Patent Application
20200147531
The present invention relates to the field of filtering, more precisely the present invention concerns a roller based apparatus for the separation of dry matter and liquid from a medium.
Separation of dry matter from liquid is known in the art. Methods such as precipitation, centrifugation and filtering are commonly used for separation purposes in a vast number of industries. The latter separation method is relevant for the present invention.
An efficient method for separating dry matter from liquid was presented in WO 03/055570 and WO 2006/002638 disclosing filtration apparatuses providing an enclosed pressure regulated separation chamber wherein a suspension is accumulated on a filter which is passed through a set of solid impermeable rollers, whereby the pressure exerted by the rollers separates liquid from the suspension. The separation chamber defined by the rollers where divided into two compartments by the filter. This roller based principle was improved in WO 2008/131780 where a filtration apparatus based on one or more pore rollers was disclosed. A pore roller is a roller with a surface comprising pores allowing permeability for fluid, in fluid contact with a channel for guiding liquid to a filtrate outlet. Thus, the pressure exerted by the rollers guides the liquid inside the pore roller through the pores in the surface. The end products are the filtrated liquid and a dry filter cake. Additional improvements of the pore roller based filtration principle were presented in WO 2014/198907.
The documents WO 03/055570, WO 2006/002638, WO 2008/131780 and WO 2014/198907 are hereby incorporated by reference in their entirety.
Provision of the pore rollers moved the filtration boundary to the surface of the pore roller instead of having the filter dividing the separation chamber into two compartments. This enabled an increased tension and contact force between the rollers resulting in an increased efficiency in the filtration and separation process. One remaining issue with the known filtration apparatuses is however that the dry filter cake may be wetted again if it comes in contact with the extracted liquid. One purpose of the present disclosure is to avoid wetting of the dry matter separated from the medium.
A first aspect of the present disclosure therefore relates to an apparatus for the separation of dry matter and liquid from a medium, comprising a plurality of press rollers, a separation chamber for receiving the medium and defined, in cross section, by the press rollers, and at least one chamber filter located inside and enclosed by the separation chamber. Preferably the at least one chamber filter is located inside the separation chamber such that and the entire filtration surface of said chamber filter(s) is enclosed by the separation chamber. The chamber filter may advantageously be configured to establish a negative pressure inside said chamber filter(s) relative to the separation chamber such that liquid in the medium is filtrated through the filtration surface and sucked into the chamber filter(s) and dry matter in the medium is passing between corresponding press roller. Similarly the apparatus can be configured such that a negative pressure can be established in said chamber filter(s) relative to the separation chamber such that liquid in the medium can be sucked into and filtrated through the chamber filter(s) and dry matter in the medium can pass between corresponding press roller.
The inventors have realized that instead of having the filtration boundary between a press roller and a filter roller, the filtration can be provided inside the separation chamber, which then can be defined by press rollers alone. Filtration inside the separation chamber can then be provided by means of one or more chamber filters. When medium passes between abutting press rollers during rotation of the press rollers the liquid is squeezed back into the separation chamber whereas dry matter passes between the press rollers to exit the separation chamber and can be collected outside, e.g. by means of a scraper mounted to remove dry matter from the outside surface of a press roller. By applying a negative pressure to the chamber filter(s) the liquid in the medium is filtered and sucked out of the separation chamber through the chamber filter(s).
Another way to handle the rewetting of the filter cake is to provide better access to the filtration boundary. A second aspect of the present disclosure therefore relates to an apparatus for the separation of dry matter and liquid from a medium, comprising a plurality of press rollers, at least one filter roller, a filter shell arranged around each filter roller so that the filter shell passes between said filter roller and two press rollers, a separation chamber for receiving the medium and defined, in cross section, by the press rollers and the filter roller(s) and/or the filter shell(s), wherein the apparatus is configured such that liquid in the medium is filtered across the filtration surface of a filter shell when medium is passing between said filter shell and a press roller.
Provision of a filter shell and a filter roller instead of a pore roller makes it possible to separate the filter shell and the corresponding filter roller.
Another embodiment utilizing filter shells and filter rollers relates to an apparatus for the separation of dry matter and liquid from a medium, comprising a plurality of smaller inner rollers, a larger filter shell arranged around each smaller inner roller, a separation chamber for receiving the medium and defined, in cross section, by the filter shell(s). This apparatus is preferably configured such that liquid in the medium is filtered across the filtration surfaces of two filter shells when medium is passing between said filter shells. This solution makes it possible to use only smaller inner rollers and larger filter shells, i.e. avoiding the use of press rollers altogether. This solution is exemplified in
In yet another embodiment the filter roller(s) of the presently disclosed filtering apparatus may be provided with a recess in the side surface. This is one way of separating the filter shell and the filter roller and with the filter shell arranged around the filter roller(s) a cavity is created by this recess “behind” the filter surface of the filter shell. Hence, during rotation of the rollers a filtration boundary is created between the filter shell and the side surface of the adjacent press roller and this boundary is facing the recess in the side surface of the corresponding filter roller. The presently disclosed apparatus may therefore be configured such that liquid in the medium is filtered towards and/or into the recess(es) when medium is passing between a filter shell and a press roller.
The inventors have realized that the wetting issue can be remedied by switching back to solid press rollers and one or more separate filter shells and by creating a cavity “behind” at least one of the rollers, i.e. the filter rollers, e.g. by means of a circumferential recess in the side surface of the filter roller(s).
Another way to separate a filter roller from the corresponding filter shell is by making the diameter of the filter shell larger than the diameter (of the end surfaces) of the filter roller. The ratio in diameters between filter roller and filter shell may be approx. 2 or more. With different diameters of filter shell and filter roller and accessible compartment is formed inside the filter shell and outside the recessed filter roller, i.e. in the cavity formed between the smaller filter roller and the larger filter shell.
The above disclosed aspects may be combined such that one or more chamber filters, as disclosed herein, may be located inside the separation chamber in combination with press rollers, and/or filter rollers (such as pore rollers) and optionally filter shells.
A further aspect of the present disclosure relates to a method for the separation of dry matter and liquid from a medium, comprising the steps of providing the herein disclosed filtering apparatus, feeding medium into the separation chamber when the rollers are rolling, and collecting liquid and dry matter being separated from the medium in the apparatus.
Further details about various technical features and the operation of the present apparatus (at least without the herein disclosed chamber filter, recessed filter roller, filter shell, inner roller and press shell) can be seen in WO 03/055570, WO 2006/002638, WO 2008/131780 and WO 2014/198907.
The present invention will now be described in more detail with reference to the drawings.
For the sake of clarity of the present text the term “separation” is used synonymously with the term “filtering”.
By the term “filter cake” is meant an accumulation of dry matter before liquid is removed according to the present invention.
A press roller is a roller with a continuous and/or impermeable surface of the roller area facing the separation chamber. A press roller can be a solid roller or can comprise an inner small roller with a corresponding larger outer press shell arranged around the inner roller thereby enclosing the inner roller, the outer press shell thereby facing the separation chamber. The outer press shell can be provided in for example metal, e.g. steel. The continuous and/or impermeable surface of the roller can be provided in for example rubber or polymer or metal, or a mix thereof.
A filter roller is a roller with a liquid permeable surface of at least a part of the roller area facing the separation chamber. An example of a filter roller is a pore roller disclosed in for example WO 2008/131780 and WO 2014/198907 where fluid is sucked through pores extending transversely in the roller. As disclosed herein a filter roller can also comprise a filter roller with a recess in the surface and a filter shell enclosing the filter roller, the recess and the filter shell thereby creating a narrow filtration boundary. As also disclosed herein a filter roller can comprise a small inner roller enclosed by a larger filter shell. In case of a filter shell it is the surface of the filter shell that is permeable.
The efficiency of the prior art pore roller based filtering apparatus could be optimized by pressure regulating the separation chamber, typically by creating an overpressure in the separation chamber and/or a vacuum in the pore rollers such that the filtered liquid was sucked into the pore rollers. The presently disclosed filtering apparatus may also be configured such that the separation chamber can be pressure regulated, because for the separation process to function properly an overpressure is usually required in the separation chamber. However, an overpressure can typically be generated when a medium containing dry matter and liquid is fed into the separation chamber. And in this case with recessed filter roller(s) the filtering boundary can be made very thin, namely the thickness of the filtration element of the filter shell. In this case it is therefore easier to physically separate the liquid and the dry matter after filtration. Hence, pressure regulation of the separation chamber is not an essential feature of the presently disclosed filtering apparatus.
The rollers may advantageously be rotated by drum motors. A drum motor (sometimes referred to as a motorised pulley) is a geared motor drive enclosed within a tubular shell providing a single component driving pulley. A drum motor typically comprises a motor (e.g. electric or hydraulic) fixed to a stationary shaft at one end of the drum and directly coupled through the motor's rotor pinion to an in-line gearbox which is fixed to the other stationary shaft. The torque is transferred from the motor via the gearbox to the drum shell through a coupling or geared rim attached to the shell or end housing. The only moving external parts are the drum shell and bearing housing. Drum motors are advantageously used in the food or pharmaceutical industry because the drum motor can be designed to withstand hygienic cleaning and service intervals can be very long. A drum motor can therefore advantageously be integrated in one or more of the rollers and the exposed drum shafts become the shafts of the corresponding rollers and the shafts can therefore be attached to sidewalls of the apparatus. These shafts do not rotate during operation of the presently disclosed apparatus.
As illustrated in the examples below the presently disclosed apparatus can be provided with four rollers, e.g. one filter roller and three press rollers or two filter rollers and two press rollers. However, the number of rollers may also be increased, e.g. to six or eight or more rollers. The advantage of increasing the number of rollers is that the axial tension between neighbouring rollers can be increased.
As stated previously a first aspect of the present disclosure relates to an apparatus for the separation of dry matter and liquid from a medium, comprising a plurality of rollers, a separation chamber for receiving the medium and defined, in cross section, by the press rollers, and at least one chamber filter located inside and enclosed by the separation chamber. The rollers can be selected from the group of press rollers and filter rollers. Preferably at least one chamber filter is located inside the separation chamber such that and the entire filtration surface of said chamber filter(s) is enclosed by the separation chamber. The chamber filter may advantageously be configured to establish a negative pressure inside said chamber filter(s) relative to the separation chamber such that liquid in the medium is filtrated through the filtration surface and sucked into the chamber filter(s) and dry matter in the medium is passing between corresponding press roller.
In a preferred embodiment the chamber filter(s) is configured to rotate during filtration, such as rotate around an axis parallel with the rotation axes of the press rollers of the apparatus. Thereby it is possible to move the filtration boundary relative to the medium in the separation chamber in order to free the filtration surface. The filtering apparatus may further comprise at least one scraping element mounted to scrape medium collected on the outside/filtration surface of the chamber filter(s). This may further help to free the filtration surface.
The chamber filter(s) may be shaped to form a body, such as a rounded body, for example cylindrical in shape. The transverse cross section of the chamber filter(s) may be elliptical, such as circular, or polygonal. The longitudinal axis of the chamber filter(s) may be arranged parallel with the longitudinal axes of the press rollers as exemplified in
An end plate 211 is also illustrated in
One advantage of placing the chamber filter inside the separation chamber is that other types of filters can be used. If the filtration boundary is defined by a filter roller and a neighboring press roller, the filter must be able to withstand the force and pressure of from the press roller whereas a chamber filter is untouched by press rollers.
Another embodiment of a chamber filter is illustrated in
In a further embodiment the chamber filter(s) is based on crossflow filtration. The chamber filter(s) may further be based on ceramic membranes, such as silicon carbide membranes. In a further embodiment the chamber filter(s) is a dead end filter, preferably ceramic, having a porous body and filtration membranes.
The inventors have realized that shells can be used as surfaces of the press rollers and/or the filter rollers, i.e. shells instead of solid rollers. The advantage of using shells is that the tolerances in the filtering apparatus can be increased because the shells can be made at least partly flexible and/or elastic, i.e. the surfaces and shape of a shell can be made to adapt to a neighboring surface which can be solid roller or another shell. Hence, the shells may be round, e.g. circular, but during operation and rotation where shells are forced against neighboring rollers or shells the applied forces can deform the shells into non-round shapes, e.g. slightly elliptical shapes, depending on the design of the filtering apparatus and the applied forces.
As also described herein filter shells and press shells might have larger diameters than the diameters of the end surfaces of the corresponding inner rollers. The diameter of the filter roller relative to the diameter of the corresponding filter shell preferably being at least 1.2, more preferably at least 1.5, more preferably at least 2, more preferably at least 2.5, more preferably at least 3. In that case the center of rotation of the shell is typically displaced from the center of rotation of the corresponding inner roller as exemplified in the drawings.
Similarly with the press rollers with an inner solid roller and an outer press shell. The outer press shell may have a larger diameter than the diameter of the inner solid roller, the diameter of the inner solid roller relative to the diameter of the corresponding outer press shell preferably being at least 1.2, more preferably at least 1.5, more preferably at least 2, more preferably at least 2.5, more preferably at least 3. Also here the center of rotation of the inner solid roller is typically displaced from the center of rotation of the corresponding outer press shell.
The presently disclosed apparatus would also work with a filter shell having the same diameter as the diameter of the end surfaces of the corresponding inner filter roller, but in that case it would almost be the same situation as with the pore roller—a pore roller does not comprise a circumferential recess, though.
Another advantage of a larger diameter of a filter shell compared to the corresponding inner filter roller is that an accessible cavity or space is created between the filter shell and the filter roller. This provides for easier access to the filtered liquid separated from the medium and thereby it is possible to avoid that the separated dry matter, i.e. the filter cake, is re-wetted because the filtered liquid can be removed from the apparatus more quickly.
Quick physical separation of liquid and dry matter may be provided by means at least one scraping element mounted to scrape filtrated liquid from the inside of the filter shell. A scraping element like a wiper for windows may be suitable for this purpose, e.g. a substantially soft rubber based scraping element. The scraping element(s) may be spring loaded towards the inside of the filter shell, i.e. to ensure a sufficient tense contact between scraping element the filter surface. Further, the scraping element(s) are preferably mounted such that the scraping interface between a scraping element and the inner surface of the corresponding filter shell is adjacent the contact interface between the outer surface of said filter shell and the neighboring press roller. I.e. the scraping element is advantageously mounted such that filtered liquid is wiped off the inside of the filter surface as quickly as possible after passing through the filtration boundary.
The simplest form of a filter shell is a cylindrical filtration element, preferably a substantially rigid filtration element. Hence, the filter shell may be a thin metallic filter. The thickness of the filter shell may be less than 5 mm, more preferably less than 3 mm, even more preferably less than 2 mm, most preferably less than 1 mm.
To further strengthen a filter shell it may be provided with one or more support rings, e.g. circular rigid, such as metallic, support rings, mounted along the inner surface of the filter shell. To avoid reducing the filtration area of the filter shell the support ring(s) may be liquid permeable, i.e. they may be filters in themselves.
In a further embodiment the filter shell(s) and/or the outer press shell(s) are flexible such that during rotation of the press rollers the filter shell(s) and/or the outer press shell(s) are formed into non-round shape(s). For example by the forced contact with the surface of neighboring press rollers.
As stated previously the filter roller of the presently disclosed filtering apparatus may be provided with a recess in the side surface as one way of remedying the rewetting issue. Similarly one or more of the press rollers may comprise a circumferential recess, i.e. a recess in the side surface of the press roller. The circumferential recess of the press roller(s) may correspond to the circumferential recess of the filter roller(s). The press rollers and the filter roller(s) may thereby be substantially identical, at least in shape. Recessed rollers are exemplified in
In case of one or more recessed rollers the corresponding filter shell is preferably configured to engage and match the circumferential recess of the corresponding filter roller. I.e. the height of the filter shell corresponds to the height of the recess of the corresponding filter roller. This is to ensure a tight and sealed connection between the filter shell and the corresponding recessed filter roller.
The filter shell may comprise collars, such as circular collars, in each end to support the structure of the shell and to provide a liquid tight engagement with the corresponding filter roller and/or the neighboring press roller. The collars may be mounted on each end of the filter shell. The collars are shaped to match the recess of the corresponding recessed filter roller, e.g. the width of the collars corresponds to the depth of the corresponding circumferential recess in the filter roller. Hence, the circular collars may be configured to engage and match the upper and lower edges of the circumferential recess of the corresponding recessed filter roller.
In case of the press rollers also comprising a recess the collars of the filter shell(s) are preferably shaped to match the combined recess of a press roller and a neighboring filter roller. E.g. the width of the collars corresponds to the sum of the depths of the circumferential recesses of a pair of neighboring press and filter rollers.
A further aspect relates to an apparatus for the separation of dry matter and liquid from a medium, comprising a plurality of press rollers, a plurality of guide rollers, at least one filter shell arranged around a part of said press rollers and a part of said guide rollers, and one or more separation chambers, such as two or three separation chambers, for receiving the medium and defined, in cross section, by a part of said press rollers, a part of said guide rollers and the filter shell(s). This apparatus is preferably configured such that liquid in the medium is filtered across the filtration surface of a filter shell when medium is passing between said filter shell and a press roller.
This solution is exemplified in
However, the separation chambers 163 can also function sequentially, i.e. filter cake exiting one separation chamber enters the next separation chamber to extract even more liquid from the filter cake. The order of the separation chambers 163 depends on the direction of rotation of the rollers.
No end plates are shown in
It is important that the engagement between the various surfaces of the rollers and the filter shells and/or the collars of the filter shell(s) can be tight because they at least partly define the separation chamber that must be kept tight. These surfaces may therefore be provided with a flexible and/or elastic surface characteristic, e.g. a rubber or rubber-like surface characteristic. Hence, the parts of the press rollers engaging with a filter shell (during rotation) may be provided with a first rubber or rubber-like surface. The top and bottom parts of the press rollers and the filter rollers that engage with each other (during rotation) may be provided with a second rubber or rubber-like surface. The parts of the filter roller(s) engaging with collars of a filter shell (during rotation) may be provided with a third rubber or rubber-like surface. And the collars of the filter shells may be provided with a fourth rubber or rubber-like surface. It may be advantageous to have different hardness of the various surfaces. E.g. the collars and the top and bottom parts of the press rollers and the filter rollers may be provided with the “softest” surface, the parts of the press rollers engaging with a filter shell may be provided with a harder surface and the surface of the circumferential recess of a filter roller may be provided with an even harder surface.
The ability to provide all rollers with rubber surface and that all rollers can be substantially identical makes it possible to reduce the cost of this apparatus compared to the pore roller based apparatus, because the rubber surfaces improve the tolerance levels in the apparatus because the flexibility of the rubber (or rubber-like) surfaces provides easier adaption of interfacing and engaging surfaces. It is furthermore possible to separate filtered liquid from the filter cake, e.g. by mechanical means, due to the ability to have a very thin and accessible filtration boundary such that suction in the process can be avoided. This can also help to reduce the cost and complexity of the apparatus.
The inventors have further realized that medium advantageously can be fed to the separation chamber by means of a screw conveyor. This is in particular the case with high viscous medium. A further aspect of the present disclosure therefore relates to an apparatus for the separation of dry matter and liquid from a medium comprising a plurality of rollers, a separation chamber for receiving the medium and defined, in cross section, by the rollers, and at least one screw conveyor for feeding medium into the separation chamber. The rollers can be any combination of press rollers, filter rollers, filter shells and/or press shells as disclosed herein. The filtration may be provided by one or more chamber filters as described herein, by filter rollers and/or by filter shells as disclosed herein.
The feeding of the medium provided by a screw conveyor may create an overpressure inside the separation chamber such that filtering across the filtration surface is provided more efficiently. An overpressure in the separation chamber may make suction in the process avoidable. The screw conveyor may advantageously be configured as a funnel towards the separation chamber as exemplary illustrated in
The screw conveyor advantageously extends along the entire length of the separation chamber such that medium is delivered all the way from entrance of the separation chamber to the opposite end of the separation chamber thereby feeding medium to all the filtration surface(s). The rate of volume transfer, i.e. the feeding of the medium, can be adjusted by the rotation rate of the screw conveyor.
The screw conveyor typically comprises a rotating helical screw blade. It may for example be a spiral blade coiled around a shaft which is driven at one end and held at the opposite end. It may also be a shaftless spiral, driven at one end and free at the opposite end. The inventors have realized that the helix of the screw blade can be “turned” towards the end of the separation chamber such that near the end of the separation chamber the feeding motion is reversed whereby medium is led back in the opposite direction. This principle is exemplified in
A screw conveyor as disclosed above can be applied to all suitable embodiments described in the present disclosure.
Perspective see through illustrations of one embodiment 1 of the presently disclosed filtering apparatus are seen in
Close up illustrations of the embodiment 1 in
In
In
A further aspect of the present disclosure relates to the use of the presently disclosed apparatus for separation of dry matter from products or elements selected from the group of: beer mask, fruit pulp and fruits such as apples, pears, berries, and grapes, and vegetables such as root vegetables such as potatoes, carrots, etc.
The invention will be described in further detail with reference to the following items:
| Number | Date | Country | Kind |
|---|---|---|---|
| 16171485.2 | May 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/062580 | 5/24/2017 | WO | 00 |
