Technical field

The present disclosure relates to a filtering apparatus for separating liquid from a slurry. The present disclosure also relates to a primary filtering unit of a filtering apparatus for separating liquid from a slurry. The present disclosure further relates to a secondary filtering unit of a filtering apparatus for separating liquid from a slurry.

Background art

Cattle, such as cows for milk or meat production produce large amounts of manure. While some of the manure is recycled as fertilizer for crop production, it is challenging to manage the large surplus volumes. Some of the surplus may be consumed in so called “over fertilizing” which in turn may cause leakage of nutrients into the environment. Other surplus is stored in lagoons. There is thus a need for efficient means or methods of collecting manure, reducing its volume and recycling valuable nutrients and other substances therein.

US4666602 shows an apparatus for dewatering manure. The apparatus comprises an elongated flume with a perforated bottom. Liquid manure is circulated through the flume by a driven paddle chain whereby liquid is drained from the manure through the holes in the bottom of the flume. The dewatered manure is subsequently fed to a separator press in which further liquid is forcefully squeezed out of the manure by interaction between perforated drum and a rubber roll. The apparatus of US4666602 is marred with several drawbacks. It occupies a lot of space and the solution of circulating a heavy flow of liquid manure by a driven paddle chain is energy intensive and may cause wear to both paddles and the flume floor.

Thus, it is an object of the present disclosure to provide an improved filtering apparatus for separating liquid from a slurry which solves at least one of the problems in the prior art. In detail, it is an object of the present disclosure to provide a filtering apparatus for separating liquid from a slurry which allows for a high degree of separation of liquid from the slurry. Moreover it is an object of the present disclosure to provide a filtering apparatus for separating liquid from a slurry which is compact, transportable and occupies little floor space. In addition it is an object of the present disclosure to provide a filtering apparatus for separating liquid from a slurry which may be operated at low cost.

Summary of the disclosure

According to the present disclosure at least one of the aforementioned objects is achieved by a filtering apparatus 1 for separating liquid from a slurry, comprising a first filtering means 10 comprising:

- a receptacle 100 for holding slurry comprising an inlet 101 for slurry and an outlet 102 for de-liquefied slurry and;

- at least one hollow cylinder 200 rotatable arranged in the receptacle 100 and comprising a liquid permeable wall portion 300 for allowing liquid of a slurry in the receptacle 100 to enter into the hollow cylinder 200 and;

a second filtering means 20 comprising:

- a liquid permeable planar filter 300 having a first face 301 arranged to receive de- liquefied slurry from the receptacle 100 and configured to allow liquid of the de- liquefied slurry to pass through the liquid permeable planar filter 300;

- an elongated scraper 400 extending along at least a portion of the first face 301 of the planar filter 300 and rotatable arranged to move de-liquefied slurry along the first side 301 of the planar filter 300

The filtering apparatus provides effective separation of liquid from the slurry. One advantage is the two-step separation of liquid. Thus, in a first step, the first filtering means removes effectively liquid from a slurry with a relatively high liquid content. The rotation of the hollow cylinders removes dry matter from circumferential liquid permeable wall of the cylinder so that at least a portion of the liquid permeable wall is exposed to the surrounding slurry. This self-cleaning function of the outer surface of the cylinders allows the first filtering means to be used for long periods without service stops. In the second step, the combination of a liquid permeable planar filter and a scraper is effective in removing a substantial portion of remaining liquid in the de- liquefied slurry from the first filtering means. Overall, the filtering apparatus may result in increasing the dry matter of a slurry in the form of manure from typical input of 6% to approximately 25%

Preferably, the second filtering means 20 comprises a liquid absorbing body 500 comprising a liquid absorbing compressible material extending along at least a portion of a second face 302 of the liquid permeable planar filter 300 and arranged to absorb liquid passing through the planar filter 300. The absorbing body increases the effectiveness of the second filtering means by draining liquid from the lower side of the liquid permeable planar filter. Preferably, the second filtering means 20 comprises at least one pressing means 600 arranged to compress at least a portion of the liquid absorbing body 500 such that liquid in the liquid absorbing body 500 is expelled. According to an embodiment the pressing means 600 may be a roll which extends at least partially between opposing first and second lateral sides 503, 504 of the liquid absorbing body 500 and arranged to move reciprocally between opposing first and second ends 505, 506 of the liquid absorbing body. The squeezing action from the pressing provides a self-cleaning function of the liquid permeable planar filter by forcing liquid back through the liquid permeable planar filter. According to an embodiment, the elongated scraper 400 comprises a center 401, dividing the scraper in a first and a second curved half scraper blade 402, 403, wherein the half scraper blades 402, 403 extend from the center 401 of the elongated scraper 400 such that when the elongated scraper is rotated in a first rotation direction, the leading side of each half-scraper blade 402, 403 is concave and when the elongated scraper 400 is rotated in a second rotation direction the leading side of each half-scraper blade 402, 403 is convex. By alternating periods of counter-clockwise and clockwise rotation of the elongated scraper, slurry may be moved towards and away from the center of the liquid permeable planar filter 300. This provides for efficient removal of liquid from the slurry since the full upper surface of the planar filter is used. It also provides for effective emptying of de-liquefied slurry from the second filtering means 20

Brief description of the drawings

Figure 1 : A perspective front view of a filtering apparatus according to a first preferred embodiment of the present disclosure.

Figure 2: A perspective side view of the filtering apparatus according to the first embodiment of the present disclosure.

Figure 3: A perspective rear view of the filtering apparatus according to the first embodiment of the present disclosure.

Figure 4a: A perspective front view from above of the filtering apparatus according to the first embodiment of the present disclosure.

Figure 4b: A schematic drawing of a scraper of the present disclosure.

Figure 5: A partially exposed view of the filtering apparatus according to the first embodiment of the present disclosure.

Figure 6: A schematic drawing illustrating the function of a first aspect of the filtering apparatus according to the first embodiment of the present disclosure.

Figure 7: A schematic drawing illustrating the function of a second aspect of the filtering apparatus according to the first embodiment of the present disclosure.

Definitions

By“slurry” is meant a mixture of solid matter and liquid, solid mater may include minerals, such as sand or clay or gravel. Solid matter may further include organic solid matter, such as fiber, vegetables, or feces. Such solid matter is typically denominated “dry matter”. The liquid may include water, urine chemical waste or mixtures thereof. Examples of slurries are manure, sludge, sewage. Manure is conventionally considered a slurry of dry matter and liquid. With regards to liquid content“slurry” or“wet slurry” contains more liquid than“de- liquefied slurry”. For example, a“slurry” or“wet slurry” in the form of manure may have a content of solid matter of 6 %. For example“de-liquefied slurry” in the form of manure may have a content of solid matter of 20 % or more. The remainder is liquid.

Detailed description of embodiments

The filtering apparatus according to the present disclosure will now be described more fully hereinafter. The filtering apparatus according to the present disclosure may however be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, this embodiment is provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those persons skilled in the art.

Figure 1 shows a filtering apparatus 1 according to the present disclosure in a perspective front view. The filtering apparatus comprises a base 2 for supporting the filtering apparatus on the ground and a top 3 which facing away from the base. The base 2 may be provided with means, e.g. openings, for engagement with forks of a lift truck which allows the filtering apparatus to be moved between locations. The filtering apparatus 1 further comprises a front 4 and opposing rear 5 (not visible) and two opposing sides 6 which extends between the base 2 and the top 3. Figure 1 also shows a vertical axis y which extends perpendicular from the ground and through the base and the top of the filtering apparatus. Vertical axis y indicate the general vertical orientation of the of the filtering apparatus 1. The filtering apparatus 1 comprises a first filtering means 10 and a second filtering means 20. The first filtering means 10 is arranged vertically above the second filtering means 20 which is supported on the base 2. The second filtering means 20 is thereby arranged downstream the first filtering means 10. The filtering apparatus may be configured to separate liquid from manure. Hereinabove and hereinafter, the first filtering means or unit 10 maybe denominated “a first filtering device 10”. Correspondingly, the second filtering means or unit 20 may be denominated“a second filtering device 20”.

The first filtering means 10 is in the following described with reference to figure 2 and 3 which shows the filtering apparatus 1 in side view. Turning to figure 2, the first filtering means 10 comprises a receptacle 100 for holding a slurry. In the embodiment shown in figure 2, the receptacle 100 is of rectangular cross-section and comprises a bottom 105, a circumferential wall which comprises a front wall 103 and a rear wall 104, arranged opposite each other, and opposing side walls 107. The receptacle 100 may also comprise a top lid 106. It is of course possible that the receptacle may have other design, for example the circumferential wall may be circular. The receptacle 100 comprises an inlet 101 for wet slurry. The inlet 101 may be arranged in the lid 106 for example in the form of an opening. The receptacle 100 further comprises an outlet 102 for de-liquefied slurry. In the embodiment of figure 2, the outlet 102 is arranged in the bottom 105 of the receptacle 100. For example the outlet 102 is an opening in the bottom of 105 of the receptacle. The outlet 102 is preferable arranged to be closed and opened. A closable valve 110 may thereby be connected to the outlet 102. The bottom 105 may thereby be funnel-shaped and the outlet 102 may be provided in the converging end of the funnel-shaped bottom 105 to facilitate removal of de-liquefied slurry from the receptacle 100.

The first filtering means 10 further comprises at least one hollow cylinder 200 which is rotatable arranged in the receptacle 100. A first end 201 of the hollow cylinder 200 may thereby be rotatably attached to the front wall 103 of the receptacle 100 and the second end 202 of the cylinder may be rotatably attached to the rear wall 104 of the receptacle. Thus, the hollow cylinder 200 may rotate around its center axis. Rotatable attachment of the hollow cylinder 200 may be achieved by attaching the ends of the hollow cylinder 200 to rotary bearings (not shown) that are arranged in the front and rear walls of the receptacle. Appropriate liquid tight sealing, such as elastomer rings, may be provided between the first and the second end 201, 202 of the cylinder and the front and rear wall 103, 104 of the receptacle in order to prevent leakage of liquid. At least a portion of the circumferential wall 203 of the hollow cylinder 200 is permeable to liquid. At least a portion of the circumferential wall 203 is thereby configured such that liquid of a slurry in the receptacle may pass through circumferential wall 203 into the hollow cylinder and such that solid matter in the slurry is substantially prevented from entering into the hollow cylinder. This may be achieved by providing holes or perforations of a predetermined cross-sectional size in in the circumferential wall 203 of the hollow cylinder. The size of the holes may be selected in dependency of the size of the solid matter in the slurry and may be determined by standard tests. For example, when the slurry is constituted by manure, the openings may be square or rectangular with a side length of 100 - 500 pm. For example 150 - 200 pm for pig manure or 200 - 500 pm for cow manure. According to an embodiment, the liquid permeable wall 203 is a fabric of metal threads, e.g. steel threads. The fabric may be a fabric of woven metal threads. The stich size, i.e. the openings between the woven metal threads have a side length of 100 - 500 pm. The diameter of the hollow cylinder may be 0.15 m.

The hollow cylinder 200 further comprises an outlet 204 for connecting the interior of the hollow cylinder 200 to a collecting receptacle 700 for liquid. The outlet 204 may be an opening in the second end 202 of the hollow cylinder 200. The outlet 204 of the hollow cylinder 200 may be connected by a tube 109 to the collecting receptacle 700.

The hollow cylinder 200 may be rotated by a motor, such as an electrical motor (not shown). Figure 3 shows a perspective rear view of the filtering apparatus 1. The second ends of the hollow cylinder 200 may thereby be connected to the motor by a drive chain 30 and gearwheels 40.

It is appreciated that the first filtering means 10 may comprise more than one hollow cylinder 200. For example the first filtering means 10 may comprise at least two cylinders 200. To achieve efficient removal of liquid in the slurry, the first filtering means 10 may comprise two or more rows of hollow cylinders 200, for example three or four more rows. Each row may comprise at least two hollow cylinders, for example three or four hollow or more cylinders. The rows of cylinders 200 are arranged above each other in vertical direction. It is appreciated that each cylinder 200 is configured, designed and arranged as described hereinabove.

Figure 6 shows the function of the hollow cylinder 200 in use during filtering of slurry (S). The hollow cylinder 200 is immersed in liquid slurry (S) contained in receptacle 100 such that the outer surface of liquid permeable wall 203 is enclosed by slurry (S). The slurry (S) exerts a pressure (P) onto to the outer surface of the liquid permeable wall 203 of the cylinder. The pressure difference thereby causes liquid (L) to flow through the openings in the liquid permeable wall 203 and into the hollow cylinder. During filtering of the slurry, a layer of de-liquefied solid matter (M) gather onto the outer surface of the liquid permeable wall 203. However, due to the rotational movement of the hollow cylinder 200 the layer of de-liquefied solid matter is constantly removed by contact with the surrounding slurry which in turn exposes the outer surface of the liquid permeable wall 203 to wet slurry. Thus, the rotational movement of the hollow cylinder 200 provides a self-cleaning function of the outer surface of the liquid permeable surface and allows the first filtering means to be used for long periods without service stops.

Since the hollow cylinder 200 is continuously emptied through the cylinder outlet 204 (see figure 2), the pressure difference between the interior of the hollow cylinder 200 and the surrounding slurry is maintained. This in turn results in a constant flow of liquid from the slurry into the hollow cylinder 200.

It is appreciated that, in use, the entire outer surface of the liquid permeable wall 203 of the hollow cylinder 200 may be in contact with wet slurry or in contact with wet slurry and solid matter.

Preferably, the outlet 102 for de-liquefied slurry is arranged underneath the hollow cylinders 200. For example as shown in figure 2, the outlet 102 is arranged in the bottom 105 of the receptacle 100 underneath the hollow cylinder/s 200. During filtration of a slurry, the de-liquefied, thickened, slurry gather in the bottom of the receptacle and may be released from the receptacle 100 through the outlet 102. The first filtering means 10 may therefore be operated in cycles of predetermined length in which de- liquefied slurry is released intermittently from the container and new slurry is intermittently introduced into the receptacle. Thus, an amount of de-liquefied slurry is released from the receptacle 100 and replaced with new slurry but the receptacle 100 is not emptied. This operation mode result in a high filtering efficiency of the first filtering apparatus. The amount of released slurry may be synchronized with the capacity of the second filtering means to optimize the output of the filtering apparatus.

The second filtering means 20 is described with reference to figures 4a, 4b and 5. Figure 4a shows an exposed view of the filtering means 20 shown in figure 1 in which the cover of the second filtering means has been removed. The second filtering means 20 comprises a liquid permeable planar filter 300 which is configured to allow liquid from a slurry to pass through the liquid permeable planar filter and such that solid matter in the slurry is substantially prevented from passing through the liquid permeable planar filter. The liquid permeable planar filter 300 may be a flat or planar thin body. That is, having a length, width or diameter which substantially exceeds its thickness. The liquid permeable planar filter comprises openings, i.e. through holes, of a predetermined cross- sectional size in the liquid permeable planar filter. The size of the opening in the liquid permeable planar filter may be selected in dependency of the size of the solid matter in the slurry and may be determined by standard test. For example, when the slurry is constituted by manure, the openings may be square or rectangular with a side length of 100 - 500 pm. According to an embodiment, the planar liquid permeable filter 300 is a flat sheet, for example a fabric of woven metal, e.g. steel, threads. The stich size, i.e. the openings between the woven metal threads have side length of 100 - 500 pm. The liquid permeable planar filter 300 has a first, upper, face 301 which is arranged to receive de-liquefied slurry from the outlet 102 of the receptacle for slurry 100. The liquid permeable planar filter 300 may thereby be arranged underneath, i.e. downstream the outlet 102 of the receptacle 100 for slurry with the upper face 301 directed towards the outlet 102. In detail, the liquid permeable planar filter 300 extend in a horizontal plane underneath the outlet 102 of the receptacle for slurry 100. The liquid permeable planar filter 300 may be circular as shown on in figure 4a. The second filtering means 20 further comprises an elongated scraper 400 which extends along at least a portion of the first face 301 of the liquid permeable planar filter 300. The elongated scraper 400 thus extend along at least a portion of, or along the entire diameter of the liquid permeable planar filter 300. The elongated scraper 400 is rotatable arranged such that the elongated scraper 400 may rotate over the first face 301 of the liquid permeable planar filter 300. The elongated scraper 400 may thereby comprise a shaft 405 which extends through the center 401 of the elongated scraper 400 and that is connected to a drive motor (not shown) which is arranged to rotate the shaft 405. When slurry is present on the first face of 301 the liquid permeable planar filter 300, the elongated scraper 400 moves the slurry over the first face 301 of the liquid permeable planar filter 300 in a rotating motion. The center 401 of the elongated scraper 400 may be arranged in the center of the liquid permeable planar filter. The liquid permeable planar filter 400 comprises an circumferential wall 303 which extends perpendicular from the periphery of the liquid permeable planar filter 300. The circumferential wall 303 may comprise a closable opening 304 (see figure 3) through which slurry may be expelled. The opening 304 comprises a lid 305 which is hinged to the circumferential wall such that the opening 304 may be opened or closed.

Figure 4b shows the elongated scraper 400 in view from above. The center 401 divides the elongated scraper 400 in two half scraper blades 402 and 403. Each half scraper blade comprises an edge 404 that is directed towards the liquid permeable planar filter and opposing sides. The edge may be a solid edge or a brush. The two half scraper blades 402, 403 are identical and curved, i.e. have an arc shape. The two scraper blades 402, 403 extend respectively in opposite direction from the center 401. The two scraper blades 402, 403 are thereby arranged such that when the elongated scraper is rotated in a first rotation direction, such as counter-clockwise, the leading side of each half-scraper blade is concave and when the elongated scraper is rotated in a second rotation direction, i.e. clockwise, the leading side of each half-scraper blade 402, 403 is convex. The general effect of this concave/convex design is that when the elongated scraper 400 is rotated the first rotational direction slurry is moved towards the center 401 of the elongated scraper by the concave form of the half scraper blades 402, 403. When the elongated scraper 400 is rotated the second rotational direction slurry is moved towards the periphery of the liquid permeable planar filter 300 by the convex side of the half scraper blades and may be expelled through the opening 304.

In the shown embodiment, the elongated scraper 400 comprises a central body 401 forming the center of the elongated scraper blade. The rotational shaft 405 extends through the central body 401. The two half-scraper blades 402, 403 are attached to the central body 401 by a respective first end on opposing sides of the rotational shaft 405 such that the two half-scraper blades are spaced apart from each other and extend in opposite direction. Alternatively, the scraper blade may be a continuous S-shaped blade.

The second filtering means 20 further comprises a compressible liquid absorbing body 500 which is arranged underneath the liquid permeable planar filter 300 to absorb liquid the passes through the liquid permeable planar filter 300.

The liquid absorbing body is following described with reference to figure 5 which shows a partially exposed view of the filtering apparatus 1 of the present disclosure. In figure 5, the liquid permeable planar filter 300 has been removed to show further features that are arranged underneath liquid permeable planar filter 300. Moreover figure 5 only shows a portion of the liquid absorbing body is shown in order to not obscure other features. However, in practice, the liquid absorbing body 500 extends along at least a portion of the second, lower, face 302 of the liquid permeable planar filter 300. Preferably, the liquid absorbing body 500 extends along substantially the entire second face 302 of the liquid permeable planar filter 300. The liquid absorbing body 500 may have any suitable form. For example the liquid absorbing body has the same form as the liquid permeable planar filter 300, e.g. circular. However, in the embodiment shown in figure 6, the liquid absorbing body 300 is rectangular and extends between the lateral sides 21, 22 and between the 23, 24 of the second filtering means 20. The liquid absorbing body 500, which may be a substantially flat block has a first, upper side 501 which is arranged adjacent or in contact with the second face 302 of the liquid permeable planar filter 300. The second side 502 of the liquid absorbing body 500 faces away from the liquid permeable planar filter (see also figure 7). The liquid absorbing body 500 may at least partially comprise or consist of a liquid absorbing and compressible material. The liquid absorbing compressible material is resilient such that it may be compressed by application of a force and return to its original shape when the force is removed. For example, the liquid absorbing compressible material may be a foam material, such as polyurethane foam. The thickness of the liquid absorbing compressible material may be 30 mm. Preferably, the liquid absorbing compressible material comprises both closed pores and open pores. Closed pores provides structural strength to the liquid absorbing body 500 and allows it to regain its original form after compression. The open pores allows the liquid absorbing body 500 to absorb liquid. Preferably, the average cross-sectional size of the pores in the liquid absorbing body 500 is greater than the openings in the planar filter 300. This reduces clogging of the pores of the liquid absorbing body and increases its life-length.

The second filtering means 20 further comprises at least one pressing means 600 that is arranged underneath the liquid absorbing body 500 and arranged to compress at least a portion of the liquid absorbing body 500 such that liquid in the absorbing body is expelled.

Returning to figure 5, the second filtering means 20 may comprises pressing means in the form of at least one roll 600. The roll 600 extends between the lateral sides of the liquid absorbing body 500 and is arranged to move reciprocally between the first end 505 and the second end 506 of the liquid absorbing body 500. In the embodiment shown in figure 6, the opposing ends of the roll 600 are movable arranged in a respective guide track 25 in the sides 21, 22 of the second filtering means 20. A drive chain 26 is coupled to the respective ends of the roll 600 and to a drive motor 27. The drive motor 27 rotates the drive chain 26, which in turn rotates and moves the roll 600 along the guide track 25. As shown in figure 5, the second filtering means 20 may comprise two or more pressing means 600, e.g. rolls.

Turning to figure 7. The arrangement of an liquid absorbing compressible body 500 and a pressing roll 600 provides distinct advantages in combination with the liquid permeable planar filter 300. Figure 8 shows schematically a liquid absorbing compressible body 500 which is arranged such that its upper, first side 501 is adjacent the second lower face 302 of the liquid permeable planar filter 300. Liquid (L) in a slurry is present on the upper, first face 301 of the liquid permeable planar filter 300. It is assumed that the portion of the absorbing body 500 in front of the pressing roll 600 is saturated with liquid (L). As the pressing roll 600 moves over the absorbing body 500 it compresses the absorbing body 500 towards the second face of the liquid permeable planar filter and expels the liquid (L) from the liquid absorbing body 500. The major part of the liquid (Ll) flows by gravity downwards and is collected in the collection receptacle 700 (not shown in figure 7). However, simultaneously a small amount of liquid (L2) is forced upwards through the liquid permeable planar filter in direction from the second face 302 to the first face 301. This is advantageous since the small amount of liquid provides a“backwash” of the liquid permeable planar filter and rinses the openings in the liquid permeable filter from small particles of solid matter. This increases the filtering effect of the liquid planar filter and reduces the frequency for maintenance stops to clean or change the liquid planar filter. A further advantage is that an under pressure is achieved behind in the portion of the absorbing body 500 that is behind the pressing roll when this portion of the absorbing body 500 expands to regain its original shape. The under-pressure causes liquid (L3) to be drawn from the liquid planar filter into the absorbing body. This provides an advantage in that the velocity of filtering of the slurry is increased.

Although a particular embodiment has been disclosed in detail this has been done for purpose of illustration only, and is not intended to be limiting. In particular it is contemplated that various substitutions, alterations and modifications may be made within the scope of the appended claims. For example, the filtering apparatus 1 according to the present disclosure is preferably configured as an integral means. However, it is also possible to utilize the first filtering means 10 and the second filtering means 20 separate from each other. Thus, the first filtering means 10 may be a separate or individual filtering unit for separating liquid from slurry. The second filtering means 20 may be a separate or individual filtering assembly for separating liquid from slurry

Moreover, while the disclosed embodiment shows the filtering apparatus 1 in a vertical configuration other designs are possible. For example, the first filtering means 10 may be arranged remotely from the second filtering means 20. De-liquefied slurry may thereby be pumped through a conduit from the first filtering means 10 to the second filtering means 20.

However, in these alternatives and in the embodiment described hereinabove, the second filtering means 20 is arranged downstream the first filtering means 10.

Moreover, although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Furthermore, as used herein, the terms “comprise/comprises” or “include/includes” do not exclude the presence of other elements. Finally, reference signs in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.