CA1140866A - Control head for a rotary-cell filter - Google Patents
Control head for a rotary-cell filterInfo
- Publication number
- CA1140866A CA1140866A CA000341036A CA341036A CA1140866A CA 1140866 A CA1140866 A CA 1140866A CA 000341036 A CA000341036 A CA 000341036A CA 341036 A CA341036 A CA 341036A CA 1140866 A CA1140866 A CA 1140866A
- Authority
- CA
- Canada
- Prior art keywords
- filter
- suspension
- cell
- underpressure
- cells
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/15—Filters with filtering elements which move during the filtering operation with rotary plane filtering surfaces
- B01D33/21—Filters with filtering elements which move during the filtering operation with rotary plane filtering surfaces with hollow filtering discs transversely mounted on a hollow rotary shaft
- B01D33/23—Construction of discs or component sectors thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/80—Accessories
- B01D33/82—Means for pressure distribution
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2201/00—Details relating to filtering apparatus
- B01D2201/28—Position of the filtering element
- B01D2201/287—Filtering elements with a vertical or inclined rotation or symmetry axis
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Filtration Of Liquid (AREA)
- Drying Of Solid Materials (AREA)
Abstract
CONTROL HEAD FOR A ROTARY-CELL FILTER
ABSTRACT OF THE DISCLOSURE
A control head for a rotary-cell filter, especially a filter having disks whose sectors are connected with overpressure and underpressure sources and upon which a filter cake collects upon immersion of the disks in the suspension to be filtered. The control head comprises a pair of relatively rotatable disks having contacting planar surfaces perpendicular to the axis of rotation of the filter, one of the disks of the head rotating with the filter while the other disk of the head is stationary. The disks are provided with passages opening at the planar contacting surfaces for sequentially communi-cating the individual filter cells with an overpressure and an underpressure source such that the interior of the filter cells, in a portion of their path before they emerge from the suspension, are connected with the underpressure source.
According to the invention, means are provided such that the filter cells additionally in the region of the immersion in the suspension are connected with an underpressure source.
ABSTRACT OF THE DISCLOSURE
A control head for a rotary-cell filter, especially a filter having disks whose sectors are connected with overpressure and underpressure sources and upon which a filter cake collects upon immersion of the disks in the suspension to be filtered. The control head comprises a pair of relatively rotatable disks having contacting planar surfaces perpendicular to the axis of rotation of the filter, one of the disks of the head rotating with the filter while the other disk of the head is stationary. The disks are provided with passages opening at the planar contacting surfaces for sequentially communi-cating the individual filter cells with an overpressure and an underpressure source such that the interior of the filter cells, in a portion of their path before they emerge from the suspension, are connected with the underpressure source.
According to the invention, means are provided such that the filter cells additionally in the region of the immersion in the suspension are connected with an underpressure source.
Description
Cross-Reference to Related Application This application is related to the subject matter of applicant's copending application Serial No. 339,268 filed November 6,1979.
Field of the Invention The present invention relates to a control head for a rotary-cell filter and, more particularly, to a rotary-cell filter of the type in which the pressure within the individual filter cells which are cyclically immersed in a suspension from which the solids are to be deposited, is controlled by a head connected with at least one external-pressure source.
Backqround of the Invention From U.S~ patent 3,283,906, for example, it is known to provide a rotary-cell filter having a horizontal filter axis and a plurality of filter disks lying in planes perpendicular to this axis, each of the filter disks being subdivided into a plurality of sectors which are individually connected to a control head and form the filter cells.
In such filters, the filtrate is removed from the interior of each filter cell, defined by sectoral surfaces of a filter medium, e.g. a filter cloth, at least in part through this control head which serves to communicate a pressure condition from an external source to the filter cell.
The solids from the suspension into which the cells are rotated into immersion and from which the cells are withdrawn at an emergence side, form filter cakes w~on the aforemen~tioned filter medium surfaces.
The control head is constituted by two relatively rotatable disk-shaped members having juxtaposed contacting \
surfaces at which the passages of the stationary control-head member and the passages of the rotatable control-head member open for selective registry and communication, depend-ing upon the angular positions of the relatively rotatable members.
The passages of the rotatable member are connected to the individual cells of the filter disk or, in parallel, to corresponding filter cells of a number of filter disks.
The passages of the stationary control-head member are connected to the pressure sources mentioned previously.
The passages, which can be channels, cutouts, groo~es, or bores, provide a timed connection between the individual filter cells and an underpressure source in such relationship that, just before the emergence of each filter cell from the suspension, the filter cell is connected with the underpressure source.
~ aturally, an overpressure source can also be provided to facilitate dislodgement of the filter cake from the filter-medium surfaces once the filter cell has been .
withdrawn from the suspension.
The control head thus serves to connect each filter cell of each filter disk in each revolution of the latter about the horizontal filter axis, depending upon the position of the filter cell, one or more times with an underpressure source and/or with an overpressure source.
The term "underpressure" is used herein to refer to a pressure which is less than the pressure surrounding the filter cell, while the term "overpressure" is used to describe a pressure greater than the pressure surrounding the filter cell.
.
1:14~t~66 When~ for example~ the filter is an ambient-pressure filter~ i.e. the pressure surrounding the filter cell is ambient or approximately atmospheric pressure~ underpressure is applied by a vacuum or a suction pump which constitutes the underpressure source while overpressure is delivered by a compressor which constitutes the overpressure source.
Frequently~ the filter shaft~ cells and basin or trough for the suspension are enclosed in a housing adapted to sus-tain a pressure different from ambient pressure. If the pressure surrounding the filter cells in this housing is greater than atmospheric pressure, the underpressure can be atmospheric pressure and the underpressure source the ambient atmosphere. The latter case applies for a so-called pressure filter.
With highly filterable suspensions~ i.e. suspensions which are not excessively ~iscous~ the filter cells shortly before emergence from the suspension are briefly connected to an underpressure source to dry out the filtrate which may have accumulated in the space between its filter-medium surfaces and hence between the filter cakes which have deposited thereon.
It should be understood that~ with such easily filter-able suspensions~ the immersion of the filter cell in the sus-pension will result in the deposit of a filter cake on the surfaces and the collection of a filtrate free from solids in the interior of the cell. After this initial application of underpressure to drain the filter cell just before emergence from the suspension~ underpressure can be applied to dry the filter cake. The control head also serves to apply an over-' pressure pulse to the filter cell, after drying and before immersion into the suspension, to dislodge the filter cake.
With poorly filterable materials, the underpressure phase for drawing off the filtrate is applied over the entire period of immersion of the filter cell in a suspen-sion. Readily filterable materials form the filter cakes rapidly so that a suction phase is only required for such materials for a brief period just before emergence.
It has been found, as noted, that the filter cell need merely be immersed in the suspension of an easily filterable material, to enable the solids to deposit, the geodetic or liquid-head pressure of the suspension itself ~, serving to drive the liquid phase through the filter-medium surfaces.
However, when the suspension bath has any signifi-cant height and the filter cells any significant dimension along this height, as is the case where the filter cells project downwardly into the suspension from a horizontal axis above the suspension, the different portions of the filter-medium surface at different levels of the liquid are exposed to different liquid heads or geodetic pressures.
Thus, even before any suction or underpressure is app~ied to the interiors of the filter cells, a prefiltra-tion effect is manifested which deposits a filter cake whose thickness varies with the pressure or head such that the cake thickness is gr~ater at the points most remote from the axis because the greater pressure appears at the lowest part in the basin or trough containing the filtrate.
This result is disadvantageous because whatever follows the initial development of a filter cake of nonuniform ~ - 4 -.,.~
.
Bf~;6 thickness does not alter the nonuniformity and hence the drying is nonuniform so that residual moisture is dis-tributed nonuniformly in the solids which are thereafter dislodged from the surface.
With filter disks having diameters of 5 meters and greater, this is a significant problem.
Objects of the Invention It is the principal object of this invention to provide an improved control head for a rotary-cell filter having a horizontal axis which avoids the disadvantages of earlier filters as enumerated above.
Another object of this invention is to provide an improved filter assembly including a control head for filter cells, which will yield a product of more uniform humidity or moisture content than earlier filters.
Still another object of this invention is to provide a filter of the rotary-cell type which is capable of more uniform collection of solids from a suspension such that the filter cake will have a more uniform thick-ness over the height of the suspension.
It is a general object of the invention to provide an improved control head for a pressure or other rotary-; cell filter in which the cells can be communicated with an underpressure and an overpressure source.
Summarv of the_Inventlon ;
These objects and others which will become apparent herèinaftér are attained in accordance with the present invention,-in a control head for the purposes described il4~ 6 wherein the two disk-shaped members are provided with passages registering with those of the other member upon rotation of the disk shaft about a horizontal axis, wherein means (e.g. further passages) are so provided or arranged that the filter cells are additionally communicated with the underpressure source in the region of their immersion into the suspension.
More specifically, the invention relates to a filter of the type in which one or more filter disks can be mounted for rotation on a common shaft or about a common axis and each of the filter disks is provided with a plurality of filter cells, which are rotated into the suspension tintroduction phase), through the suspension (immersion phase), withdrawn from the suspension (emergence phase), and swung above the suspension (drying and dis-lodgement phases).
According to the invention, the control head, apart from communicating the filter cells with the under-pressure source during the emergence and drying phases and with the overpressure source during the dislodgement pha.se, communicates an underpressure source with the filter cells in the introduction phase.
Thus, immediately upon immersion of the filter cells into the suspension an initial suction is applied which results in the initial formation of a filter cake which thereafter appears to limit or preclude the growth of the filter cake by the geodetic pressure of the suspen-sion on the filter-medium surfaces until the next suction step is applied just prior to emergence.
It will be understood that this limitation of ~ -- 6 --.
.
. .
86~
growth in the filter cake is not an exclusion of such growth, but appears to merely block the speed of the initial growth to which the nonuniform thickness has been attributed heretofore. In other words, if filter growth continues during the immersion phase between the application of under-pressure, the growth is such as not to result in nonuniform filter-cake thickness.
The additional communication should be effected through an angle of about 30 from the horizontal, i.e., an angle measured from the level of the liquid through about 30 into the suspension.
According to a further broad aspect of the present invention there is provided a rotary cell filter comprising a housing formed with a trough adapted to receive an easily filterable suspension to be filtered. At least one set of filter cells extends radially outwardly from a horizontal axis in at least one plane perpendicular thereto.
Each ~lter cell is provided with a filter-medium surface upon which a cake of solids from the suspension can collect.
At least one control head ~s provided and having a stationary member and a rotatable member contacting each other along a planar surface perpendicular to the axis. The rotatable member is formed with angularly equispaced passages each commun~cating with a respective one of the filter cells.
The stationary member is provided with a plurality of spaced-apart passages successively alignable with the passages of the rotatable member and connected respectively to at least one underpressure source and an overpressure source for successively withdrawing liquid from each filter cell immediately before its emergence from the suspension, drawing .
~ - 7 -~., j,f 1~4~ i6 air through the filter cakes subsequent to emergence from the suspension, and pressurizing each filter cell to clislodge the filter cake prior to immersion of the filter cell in the suspension. Means is provided for rotating the rotatable member and the filter cells conjointly.
The improvement in the filter comprises means including at least one passage formed in the stationary member for subjecting the interior of each filter cell to an under-`; pressure immediately upon immersion of each filter cell into the suspension while preventing the withdrawal of liquid from each filter cell while it it immersed in the suspension between the applications of underpressure immediately upon immersion and immediately prior to emergence, the underpressure being applied to each filter cell over an angular displacement of about 30 upon immersion of these filter cells in the suspension.
Brief Description of the D.rawinas The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference ; being made to the accompanying drawings in which:
FIG. 1 is a side elevational view, partly broken away and partly in diagrammatic form, illustrating a disk .; filter in accordance with the invention; and FIG. 2 is a partial section taken along the line II-II of FIG. 1.
Specific Description The apparatus of FIG. 1 comprises a filter trough 1 which can contain the suspension as, for example, described in U.S. patent 3,283,906, four filter disks 2,3 ., .
. ) - 8 ---- ' : ' having their lower halves immersed in the suspension.
Each of the filter disks comprises eight segment-shaped filter cells 4, covered with a filter medium 4a along the opposite surface and supported, for example, by a frame 4_.
Each of these filter cells is fixed to a hub 6 keyed to a shaft 8. Each hub 6 also carries support rods 5 which fit between the segments 4 and act as spacers and holds therefor. The shaft 8 is formed by the hubs 6 and spacers 7 and 7a, the shaft being journalled in bearings 9a and the end walls 9 of the filter trough 1.
A motor 11 is connected by a belt 10 to the left-hand end of the shaft to rotate the latter.
A pair of control heads 12 and 13 are provided at the opposite ends of the shaft, the control heads being mirror-symmetrical to one another.
Each of the control heads comprises a rotatable disk-shaped sealing chamber 14 or 15 coupled with the shaft and a distributing disk member 16 and 17 fixed to a housing as represented by brackets 18 or 19, respectively, shown only schematically.
The shaft 8 is provided in its hubs 6, its spacers 7, its pulley lOa and in the two rotatable chambers 14, 15, with thrQughgoing passages 20 formed as bores equal in number to the filter cells. In the embodiment shown, therefore, eight angularly equispaced axial bores are thus provided, each being connected by a radial bore 21 in each hub with the respective inner end of the filter cell 4.
The control head 12 may serve the filter disks 2 while the control head 13 serves the filter disks 3.
3Ç;6 The stationary member 16 or 17 open at planar surfaces against oppositely turned surfaces of the rotatable disks 14 or 15 with four sector-shaped passages 22 through 25 radially at the same level as the bores 20 so as to register with these bores.
From each of these sector-shaped passages 22 through 25 a pipe 26, 27, 28 or 29 leads out of the stationary member 16 or 17 of the respective control head.
Pipes 26 and 27 are connected to a first under-pressure source 30, e.g. a vacuum pump when the filtercells are exposed to ambient pressure, or the atmosphere when the filter cells are in a pressurized housing.
Pipe 28 is connected to a second underpressure source 31 and the pipe 29 is connected to the pressure source 32 which can be a compressed air tank.
The passages are so disposed that, in each complete rotation of the filter cell 4 about the axis of the shaft 8, upon rotation thereof, communicates three times with an underpressure source 30 or 31 and once with the compressed air source 32.
The passages 22 and 23, which are connected to the underpressure sources 31, are so disposed that each filter cell 4 is subjected to reduced pressure briefly immediately upon immersion in the suspension and briefly immediately prior to withdrawal from the suspension.
The first suction phase draws filtrate through the filter rapidly and forms a uniform cake in a first cake deposition zone, while the second application of suction constitutes a second cake deposition zone. Between these two zones suction is not applied nor is any significant . .
.
.` : , ,- ', ~ '~- '.
deposition of solids permitted. The first cake-deposition zone extends angularly through about 30 as represented at 34 in FIG. 2.
With further rotation of the shaft 8 in the counterclockwise direction (arrow 33 in FIG. 2), the drained filter cell is lifted above the suspension and is connected via line 28 with suction source 31 which draws air through the filter cake to dry the latter (drying zone).
sefore reentry into the suspension, the filter cell communicates via passage 25 and pipe 29 with the compressed air source to introduce a pulse of compressed air to dislodge the filter cake which can be carried away by any conventional means.
The use of two control heads eliminates the need for passages extending the entire length of the shaft and thus permits passages of reduced length to be used.
.~
Field of the Invention The present invention relates to a control head for a rotary-cell filter and, more particularly, to a rotary-cell filter of the type in which the pressure within the individual filter cells which are cyclically immersed in a suspension from which the solids are to be deposited, is controlled by a head connected with at least one external-pressure source.
Backqround of the Invention From U.S~ patent 3,283,906, for example, it is known to provide a rotary-cell filter having a horizontal filter axis and a plurality of filter disks lying in planes perpendicular to this axis, each of the filter disks being subdivided into a plurality of sectors which are individually connected to a control head and form the filter cells.
In such filters, the filtrate is removed from the interior of each filter cell, defined by sectoral surfaces of a filter medium, e.g. a filter cloth, at least in part through this control head which serves to communicate a pressure condition from an external source to the filter cell.
The solids from the suspension into which the cells are rotated into immersion and from which the cells are withdrawn at an emergence side, form filter cakes w~on the aforemen~tioned filter medium surfaces.
The control head is constituted by two relatively rotatable disk-shaped members having juxtaposed contacting \
surfaces at which the passages of the stationary control-head member and the passages of the rotatable control-head member open for selective registry and communication, depend-ing upon the angular positions of the relatively rotatable members.
The passages of the rotatable member are connected to the individual cells of the filter disk or, in parallel, to corresponding filter cells of a number of filter disks.
The passages of the stationary control-head member are connected to the pressure sources mentioned previously.
The passages, which can be channels, cutouts, groo~es, or bores, provide a timed connection between the individual filter cells and an underpressure source in such relationship that, just before the emergence of each filter cell from the suspension, the filter cell is connected with the underpressure source.
~ aturally, an overpressure source can also be provided to facilitate dislodgement of the filter cake from the filter-medium surfaces once the filter cell has been .
withdrawn from the suspension.
The control head thus serves to connect each filter cell of each filter disk in each revolution of the latter about the horizontal filter axis, depending upon the position of the filter cell, one or more times with an underpressure source and/or with an overpressure source.
The term "underpressure" is used herein to refer to a pressure which is less than the pressure surrounding the filter cell, while the term "overpressure" is used to describe a pressure greater than the pressure surrounding the filter cell.
.
1:14~t~66 When~ for example~ the filter is an ambient-pressure filter~ i.e. the pressure surrounding the filter cell is ambient or approximately atmospheric pressure~ underpressure is applied by a vacuum or a suction pump which constitutes the underpressure source while overpressure is delivered by a compressor which constitutes the overpressure source.
Frequently~ the filter shaft~ cells and basin or trough for the suspension are enclosed in a housing adapted to sus-tain a pressure different from ambient pressure. If the pressure surrounding the filter cells in this housing is greater than atmospheric pressure, the underpressure can be atmospheric pressure and the underpressure source the ambient atmosphere. The latter case applies for a so-called pressure filter.
With highly filterable suspensions~ i.e. suspensions which are not excessively ~iscous~ the filter cells shortly before emergence from the suspension are briefly connected to an underpressure source to dry out the filtrate which may have accumulated in the space between its filter-medium surfaces and hence between the filter cakes which have deposited thereon.
It should be understood that~ with such easily filter-able suspensions~ the immersion of the filter cell in the sus-pension will result in the deposit of a filter cake on the surfaces and the collection of a filtrate free from solids in the interior of the cell. After this initial application of underpressure to drain the filter cell just before emergence from the suspension~ underpressure can be applied to dry the filter cake. The control head also serves to apply an over-' pressure pulse to the filter cell, after drying and before immersion into the suspension, to dislodge the filter cake.
With poorly filterable materials, the underpressure phase for drawing off the filtrate is applied over the entire period of immersion of the filter cell in a suspen-sion. Readily filterable materials form the filter cakes rapidly so that a suction phase is only required for such materials for a brief period just before emergence.
It has been found, as noted, that the filter cell need merely be immersed in the suspension of an easily filterable material, to enable the solids to deposit, the geodetic or liquid-head pressure of the suspension itself ~, serving to drive the liquid phase through the filter-medium surfaces.
However, when the suspension bath has any signifi-cant height and the filter cells any significant dimension along this height, as is the case where the filter cells project downwardly into the suspension from a horizontal axis above the suspension, the different portions of the filter-medium surface at different levels of the liquid are exposed to different liquid heads or geodetic pressures.
Thus, even before any suction or underpressure is app~ied to the interiors of the filter cells, a prefiltra-tion effect is manifested which deposits a filter cake whose thickness varies with the pressure or head such that the cake thickness is gr~ater at the points most remote from the axis because the greater pressure appears at the lowest part in the basin or trough containing the filtrate.
This result is disadvantageous because whatever follows the initial development of a filter cake of nonuniform ~ - 4 -.,.~
.
Bf~;6 thickness does not alter the nonuniformity and hence the drying is nonuniform so that residual moisture is dis-tributed nonuniformly in the solids which are thereafter dislodged from the surface.
With filter disks having diameters of 5 meters and greater, this is a significant problem.
Objects of the Invention It is the principal object of this invention to provide an improved control head for a rotary-cell filter having a horizontal axis which avoids the disadvantages of earlier filters as enumerated above.
Another object of this invention is to provide an improved filter assembly including a control head for filter cells, which will yield a product of more uniform humidity or moisture content than earlier filters.
Still another object of this invention is to provide a filter of the rotary-cell type which is capable of more uniform collection of solids from a suspension such that the filter cake will have a more uniform thick-ness over the height of the suspension.
It is a general object of the invention to provide an improved control head for a pressure or other rotary-; cell filter in which the cells can be communicated with an underpressure and an overpressure source.
Summarv of the_Inventlon ;
These objects and others which will become apparent herèinaftér are attained in accordance with the present invention,-in a control head for the purposes described il4~ 6 wherein the two disk-shaped members are provided with passages registering with those of the other member upon rotation of the disk shaft about a horizontal axis, wherein means (e.g. further passages) are so provided or arranged that the filter cells are additionally communicated with the underpressure source in the region of their immersion into the suspension.
More specifically, the invention relates to a filter of the type in which one or more filter disks can be mounted for rotation on a common shaft or about a common axis and each of the filter disks is provided with a plurality of filter cells, which are rotated into the suspension tintroduction phase), through the suspension (immersion phase), withdrawn from the suspension (emergence phase), and swung above the suspension (drying and dis-lodgement phases).
According to the invention, the control head, apart from communicating the filter cells with the under-pressure source during the emergence and drying phases and with the overpressure source during the dislodgement pha.se, communicates an underpressure source with the filter cells in the introduction phase.
Thus, immediately upon immersion of the filter cells into the suspension an initial suction is applied which results in the initial formation of a filter cake which thereafter appears to limit or preclude the growth of the filter cake by the geodetic pressure of the suspen-sion on the filter-medium surfaces until the next suction step is applied just prior to emergence.
It will be understood that this limitation of ~ -- 6 --.
.
. .
86~
growth in the filter cake is not an exclusion of such growth, but appears to merely block the speed of the initial growth to which the nonuniform thickness has been attributed heretofore. In other words, if filter growth continues during the immersion phase between the application of under-pressure, the growth is such as not to result in nonuniform filter-cake thickness.
The additional communication should be effected through an angle of about 30 from the horizontal, i.e., an angle measured from the level of the liquid through about 30 into the suspension.
According to a further broad aspect of the present invention there is provided a rotary cell filter comprising a housing formed with a trough adapted to receive an easily filterable suspension to be filtered. At least one set of filter cells extends radially outwardly from a horizontal axis in at least one plane perpendicular thereto.
Each ~lter cell is provided with a filter-medium surface upon which a cake of solids from the suspension can collect.
At least one control head ~s provided and having a stationary member and a rotatable member contacting each other along a planar surface perpendicular to the axis. The rotatable member is formed with angularly equispaced passages each commun~cating with a respective one of the filter cells.
The stationary member is provided with a plurality of spaced-apart passages successively alignable with the passages of the rotatable member and connected respectively to at least one underpressure source and an overpressure source for successively withdrawing liquid from each filter cell immediately before its emergence from the suspension, drawing .
~ - 7 -~., j,f 1~4~ i6 air through the filter cakes subsequent to emergence from the suspension, and pressurizing each filter cell to clislodge the filter cake prior to immersion of the filter cell in the suspension. Means is provided for rotating the rotatable member and the filter cells conjointly.
The improvement in the filter comprises means including at least one passage formed in the stationary member for subjecting the interior of each filter cell to an under-`; pressure immediately upon immersion of each filter cell into the suspension while preventing the withdrawal of liquid from each filter cell while it it immersed in the suspension between the applications of underpressure immediately upon immersion and immediately prior to emergence, the underpressure being applied to each filter cell over an angular displacement of about 30 upon immersion of these filter cells in the suspension.
Brief Description of the D.rawinas The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference ; being made to the accompanying drawings in which:
FIG. 1 is a side elevational view, partly broken away and partly in diagrammatic form, illustrating a disk .; filter in accordance with the invention; and FIG. 2 is a partial section taken along the line II-II of FIG. 1.
Specific Description The apparatus of FIG. 1 comprises a filter trough 1 which can contain the suspension as, for example, described in U.S. patent 3,283,906, four filter disks 2,3 ., .
. ) - 8 ---- ' : ' having their lower halves immersed in the suspension.
Each of the filter disks comprises eight segment-shaped filter cells 4, covered with a filter medium 4a along the opposite surface and supported, for example, by a frame 4_.
Each of these filter cells is fixed to a hub 6 keyed to a shaft 8. Each hub 6 also carries support rods 5 which fit between the segments 4 and act as spacers and holds therefor. The shaft 8 is formed by the hubs 6 and spacers 7 and 7a, the shaft being journalled in bearings 9a and the end walls 9 of the filter trough 1.
A motor 11 is connected by a belt 10 to the left-hand end of the shaft to rotate the latter.
A pair of control heads 12 and 13 are provided at the opposite ends of the shaft, the control heads being mirror-symmetrical to one another.
Each of the control heads comprises a rotatable disk-shaped sealing chamber 14 or 15 coupled with the shaft and a distributing disk member 16 and 17 fixed to a housing as represented by brackets 18 or 19, respectively, shown only schematically.
The shaft 8 is provided in its hubs 6, its spacers 7, its pulley lOa and in the two rotatable chambers 14, 15, with thrQughgoing passages 20 formed as bores equal in number to the filter cells. In the embodiment shown, therefore, eight angularly equispaced axial bores are thus provided, each being connected by a radial bore 21 in each hub with the respective inner end of the filter cell 4.
The control head 12 may serve the filter disks 2 while the control head 13 serves the filter disks 3.
3Ç;6 The stationary member 16 or 17 open at planar surfaces against oppositely turned surfaces of the rotatable disks 14 or 15 with four sector-shaped passages 22 through 25 radially at the same level as the bores 20 so as to register with these bores.
From each of these sector-shaped passages 22 through 25 a pipe 26, 27, 28 or 29 leads out of the stationary member 16 or 17 of the respective control head.
Pipes 26 and 27 are connected to a first under-pressure source 30, e.g. a vacuum pump when the filtercells are exposed to ambient pressure, or the atmosphere when the filter cells are in a pressurized housing.
Pipe 28 is connected to a second underpressure source 31 and the pipe 29 is connected to the pressure source 32 which can be a compressed air tank.
The passages are so disposed that, in each complete rotation of the filter cell 4 about the axis of the shaft 8, upon rotation thereof, communicates three times with an underpressure source 30 or 31 and once with the compressed air source 32.
The passages 22 and 23, which are connected to the underpressure sources 31, are so disposed that each filter cell 4 is subjected to reduced pressure briefly immediately upon immersion in the suspension and briefly immediately prior to withdrawal from the suspension.
The first suction phase draws filtrate through the filter rapidly and forms a uniform cake in a first cake deposition zone, while the second application of suction constitutes a second cake deposition zone. Between these two zones suction is not applied nor is any significant . .
.
.` : , ,- ', ~ '~- '.
deposition of solids permitted. The first cake-deposition zone extends angularly through about 30 as represented at 34 in FIG. 2.
With further rotation of the shaft 8 in the counterclockwise direction (arrow 33 in FIG. 2), the drained filter cell is lifted above the suspension and is connected via line 28 with suction source 31 which draws air through the filter cake to dry the latter (drying zone).
sefore reentry into the suspension, the filter cell communicates via passage 25 and pipe 29 with the compressed air source to introduce a pulse of compressed air to dislodge the filter cake which can be carried away by any conventional means.
The use of two control heads eliminates the need for passages extending the entire length of the shaft and thus permits passages of reduced length to be used.
.~
Claims (3)
1. In a rotary-cell filter comprising:
a housing formed with a trough adapted to receive an easily filterable suspension to be filtered;
at least one set of filter cells extending radially outwardly from a horizontal axis in at least one plane per-pendicular thereto, each filter cell being provided with a filter-medium surface upon which a cake of solids from said suspension can collect;
at least one control head having a stationary member and a rotatable member contacting each other along a planar surface perpendicular to said axis, said rotatable member being formed with angularly equispaced passages each communi-cating with a respective one of said filter cells, said sta-tionary member being provided with a plurality of spaced-apart passages successively alignable with the passages of said rotatable member and connected respectively to at least one underpressure source and an overpressure source for succes-sively withdrawing liquid from each filter cell immediately before its emergence from the suspension, drawing air through the filter cakes subsequent to emergence from the suspension, and pressurizing each filter cell to dislodge the filter cake prior to immersion of the filter cell in said suspension; and means for rotating said rotatable member and said filter cells conjointly, the improvement which comprises:
means including at least one passage formed in said stationary member for subjecting the interior of each filter cell to an underpressure immediately upon immersion of each filter cell into said suspension while preventing the with-drawal of liquid from each filter cell while it is immersed in the suspension between the applications of underpressure immediately upon immersion and immediately prior to emergence, the underpressure being applied to each filter cell over an angular displacement of about 30° upon immersion of these filter cells in the suspension.
a housing formed with a trough adapted to receive an easily filterable suspension to be filtered;
at least one set of filter cells extending radially outwardly from a horizontal axis in at least one plane per-pendicular thereto, each filter cell being provided with a filter-medium surface upon which a cake of solids from said suspension can collect;
at least one control head having a stationary member and a rotatable member contacting each other along a planar surface perpendicular to said axis, said rotatable member being formed with angularly equispaced passages each communi-cating with a respective one of said filter cells, said sta-tionary member being provided with a plurality of spaced-apart passages successively alignable with the passages of said rotatable member and connected respectively to at least one underpressure source and an overpressure source for succes-sively withdrawing liquid from each filter cell immediately before its emergence from the suspension, drawing air through the filter cakes subsequent to emergence from the suspension, and pressurizing each filter cell to dislodge the filter cake prior to immersion of the filter cell in said suspension; and means for rotating said rotatable member and said filter cells conjointly, the improvement which comprises:
means including at least one passage formed in said stationary member for subjecting the interior of each filter cell to an underpressure immediately upon immersion of each filter cell into said suspension while preventing the with-drawal of liquid from each filter cell while it is immersed in the suspension between the applications of underpressure immediately upon immersion and immediately prior to emergence, the underpressure being applied to each filter cell over an angular displacement of about 30° upon immersion of these filter cells in the suspension.
2. The improvement defined in claim 1 wherein said passages in said rotatable member are axial bores.
3. The improvement defined in claim 2 wherein each of said filter cells is a segment of a filter disk lying in single plane perpendicular to said axis and provided with a common hub to form a single filter disk, a plurality of such filter disks being provided in axially spaced relationship, said hubs and spacers between hubs forming a common shaft journaled in said housing, a respective said control head being provided at each end of said shaft.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2852175.7 | 1978-12-02 | ||
| DE19782852175 DE2852175A1 (en) | 1978-12-02 | 1978-12-02 | Rotating cell filter control face plate - effecting submerged two vacuum and emerged one vacuum and one compressed air application |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1140866A true CA1140866A (en) | 1983-02-08 |
Family
ID=6056133
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000341036A Expired CA1140866A (en) | 1978-12-02 | 1979-11-30 | Control head for a rotary-cell filter |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5579019A (en) |
| CA (1) | CA1140866A (en) |
| DE (1) | DE2852175A1 (en) |
| SU (1) | SU1056877A3 (en) |
| ZA (1) | ZA794845B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE451948B (en) * | 1985-05-02 | 1987-11-09 | Hedemora Ab | FILTER FOR CONTINUOUS FILTERING UNDER PRESSURE OF A SUSPENSION |
| DE4123143C1 (en) * | 1991-07-12 | 1992-11-12 | Werner Prof. Dr.-Ing. 6740 Landau De Stahl |
-
1978
- 1978-12-02 DE DE19782852175 patent/DE2852175A1/en not_active Withdrawn
-
1979
- 1979-09-12 ZA ZA00794845A patent/ZA794845B/en unknown
- 1979-10-31 SU SU792836781A patent/SU1056877A3/en active
- 1979-11-30 CA CA000341036A patent/CA1140866A/en not_active Expired
- 1979-12-03 JP JP15569879A patent/JPS5579019A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2852175A1 (en) | 1980-06-12 |
| ZA794845B (en) | 1980-09-24 |
| JPS5579019A (en) | 1980-06-14 |
| SU1056877A3 (en) | 1983-11-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |