DEVICE FOR THE SEPARATION OF A PRODUCT IN A LIQUID FRACTION AN IN A NON-LIQUID FRACTION

Abstract

Device for the separation of a product in a liquid fraction and in a non-liquid fraction, consisting of a supply device and a transport zone which ends in a cylindrical tube provided with a dewatering zone with lateral perforations, whereby part of the liquid fraction of the product is forced out through the perforations of the press zone with formation of a pressed press cake that is pushed to the exit thereof, whereby a good separation of liquid from the solid pressed press cake is obtained.

Claims

1. Device for the separation of a product (2) in a liquid fraction (22) and in a non-liquid fraction (13), comprising a transport pump (3) which sucks in the product (2) from a barrel or supply device (9) and pumps the product under pressure to a transport zone (4) which ends in a cylindrical tube (11) provided with a dewatering zone (12) with lateral perforations, whereby during the transport of the product through the cylindrical tube a part of the liquid fraction of the product (2) is forced out through the perforations (P) of the press zone (12) as a result of the prevalent overpressure such that during the transport movement in the cylindrical tube (11) a press cake (13) is created which due to the pump pressure is forced further through the cylindrical tube (11) to the exit thereof, whereby the exit of the pressed press cake (13) from the cylindrical tube (11) is restricted by a controlled recoiling counter pressure plate (16) which when making room for the exiting dewatered press cake (13) exercises a controlled counter force on this press cake such that the pressure at the entry of the cylindrical tube remains within the desired limits to thus obtain a good separation of liquid (16) and a solid dewatered press cake (13) in the cylindrical tube (11), whereby the counter pressure plate (16) moving in a controlled way not only recoils, but sometimes also stops in a controlled way or even moves against the movement of the press cake (13) and this with varying forces, after which in a following phase the counter pressure plate (16) is moved further to the right in the direction of the moving pressed press cake (13), such that now no more pressure is exercised on the press cake (13), and the press cake (13) will subsequently spontaneously break off and fall down in a collector (21), or is actively removed from the flow path of the digestate (2) by a mechanical separator (18) with a movable ram (19, 19) and this in a direction that is completely or partly perpendicular to the direction of the flow path of the product.

2. Device according to claim 1, wherein the transport pump is specifically a volumetric pump.

3. Device according to claim 1, wherein the press part (5) can be separated from the pump part (3) because a valve is provided in the transport zone (4) or in the cylindrical tube (11).

4. Device according to claim 1, wherein the pump part 3 is directly connected to the press part (5).

5. Device according to claim 1, wherein the operation of the counter pressure system (15) is adjusted in the sense that the counter pressure plate (16) does not move uniformly from left to right, but periodically stops or even briefly goes back from right to left in between and this with varying counter pressures.

6. Device according to claim 1, wherein the counter pressure system is such that it can also partially penetrate into the cylindrical tube 11 or perforated zone 12 to thus obtain a better pressing.

7. Device according to claim 1, wherein the press part (5) is divided over two or more parallel press parts (5, 5), each with its own cylindrical tube (11, 11) with perforated zone (12, 12) and with its own counter pressure system (15, 15). The press parts are fed by a shared pump part (3) that supplies the product via a transport zone (4) with branches to each of the press parts (5, 5), whereby the press parts are operated synchronously.

8. Device according to claim 7, wherein the various press parts are operated with a certain time shift to thus obtain a more uniform operation of the system.

9. Device according to claim 1, wherein the pump part (3) is divided over two or more parallel pump parts (3, 3), which each end in the transport zone (4) to thus obtain a greater pump capacity.

10. Device according to claim 9, wherein between each pump part (3, 3) and the transport zone (4) valves are built in to prevent interaction between the pump parts and to thus obtain a more continuous product supply to the press parts.

11. Device according to claim 1, wherein the perforations (P) in the cylindrical press zone (11) have a conical shape whereby the diameter of the perforations on the inside (24) of the press zone (12) is smaller than the diameter of the perforations on the outside (25) of the press zone (12).

12. Device according to claim 1, wherein the perforations (P) in the press zone (11) are slit shaped.

13. Device according to claim 1, wherein the press zone (11) is not cylindrical but broadens towards the outlet.

14. Device according to claim 1, wherein the press zone (11) is not cylindrical but gets narrower toward the outlet.

15. Device according to claim 1, wherein the cross section of the press zone (11) is not round but polygonal.

16. Device according to claim 1, wherein a controlled interaction exists between the pressure or the flow of the pump part and the controlled counter pressure or speed of the counter pressure system of the press part.

17. Device according to claim 2, wherein the press part (5) can be separated from the pump part (3) because a valve is provided in the transport zone (4) or in the cylindrical tube (11).

18. Device according to claim 2, wherein the pump part 3 is directly connected to the press part (5).

19. Device according to claim 3, wherein the pump part 3 is directly connected to the press part (5).

20. Device according to claim 2, wherein the operation of the counter pressure system (15) is adjusted in the sense that the counter pressure plate (16) does not move uniformly from left to right, but periodically stops or even briefly goes back from right to left in between and this with varying counter pressures.

Description

[0032] With the intention of better showing the characteristics of the invention, hereinafter, by way of an example without any limiting nature, a number of preferred embodiments are described of a device according to the invention for the dewatering of digestate that is conditioned, or not, for improved dewaterability by addition of additives, with reference to the accompanying drawings, wherein:

[0033] FIG. 1 schematically and in cross-section shows a device for the dewatering of digestate according to the invention with one pump part and one press part ( );

[0034] FIGS. 1a, 1b, 1c and 1d show various phases of the press process and of the removal of the press cake;

[0035] FIG. 2 in cross-section shows a variation of FIG. 1 but now with one pump part and two press parts;

[0036] FIG. 3 in cross-section shows a perforation of the perforated part of the dewatering zone.

[0037] FIG. 1 schematically shows a device 1 for the dewatering of digestate 2, consisting of one pump part 3, a transport zone 4 and one press part 5. The pump part 3 consists of a pump piston 6 that moves in a pump cylinder 7 and is driven by a drive cylinder 8. The product is supplied to the pump cylinder 7 from a supply zone 9 when the shutoff valve 10 is opened and the pump piston 6 moves back such that the digestate 2 is sucked into the pump cylinder 7. The sucked in amount of digestate 2 is then pumped by the pump piston 6 under pressure via the transport zone 4 to the press part 5, whereby the shutoff valve 10 is closed. The transport zone can have various forms, such as a transport pipe, a collector or a transition piece or can be non-existent if the pump part is directly connected to the press part.

[0038] The press part consists of a cylindrical tube 11 which comprises a zone 12 with lateral wall perforations (P). During the movement of the digestate 2 from left to right through this zone, due to the pressure difference across the perforations from the inside to the outside, water or liquid 22 will exit through the perforations P and thus during the movement of the product through the cylindrical tube 11 a cake of dewatered digestate 13 will be formed in this cylindrical tube 11. This cake 13 is forced toward the open end 14 of the cylindrical tube 11 by the present pressure. At the open end 14 of the cylindrical tube 11, a counter pressure system 15 pushes against the exiting cake of pressed digestate.

[0039] The counter pressure system 15 consists of a counter pressure plate 16 that is powered by a cylinder 17. The counter pressure plate 16 recoils slowly and in a controlled manner while continuing to exercise a counterforce on the exiting press cake 13, such that the pressure in the cylindrical tube 11 remains sufficiently high to obtain a good liquid separation through the perforations of the cylindrical tube 11 and the press cake 13 does not exit sooner than desired.

[0040] FIG. 1a shows how in a first phase a press cake 13 of dewatered digestate 13 forms against the counter pressure plate 16 at the open end 14 of the cylindrical tube 11.

[0041] FIG. 1b shows how in a second phase the press cake 13 exits from left to right and the counter pressure plate 16 also moves from left to right. During this movement the counter pressure plate exercises a counter pressure force Fc from right to left. The balance of forces is formed by on the one hand the driving force Fp from left to right, i.e. the pump pressure*the surface area of the cross-section of the cylindrical tube 11, and on the other hand the counter pressure force from right to left exercised on the exiting press cake 13 by the counter pressure plate 16 and the frictional force Ff from right to left resulting from the friction of the press cake 13 against the wall of the cylindrical tube 11.

[0042] When the counter pressure plate 16 is located at a distance, which can be chosen, from the free outlet of the cylindrical tube 11, the pump operation of the pump part 1 is temporarily halted by stopping the pump's drive cylinder 8. This means the press cake 13 will not exit any further.

[0043] FIG. 1c shows how in a third phase the counter pressure plate 16 of the counter pressure system 15 has moved further to the right, such that now no pressure is exercised anymore on the press cake 13. The press cake 13 will then spontaneously break off and fall down in a collector 21, or be actively removed from the flow path of the digestate 2 by a mechanical separator 18.

[0044] FIG. 1d shows the operation of the mechanical separator 18 which consists of a ram 19 powered by a drive cylinder 20. The ram 19 moves laterally on the product direction and pushes against the exited press cake 13 to remove it. The ram 19 then returns to its resting position outside the flow path of the product and outside the volume within which the counter pressure device 15 moves.

[0045] The counter pressure plate 16 of the counter pressure device 15 is then moved as much as possible to the left until the desired counter pressure is achieved. The counter pressure plate 16 hereby presses against a remainder of the press cake 13 that is still sticking out of the cylindrical tube 11 or against the end of the dewatering cylinder. As soon as the counter pressure plate 16 has achieved the desired position, the pump operation of the pump part 1 can be resumed again. This will result in the cycle described above to repeat itself, more specifically the dewatering of the digestate supplied under pressure during the transport movement from left to right, the forming of a press cake, the controlled exit of the press cake, and the removal of the press cake 13.

[0046] When the pump piston 6 has travelled its complete stroke from left to right, the pump operation is interrupted to supply fresh digestate again to the pump cylinder 7 through the shutoff valve 10 while the pump piston is moved from right to left. There is no movement hereby in the press part 5 until the pump operation is started again and the counter pressure system 15 remains idle.

[0047] Optionally, a valve is provided in the transport zone 4 or in the cylindrical tube 11. When the pump piston moves from right to left (to supply fresh digestate), it can prevent product from flowing back from the transport zone 4 or from the press part 5 or air from being sucked in through the perforations of the cylindrical tube 11.

[0048] Optionally, the operation of the counter pressure system 15 can be adjusted in the sense that the counter pressure plate 16 does not move uniformly from left to right, but periodically stops or even briefly goes back from right to left in between and this with varying counter pressures. The purpose is to obtain a better and more complete dewatering of digestate in the dewatering zone. In particular this may also be necessary to form a firm press cake 13 toward the open end of the cylindrical tube 11 upon the initial start of the press.

[0049] Optionally, the counter pressure system is made such that it can also partially penetrate into the cylindrical tube 11 or perforated zone 12 to thus obtain a better pressing.

[0050] FIG. 2 shows a variant of the device for the dewatering of digestate according to the same operating principle as the device of FIG. 1, but consisting of one pump part 3 and two press parts 5 and 5. As shown in the embodiment of FIG. 1, fresh digestate is supplied to the transport zone 4 under pressure by the pump part. In this case, this transport zone consists of a manifold from where the digestate is supplied to each of the two press parts 5 and 5 possibly via shut-off valves 23 and 23. These shut-off valves are not necessary when the semi-continuous operation of the press parts 5 and 5 is synchronous.

[0051] When the operation of the press parts is not synchronous, for example with a phase shift of 180, the shut-off valve 23 is closed at the moment when the supply of product under pressure to the press device 5 needs to be stopped with a view to the removal of the exited press cake. However, the pump device 3 continues to supply product under pressure to the second press device 5 via the opened shut-off valve 23.

[0052] Idem ditto, the shut-off valve 23 is closed when the cake is removed from the second press device 5 and meanwhile the press device 5 can be fed via the opened shut-off valve 23.

[0053] In the shown position in FIG. 2, the operation of the press parts is not synchronous. The press part 5 receives a supply of fresh digestate through the pump device 3 via the opened shut-off valve 23 and the formed pressed press cake gradually exits from left to right. The press part 5 receives no supply of fresh digestate now that the shut-off valve 23 is closed and the exited press cake is removed by the mechanical separator 18.

[0054] FIG. 3 shows a cross-section of perforations (P) in the cylindrical tube 11 on the level of the perforation zone 12, in which the conical shape of the perforation (P) is visible with a smaller diameter 24 on the inside of the cylindrical tube than the diameter 25 on the outside of the cylindrical tube 11.

[0055] It goes without saying that the form of the supply and discharge pipes and of the press zones does not necessarily have to be cylindrical in cross-section, but this is more advantageous to withstand the maximum occurring pressures.

[0056] Obviously, the transport pump can also be a piston pump but also a helicoidal pump for example, and a device for the dewatering of digestate according to the invention can also be used for the dewatering of another viscous thick matter than a digestate of a fermentation.

[0057] The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a device for the separation of a product in a liquid fraction and in a non-liquid fraction can be realised in all kinds of forms and dimensions without departing from the scope of the invention as described in the following claims.