to applicant, there is no system
to control the
degree o:Fhumidity of the solids discharged from the machine.
OBJECT OF THE INVENTION
It is therefore the main object of the present invention to provide a
centrifi.~gal
apparatus for separating solids from liquids in a solid-liquid mixture which
enables the
operator to obtain solids with a selected degree of humidity.
Another object of the present invention is to provide an apparatus of the
character described which is more particularly adapted for treating pig manure
and other types
of waste produced by the food industry.
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CA 02228340 1998-O1-30
Another object of the invention is to provide an apparatus of the character
described which is of simple construction, easy to operate and is inexpensive
to build.
SUMMARY OF THE INVENTION
This invention is a centrifugal apparatus for separating solids from liquids
in
a solid liquid mixture. The apparatus comprises support means, a rotor
supported by said
support means for rotation about an upright axis, said rotor including an
upwardly diverging
frusto-conical primary filter screen, an imperforate ring surrounding and
merging with the
larger diameter upper end of said primary screen, a circular secondary filter
screen coaxial
with said primary screen, upstanding from said ring and radially outwardly
located relative to
said upper end of said primary screen, scraper means movably supported by said
support
means fon movement between an operative scraping position in sliding and
scraping contact
with the top surface of said ring and with the inner surface of said secondary
screen and an
inoperative position clearing both said surfaces, and solids discharge means
fixed to said
support means and communicating with said scraper means to discharge to the
outside of said
apparatus solids scraped by said scraper means.
Preferably, said discharge means include an elongated discharge conduit
generally horizontal, tangent to said secondary filter screen and overlying
said secondary filter
screen, said scraper means defining a scraper conduit generally tangent to and
located radially
inwardly ~of said secondary filter screen, having an outlet communicating with
said discharge
conduit, ;aid scraper conduit fi~rther having an inlet, a bottom wall, and a
radially outer side
wall, said bottom wall and said radially outer side wall forming a first and a
second scraping
edge respectively at the inlet of said scraper conduit, said scraper conduit
pivotally mounted
at its outlet about a generally horizontal pivot axis for pivotal movement
between said
operative and said inoperative position, said bottom wall being upwardly
inclined from said
inlet to said outlet of said scraper conduit and having said first and second
scraping edges in
scraping and sliding engagement with said ring top face and with said
secondary filter screen
inner face respectively when said scraper conduit is in its operative
position, said scraper
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conduit clearing the space above said ring and inwardly of said secondary
filter screen and
overlying; said secondary filter screen when said scraper conduit is in its
inoperative position.
Preferably, the secondary filter screen is cylindrical.
Preferably, the rotor fixrther includes an imperforate cup shape member
secured to and closing the smaller diameter lower end of said primary filter
screen and further
include an upright rotor shaft extending through said cup shape member, the
latter and said
primary screen being coaxial with said rotor shaft, said cup shape member
having an upwardly
flaring inner surface.
Preferably, the support means includes a casing having a side wall and a
bottom wall, said rotor shaft extending through said casing, said casing
enclosing said rotor
and filrther including a cover closing the top of said casing, said shaft
being journaled in said
cover and in said bottom wall, and further including securing means for
securing said cover
to said casing and for leveling said cover with respect to said casing, and
fizrther including
power means todrive said rotor shaft.
Feeding means are provided for feeding a solid liquid mixture into said cup
shape member, said feeding means including a tubular portion spacedly
surrounding said shaft
above said cup shape member and opening into said cup shape member, said
tubular portion
being secured to said cover and fixrther including an inlet tube in
communication with said
tubular portion.
Preferably, said feeding means fixrther include a helical rib surrounding and
secured to said rotor shaft in the region thereof disposed within said tubular
portion.
Preferably, said radially outer wall of said scraper conduit makes an included
angle of less than 90 degrees with a radial line joining said upright axis
with said second
scraping edge when said scraper conduit is seen in top plan view.
Preferably, said cover has air inlet openings to admit air within said primary
screen to ficilitate drying of the solids withing said primary screen.
Preferably, the apparatus further includes power means to pivot said scraper
conduit between its operative and inoperative positions.
CA 02228340 1998-O1-30
Preferably, said last named power means is a plunger actuated by an
electromagnet.
BRIEF DESCRIPTION OF THE ENCLOSED DRAWINGS
S Figure 1 is a cut-away perspective view of the centrifugal apparatus of the
invention;
Figure 2 is a vertical cross-section of the same;
Figure 3 is a top plan view of the apparatus;
Figure 4 is a partial perspective view showing the rotor assembly consisting
of the primary filter, the imperforate top ring and the secondary filter; and
Figure 5 is a vertical cross-section of the rotor assembly and of the scraper
and
discharge; conduits, the scraper conduit being shown in full line operative
and in dotted line
inoperative position.
l5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The centrifugal apparatus of the invention comprises a casing 2 supported by
vertical legs 3, a cover 4 for the casing 2 and a rotor 6 located within
casing 2. The rotor 6
is driven into rotation about a vertical axis by means of an electric motor 8
secured to the legs
3 by transverse bars 9. Casing 2 comprises a cylindrical side wall 10 and a
bottom wall 12
with a liquid outlet tube 14.
The cover 4 includes a marginal portion 18, a central portion 20 and an
intermediate trough portion 22. Marginal portion 18 is provided at its lower
end with an
upper rin~;16a which is coaxial with a lower support ring 16b secured to the
top edge of side
wall 10 o:F casing 2. A series of bolts (not shown), are interposed between
the two rings 16a,
16b all around casing 2 and serve to adjust the level of cover 4 with respect
to casing 2. A
solid-liquid inlet tube 24 is secured to the central portion 20 of the cover 4
and communicates
with the top portion of a funnel 26 which is secured to cover 4 and extends
downwardly
therefrom, consisting of a top enlarged portion 26a and of a bottom tubular
portion 26b.
Cover 4 is further provided with air inlet openings 28.
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Rotor 6 comprises a shaft 30 secured to the shaft 32 of electric motor 8 by a
flexible G~upling 34. The rotor shaft 30 extends through casing 2 being
journaled in a bottom
journal 3i5 carried by bottom wall 12 and in a top journal 38 carried by
central portion 20 of
cover 4. A rotary seal 40 carried by the casing bottom wall 12 surrounds shaft
30.
The rotor 6 further includes a primary filter 42 which is of generally frusto-
conical shape and which flares upwardly being coaxial with vertical shaft 30.
Primary filter
screen 4f, is composed of a fine mesh filter screen 44 surrounded by a
perforated backing 46;
filter screen 44 has, for instance a mesh size of 50 microns. A cup shape
imperforate member
48 is secured to and closes the bottom of the primary filter 42; cup shape
member 48
surrounds and is coaxial with shaft 32 and is secured thereto by its bottom
wall 52..
Lower end 54 of backing 46 is secured to the top edge of the cup shape
member ~18. The inner face 50 of cup shape member 48 is slightly upwardly
flaring as shown
in figure 2.
The top larger diameter end of perforated backing 46 is secured to a flat
imperforate ring 56 which surrounds the primary filter screen 42 and has a top
horizontal
surface 60.
A secondary filter 62 of generally cylindrical shape is secured to the
marginal
portion of imperforate ring 56 and is also composed of a fine mesh filter
screen 64 with a
surrounding perforated backing 66.
A discharge conduit 70 is fixed to cover 4, extends through marginal portion
18 into trough portion 22, and is tangent to and overlies secondary filter
screen 62, being
provided) with an enlarged outlet 72; a scraper conduit 74 is pivoted to and
communicates
with the inlet of discharge conduit 70. Scraper conduit 74, when seen in top
plan view, is
located ra.dially inwardly of screen 62.. The pivotal connection of conduit 74
is indicated at
76 in figure 5, it is horizontal and the scraper conduit 74 is provided with
an upwardly
extending; crank arm 78 to which is pivotally connected a plunger rod 80 of an
electro-magnet
82 securE;d to cover 4.
The scraper conduit 74 has a bottom wall 84 and an radially outer wall 86
forming at the inlet of the scraper conduit a bottom scraping edge 88 and a
radially outer
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scraping edge 90. Outer wall 86 makes an included angle of less than 90
degrees with a radial
line joining the axis of rotor shaft 30 with outer scraping edge 90. As shown
in figure
S,scraper conduit 74 can take an operative position under the action of the
electro-magnet 82
in which its bottom wall 84 is downwardly inclined with the scraping edges 88
and 90 in
respective scraping engagement with the top face of imperforate ring 56 and
with the radially
inner surface of the fine mesh filter screen 64 of the secondary filter 62.
Upon action of the electro-magnet 82, the scraper conduit is pivotally raised
to an elevated inoperative position in which the inlet end of the scraper
conduit is disposed
above the top edge of the rotating secondary filter 62 so as to clear the
same. The scraper
conduit 'l4 freely extends through a cover opening 92.
A helical rib 94 is secured to and surrounds rotor shaft 30 in the portion
thereof surrounded by the lower tubular portion 26b of funnel 26. Preferably,
rotor 6 is
provided with a heating system (not shown) to cause melting of any fats in the
mixture which
might clog the filters 42 and 62.
The apparatus of the invention operates as follows:
Scraper conduit 74 is in raised inoperative position.
T'he rotor 6 is rotated by motor 8 at a selected speed, the solid-liquid
mixture
is fed through inlet tube 24 into the funnel 26 and falls into the bottom of
cup shape member
48. Rib 94 serves to positively feed the mixture and avoids any clogging
within funnel 26.
The mixture is further pulverised within the cup shape member and under
centrifi~gal force
moves upwardly against the upwardly flared wall 50 until it reaches the
primary filter. Due
to the conicity of the latter, the solids move upwardly along the inner
surface of the primary
filter 42 while the liquid is filtered out and falls within casing 2 to be
discharged through
outlet tube 14. The solids move over the ring 56 force and are pushed against
the inner
2S surface of the secondary filter; the latter being upright, the solids
accumulate against the
secondary filter 62. After a certain number of revolutions, the scraper
conduit 74 is lowered
to its operative position to scrape the solids and discharge the same to the
exterior through
the discharge conduit 70. The scraper edges 88 and 90 scrape the ring top
surface and the
inner surface of the secondary filter respectively. It will be noted that the
additional rotation
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of the solids against the secondary filter is sufficient to considerably
decrease the humidity
content of the solids, so much so that the centrifizgal force at the secondary
filter is greater
than at the top edge of the primary filter, the centrifugal force being
porportional not only to
the square of the rotational speed of, but also to the radial distance from
the rotational axis.
A sample of pig manure containing 10 per cent solids was supplied at a rate
of 600 gallons per hour to an apparatus of the invention in which the rotor of
a 32 inches
external diameter was rotated at 900 Rpm to obtain a centrifugal force at the
secondary filter
of about '910 g. The conicity of the primary filter was 3 5 degrees. 100
microns filter screen
mesh wa:~ used. A Venturi effect was produced causing air to enter into filter
42 through air
openings. 28 to further aid in the drying of the solids. The liquid was
filtered out and after
only a fe~N fiuther rotations of the solids within the space enclosed by the
secondary filter, the
humidity content of said solids was reduced to about 50 per cent. Filter
plugging was
completely eliminated by induction heating of the primary filter to obtain a
90 degree
centigrade temperature, sufficient to melt the fat contents of the manure. The
discharged
manure solids with a 50 per cent humidity content were suitable for burning or
for use as a
fertilizer to be spread directly on fields since they do not have any bad
odour. The liquid
collected was further treated to obtain pure water with the disolved
ingredients being
recuperated and disposed of. A suitable secondary treatment of the collected
liquid was
filtration through sand or ultra-filtration with ozone treatment or reverse
osmosis.
It has been found that the apparatus of the invention can be used to filter
out
not only pig manure but all kinds of organic matter containing waste. The
rotational speed
of rotor E. can be increased up to about 3000 Rpm to obtain a centrifugal
force of about 3000
g depending on the mixture to be filtered.
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