CA1046427A - Filter cake removal by applying detaching coating to filter bands - Google Patents
Filter cake removal by applying detaching coating to filter bandsInfo
- Publication number
- CA1046427A CA1046427A CA171,784A CA171784A CA1046427A CA 1046427 A CA1046427 A CA 1046427A CA 171784 A CA171784 A CA 171784A CA 1046427 A CA1046427 A CA 1046427A
- Authority
- CA
- Canada
- Prior art keywords
- bands
- detaching
- filter
- suspension
- filter apparatus
- 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
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B9/00—Presses specially adapted for particular purposes
- B30B9/02—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material
- B30B9/24—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using an endless pressing band
-
- 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
- B01D33/04—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering
- B01D33/042—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering whereby the filtration and squeezing-out take place between at least two filtering bands
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/02—Precoating the filter medium; Addition of filter aids to the liquid being filtered
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Filtration Of Liquid (AREA)
- Paper (AREA)
Abstract
Abstract of the Disclosure This invention relates to an improvement in a circulating filter apparatus having upper and lower double sieve bands which are guided over transversely positioned rollers, the improvement com-prising means for applying a detaching material to at least one of said upper and lower sieve bands prior to the inlet of material to be filtered.
Description
AN 205~
FILTER CAKE REMOVAL BY APPLYING DETACHING
COATING TO FILTER BANl:)S
The present invention relates to a process for removing, or detaching, the filter cake from circulating filter means, and to an apparatus for carrying out this process, particularly in connection with drainage machines with double screen bands which are guided over transversely positioned rolls.
This process serves for achieving the easy removal of the filter cake from the filtering means.
1~ During the squeezing operation of the filter cake in drainage machines it has been found that residues thereof will constantly remain in the wire mesh of the screen and are returned again into the material inlet during the rotation of the screen. Because of this effect, a decrease in efficiency must be expected at all times so that already when the machine is designed, this material reflux must be taken into account. Furthermore, the contamination of the draining filtrate cannot be avoided.
For the purpose of obviating the aforementioned disadvantages it is known in the art to admix an auxiliary agent or filter aid to the substance to be filtered in order to facilitate the detachment or removal of the filter cake. Particularly in the case of chamber filter presses, a prior rinsing of the screens with an auxiliary separating layer (a pre-coat) has become known in the art. This operation is referred to as a ... ~ !`
discontinuous coating, as it is carried out in chamber filter presses.
It is an undesirable consequence of this method that, during the addition to the substance of the auxiliary agent or filter aid, a very considerable consumption of the latter is observed. The consumption thereof as such would not present the cardinal problem, but ,.~
:
~ AN 205~
~O~Z7 undesirable is primarily the change in the pH value of the discharging or draining filtrate and, respectively, of the filter cake, which is separated therefrom. Also, a rather significant expenditure with respect to apparatus is required for this method. It is necessary to provide for control members or means which continuously mix the auxiliary separating material into the substance to be filtered. In order to bring a sufficient amount of the auxiliary separating material to the upper side and/or the underside of the suspension, i.e. within the area of contact with the sieve or screen bands, an intimate inter-mixture of the suspension with the auxiliary separating material is required. A uniform distance of the filter cake residue from the sieve or screen band is not achieved thereby.
It is also known in the art to clean the sieves or screens me-chanically. Used for skimming or stripping were so-called scraper means which were intended to clean the screens. While the screen is indeed freed as a result from larger quantities of filter cake resi-dues, so much of the cake remains in the mesh that an additional cleaning operation becomes necessary. ;
Based on and starting out with this state of the art in mind, the present invention was conceived with the object of bringing about a decrease in the amount of auxiliary separating material to be consumed, and an improvement regarding the detachability of the filter cake from the filter means. It is intended that this should be achieved without control members or means and as nearly as possible in a continuous manner. Furthermore, it should be possible to adapt the amount of the auxiliary separating material correspondingly to the degree of moisture.
This object is achieved, in accordance with the present inven-tion, in that, prior to the inlet of the suspension, an auxiliary ~04~ 9rZ7 AN 2 05 8 separating layer is continuously applled to the upper and the lower sieves or screens, and in that it is composed of, for example, a llme or ash suspension. In order that it be possible to carry out the inven-tive process, it is proposed according to a further embodiment of the present invention that disposed at the reversing rollers ahead of the material inlet is an application roll with a lime or ash suspension pro-vided thereon, which brings about the metering and distribution of the detaching suspension, whereby a surface part of the application roller dips, or is immersed, into open supply containers, and is covered with ' 10 detaching suspension, thus feeding or transporting the amount adhering to the application roller to the sieve or screen bands.
The present invention will now be further described hereinafter on the basis of one embodiment thereof and with reference to the accom-panying drawings, wherein Figure 1 is a side view of a drainage machine with application rolls; and Figure 2 illustrates a section of an application roll, at an enlarged scale.
Figure 1 illustrates a drainage machine in a side view thareof. ~
It is composed of a stand 1 to which the lower frame 2 is secured. The ~ ' upper frame 3 is pivotally disposed at a perpendicularly positioned arm of the lower frame 2. Mounted at the end of the lower frame 2 is the rearward reversing roller 6. Disposed at the upper side of the lower frame are a plurality of lower rollers 22. Likewise, the corresponding upper rollers 23 are rotatably mounted on the upper frame 3. The upper reversing roller 8 is positioned at the end of the upper frame 3.
Finally, also disposed at the stand 1 are the two main rollers 9 and 10 so as to be superimposed, Positioned at the end of the stand 1 are the .
.
drlve rollers 11 and 12, serving for driving the screen bands 19 and 20.
Accordingly, the upper and lower rollers 22 and 23 thus constitute the wedge portion 4, and the rollers 9 and 10 constitute the main pressing or squeezing portion 5. For purposes of guiding the sieve or screen bands 19 and 20, the carrying rollers 1~L and 13 are secured to the uppermos-t and lowermost points in a manner known per se.
For the upper sieve or screen 19, the application roller 16 is provided at the reversing roller 8 in the upper area or portion of the side ~acing away from the machine. Analogously, an application roller 15 is mounted for the lower sieve or screen 20 at the reversing roller 6 in the lower area or portion of the side facing away from -the machine.
This construction has the purpose of assuring that, prior to the inlet of the suspension, an auxiliary separating coating or layer is continu- :
ously applied to the upper and/or to the lower screen band 19 and/or 20, this separating layer being composed, for example, of a lime or an ash suspension. In order that it be pGssible to apply the detaching suspension 17 onto the screen bands, a certain quantity thereof is maintained in a supply container 18 so that the application rollers 15 and 16 may be partially immersed therein, i.e., they are uniformly moistened. The application rollers 15 and 16 are simultaneously driven because of their contact with the moving screen bands 19 and 20. One surface portion of each of the application rollers is at all times in contact with the separating suspension 17. The application rollers 15 and 16 have the same width as the screen bands 19 and 20, and the supply containers likewise have the identical width, so that detaching suspension 17 is continuously applied to the screen. Obviously the case may arise where too general an amount of the separating suspen-sion 17 is applied to the screen bands 19 and 20, particularly if the 10~6 ~2~ AN 2 0 5 8 detaching suspension is somewhat thickened. In order to avoid this occurrence, a scraping means 21 is provided, as illustrated in Figure
FILTER CAKE REMOVAL BY APPLYING DETACHING
COATING TO FILTER BANl:)S
The present invention relates to a process for removing, or detaching, the filter cake from circulating filter means, and to an apparatus for carrying out this process, particularly in connection with drainage machines with double screen bands which are guided over transversely positioned rolls.
This process serves for achieving the easy removal of the filter cake from the filtering means.
1~ During the squeezing operation of the filter cake in drainage machines it has been found that residues thereof will constantly remain in the wire mesh of the screen and are returned again into the material inlet during the rotation of the screen. Because of this effect, a decrease in efficiency must be expected at all times so that already when the machine is designed, this material reflux must be taken into account. Furthermore, the contamination of the draining filtrate cannot be avoided.
For the purpose of obviating the aforementioned disadvantages it is known in the art to admix an auxiliary agent or filter aid to the substance to be filtered in order to facilitate the detachment or removal of the filter cake. Particularly in the case of chamber filter presses, a prior rinsing of the screens with an auxiliary separating layer (a pre-coat) has become known in the art. This operation is referred to as a ... ~ !`
discontinuous coating, as it is carried out in chamber filter presses.
It is an undesirable consequence of this method that, during the addition to the substance of the auxiliary agent or filter aid, a very considerable consumption of the latter is observed. The consumption thereof as such would not present the cardinal problem, but ,.~
:
~ AN 205~
~O~Z7 undesirable is primarily the change in the pH value of the discharging or draining filtrate and, respectively, of the filter cake, which is separated therefrom. Also, a rather significant expenditure with respect to apparatus is required for this method. It is necessary to provide for control members or means which continuously mix the auxiliary separating material into the substance to be filtered. In order to bring a sufficient amount of the auxiliary separating material to the upper side and/or the underside of the suspension, i.e. within the area of contact with the sieve or screen bands, an intimate inter-mixture of the suspension with the auxiliary separating material is required. A uniform distance of the filter cake residue from the sieve or screen band is not achieved thereby.
It is also known in the art to clean the sieves or screens me-chanically. Used for skimming or stripping were so-called scraper means which were intended to clean the screens. While the screen is indeed freed as a result from larger quantities of filter cake resi-dues, so much of the cake remains in the mesh that an additional cleaning operation becomes necessary. ;
Based on and starting out with this state of the art in mind, the present invention was conceived with the object of bringing about a decrease in the amount of auxiliary separating material to be consumed, and an improvement regarding the detachability of the filter cake from the filter means. It is intended that this should be achieved without control members or means and as nearly as possible in a continuous manner. Furthermore, it should be possible to adapt the amount of the auxiliary separating material correspondingly to the degree of moisture.
This object is achieved, in accordance with the present inven-tion, in that, prior to the inlet of the suspension, an auxiliary ~04~ 9rZ7 AN 2 05 8 separating layer is continuously applled to the upper and the lower sieves or screens, and in that it is composed of, for example, a llme or ash suspension. In order that it be possible to carry out the inven-tive process, it is proposed according to a further embodiment of the present invention that disposed at the reversing rollers ahead of the material inlet is an application roll with a lime or ash suspension pro-vided thereon, which brings about the metering and distribution of the detaching suspension, whereby a surface part of the application roller dips, or is immersed, into open supply containers, and is covered with ' 10 detaching suspension, thus feeding or transporting the amount adhering to the application roller to the sieve or screen bands.
The present invention will now be further described hereinafter on the basis of one embodiment thereof and with reference to the accom-panying drawings, wherein Figure 1 is a side view of a drainage machine with application rolls; and Figure 2 illustrates a section of an application roll, at an enlarged scale.
Figure 1 illustrates a drainage machine in a side view thareof. ~
It is composed of a stand 1 to which the lower frame 2 is secured. The ~ ' upper frame 3 is pivotally disposed at a perpendicularly positioned arm of the lower frame 2. Mounted at the end of the lower frame 2 is the rearward reversing roller 6. Disposed at the upper side of the lower frame are a plurality of lower rollers 22. Likewise, the corresponding upper rollers 23 are rotatably mounted on the upper frame 3. The upper reversing roller 8 is positioned at the end of the upper frame 3.
Finally, also disposed at the stand 1 are the two main rollers 9 and 10 so as to be superimposed, Positioned at the end of the stand 1 are the .
.
drlve rollers 11 and 12, serving for driving the screen bands 19 and 20.
Accordingly, the upper and lower rollers 22 and 23 thus constitute the wedge portion 4, and the rollers 9 and 10 constitute the main pressing or squeezing portion 5. For purposes of guiding the sieve or screen bands 19 and 20, the carrying rollers 1~L and 13 are secured to the uppermos-t and lowermost points in a manner known per se.
For the upper sieve or screen 19, the application roller 16 is provided at the reversing roller 8 in the upper area or portion of the side ~acing away from the machine. Analogously, an application roller 15 is mounted for the lower sieve or screen 20 at the reversing roller 6 in the lower area or portion of the side facing away from -the machine.
This construction has the purpose of assuring that, prior to the inlet of the suspension, an auxiliary separating coating or layer is continu- :
ously applied to the upper and/or to the lower screen band 19 and/or 20, this separating layer being composed, for example, of a lime or an ash suspension. In order that it be pGssible to apply the detaching suspension 17 onto the screen bands, a certain quantity thereof is maintained in a supply container 18 so that the application rollers 15 and 16 may be partially immersed therein, i.e., they are uniformly moistened. The application rollers 15 and 16 are simultaneously driven because of their contact with the moving screen bands 19 and 20. One surface portion of each of the application rollers is at all times in contact with the separating suspension 17. The application rollers 15 and 16 have the same width as the screen bands 19 and 20, and the supply containers likewise have the identical width, so that detaching suspension 17 is continuously applied to the screen. Obviously the case may arise where too general an amount of the separating suspen-sion 17 is applied to the screen bands 19 and 20, particularly if the 10~6 ~2~ AN 2 0 5 8 detaching suspension is somewhat thickened. In order to avoid this occurrence, a scraping means 21 is provided, as illustrated in Figure
2. It is composed of a strip or ledge which also corresponds to the length of the application roller. By means of a displacement of the horizontal position, as indicated by the arrow, it is possible to addi-tionally regulate the desired amount of the detaching suspension 17.
It is understood that the detaching suspension 17 could be applied to the screen bands 19 and 20 also in a different manner and fashion. For example, the detaching suspension 17 could be applied in a uniform manner by way of a distributing tube 24 which is mounted transversely to the traveling direction of the screen bands 19 and 20, and toward which bands the nozzle-like openings 25 are directed.
The arrangement of the distributing tube 24 is advantageously made in the area or region of the reversing rollers 6 and 8 prior to the inlet of material. (Not shown in the drawings.) It is also possible, however, to position the tube within the screen section between the reversing rollers 6 and 8 and the carrying or supporting rollers 13 and 14. It is essential that the detaching suspension 17 be applied in a uniform . .. . .
distribution onto the screen bands 19 and 20 prior to the inlet of material.
The use of the present process for purposes of detaching the .
filter cake in circulating filter means assures, in the first place, that the filtrate and/or the filter cake will retain at all times a desired pH
value. In addition thereto, a small amount of auxiliary separating layer or coating, which consists for example of a lime or ash suspen-sion, is sufficient to separate the filter cake during ejection exactly from the screèn bands. This results in, or produces, at all times a .'' ' .
~`~ AN 2058 ~0~4Z'7 clean screen band for the new inlet of material in drainage machlnes without involving a significant expenditure.
It will be obvious to those skilled in the art that many modifi-cations may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications .
~, -. ' ~ , ~ , , .- ~ :
It is understood that the detaching suspension 17 could be applied to the screen bands 19 and 20 also in a different manner and fashion. For example, the detaching suspension 17 could be applied in a uniform manner by way of a distributing tube 24 which is mounted transversely to the traveling direction of the screen bands 19 and 20, and toward which bands the nozzle-like openings 25 are directed.
The arrangement of the distributing tube 24 is advantageously made in the area or region of the reversing rollers 6 and 8 prior to the inlet of material. (Not shown in the drawings.) It is also possible, however, to position the tube within the screen section between the reversing rollers 6 and 8 and the carrying or supporting rollers 13 and 14. It is essential that the detaching suspension 17 be applied in a uniform . .. . .
distribution onto the screen bands 19 and 20 prior to the inlet of material.
The use of the present process for purposes of detaching the .
filter cake in circulating filter means assures, in the first place, that the filtrate and/or the filter cake will retain at all times a desired pH
value. In addition thereto, a small amount of auxiliary separating layer or coating, which consists for example of a lime or ash suspen-sion, is sufficient to separate the filter cake during ejection exactly from the screèn bands. This results in, or produces, at all times a .'' ' .
~`~ AN 2058 ~0~4Z'7 clean screen band for the new inlet of material in drainage machlnes without involving a significant expenditure.
It will be obvious to those skilled in the art that many modifi-cations may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications .
~, -. ' ~ , ~ , , .- ~ :
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a circulating filter apparatus having upper and lower double sieve bands which are guided over transversely positioned rollers, the improvement which comprises means for applying a lime suspension or an ash suspension as a detaching material to at least one of said upper and lower sieve bands prior to the inlet of material to be filtered.
2. A filter apparatus according to claim 1 in which said means comprises at least one application roller means partially immersed in a container of said detaching material, and scraper means for metering said detaching material on said application roller means.
3. A filter apparatus according to claim 1 in which said means comprises application roller means positioned adjacent a reversing roller for each of said upper and lower sieve bands.
4. A filter apparatus according to claim 1 in which said means comprises distributing tube means having nozzle-like openings therein, said distributing tube means being positioned adjacent reversing rollers for said upper and lower sieve bands.
5. A process for facilitating the detachment of filter cake from sieves of a filter apparatus having upper and lower sieve bands which comprises applying a lime suspension or an ash suspension as an auxiliary separating material to both of said sieve bands prior to the inlet of material to be filtered.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT4373A AT320419B (en) | 1973-01-03 | 1973-01-03 | Method for loosening the filter cake from rotating sieve webs |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046427A true CA1046427A (en) | 1979-01-16 |
Family
ID=3480013
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA171,784A Expired CA1046427A (en) | 1973-01-03 | 1973-05-18 | Filter cake removal by applying detaching coating to filter bands |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS4997964A (en) |
| AT (1) | AT320419B (en) |
| CA (1) | CA1046427A (en) |
| DE (1) | DE2316428A1 (en) |
| FR (1) | FR2212167B1 (en) |
| GB (1) | GB1404094A (en) |
| NL (1) | NL7306528A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5032568A (en) * | 1973-06-13 | 1975-03-29 |
-
1973
- 1973-01-03 AT AT4373A patent/AT320419B/en not_active IP Right Cessation
- 1973-04-02 DE DE2316428A patent/DE2316428A1/en active Pending
- 1973-04-04 GB GB1609073A patent/GB1404094A/en not_active Expired
- 1973-04-20 JP JP48044276A patent/JPS4997964A/ja active Pending
- 1973-05-10 NL NL7306528A patent/NL7306528A/xx not_active Application Discontinuation
- 1973-05-18 CA CA171,784A patent/CA1046427A/en not_active Expired
- 1973-12-17 FR FR7345630A patent/FR2212167B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2212167B1 (en) | 1980-06-27 |
| DE2316428A1 (en) | 1974-07-11 |
| NL7306528A (en) | 1974-07-05 |
| GB1404094A (en) | 1975-08-28 |
| JPS4997964A (en) | 1974-09-17 |
| AT320419B (en) | 1975-02-10 |
| FR2212167A1 (en) | 1974-07-26 |
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