FILTER DEVICE

Abstract

A filter device, in particular for processing, preferably for filtering, back-flush quantities which originate from a filter which can be arranged upstream of the filter device, having a - primary stage (10) for receiving the respective back-flush quantity, - secondary stage (12) for filtering off the back-flush quantity from the primary stage (10), and - tertiary stage (14) for returning the purified back-flush quantity into a process circuit (16), characterized in that a flow divider (20) is inserted in the primary stage (10) and, if a predeterminable fluid quantity in the primary stage (10) is exceeded, forwards the associated excess quantity into the tertiary stage (14) while bypassing the secondary stage (12).

Description

[0001] filter device

[0002] To ensure the safe and efficient operation of filter systems over extended periods of operation, it is common practice, particularly in larger systems, to backwash and thereby regenerate the filter elements involved in the filtration process. During each backwash phase, a partial flow of the filtrate flows through the filter element to be cleaned in the opposite direction to detach the dirt from the element and discharge it along with the outflowing backwash stream. Given the extreme environmental impact of the contaminated backwash fluid, disposal is problematic. At least for larger quantities of rinsing fluid, post-treatment or processing is required, such as filtration to separate incinerable contaminants.When filtering heavy oils, such as those used to operate large diesel engines such as marine diesel engines, the high viscosity of the heavy oil complicates both the backwashing process in the primary filter, which is located upstream of the processing filter device, and the filtering process required for processing. Such a primary filter, which in technical terms is also referred to as an automatic filter, is shown as an example in DE 10 2004 037 280 A1 and relates to a backwashing filter device for the use of filter elements that can be accommodated in a filter housing with a filter inlet and an outlet for the fluid to be filtered, wherein the filter elements can be flowed through in both directions for filtration or backwashing, and wherein one filter element performs the filtration simultaneously and at least one other filter element can be backwashed to clean its effective filter surface.

[0003] Such primary or automatic filters serve as protective filters in many process applications, with the backwash flow generated during backwashing often being released back into the process cycle without further treatment. For example, in ballast water treatment on ships, seawater is automatically filtered in the first treatment stage, and the resulting backwash fluid is discharged back into the sea. A similar situation applies to automatic filters that protect heat exchangers in the cooling circuit of a power plant from coarse contaminants in river water. Here, too, the backwash fluid can be discharged back into the surface water. In some industrial processes, however, the nature of the fluid and its constituents may make it necessary to recycle the backwash flow in order to reuse the fluid and close the process cycle without contact with the environment.

[0004] For this purpose, a filter device has already been proposed in DE 10 2015 002 767 A1, in particular for processing, preferably for filtering backwash quantities which originate from a filter which can be connected upstream of the filter device, with a

[0005] - Primary stage for receiving the respective backwash volume,

[0006] - Secondary stage for filtering the backwash volume from the primary stage, and - Tertiary stage for returning the cleaned backwash volume to a process circuit.

[0007] Because in this known solution a control device supplies the respective backwash quantities to the respective filter element in portions, reliable filtration can be carried out even at higher viscosity, for example in the case of heavy oil filtration. The control device has a control chamber with a separating piston which divides the control chamber into a first and a second fluid space, wherein the first fluid space serves to accommodate the respective backwash quantity and the second fluid space can be pressurized with a compressed gas at a predeterminable working pressure, so that the backwash quantity is displaced by means of the separating piston from the first control chamber into an adjoining filter chamber with a filter element, which returns the thus filtered backwash quantity to the process circuit in a processed form.Although this known solution leads to very good treatment results for the backwash volume from primary or automatic filters, practice has shown that this solution reaches its limits when large quantities of backwash fluid are generated. The backwash volume generated by an automatic filter is highly dependent on the process conditions and can therefore vary considerably, particularly leading to very high quantities of backwash fluid for post-treatment.

[0008] Because the known solution requires the separating piston to be extended and retracted each time to receive the backwash fluid and to forward it to the filter chamber, continuous operation is not possible, so that the known backwash quantity treatment system reaches its limits, especially with large quantities of backwash fluid.

[0009] Based on this prior art, the invention seeks to further improve the known backwash fluid filter device, in particular to provide a suitable solution even for large backwash volumes. This object is achieved by a filter device having the features of patent claim 1 in its entirety.

[0010] By virtue of the fact that, according to the characterizing part of patent claim 1, a flow divider is used in the primary stage which, when a predeterminable fluid quantity is exceeded in the primary stage, passes the excess quantity to the tertiary stage, bypassing the secondary stage, a solution is created which enables continuous operation within the scope of backflushing fluid treatment, so that even extremely large quantities of backflushing fluid can be safely recycled into the process circuit.

[0011] The inventive solution is highly process-reliable, and the flow divider mentioned allows a type of bypass operation using different filter stages. A type of fine filter stage continuously filters the backwash volumes. Any excess volumes are diverted via the flow divider and subjected to rapid coarse filtration, thus allowing even very large volumes of backwash fluid to be managed. Finally, the residual fluids, both through fine filtration and coarse filtration, reach the subsequent tertiary stage, which allows the discharge of the purified backwash volumes into the otherwise closed process circuit of the system.

[0012] If an even larger quantity of backwash fluid accumulates for a short time and the fluid level within the primary stage, in the form of a depressurized feed tank, exceeds the installation height of the filter or strainer basket, an additional, but now untreated, partial flow flows through the upper opening of the strainer basket over its bottom towards the tertiary stage. This ensures that the feed tank of the backwash flow treatment unit can never overflow and, even at the maximum backwash flow, a backflow never occurs, which would ultimately lead to the shutdown of the backwash flow treatment filter. Independent of the above considerations, the backwash flow treatment unit is of course also suitable if backwash flows to be treated discontinuously and only in small quantities from the primary or automatic filter reach the filter device according to the invention.

[0013] In a further preferred embodiment of the filter device according to the invention, the flow divider is provided with a backwash device that cleans it of contaminants that reach the unfiltered side of the primary stage. The backwash device for the flow divider is preferably formed by a drivable backwash arm that can be moved along the inner circumference of the screen basket and guides a backwash fluid from the inside out through the screen structure of the screen basket. In order to be able to clean the cylindrical filter screen as needed, a backwash device is arranged axially in the filter or screen basket. This backwash device, for example by means of spray nozzles, forces clean fluid, such as tap water, under pressure from the inside out through the filter or screen material of the basket, counter to the filtration direction.

[0014] The dirt removed during the backwash process can then settle in the feed or storage tank and, as part of the backwash liquid that is usually treated, is finally transported to the secondary stage. This stage consists of individual filter units featuring a bag or pocket filter, the unfiltered side of which is connected to the primary stage and the filtrate side to the tertiary stage. In this way, the feed tank can be kept free of dirt even during long-term operation. Preferably, the inflow from the primary or automatic filter into the feed tank occurs below the bottom of the filter or strainer basket and outside the longitudinal axis in a tangential flow, resulting in a cyclonic flow in the feed tank.

[0015] To monitor the system status, the fill level in the feed tank is preferably monitored. This allows, for example, a signal to be sent to a higher-level control system that controls, among other things, the primary or automatic backwash filter as soon as partial flows are generated via the strainer basket or the overflow thus formed toward the tertiary stage.

[0016] In a particularly preferred embodiment of the filter device according to the invention, several filter units are connected in parallel such that at least one bag or pocket filter of a filter unit can be replaced with a new unit, while the other filter units continue to clean the resulting backwash contaminants. This allows for bag or pocket filter replacement without having to interrupt the ongoing filtration by means of the secondary stage.

[0017] In the following, the solution according to the invention is explained in more detail using an exemplary embodiment. In this case, in a schematic representation and not to scale, the

[0018] Figure 1 shows, in the form of a simplified process diagram, the essential components of the filter device for backwash quantity treatment;

[0019] Figure 2 is a perspective top view of the essential components of such a system according to Figure 1; and Figure 3 is a simplified representation of a bag or pocket filter used in the filter device according to Figures 1 and 2.

[0020] As Figure 1 shows, the filter device for backwash quantity processing has a primary stage 10 for receiving the respective backwash quantity and a secondary stage 12 for filtering the backwash quantity from the primary stage 10. Furthermore, a tertiary stage 14 is provided for returning the cleaned backwash quantity to a process circuit 16 of an overall system, only partially shown in Figure 1. The primary stage 10 has a fluid inlet 18, which is part of the process circuit 16 and which, viewed in the direction of the arrow, allows the inflow of backwash fluid in a tangential direction, so that a cyclonic inlet flow is achieved within the primary stage 10. The fluid inlet 18 is fluid-conductingly connected to the fluid outlet for backwash quantity fluid, for example to the corresponding outlet of the backwash filter device according to DE 10 2004 037 280 A1, although this is not shown in more detail.

[0021] In the primary stage 10, a flow divider 20 is used which, when a predetermined amount of fluid is exceeded in the primary stage 10, passes the excess amount directly into the tertiary stage 14, bypassing the filtering secondary stage 12.

[0022] As further shown in Figures 1 and 2, the primary stage 10 has a pressureless feed tank 22 which has an inlet for the respective backwash quantity from the backwash filter device via the fluid inlet 18 and an outlet 24 for the delivery of the respective backwash quantity to the secondary stage 12. Pressureless means that the feed tank 22 has ambient pressure inside.

[0023] The flow divider 20 is made of a hollow cylindrical strainer basket

[0024] 26 is formed, which is arranged above a predeterminable lower fill level limit 28 in the feed tank 22 and is connected via a fluid connection 30 to the tertiary stage 14, into which the backwash filtrate from the secondary stage 12 can be discharged. The screen basket 26, with its upper opening 32, forms an overflow for an excess quantity in the feed tank 22, wherein the excess quantity flowing over the upper edge of the screen basket 26 can be discharged to the tertiary stage 14 via the interior 34 of the screen basket 26 and the fluid connection 30. The fluid connection 30 is formed from a pipe, one of which opens into the bottom of the screen basket 26 and, after passing through the bottom of the feed tank 22, opens out above the tertiary stage 14 with its other open end.

[0025] As can also be seen from Figure 1 and not shown in Figure 2, the flow divider 20 has a backwash device 36, which is only shown in principle in Figure 1. The backwash device 36 allows the outside of the screen basket 26 to be cleaned of contaminants that reach the unfiltered side of the primary stage 10 by being introduced into the feed tank 22 and depositing on the outside of the screen material of the screen basket 26. The backwash device 36 for the flow divider 20 has a drivable backwash arm 38, which is driven by an electric motor M so as to be movable in rotation along the inside of the screen basket 26.According to the illustration in Figure 1, the backwash arm 38 has a conical flushing device 40 at its end, which is provided with individual spray nozzles (not shown). This makes it possible to press clean fluid, such as tap water, against the direction of filtration with pressure from the inside to the outside through the filter or sieve material of the sieve basket 26, so that the latter is cleaned of particle contamination, which sinks towards the bottom of the feed tank 22 due to gravity. A flushing line 42 is used to supply the clean fluid. This flushing line interacts with the backwash arm 38 and allows the distribution of cleaning fluid via the spray nozzles of the flushing device 40. The flow direction of the.

[0026] The direction of the rinsing fluid is again shown in Figure 1 with an arrow.

[0027] As can be seen in particular from Figure 2, the secondary stage 12 is formed from individual filter units 44, with four filter units 44 being used in the present case. The four filter units 44 are supplied at the head end by a horizontally running distribution line 46, which is connected to the outlet 24 of the feed tank 22. A manually operable shut-off valve 48 is connected between the distribution line 46 and each head-end inlet of a filter unit 44. A bag or pocket filter 50 is used in each filter unit 44, as shown by way of example in its operating position in Figure 3. The respective bag or pocket filter 50 is connected with its unfiltrate side 52 to the primary stage 10 and with its filtrate side 54 to the tertiary stage 14.The fluid to be cleaned flows through the bag or pocket from the inside out, as shown in Figure 3, and any particulate contamination present in the backwash fluid deposits on the inside of the filter element material 56. In this case, the filter is open at the top and closed at the bottom, so that the unfiltered material flows from the top into the open opening 58, starting from the open shut-off valve 48. The backwash fluid cleaned by the element material 56 then reaches the filtrate side 54, formed by a cavity between the outer peripheral side of the cylindrical element material 56 and the cylindrical inner peripheral side of the filter housing 60 for a filter unit 44.

[0028] As further shown in Figure 2, the filter housings 60 of the individual filter units 44 rest on a grate 62 of the tertiary stage 14 at the bottom, which is formed by a rectangular discharge tank 64. The backwash fluid cleaned by the filter units 44 can thus collect in the discharge tank 64 before being returned to the process circuit 16 in the direction of the arrow by means of a suppression or vacuum pump 66.

[0029] Such bag or pocket filters 50 as shown in Figure 3 can be used both as surface filters and as depth filters. Preferably, a textile filter medium is used for the element material 56, whereby, in any case within the scope of a type of fine filtration, the filter fineness for the bag or pocket filter 50 is selected to be significantly finer than the filter fineness for the sieve body of the sieve basket 26. In this respect, the cleaned backwash fluid can settle in the discharge tank 64 before being pumped back into the fluid circuit 16 via the vacuum pump 66.

[0030] As can also be seen from Figure 2, the feed tank 22 is elevated above the top of the discharge tank 64 via individual support legs 68, so that the fluid connection 30 to the strainer basket 26 opens with its lower free end above the discharge tank 64. In any case, the flow divider 20 is only used when the fluid level of the backwash quantity exceeds the lower fill level limit 28 in the feed tank 22; otherwise, the backwash quantity to be cleaned passes via the fluid inlet 18 and through the interior of the feed tank 22 directly into the outlet 24 and from there via the distribution line 46 and the individual open shut-off valves 48 to the filter units 44.Since, as shown in Figure 2, several filter units 44 are connected in parallel in such a way that at least one bag or pocket filter 50 of a filter unit 44 can be exchanged from above for a new unit (see Figure 3), the other filter units 44 can continue to clean the resulting backwash quantities of contaminants, thus enabling a continuous processing process for backwash quantities. As already explained, the resulting backwash quantities of an automatic filter, for example according to the teaching of DE 10 2004 037 280 A1, can be highly dependent on the process conditions and thus vary greatly. The rinsing frequency is directly dependent on the dirt concentration and the selected filter fineness in the primary filter. A medium-sized filter of this type, for example, produces a liquid quantity of 500 μl per backwash during a rinsing time of approximately 10 seconds.A typical design requires a filter to be flushed approximately four times per hour; therefore, 2 m 3 / h of backwash liquid is required for further treatment.

[0031] Since the dirt concentration on the unfiltered side of a backwash filter is rarely constant and the flow rates can also vary, such filters are often flushed more frequently in practice. From continuous flushing to one flush per hour, basically anything is possible and even realistic in exceptional cases. For the example assumed here, this means that for this medium-sized backwash filter, a backwash flow of 0.5 m 3 up to 180 m 3 / h could occur. If the resulting backwash volume is to be treated in a second stage, i.e., with the backwash volume treatment system according to the invention presented here, the question arises as to how large this treatment stage should be. If an interruption of the overall process is excluded, i.e., switching off the backwash filter as a primary or automatic filter, the backwash volume treatment system would have to be designed for the worst case, i.e., for the treatment of 180 m 3 / h. Such a design would ultimately result in very large and therefore costly devices, for which a corresponding solution is shown in DE 10 2015 002 767 A1, which experience has shown to question the implementation of such an overall solution. The associated investment would be disproportionately expensive. However, since process reliability is often the only priority, it has now been recognized as more than sensible to implement a smaller backwash quantity treatment device according to the invention and to accept that at times not the entire backwash quantity is optimally finely filtered via the filter units 44, but that, depending on the resulting flushing quantity, partial flows are passed on via the coarser filter with the screen basket 26 or, if necessary, even returned to the process circuit 16 via the bypass function of the flow divider 20, without further treatment via the tertiary stage 14.This solution has no equivalent in the state of the art.

Claims

Patent claims 1. Filter device, in particular for processing, preferably for filtering backwash quantities originating from a filter upstream of the filter device, comprising a - Primary stage (10) to receive the respective backwash volume, - Secondary stage (12) for filtering the backwash volume from the primary stage (10), and - Tertiary stage (14) for returning the cleaned backwash quantity to a process circuit (16), characterized in that a flow divider (20) is used in the primary stage (10) which, when a predefinable fluid quantity is exceeded in the primary stage (10), directs the excess quantity to the tertiary stage (14) bypassing the secondary stage (12).

2. Filter device according to claim 1, characterized in that the primary stage (10) has a pressureless pre-tank (22) which has an inlet (18) for the respective backwash quantity from the filter and an outlet (24) for the discharge of the corresponding backwash quantity to the secondary stage (12).

3. Filter device according to claim 1 or 2, characterized in that the flow divider (20) is formed from a sieve basket (26) which is arranged above a predefinable lower fill level limit (28) in the feed tank (22) and is connected to the tertiary stage (14) via a fluid connection (30), into which the backwash filtrate of the secondary stage (12) can be discharged.

4. Filter device according to one of the preceding claims, characterized in that the sieve basket (26) has an upper opening (32) to provide an overflow for excess quantity in the feed tank (22) a filter device according to one of the preceding claims, characterized in that the flow divider (20) has a backwash device (36) that cleans it of contaminants that reach the unfiltered side of the primary stage (10). A filter device according to one of the preceding claims, characterized in that the backwash device (36) for the flow divider (20) is formed from a driveable backwash arm (38) that is movable along the inner circumference of the filter basket (26) and guides a backwash fluid from the inside to the outside through the screen structure of the filter basket (26).A filter device according to any one of the preceding claims, characterized in that the secondary stage (12) consists of individual filter units (44) which have a bag or pocket filter (50) connected with its unfiltrate side (52) to the primary stage (10) and with its filtrate side (54) to the tertiary stage (14). A filter device according to any one of the preceding claims, characterized in that several filter units (44) are connected in parallel arrangement such that at least one bag or pocket filter (50) of a filter unit (44) can be replaced with a new unit, while the other filter units (44) continue to clean the backwash quantities of contaminants. A filter device according to any one of the preceding claims, characterized in that the filter fineness of the sieve basket (26) is selected to be coarser than the filter fineness for the bag or pocket filter (50) of a respective filter unit (44). Filter device according to one of the preceding claims, characterized in that the backwash filtrate of the tertiary stage (14) can be returned to the subsequent process circuit (16) by means of a fluid pump, preferably in the form of a vacuum pump (66).