SE509090C2 - Device for dewatering a slurry suspension - Google Patents

Abstract

A device for dewatering sludge comprises a plurality of screening means (11) that are located at different levels, said screening means comprising hole-provided tube pieces which communicate with a common manifold (12) and through which water may pass in a direction from the outside and inwards, without the solid constituents of the sludge being carried along by the water. When necessary, the screening means may be back-flushed in order to keep them clean, shut-off valves (24) acting between the differently high situated screening means with the purpose of individually interrupting the communication between the manifold (12) and the screening means (11) that land(s) up above the surface (9) of the slurry (8), according as its level sinks during a dewatering operation.

Description

20 25 35 509 090 recipient than the next well which is in line to be emptied, 2 in that even these devices in practice require the addition of flocculant to the raw sludge.

The object of the present invention is to obviate the above-mentioned disadvantages of the prior art and to create an improved device for dewatering sludge suspensions. A basic object of the invention is thus - in a broad aspect - to In a narrower aspect, the invention aims to create a drainage device particularly suitable for sludge suction vehicles which can be built into a pressure tank without significantly encroaching on the load capacity of the tank. A further object of the invention is to create a dewatering device intended for sludge suction vehicles which for its function does not require the addition of flocculants or other chemicals to the raw sludge. for the achievement of un pressure resp. overpressure inside the pressure tank in order to continuously maintain a good separating effect during a dewatering operation. It is a further object of the invention to create a dewatering device which enables direct return of the separated water to the well from which the raw sludge is sucked up. Another object is to create a drainage device that can be built in afterwards into existing pressure tanks in sludge suction vehicles.

According to the invention, at least that basic object is achieved by means of the features stated in the characterizing part of claim 1. Advantageous embodiments of the invention are further defined in the dependent claims. 1 1. . ] .E å. .

In the drawings: Fig. 1 is a schematic side view of a sludge suction vehicle with a pressure tank comprising two drainage devices according to the invention, Fig. 2 is a cross section through the pressure tank of the vehicle according to Fig. 1, Fig. 3 is an enlarged longitudinal section through a portion of the pressure wall of the pressure tank, together with two screenings included in the device according to the invention, Pig 4 a perspective view showing said screenings included in a screen unit mounted at a certain level in the tank, individual screening unit screw screws, Fig. 6 a side view of a sludge suction vehicle with a pressure tank inside which is mounted a drainage device according to the invention, Figs. 7 and 8 sections of Fig. 6 showing details of the device according to the invention, and Fig the range of two devices according to the invention.

In Figs. 1 and 2, 1 generally denotes a container in the form of a pressure tank mounted on a vehicle 2 in the form of a car. The tank 1 is usually composed of a cylinder or cylinder wall 3 together with two ends 4, 4 '. Associated with the tank are two dewatering devices 5, 5 'according to the invention which are identically similar, although mirror-inverted. The two devices are connected via main lines 6 to a common outlet 7 for discharging separated water. In this context, it should be pointed out that the pressure tank in its practical implementation also includes a pipe socket (not shown) for suction of raw sludge and discharge of dewatered sludge mass as well as a compressor-driven unit (not shown) to alternately create negative pressure and overpressure inside the tank. In Fig. 2, 8 denotes a raw sludge or a sludge suspension whose surface or liquid level is denoted 9.

Above the surface 9 of the suspension there is an air-filled space 10.

Characteristic of the invention is that the individual dewatering device, for example the device 5, comprises a plurality of sildos 11 located at different levels inside the tank 1 which each communicate with a common collection line 10 15 20 25 30 35 509 090 12. This collection line turns into the example in the aforementioned 4 main pipeline 6. In the preferred exemplary embodiment, sieves 11 are arranged at each level along the manifold 12, one of which projects rearwardly from the manifold and the other in the forward direction. Each pair of sildos forms a sieve unit on a single level inside the tank.

Reference is now made to Figures 3-5 which illustrate in more detail the nature of the herringbone. As can be seen from Fig. 4, the individual screen means comprises a rigid or dimensionally stable pipe section 13 which at its one end is connected to a coupling in the form of a T-coupling 14 and which at its opposite end is closed and in the example the pipe section has an outside with In the longitudinal surfaces are recessed a plurality of relatively small wounds a threaded pin 15. polygonal, more precisely hexagonal cross-sectional shape. flat, hole 16 through which water can pass, more precisely in the direction from the outside and in during the operation of the herring. In addition to the filter piece, this consists of a 13. In the example shown in Fig. 5, the screw element 18 has through which water (or possibly rinsing agent) can pass. preferred, but of a comparatively thin strip with a cross-sectional rectangular shape, the projections 19 being embossed (in a special machine) along one side of the strip, while the opposite side is substantially smooth or unworked. In series production, the projections 19 are placed at equal distances from each other, whereby the openings between the projections become equally wide. By giving the projections 19 different heights of different screw elements, the height of the individual channel 20 and thus the cross-sectional area can be varied for different purposes. In other words, the filter casings with different drainage capacity can be manufactured in a simple way. In practice, the width of the individual channel can amount to 0.5 - 2, suitably about 1 mm, while the height can vary within the range 0.01 - 0.50, suitably 0.10 - 0.20 mm. In other words, can the cross-sectional area of the channel in the area of the inner edge of the strip element amount to fractions of a square millimeter, eg 0.1 - 0.2 mm? In this connection it should be pointed out that the height of the individual duct can also be successively reduced in the direction towards the outer edge of the strip element, whereby the outwardly facing inlet side of the duct (the liquid passes in the direction from outside and in through the filter casing) can be even smaller.

As is clear from Fig. 4, the individual filter housing 17 can be threaded onto the hexagonal tube 13 and secured thereon between the T-coupling 14 and a clamping mechanism which in the example includes a sleeve 21 and a clamping nut 22 which can be tightened on the threaded pin 15. With By means of the clamping mechanism 21, 22, the helical belt element 18 can be compressed so that the opposite sides of the belt are pressed tightly against each other, ie the projections 19 on one side of the belt will be distinctly pressed against the flat side of a nearby belt portion. The individual screen unit comprising two screen devices 11 connected via the T-coupling 14 is connected to the manifold 12 via a branch line 23. In connection with this branch line, in accordance with the principle of the invention, a valve designated in its entirety by 24 is provided by means of communication between the strainer unit and the overhead line can be interrupted, ie the individual strainer unit can be switched off. In the example shown, the branch line 23 intersects the cylinder wall of the tank in the radial direction, the various valves together with the collecting line 12 and the main line 6 being located externally. It should also be pointed out that the two screen devices 11 are axially oriented, ie placed parallel to the cylinder wall 3, and located at a short distance from it. With regard to the dimensions of the individual screen device 11, it should be pointed out that the surface-mounted filter housing 18 has a cylindrical basic shape, the length of the housing advantageously, although not necessarily, being at least ten times larger than its diameter. In practice, the outer diameter of the filter casing 17 can be in the range 30 - 70, suitably 40 - 60 mm, the minimum length of the casing being 300 mm. The distance between the cylinder wall 3 and the nearest portion of the filter housing or screen may advantageously be less than the diameter of the screen. In relation to the total volume of the pressure tank, which can amount to 5-15 m3, the sieves included in the device according to the invention have a total volume which is extremely small, for example in the range 20 - 50 dmz.

As can be seen from Fig. 2, the lower screen units or devices in each device 5, 5 'are located in the area of the bottom of the pressure tank 509 090, while the upper screen units are located near the central upper part of the tank 6. The intermediate screen units are advantageously equidistantly located at different levels. The level difference between nearby screen units can in practice be in the range 100 - 400, preferably 200 - 300 mm.

E .. J. i. I _ Raw sludge from the well to be emptied is taken via a pipe socket (not shown) into the tank 1 by means of the conventional compressor of the vehicle together with the associated suction / pressure unit (not shown). More specifically, the sludge is sucked in by said unit creating a negative pressure in the tank. After suction, for example, to full height in the tank, both are started to be executed. More specifically, this is kept in place (to be opened. In addition, the drainage devices 5, 5 * are reversed. the function of the pressure unit so that the compressor creates an overpressure inside the tank. Due to this overpressure, the water contained in the sludge is forced through the filter casings 18 of the various screeners in the direction from the outside in and further through the holes in the supporting pipe pieces 13 to be fed via the branch lines 23 to the manifold 12 and further through the main line 6 to both devices. common outlet 7. Via the associated hose, the water can then be led back to the emptied well.

As the water passes through the individual filter housing 18, the solids that are larger than the channels 20 are stopped. Because these years are extremely small, even very small solids are prevented from accompanying the water into the interior of the herring.

The constituents which are stopped in this way without accompanying the water are of course deposited on the outside of the herring device, forming a successively thickening particle layer on the outside of the device.

In parity with this, the liquid feed capacity through the screen device is reduced.

To ensure a good separation effect during a tank emptying operation, the strainer should be backwashed intermittently.

This is done by the vehicle's compressor briefly changing working methods to create a negative pressure inside the tank for a short period, eg 5 - 15 seconds. In this way, a purge medium in the form of the air in the interior of the screen is caused to pass the individual filter casing inside and out, whereby said particle layer on the outside of the screen is removed.

As the water freed from solid particles is emptied from the tank, the sludge or liquid level in the tank, ie the surface 9, will decrease, all while exposing the top screen units inside the tank. To the extent that the branch line 23 from the individual screen unit would always be open to the manifold 12, the aforementioned backwashing of the screen devices would be impossible to carry out, since the negative pressure in the tank would suck air through the exposed screen units without having any appreciable effect on the screen units. However, due to the presence of the valves 24, the individual screen units can be individually shut off from the manifold 12 as the sludge level 9 decreases. In this way, stolen air cannot pass through the screen units located above the sludge level. In other words, it is ensured that an effective backwashing effect is achieved in all sieve units in the sludge suspension which still have their valves open.

Reference is now made to Figures 6-9, which show an alternative embodiment, which in practice is preferable at such latitudes where temperatures below the freezing point of the water may prevail. In this case, the two drainage devices 5, 5 'of the pressure tank 1 are located in their entirety internally in the tank, ie not only the various sieves 11 but also the main line 6 and the collection line 12. This internal location ensures that the separation risks the water - as small as the raw sludge in the tank - freeze. The internal location also has the advantage that the individual dewatering device can be manufactured as a cassette which can be retrofitted in existing pressure tanks in that no branch lines need to cut through the cylinder wall of the tank. Thus, the herringbone 11 can be supported inside the tank by being connected at one end to the manifold 12, which is suitably attached to the inside of the cylinder wall, and with its opposite end being supported by a bracket or a strut 25 (see Fig. 8) . line, the individual dewatering device still has a volume that constitutes only a small fraction of the entire volume of the tank.

Although the manifold is internally located, it can be seen from Fig. 7 that each of the two sieves 118 forming a sieve unit at each individual level is connected to the manifold 12 via a valve 24. It is also conceivable that instead of two valves use only one valve which is arranged in the manifold 12 between two adjacent screen units at different levels. mil] 3.E.]. V E..

The invention is not limited only to the embodiments described and shown in the drawings. Thus, the invention is also applicable in connection with such sludge suspensions which are not stored in a pressure tank or even in a container. Thus, it is possible to achieve a backwashing effect other than by creating a negative pressure in a pressure tank. Thus, a special backwashing unit can be connected to the individual dewatering device with the aid of which a rinsing agent, eg air and / or water, can be flushed through the filter spaces of the strainer in the direction from the inside out. Here too, however, it is essential that shut-off valves are present between sildons at different levels so that the effective backwashing effect can be maintained even when the level of sludge suspension falls. Although the filter casing described in connection with Figures 3-5 on the outside of the associated support pipe section is preferred in practice, it is in itself conceivable to use other forms of filtering casings which can be cleaned by backwashing. In this context, it should also be pointed out that the term "perforated pipe section" as used in the claims is to be interpreted in the broadest sense.

Thus, the described filter casing can also be regarded as a perforated piece of pipe in that this casing can be carried in another way than by means of the support pipe 13 shown in the drawings, for example a number of rigid rods or booms mounted inside the casing. Furthermore, the device according to the invention is useful for distinguishing from water or similar liquid other constituents than such faecal particles which are included in normal well sludge, for example oil or fat particles.

Claims (6)

10 20 25 35 509 090 Bål fi nikrâï Device for dewatering a sludge suspension, characterized in that it comprises a plurality of differentially locatable screeners (11) including perforated pipe pieces (13), which communicate with a common manifold (12) and through which water can pass in the direction from the outside in without the sludge's solid or non-aqueous constituents accompanying the water, whereby the devices can be backwashed to keep them clean if necessary, and shut-off valves (24) acting with information to individually interrupt the communication between the collection (11) as its level drops the pipe and the herring (s) that end up above the surface (9) of the sludge suspension (8) during a dewatering operation. Device according to claim 1, characterized in that it is mounted inside a container in the form of a pressure tank (1). Device according to claim 2, wherein the pressure tank (1) forms part of and has the shape of a horizontal cylinder - a sludge suction vehicle (2) there with opposite ends, characterized therefrom, (11) placed on the inside of the cylinder with a lower sildon located the various sildons included in the device are long narrow and close to a bottom part of the tank and an upper sildon located near the top of the tank, all sildons being oriented substantially and located axially, ie parallel to the cylinder wall, at a short distance from the cylinder wall. k ä n n e - (il) comprises an arrangement arranged on the outside thereof, Device according to one of the preceding claims, characterized in that the individual screen device, in addition to said pipe section (13), has a filter-forming housing element (17) consisting of a helical, elastic (18) projection between which are defined microscopes. along its helically extensively small channels (20) through which water and / or flushing agents can pass, but not solid or non-aqueous constituents larger than the channels. 10 5Û9 090 10 Device according to claim 4, characterized in that the screw element (18) is arranged between a fixed stop means, for example a T-coupling, at one end of the pipe piece and a clamping mechanism (15) arranged at the opposite end thereof. 21, 22) by means of which the abutting, helical portions of the element can be pressed against each other, the element being demountable by removing the clamping mechanism. Device according to one of the preceding claims, characterized in that (13) has an outer surface with a polygonal, eg hexagonal cross-sectional shape, and that the surrounding filter casing (17) has a cylindrical basic shape, the length of the casing being at least ten times its diameter. that the pipe piece