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Patent 1083976 Summary

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(12) Patent: (11) CA 1083976
(21) Application Number: 1083976
(54) English Title: METHOD AND APPARATUS FOR THE FILTRATION OF A SUSPENSION OR EMULSION
(54) French Title: METHODE ET APPAREIL POUR LE FILTRAGE D'UNE SUSPENSION OU D'UNE EMULSION
Status: Term Expired - Post Grant
Bibliographic Data
(51) International Patent Classification (IPC):
  • B01D 17/04 (2006.01)
  • B01D 33/00 (2006.01)
(72) Inventors :
  • HJELMNER, ULF R. (Sweden)
  • LARSSON, HANS F. (Sweden)
(73) Owners :
  • REDERIAKTIEBOLAGET NORDSTJERNAN
(71) Applicants :
(74) Agent: JOHNSON & HICKS
(74) Associate agent:
(45) Issued: 1980-08-19
(22) Filed Date: 1977-03-02
Availability of licence: N/A
Dedicated to the Public: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
7602999-0 (Sweden) 1976-03-03

Abstracts

English Abstract


ABSTRACT
A method for filtering a liquid which consists of supplying
a liquid to a filter bed and causing the same to move upwardly therethrough
and, at the same time, continuously removing filter medium particles
from the bottom of the bed to a wash device and allowing the removed
particles to flow through the wash device downwardly counter-current
to the flow of filtered liquid upwardly therethrough. The apparatus
consists of a casing for confining the zone of filter medium particles
in the lower portion providing a filter bed and for confining a zone of
filtered liquid above the filter bed. Means are provided, such as an
air pump, for continuously removing filter medium particles from the
bottom of the filter bed and transporting the same upwardly therethrough
to an upper portion of the casing and discharging the same into an open
ended pipe of a wash device disposed in the upper portion of the casing.
An outlet in the upper portion of the casing defines the upper surface
of the zone of filtered liquid maintained above the filter bed. The
pipe of the wash device has an open bottom end through which the washed
filter medium particles are discharged onto the top of the filter bed
and into which also the filtered liquid flows and upwardly through the
wash pipe discharging at an elevation lower than the discharge of filtered
liquid from the casing. A deflector is provided below the open bottom
end of the wash pipe for spreading the washed filter medium particles on
the top of the filter bed. The liquid to be filtered is supplied directly
into the filter bed in the lower portion of the casing and at a higher
elevation than the elevation from which the filter medium particles are
removed continuously and transported to the wash device.


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an exclusive property
or privilege is claimed are defined as follows:
1. A method of filtering a suspension or emulsion comprising
supplying the suspension to be filtered to a filter bed of filter medium
particles at a position above the bottom of the bed, causing the suspension
to flow in a direction upwardly through the filter bed, maintaining a
zone of filtered liquid phase above the filter bed, withdrawing filter
medium particles from the lower part of the filter bed thereby causing
the filter medium to flow downwardly counter-current to inflow of the
suspension, transporting the filter particles, withdrawn from the filter
bed, to a wash path for washing the dirtied filter medium during flow
along the wash path in counter-current to a wash liquid, causing a portion
of the filtered liquid phase discharged from the filter bed and maintained
in the zone thereabove to flow in a direction upwardly along the wash
path and thereby providing the wash liquid, and returning the washed
filter medium to the top surface of the filter bed zone.
2. A method according to claim 1 including the step of momentarily,
at least once, increasing the relative velocity between the filter medium
and the wash liquid during the washing.
3. A method according to claim 2 including the step of decelerating,
at least once, the flow velocity of the filter medium during the
washing.
4. A method according to claim 3, characterized in that said decelera-
tion takes place along a zone of the wash path followed by said
momentary increase.
11

5. A method according to claims 2, 3 or 4 including the step
of breaking up caked aggregates of filter medium particles, caused by the
dirtying of the filter medium, prior to the washing.
6. A method according to claim 1 including the step of controlling
the quantity of the wash liquid flowing along the wash path.
7. A method according to claim 6, characterized in that the
quantity of wash liquid is controlled by adjustment of outflow of dirtied
wash liquid obtained during the washing.
8. A method according to claim 6, characterized in that the
quantity of wash liquid is controlled by changing the level of the zone
of filtered liquid phase.
9. A method according to claim 1, characterized in that the
quantity of the filter medium transported to the wash path is controlled
by quantity sensing or pressure sensing of the suspension prior to the
supply thereof to the filter bed zone.
10. A method according to claim 1, wherein air is used to transport
the filtered filter medium and wherein air coming from a supply to
transport the dirtied filter medium is prevented from infiltrating
into the filter bed zone by being trapped and then discharged.
11. A filtration apparatus for filtering a suspension, emulsion
or the like comprising a confined zone of filter medium particles forming
a filter bed extending in a vertical direction of the apparatus,
inlet means for directing the suspension into the filter bed zone at a
position above the bottom thereof so that there is space located below
said inlet means in free communication with the filter bed zone and to
which space the filter medium is continuously supplied by flow in a
12

direction downwards, means for confining a zone of filtered liquid phase,
obtained by the filtration, above said filter bed, a transport device
for hauling the filter medium supplied to said space and dirtied by the
filtration up to a wash device arranged and constructed for washing in
counter-current between the filter medium and a wash liquid and provided
with means for returning the washed filter medium to the top surface of
the filter bed, said transport device comprising a pipe extending from
said space below said inlet means through the filter bed zone and to
said zone for the filtered liquid phase and a wash device having
an upper part connected to said pipe and a lower part provided with
at least one inlet means communicating with said zone for the filtered
liquid phase.
12. A filtration apparatus according to claim 11, characterized
in that the wash device is immersed into the zone for filtered liquid
phase and has its inlet means positioned above the filter bed zone.
13. A filtration apparatus according to claim 11 or 12, character-
ized in that the transport device and the wash device are positioned
centrally in the apparatus.
14. A filtration apparatus according to claim 12, characterized
in that the wash device comprises a pipe having an open bottom end providing
said inlet for the filtered liquid phase to the wash pipe.
15. A filtration apparatus according to claim 14, characterized
in that the pipe of the wash device is concentrically arranged around an
upper portion of the pipe of the transport device.
16. A filtration apparatus according to claim 11, characterized
in that the wash device is provided with at least one means for momentarily
13

increasing the velocity of a wash liquid.
17. A filtration apparatus according to claim 16, characterized
in that the wash device is provided with at least one means for decelerat-
ing the velocity of the filter medium.
18. A filtration apparatus according to claim 17, characterized
in that said velocity-increasing means and decelerating means are provided
by a common unit.
19. A filtration apparatus according to claim 18, characterized
in that said velocity-increasing and decelerating means consists of at least
one perforated disc extending across the flow path in the wash device.
20. A filtration apparatus according to claim 19, characterized
in that there are at least two discs arranged in series in spaced apart
relation in the flow path and wherein the holes in the two discs are
displaced relative to each other in the flow path.
21. A filtration apparatus according to claims 11, 12 or 14
including means in an upper part of the wash device for breaking up
caked aggregates of filter medium caused by the dirtying of the
filter medium.
22. A filtration apparatus according to claim 11, characterized
in that the wash device is provided with an outlet for wash liquid
dirtied during the washing and which outlet is adjustable in size for
controlling the quantity of wash liquid.
23. A filtration apparatus according to claim 11, characterized
in that the transport pipe is provided with inlets for air adjacent its
14

lower end portion for the transport of the dirtied filter medium up
to the wash device, said air being supplied through a channel extending
through the wash device and along the transport pipe.
24. A filtration apparatus according to claim 23, including
means, arranged above said air inlets, for catching air that escapes
into the filter medium.
25. A filtration apparatus according to claim 24, wherein
said air catching means also provides means for guiding the filter
medium in its flow downwardly into the lower portion of the apparatus.
26. A filtration apparatus according to claim 24, characterized
in that said air catching means consists of a funnel arranged upside
down and having its small end snug against the transport pipe, said
funnel being in its small end portion provided with outlet means for
supplying the caught air to a discharge channel extending through the
filter bed.
27. A filtration apparatus according to claim 26, wherein said
discharge channel extends upwardly along the transport pipe and through
the wash device.
28. A filtration apparatus according to claim 11, characterized
in that at least a portion of the apparatus surrounding the filter bed
and the zone of filtered liquid phase is built up by plane walls forming
a multi-edge form in cross-section and that several said apparatuses are
abutting each other joined to an integral group forming a filtration
plant in which the walls facing each other in adjacent apparatuses are
removed and remaining walls form or along remaining walls is provided a
continuous outer wall for the filtration plant.

29. A filtration apparatus according to claim 28, characterized
in that a common outlet channel for the liquid phase discharged from the
zone of filtered liquid phase is arranged for several adjacent filtration
apparatuses.
30. A filtration apparatus according to claim 29, characterized
in that the filtration apparatuses in the group are arranged in at least
two rows having said common outlet channel for all filtration apparatuses
in each row.
31. A filtration apparatus according to claims 28, 29 or 30,
characterized in that a common outlet channel for the dirtied wash
liquid obtained during the washing is arranged for several adjacent filtra-
tion apparatuses.
32. A filtration apparatus according to claim 30, characterized
in that the common outlet channel for the dirtied wash liquid is arranged
for all filtration apparatuses in adjacent rows.
33. A filtration apparatus comprising:
(a) a casing for confining a zone of filter medium particles
in a lower portion thereof to provide a filter bed and
for confining a zone of liquid above the filter bed and
which liquid has passed through the filter zone during
use of the apparatus;
(b) a first outlet from the upper portion of the casing
for discharging filtered liquid, said outlet defining
an upper surface of the zone of liquid above the filter
bed;
(c) a wash device disposed in the upper portion of the
casing and comprising a pipe extending vertically in
16

the liquid zone and having respectively upper and lower
open ends;
(d) means for continuously removing filter medium particles
from the bottom of the filter bed and transporting the
same upwardly therethrough to the upper portion of the
casing and discharging the same into the open upper end of
the pipe of the wash device;
(e) a second outlet for discharging filtered liquid from said
zone of liquid, said second outlet communicating with the
open upper end of the pipe of the wash device and being
disposed at an elevation lower than said first outlet;
and
(f) inlet means for supplying a liquid, to be filtered, to
the filter bed at an elevation higher than the position
at which the filter medium particles are removed from
the filter bed.
34. A filtration apparatus as defined in claim 33 wherein said
means for removing the filter medium particles and transporting the same
includes a pipe passing through the pipe of the wash device and terminating
near the bottom of the filter bed.
35. A filtration apparatus as defined in claim 33 wherein said
inlet means includes at least one pipe having an outlet discharging
vertically upwardly into the filter bed and means for deflecting filter
medium particles moving downwardly away from the outlet of said pipe.
36. A filtration apparatus as defined in claims 33, 34 or 35
wherein a bottom end portion of the lower portion of the casing tapers
inwardly and wherein the filter medium particles are removed from said
end portion.
17

37. A filtration apparatus as defined in claims 33, 34 or 35
including at least one perforated plate in and extending across the pipe
of the wash device.
38. A filtration apparatus as defined in claims 33, 34 or 35
including at least one deflector below the open bottom end of the pipe of
the wash device for spreading washed filter medium particles discharged
therefrom.
39. A filtration apparatus comprising:
(a) a casing having outer side walls and a bottom wall
providing means to confine a bed of filter medium
particles in the lower portion thereof and a liquid
in an upper portion thereof;
(b) inlet means for supplying a liquid, to be filtered,
to the lower portion of the casing at a position spaced
above the bottom wall thereof;
(c) a first outlet in the upper portion of the casing for
discharging filtered liquid that has flowed upwardly
through a filter bed in the lower portion of the
casing;
(d) a first conduit having an inlet thereto adjacent the
bottom wall of the casing and an outlet in the upper
portion of the casing, said conduit providing a path
for transporting filter medium particles from the
lower portion of the casing to the upper portion;
(e) a second conduit surrounding in spaced apart relation an upper
portion of said first conduit and extending along a portion of the
length thereof, said second conduit having a first inlet
for receiving filter medium particles discharged from
the outlet of the first conduit and a first outlet
18

for discharging the filter medium particles at an
elevation higher than the top surface of the filter bed,
said first outlet from said second conduit serving as
an inlet for liquid that has passed upwardly through
the filter bed; and
(f) a second outlet from said second conduit adjacent said
first inlet thereto for discharging liquid that has
flowed upwardly through said second conduit, from the
upper portion of the casing, said second outlet being
at a lower elevation than the first outlet from the
casing.
19

Description

Note: Descriptions are shown in the official language in which they were submitted.


"o~s~6
The pre~ent invention relates to a method for the filtration of
a suspension or emulsion and also to apparatus for carrying out the
method.
In the filtration of a suspension or emulsion, it is previously
known tc supply the suspension (or emulsion) to a filter bed consisting
of a filter medium of particles enclosed in a tank. The suspension
flows upwardly through the filter bed and, in some appropriate manner, ~ ;
the filtered liquid phase obtained by the filtratlon is discharged from
the filter bed through outlet means provided with some appropriate cover
means, for instance, jalousi wall or screen, to prevent the filter medlum
from escaping with the filtered liquid phase~ In one such type of
filtration apparatus it is also known, in order to obtain a continuously
operating filtration apparatus, i.e. without shutting off the filtration
during the cleaning of the filter medium, to allow the filter medium,
while the filtration is going on, to flow downwardly through the filtra-
tion tank, remove the dirtied (contaminated) filter medium in the
course of filtration from the ba~e of the tank to a pipe positioned out-
side of the tank, allow the dirtied filter medium to pass through a
washing devlce, and return the cleaned filter medium from the washing -~
., : . .
device to the surface of the filter bed ln the tank. In another known
, :, .
filtration apparatus, likewise provided with a washlng device positioned
outside of the filtration tank but without filtration in counter-current
between the filter medium and the suspension, the filtration oE the filter ;-
medium takes place during the flow thereof in counter-current to the ;
wash liquid which is taken out from the pipe for delivering the suspension
to be filtered.
The object of the present invention i8 to provide a continuously
operating filter which, by simple means, provides reliable operation,
high capacity in relation to required space, substantially always the
same filtering capacity and efficient washing of the filter medium. `~
The filter, besides utilizing the advantage of an effective use of
'.~
''.................................................................. : `':

3~76
;
the filter bed by counter-current flow (known per sP) between the filter
medium and the suspension during the filtration, also utilizes the
advantage of improved washing by counter-current flow between the filter
medium and the wash liquid (likewise known per se but in another filtering
application3.
The present invention, as mentioned above in connection with the
statement of prior art, relates to a method for the filtration of a sus-
pension or emulsion wherein the suspension is supplied to ~ zone of filter
medium of particles forming a filter bed, flows in the direction upwardly
through the filter bed during the filtration and is discharged from the
filter bed as filtered liquid phase. During filtration the filter medium
flows in a direction downwardly through the filter bed zone in counter-
current to the suspension past the inflow of the suspension into the filter
bed. The filter medium is thereafter transported from the filter bed to a
wash path and washing of the dirtied filter medium takes place during
flow in counter-current to a wash liquid. The washed filter medium is
then returned to the top surface of the filter bed zone.
The novel and characterizing features of the method according ;
to the invention is that at least a part of the filtered liquid phase
is discharged from the filter bed zone for maintaining above this zone
a zone of filtered liquid phase, that the transport of the dirtied
filter medium takes place upwards through a defined passage of the filter
bed zone, and that said counter-current washing of the dirtied filter
medium along the wash path takes place during flow of the dirtied filter
medium in counter-current to the filtered liquid phase utilized as wash
liquld, which liquid phase is supplied to the wash path from said zone of
filtered liquid phase.
Thus, according to the invention, the total filtering and washing
process can take place within the filtration apparatus and the filtered
or clarified liquid obtained by the filtration is, in a simple and
advantageous manner, utilized as wash liquid.

~l33976 :~
Within the E~me of the present lnvention and as will become evident
hereinafter, further improvements are provided with a view to making the -
washing as well as the filtration still more effec~ive. During the wash-
ing the relative velocity between the filter medium and the wash liquid
is momentarily increased at least once which creates espeeially favourable
conditions for washing the filter medium. Decelerating the filter medium
at least once and increasing the contact tim~ between the filter medium ,~'
and the wash liquid results in an increased effectiveness of the washing
and also breaks caked aggregates of filter medium caused by the dirtying.
;
Also, according to the invention, the quantity of the wash liquid flowlng
along the wash path can be controlled. As to the quantity of filter medium
transported to the wash path, this quantity can, according to the invention,
also be automatically controlled in order to constantly achieve an
appropriately adapted flow of filter medium to the wash path and this
control can be made by sensing quantity or pressure of the suspension
before its supply to the filter bed zone. Finally, by a method
according to the invention, air supplied for the transport of
the dirtied filter medium can be prevent from infiltrating
the filter bed zone by being previously ~rapped and dis- -
- 20 charged, whereby risk for local fluidizing of the filter bed, which could
result in substantiaI reduction of the ~iltering capacity of the filter
bed, is eliminated.
The invention also relates to a filtration apparatus for carrying ;~
out the above-mentloned method. The filtration apparatus includes a zone
of filter medium particles forming a filter bed, inlet means for the suspension
or emulsion to be filtered positioned in the lower part of the filter
bed zone for su~pension flow during the filtration in the direction up-
wards ~hrough the filter bed, a space located below said inlet means and
being in free communication with the filter bed zone, to which space the
filter medium continuously is supplied by flow in the direction downwards
`:~

3976
through the filter bed zone, and a transport device for hauling the
filter medium supplied to said space and dirtied by the filtration
up to a wash device which is arranged and constructed for washing in
; counter-current between the filter medium and a wash liquid alld provided
with means for returning the washed filter medium to the top surface of the
filter bed. In the filtration apparatus of the present invention there
is maintained, above the filter bed zone, a zone of filtered liquid
phase obtained by the filtra~ion. The transport device comprises a pump
havlng a pipe extending upwardly through the filter bed zone to at least
the upper part of said zone of filtered 'iquid phase and i9 connected
to the upper part of the wash device. The lower part of the wash device
is provided with at least one inlet means which is connected to said zone
of filtered liquid phase. In a preferred embodiment of the invention which,
in respect to operation and construction, is simple, the wash device is
immersed in said zone of filtered liquid phase and has its lower end
located above the filter bed zone.
The invention is illustrated by way of e~ample with reference to the
accompanying drawings in which:
Fig. 1 is a vertical section of a filtration apparatus in accordance
with this invention;
Fig. 2 i9 an enlarged view of the upper portion of the filtration
apparatus shown in Fig. 1 illustrating more clearly the wash device; and
Fig. 3 is a top schematic view illustrating a filtration unit composed
of a number of the Eiltration apparatu~es shown in Fig. 1.
Referring to Fig. 1, there i8 shown a particle filter medium 1
confined in a tank having walls 2 and a funnel or cone-shaped bottom 3.
The base of the cone preferably conforms to the shape of the tank as deflned
by the walls 2.
The filter medium may be sand or other materials, such as particles
of a plastics material or mixtures of several materials. A mixture of
several grain slze fractions can be used in a continuously operatlng filter
~ 4 ~

1~)83~76
according to the invention which is contrary to conventional techniques,
depending on what is to be ~filtered and how effective the filtration
is to be carried out. A man skilled in the art can, by tests, determine
the most suitable material and grain size in each particular case.
The suspension or emulsion to be filtered is supplied, as shown
by arrow A, to the tank through inlet 4 which preferably is located as
shown near the bottom of the tank. The flow of the suspension into the
filter bed takes place in the lower part of the filter bed via a number
of pipes 5 having outlets 6. A roof 7 is arranged above the outlet of
each pipe to prevent the filter medium from being in direct contact with
the outlets and to expose a larger surface of the filter medium to the
supplied suspension. By this, the risk of clogging the filter owing to
substantial momentary dirtying of the filter medium close to the pipe
outlets is reduced. The roof 8 have a V-shaped croæs-sect~on and owing to
this and to the arrangement of the pipe outlets with roofs, the movement
of the filter medium downwards is considerably reduced. The arrange-
ment of having the pipe outlets 6 in the lower part of the filter bed
~ provides an advantage in that the filter medium being the dirtiest,
; i.e. the filter medium passing the roof~ and the pipe outlets, continues
downwards and is no more utilized for filtration. By this the risk of
clogging is reduced since new filter medium can be exposed to the incoming
suspension. The incoming suspension flows, in co~mter-current to the
filter medium, upwardly through a zone of the filter bed towards
increasingly cleaner Eilter medium. The filtered liquid phase obtained
during the flow of the suspension upwards through the filter bed zone is ~-
kept as a zone 8 of filtered liquid phase above the filter bed and
its surface level is, in the embodiment shown, fixed by discharging the
filtered liquid phase from the filtration apparatus via a weir 9
to an outlet (arrow B).
In the tank bottom 3, down into which the dirty filter medium flows,
the intake of some conveying or pumping devlce 10 is located.
5 -
. .
'

~OE~397~;
As appears from the illustrated embodlment, the conveying device extends
centrally through the apparatus and can for lnstance consist of a mammoth
pump. Such a pump operates with air as transport medlum and the air is
supplied from above downwardY along a pipe 11 extending alongside a tran~-
port pipe 12 forming a part of the conveying device. The air is ~upplied
to the transport pipe 12 through hole~ ~n~t shown) in the lower part of
the pipe. The fil~er medium i8 transported (arrow C) by the air through
the pipe 12 up to a wash device 13 (de~cribed hereinafter~ positioned
above the filter bed.
If the air conducted into the mammoth pump for some reason should - ;
extrude through the lower part of the transport pipe 12 and infiltrate
the filter medium, there is a risk of local fluidizing of the filter
medium resulting in a substantial reduction of the filtering capacity of
the filter. In arder to prevent such a disturbance, a funnel 14,
turned upside down, is placed above and around the lntake of the pump.
The funnel catches the escaped alr and discharges the same through holes
in the top end of the funnel into a pipe 15 extending alongside the
transport pipe. The funnel also eerves as guide means for the flow of
; the filter medium downwards 80 that a uniform flow profile (flow character-
istic) is obtained over the cross-section of the apparatus.
The above-described roof~ 7 positioned above the outlets 6 of
the inlet pipes contrlbute, as well as the funnel 14, to achieve desired
flow proile. Such rooE~ can, although not shown, in order to still
more ensure desired flow profile, be arranged ln the filter bed at other
places and wlthout being associated with inlets of the suspension into
the filter bed through the outlets 6.
The wash device 13 is ~hown in larger scale in Fig. 2. The filter
medium to be washed arrives from the upper end of the transport pipe 12,
turns ~arrow D) and flows downward~ along a wash path formed by the space
between the tran~port pipe 12 and an outer pipe 16. The outer pipe 16 is
preferably concentrically arranged relative to the transport plpe 12.
,
`~ - 6 - ~

1083~
The filter medium can, owing to its dirtiness, contain clumps and these
are broken up by striking a plate 17 or the like positioned in the flow
path of the filter medium. The veloclty of fall of the filter medium
is also decelerated by the plate 17. The filter medium hits thereafter,
further down in the wash path, an intermediate partition 18 provided with
holes 19, preferably followed by a number of additional intermediate
partitions o~ similar shape. In the embodiment shown there are five
intermediate partitions. The holes 19 in two adjacent partitions are
preferably displaced in relation to each other, so that a vertical free
; lO passage for the filter medlum is prevented. Owing to this, there is a
frequent deceleration of the filter medium during its passage thr~ugh
the wash device. The filter medium flows downwardly counter-current to
an upwardly flowing wash liquid. The velocity of the wash liquid becomes
momentarily higher when it flows through the holes in the intermediate
partitions which results in particularly favourable conditions for the
washing of the filter mediu~.
The filtered liquid phase in zone 8 positioned above the filter
bed is used as wash liquid. The wash device is in this respect immersed
in the filtered liquid phase in zone 8 and, as shown with arrow E in
2~ the illustrated embodlment, the ~sh liquid, i.e. the filtered liquid
phase, is supplied to the wa~h path througb an opening 20 between the
lower end of the outer pipe 16 and the transport pipe 12 and Plows upwards
along the wa~h path. The wash liquld which becomes dlrty during the
washing, i.e. the re~ect, is discharged from the wash path as shown
with arrow F, flows over a weir 21 and i9 discharged from the apparatus
as shDwn with arrow G. Thig weir can be adjustable as to its height
and width position, thereby making it possible to control the quantity
of wash liquid. For instance, the quantity of wash liquid is increased
upon lowering of the weir. The quantity of wash liquid is also automatic-
ally increased when the level of the filtered liquid above the filterbed rises, for instance by increased load on the filtration apparatus.
7 -

l~J83S~t76
In order to gulde the filter medium~ discharged from the transport
pipe 12, downwardly to the wash path and in order to separate the reject
from the incoming Eilter medium, a pipe 22 is arranged between the outer
pipe 16 ~nd the transport pipe 12, such pipe 22 being lowered a distance
past the top end of the transport pipe.
The pipe 22 projects out beyond the outer pipe 16, and air supply
pipe 11 and alr discharge pipe 15 pass through the pipe 22. The pipe 22
also encloses a device 23 for capturing air from the transport pipe 12
containing filter medium. In the illustrated embodiment this capturing
device consists of downwardly facing cones and upwardly facing truncated
cones, alternately arranged.
Although not shown, a part of the filtered liquid phase can, if
desired, be taken out within the filter bed zone below its top surface
by arranging outlet pipes for filtered liquid phase. The inlets to such
outlet pipes preferably are located substantially vertically above the
outlets of inlet pipes 6. Also, if desired, roofs can be placed over
the inlets to such pipes in conformity with the roofs 7 located above the
; outlets of inlet pipes 6. By taking out the filtrated liquid phase
through such outlet pipes having their inlets positioned within the filter
2Q bed zone, below the top surface thereof, a satisfactory filtrated liquid
phase is ensured also upon, for instance, possible shutdowns in the wash
device, in which case the filtered liquid phase existing above the filter
bed could be dirty.
Below the bottom end of the wash device a cone 24 is arranged for
spreading the filter material coming from the wash device out over the
top surface of the filter bed. Moreover, the cone 24 is provided with a
suitable number of holes 25 in order to obtain a supply of filter medium
particles to the surface of the filter bed positioned below the cDne.
s ~
Besides the above described automatic control of the wash liquid
quantity, also an automatic control of the quantity of filter medium
supplied to the wash can, although not shown~ be accomplished. By placing
, ~ ' .
,:
'' ,

~ 39176
a quantity sensing or pressure sensing means ln the supply pipe for
the suspension (in ~ig, 1 indicated with the arrow A) a signal indicating
a change, for instance a pressure lncrease owing to accumulation of
suspended material in the filter bed, is obtained. This signal can~in
a manner known per se~be used for the control of the capacity of the
conveying or pumpin~ device 10 so that the transported quantity of
filter medium to the wash device is increased or decreased.
In the embodiment described above and shown on the drawings, the
wash device is immersed in the zone 8 of filtered liquid phase and
~,
the filtered liquid phase is from this zone admitted as wash liquid
into the wash device through the opening 20. The filtered liquid
phase utilized for the washing can, however, alternatively be laterally
admitted through one or several openings in the outer pipe 16 at the
lower portion thereof. In another alternative embodiment, not shown,
in which likewise filtered liquid pha~e from the zone 8 i9 utilized as
wash liquid, at least a part of the wash device is immersed in and
separately arranged relative to the filter bed and one or several pipes
are drawn from the zone 8 to the lower portion of the wash device for
the supply of the wash liquid to the wash device so positioned.
A ~iltration apparatus according to the invention, for instance,
the preferred embodiment described above and shown in Figs. 1 and 2,
makes a construction with comparatively small dimension~ possible and
thereby the advantage is achieved that the apparatus i~ easy to handle
and ea~y to attend in operation. Moreover, owing to the act that all
elements required for the contimlously operating apparatus are positioned
within the apparatus and furthermore that certain devices, for instance
the wash device and the conveying or pumping device, can be formed as
units, the apparatus is well adapted to be built as a module. When greater
filtration capacities than one single apparatus can produce are required
it is possible to build together, in a simple and advantageous way,
several apparatuses into one large filtrat~on plant. Such a filtration
. .
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plant is exemplified and somewhat schematically shown in Fig. 3 and
comprises a group of eight module-built filtration apparatuses joined
together. All devices and elements required for the operation of a
filtration apparatus according to the invention, for instance a filtra-
tion apparatus as shown in ~igs. 1 and 2, are embodied in each module.
However, the walls 2, which border against each other in the group, are
removed (the dashed lines in Fig. 3 are intended to illustrate the upper ~-
edge of the bottoms 3). Furthermore, for each row 29 of filtration
apparatuses there is a common outlet 26 for the filtered liquid phase
discharged from each filtration apparatus (arrow B in Figs. 1 and 2)
and for both rows 29 there is a common outlet 27 for the re~ect from the
wash device (arrow G in Figs. 1 and 2). It is apparently not necessary
to arrange these common outlets 26 and/or 27 as shown but such an arrange-
ment obviously simplifies the construction. The outer wall 28 enclosing
the filtration apparatus can consist of walls 2 in each filtration
apparatus, but alternatively all walls 2 in each filtration apparatus can
be removed and a separate outer wall be built around the filtration
plant.
As is al80 eYident from Fi8. 3, each apparatus module has a hexagonal
- ~ .
form in cross-section. This form sl~ows ~imple joining to larger filtra-
tion plants. Other forms are, however, possible to u~e, for instance,
square, which also allows simple ~oining. A square form can, however,
compared with for instance hexagonal form be less suitable owlng to the
fact that the filter medium situated in the corners is decelerated in its
movement downwards and thus less active in the filtration. -~
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Representative Drawing

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Administrative Status

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Event History

Description Date
Inactive: IPC from MCD 2006-03-11
Inactive: Expired (old Act Patent) latest possible expiry date 1997-08-19
Grant by Issuance 1980-08-19

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
REDERIAKTIEBOLAGET NORDSTJERNAN
Past Owners on Record
HANS F. LARSSON
ULF R. HJELMNER
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Abstract 1994-04-07 1 41
Drawings 1994-04-07 3 123
Claims 1994-04-07 9 307
Cover Page 1994-04-07 1 34
Descriptions 1994-04-07 10 451