DE20007226U1 - Device for filtering and separating in particular biologically organic flow media - Google Patents

Description

ROCHEM RO-Wasserbehandlung GmbH, Stadthausbrücke 1 - 3, 20355 Hamburg

Device for filtering and separating, in particular, biologically organic flow media

Describe bunq

The invention relates to a device for filtering and separating, in particular, biologically organic flow media by reverse osmosis and micro-, ultra- and nanofiltration, comprising a plurality of spaced-apart flat filter elements around which the flow medium flows, such that a plurality of separate stacks of filter elements are arranged behind and/or next to one another, the stacks being surrounded behind and/or next to one another by the flow medium and the permeate collected by the filter elements being introduced into drain bolts passing through the stacks of filter elements and being discharged via permeate drains.

Such a device is known (EP-A-0 707 884). The known device has a housing in which the stacks of filter elements are arranged one behind the other, the housing having an inlet for the medium to be separated, an outlet for the retentate and an outlet for the permeate, which is suitably discharged from the filter elements, collected and discharged to the outside via the permeate outlet for further use. Within the housing in which the stacks are arranged, an open channel is created for the flow medium, whereby the type of arrangement of the stacks of filter elements allows extremely high flow velocities of the flow medium between the inlet of the flow medium and the outlet of the flow medium leaving the device as retentate, thus preventing the formation of deposits, for example in the form of a filter cake, on the filter elements, since the stacks of filter elements have virtually no dead zones for the flow medium flowing in a longitudinal channel and the flow medium can flow from the inlet to the outlet of the device with virtually no deflection.

Both municipal and commercial wastewater often contain a high biologically organic content, which is often referred to as a high biomass concentration, which can only be controlled with very high equipment and/or process costs if the liquid solvent, usually water, is to be extracted from such biologically organically contaminated flow media. The extraction of the aqueous solvent can serve the purpose of concentrating the flow medium in order to be able to degrade it optimally, and/or extracting the aqueous medium from the flow medium, for example to produce service water and even

To be able to obtain drinking water from the flow medium contaminated with biologically organic substances.

One requirement that is placed on such devices is that they must be functional when the flow medium itself is virtually stationary or is only moving at a very low speed, i.e. when the flow medium has speed conditions such as those found in sewage treatment tanks, open waters and also in bioreactors. It is therefore not possible to use high, possibly extremely high flow speeds of the flow medium, such as those found between the inlet of the flow medium and the outlet of the flow medium leaving the known device mentioned above as retentate, with all the resulting consequences for the trouble-free and continuous operation of such a device.

In many cases, there is also the requirement that the energy requirement for the continuous and uninterrupted operation of such a device should be extremely low, since such devices should also be able to be operated essentially independently of existing power supply networks, so that for this reason too, high flow medium pressures or flow velocities generated by electric pumps and the like, as in the known device, cannot be generated.

It is therefore the object of the present invention to create a device of the type mentioned at the outset which is capable of safely separating liquids with a high biologically organic and/or inorganic content of ingredients, whereby the device must be capable of carrying out its separation task,

to manage with the lowest flow velocities of the flow medium up to the point of standstill and to largely avoid deposits in the form of a filter cake on the filter elements, whereby the device should be able to be operated efficiently and continuously with very low energy consumption, largely maintenance-free and yet have a low energy consumption.

The object is achieved according to the invention in that the permeate can be generated essentially by building up a negative pressure at the permeate outlet compared to the flow medium which is essentially at the level of the ambient or atmospheric pressure.

The advantage of the solution according to the invention is essentially that the entire device, which basically does not require a housing surrounding the device, simply needs to be immersed in the flow medium, for example a sewage tank, a free body of water or even a bioreactor, and only a suitable negative pressure needs to be applied to the permeate outlet of the device, for example by a vacuum pump which generates a vacuum of 0.5 to 0.9 bar. The very great advantage of the device according to the invention is not only that virtually no housing is required and the device needs to be immersed in the flow medium at any suitable point, but also that the separation of the flow medium is essentially exclusively caused by the negative pressure on the permeate side, namely by setting the optimal pressure difference between the flow medium and the permeate or by setting a suitable pressure ratio between the flow medium

and permeate. In addition, the device advantageously also allows the formation of extremely large membrane surfaces in the smallest of spaces, whereby no consideration needs to be given to specifications on the housing side. If the membrane surface of the device is not sufficient to achieve the desired degree of concentration of the retentant leaving the device, which also applies to the desired degree of purity of the permeate leaving the device, the device can be easily enlarged in its membrane surface by assigning further stacks of filter elements to the device, which is designed in such a way that this can also be done retrospectively in a simple manner.

According to an advantageous embodiment of the device, the filter elements are designed in the form of membrane cushions, as are generally known in membrane separation technology. It should be noted, however, that the filter elements in the form of membrane cushions are not the only way of designing the filter elements. It is certainly possible to use filter elements that consist of only one membrane layer if design measures ensure that the side of the membrane element facing away from the flow medium, i.e. the permeate side, is effectively sealed against the flow medium, thus ensuring that the flow medium cannot mix with the permeate again.

Advantageously, in the membrane cushions between the outer membrane elements delimiting them or the outer membrane element delimiting a filter element on one side, at least one flat, dimensionally stable stabilizing element is provided to create a

high inherent stability of the membrane cushion. In principle, it is of course possible to stabilize the filter elements, whether in the form of single-element membrane elements or in the form of membrane cushions, through external measures so that they are not pressed against one another or do not even partially touch one another during operation of the device. Failure to provide these measures would result in the membrane surface being restricted and thus the separation performance being reduced. Furthermore, the selective separation layer of the membrane elements can be damaged if they come into contact and contact can also lead to the membrane elements sticking together, which in turn can create deposit starting points that can lead to the filter elements becoming completely blocked. Coarse ingredients can also be found in heavily contaminated flow media, which in the case of mechanically unstable filter elements can lead to the filter elements touching one another during operation, with the disadvantageous consequences described above. For this reason, it is advantageous to arrange at least one flat, dimensionally stable stabilizing element in the membrane cushions between the outer membrane elements that delimit them or, if only one-sided membrane elements are used, above or below the membrane element in the case of filter elements that are only designed in the form of a membrane element, in order to create a high level of inherent stability of the filter element. Such a design of the device is advantageously free of external spacer elements, as are also known in the prior art, whereby this design of the filter elements free of spacer elements has the very great advantage that the flow medium can reach all sides of the filter element without interference, which is particularly important for

This is of great advantage for stationary or only slightly moving flow media.

The filter elements themselves are advantageously made of a polymer or a polymer mixture, in which case they are referred to as polymer membranes. Polymer membranes are known in the state of the art for a wide variety of separation tasks with a wide variety of chemical compositions and are selected to suit the separation tasks to be accomplished.

In addition to filter elements made of polymer or polymer mixtures, filter elements made of ceramic materials can also be provided, which are able to solve special separation tasks that are difficult, or sometimes impossible, to solve with polymer membranes, especially when the flow medium has temperatures at which polymer membranes or polymer mixture membranes are no longer stable.

The stabilizing element itself advantageously consists of a material that is sufficiently temperature and pressure stable so that the filter element to which the stabilizing element is assigned inside or outside does not deform or only deforms slightly.

In order to improve the flow of the permeate, i.e. to reduce the energy expenditure on the permeate side, it is advantageous to make the stabilizing element out of a porous material. This allows the permeate to reach the permeate flows of the device with even less energy expenditure, since the porous design of the material enables better flow of the permeate from the permeate side of the membrane.

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Basically, the stabilizing element is advantageously made of plastic and/or a metallic material and/or a ceramic material, although combinations of the aforementioned materials are also possible to form the stabilizing element. The material of the stabilizing element is also selected according to compatibility criteria with the flow medium and the expected temperature conditions.

It was pointed out at the beginning that the device should also be designed from the point of view of simplicity and thus of being able to be implemented cost-effectively, which also has advantages in terms of its possible mass use on the one hand and its manufacturability and ease of maintenance on the other. In order to pay even greater attention to this aspect, it is advantageous to design the drain bolt in such a way that it has a plurality of openings arranged around a circumference and distributed over its length for the entry of the permeate into a drain hole which essentially passes axially through the drain bolt. This design makes it possible to use standard semi-finished pipe products, as are commercially available, for example made of plastic or glass-fiber-reinforced plastic or of metallic tubular materials to form the drain bolt. In this way, simple drainage channels can also be formed in the axial direction in the drainage bolt and these channels can be broken through at certain distances from the pipe interior, so that on the one hand the mechanical stability of the drainage bolt is maintained and on the other hand a uniformly distributed permeate drainage option is provided around the cross section of the drainage bolt.

The axially formed or aligned grooves and openings can be formed in a relatively simple manner, for example by means of a disc milling cutter with a small disc diameter.

Advantageously, the filter elements of the stack are spaced apart from one another in such a way that the filter elements do not touch one another during operation of the device, the disadvantages of touching having already been pointed out above.

Advantageously, the filter elements can be spaced apart from one another in such a way that annular spacer elements are provided. Such a design is preferably selected when the filter elements or the filter element stacks are only traversed by a single drain bolt, but it is also possible in principle to provide annular spacer elements if, for example, two drain bolts traverse a stack of filter elements. Nevertheless, in the latter case, the filter elements can advantageously be spaced apart from one another in such a way that strip-shaped spacer elements are used, which each have a hole at the distance of the bores for the two drain bolts, which in this case are spaced apart from one another, through which a drain bolt passes.

The spacer elements, whether ring-shaped and/or strip-shaped, can also be designed in such a way that, in addition to their spacing effect, they also have a sealing effect against a permeate discharge space, so that the variety of parts for forming a stack of filter elements can be reduced.

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The stacks of filter elements themselves can preferably be held together by struts which delimit the stacks on both sides and are spaced apart, wherein spacers can preferably be provided between the struts which connect the struts to one another at a predetermined distance, whereby the necessary axial pressure is also exerted on the respective stacks of filter elements in order to make them sufficiently pressure-tight, including the spacer elements and, if necessary, separate seals.

Nevertheless, the aforementioned design of the holding and pressure-tight connection of the filter elements or the stack of filter elements is a very simple but nevertheless very effective way of holding and fastening, which has already proven itself in in situ applications under real operating conditions in wastewater treatment tanks and in flowing waters.

The invention will now be described in detail with reference to the following schematic drawings using an exemplary embodiment.

Fig. 1 in front view in partially broken representation a device consisting of four stacks of filter elements,

Fig. 2 is a side view of the illustration in Fig. 1

Fig. 3 a AbI bolt on, two of which in the case shown in Fig.

1 illustrated design of the device

per filter element stack, on average,

Fig. 4 a side view of the AbI bolting according to Fig. 3 rotated by 90 ° and partly in section,

Fig. 5 is a section through the drain bolt along the line A-B of Fig. 4,

Fig. 6 is a plan view of a filter element in the form of a membrane cushion used in the stacks of the device,

Fig. 7 is a plan view of a stabilizing element arranged in the membrane cushion according to Fig. 6 between the two outer limiting membrane elements,

Fig. 8 in side view a stabilizing element according to Fig. 7,

Fig. 9 a strip-shaped spacer element and a ring-shaped spacer element indicated in outline by dash-dot lines in plan view and

Fig. 10 is a side view of the spacer element shown in Fig. 9.

Reference is first made to the illustration of Fig. 1, which shows the view of the device 10 from the front, and Fig. 2, which shows a view of the front side of the device 10 shown in Fig. 1.

The device 10 is intended for filtering and separating flow media 11, in particular flow media 11 which have a high biomass concentration, for example 45 g/l. In the example of Fig. 1, the device 10 comprises four stacks 13 of

Filter elements 12, which here are designed as membrane cushions, for example, see also Fig. 6-8. The number of filter elements 12 per stack 13 is determined by the membrane area to be realized in the device 10.

In the embodiment of the device 10 shown here in the figures, each stack 13 of filter elements 14 is traversed by two drain bolts 15, as shown in particular in Figs. 3, 4 and 5 in an enlarged scale compared to the illustration in Fig. 1. It should be noted that such embodiments of filter elements 12 or stacks 13 are also possible in which only one drain bolt 15 passes through them instead of two drain bolts 15. In principle, however, more than two drain bolts 15 can also be provided per stack 13 or per filter element 12 if, for example, due to the low operating pressures, which will be discussed further below, the permeate 14 is to be drained as undisturbed as possible from the filter elements 12.

The number of filter elements 12 that form a stack 13 can basically also vary from stack to stack of the device 10, if, for example, different spacing elements 17 are selected in a stack 13, but the individual stacks 12 have different numbers of filter elements 12. A design as mentioned last can be useful, for example, if the flow medium 11, in the example of Fig. 1, passes through the device 10 from left to right, so that the distances between the filter elements from stack to stack 13, here in the example of the representation of Fig. 1, from left

to the right. The different spacing of the filter elements 12, which is essentially formed by the spacing elements 17, which will be discussed further below, can vary, for example, in the range from 1 to 10 nm, taking into account the different biomass concentrations or other contamination concentrations in the flow medium 11 or, to stay with the example of Fig. 1, the increase in the concentration of the flow medium 11 from left to right.

The flow medium 11 flows around the filter elements 12 which are combined to form stacks 13. If the filter elements 12 are designed in the form of membrane cushions, the separation effectiveness of the membrane cushions is essentially doubled compared to filter elements 12 with only one membrane element 120, since they can be acted upon by the flow medium 11 on their two more separation-active membrane element sides. The stacks 13 can be arranged next to one another, as shown in Fig. 1 and 2, so that the flow medium 11 can sweep or flow over the filter elements 12. However, it is also possible to provide stacks 13 arranged behind and/or next to one another. The device 10 thus allows the stacks 13 with the filter elements 12 to be arranged in rows and/or columns. Due to its modular design, the device 10 can therefore be directly adapted to the type of flow medium or the degree of concentration of impurities in the flow medium.

The stacks 13 of filter elements 12 are limited on both sides by struts 19, 20, which can be T-shaped or L-shaped. The clear distance between the two struts 19, 20 can be adjusted by spacers 21, 22, which are

The length of the spacers 21, 22 is determined according to the number of filter elements 12 per stack 13 as well as the spacer elements 17 provided between the filter elements and the thickness of the filter elements 12.

The drain bolt 15 shown in various views in Fig. 3 - 5, in which the permeate 14 coming from the filter elements 12 is collected and discharged to the outside, see also Fig. 1, is designed for filter elements 12 which are designed in the form of membrane cushions, as shown in Fig. 6-8. A permeate bolt 15 essentially consists of a tube which is available as a tubular semi-finished product. Distributed over the circumference, in the present case at four points distributed over the circumference, see also Fig. 5, are drainage channels 152 which do not break through the wall of the drain bolt 15. Only a predetermined number of openings 150 are arranged in the drain bolt 15, distributed over the length and circumference, through which the permeate 14 can reach the drain bore 151 of the drain bolt 15, which passes axially through the drain bolt 15. The number of openings 150 and the number of drainage channels 152 per drainage bolt 15 can be suitably selected depending on the length of the drainage bolt 15, its diameter and also depending on the permeate 14.

The structure of the filter elements 12 designed in the form of membrane cushions is known in the art, so that reference can be made to EP-G-O 129 663, in which the typical structure of a filter element 12 designed as a membrane cushion is described. The special feature of the membrane cushions used here in the device 10 is that between the respective delimiting

At least one flat, dimensionally stable stabilizing element 122 is provided for each of the outer membrane elements 120, 121, see Figs. 7 and 8. The dimensionally stable stabilizing element 122 can provide a high level of inherent stability for the membrane cushion, so that it ensures that the membrane cushions do not touch one another during operation of the device 10. The stabilizing element 122 can also be made of plastic and/or a metallic material and/or a ceramic material and can be homogeneous or porous, in the latter case allowing the permeate 14 to flow away more smoothly.

The filter elements 12 are formed by ring-shaped and/or strip-shaped spacer elements 17, 18, see Figs. 9 and 10. The spacer elements 17, 18 have holes 170, 180, wherein the holes 180 are spaced apart from one another in such a way that they correspond to the distance between the holes of the filter element 12 designed as a membrane cushion, which form the permeate drainage holes 123 there. The spacer elements 17, 18 can, if they consist of elastomeric material, for example, simultaneously have a sealing function, so that the permeate 14 produced by the filter element 12, here in the form of membrane cushions, can flow inside the membrane elements 120, 121 to the permeate drainage holes 123 and from there into the drainage channels 152 of the drainage bolt 15 passing through the permeate drainage holes 123 and the spacer elements 17, 18. From the drainage channels 152, the permeate 14 passes through the openings 150 in the drainage bolt 15 into the drainage bolt bore 151 and is discharged to the outside.

During operation of the device 10, which may be installed, for example, in a sewage treatment plant, an open body of water or

can also be immersed in a bioreactor, after being introduced or immersed in the flow medium 11, the latter flows around all of the filter elements 12. Suitable line connections are laid at the permeate outlets 16 of the outlet bolts 15 so that a vacuum pump connected to it, which generates a negative pressure, for example in the range between 0.5 - 0.9 bar, compared to the ambient or atmospheric pressure at which the flow medium 11 is located, is used. The negative pressure causes the flow medium 11 to separate in the filter element 12 so that permeate 14 is generated which is conveyed via the filter element 12 or in the interior of the filter element 12 designed as a membrane cushion to the outlet channels 152 of the outlet bolt 15 and from there flows via the openings 150 into the outlet bore 15 and from there is discharged to the outside. For the intended operation of the device 10, it is only necessary to provide a vacuum pump to generate a slight negative pressure on the permeate side of the filter element 12 or the membrane cushion.

Tests with the device 10 have shown that it cannot be ruled out under all circumstances that deposits from the impurities contained in the flow medium will form on the filter elements 12 during operation of the device 10. The separation of the flow media 11 used according to the invention by generating a slight negative pressure on the permeate side compared to the flow medium 11 which is essentially at the level of the ambient or atmospheric pressure has shown that the deposits forming on the filter element 12 have a different mechanical consistency than, for example, deposits on filter elements which are operated in devices which operate at a high pressure or a high flow rate.

of the flow medium (high feed pressure, high feed speed). The advantage of the device 10 according to the invention is thus also evident in a further area, namely that the deposits that may form on the filter elements 12 can be removed very easily, for example by backwashing the permeate side of the filter elements 12, for example with pure water, so that the only slightly adhering, porous deposits are released from the filter element 12 and absorbed by the flow medium 11.

The operation of the device 10 according to the invention can be further improved by swirling the flow medium with air and also by providing a circulation pump to allow the flow medium to pass over the surfaces of the filter elements 12, i.e. the surfaces of the membrane elements 120, 121, at a low speed. This also makes it possible to counteract a deposit forming on the filter element 12 with little energy expenditure.

18 List of references

10 Device

11 Flow medium

12 Filter element, membrane cushion

Membrane element Membrane element Stabilization element Permeate drainage hole

13 stacks

14 Permeate

15 Drain bolts

Breakthrough Drain hole Drain channel

16 Permeate outlet

17 Spacer element (ring-shaped) hole

18 Spacer element (strip-shaped) hole

19 Strut

20 strut

21 spacers

22 spacers

Claims (16)

1. Device ( 10 ) for filtering and separating, in particular, biologically organic flow media ( 11 ) by reverse osmosis and micro-, ultra- and nanofiltration, comprising a plurality of flat filter elements spaced apart from one another, around which the flow medium ( 11 ) flows, such that a plurality of separate stacks ( 13 ) of filter elements ( 12 ) are arranged one behind and/or next to one another, wherein the stacks ( 13 ) are around one behind and/or next to one another by the flow medium ( 11 ) and wherein the permeate ( 14 ) collected by the filter elements ( 12 ) is introduced into drain bolts ( 15 ) passing through the stacks ( 13 ) of filter elements ( 12 ) and is discharged via permeate drains ( 16 ), characterized in that the permeate ( 14 ) is essentially separated by building up a negative pressure at the permeate drain (16). 16 ) can be generated relative to the flow medium ( 11 ) which is essentially at the level of the ambient or atmospheric pressure. 2. Device according to claim 1, characterized in that the negative pressure on the permeate side is generated by a vacuum pump which is connected to the permeate outlet ( 16 ). 3. Device according to one or both of claims 1 or 2, characterized in that the negative pressure on the permeate side is in the range from 0.4 to 0.9 bar. 4. Device according to one or more of claims 1 to 3, characterized in that the filter elements ( 12 ) are designed in the manner of membrane cushions. 5. Device according to claim 4, characterized in that in the membrane cushions between the respective outer membrane elements ( 120 , 121 ) delimiting them, at least one flat, dimensionally stable stabilizing element ( 122 ) is arranged in order to create a high inherent stability of the membrane cushion. 6. Device according to one or more of claims 1 to 5, characterized in that the filter elements ( 12 ) consist of a polymer or polymer mixture. 7. Device according to one or more of claims 1 to 5, characterized in that the filter elements ( 12 ) consist of a ceramic material. 8. Device according to one or more of claims 5 to 7, characterized in that the stabilizing element ( 122 ) consists of porous material. 9. Device according to one or more of claims 5 to 8, characterized in that the stabilizing element ( 122 ) consists of plastic and/or a metallic material and/or a ceramic material. 10. Device according to one or more of claims 1 to 9, characterized in that the drain bolt ( 15 ) has a plurality of openings ( 150 ) arranged around a circumference and distributed over its length for the entry of the permeate ( 14 ) into a drain bore ( 151 ) which passes essentially axially through the drain bolt ( 15 ). 11. Device according to one or more of claims 1 to 10, characterized in that the filter elements ( 12 ) of the stack ( 13 ) are spaced apart from one another in such a way that the filter elements ( 12 ) do not touch one another during operation. 12. Device according to claim 11, characterized in that annular spacer elements ( 17 ) are provided for spacing the filter elements ( 12 ) from one another. 13. Device according to claim 11, characterized in that strip-shaped spacer elements ( 17 ) are provided for spacing the filter elements ( 12 ) from one another. 14. Device according to one or both of claims 12 or 13, characterized in that the spacer elements ( 17 , 18 ) have a sealing effect with respect to a permeate discharge space. 15. Device according to one or more of claims 1 to 14, characterized in that the stacks ( 13 ) of filter elements ( 12 ) are held together by struts ( 19 , 20 ) which delimit the stacks ( 13 ) on both sides and are spaced apart. 16. Device according to claim 15, characterized in that the struts ( 19 , 20 ) can be connected to one another by spacers ( 21 , 22 ).