METHOD AND DEVICE FOR WASHING A FILTER CAKE ON A FILTER MEDIUM

Description

[0001] The invention relates to a method for washing a filter cake on a filter medium, in which the filter cake is filtered from a suspension, wherein the filter cake forms a mass of solid particles with remaining mother liquid, and for washing at least a region of the filter cake on a top side facing away from the filter medium is exposed to a washing fluid, which, due to an applied pressure difference to the filter cake, migrates from the top side towards the filter medium and thereby drives off remaining mother liquid towards the filter medium and flows off as washing filtrate on a filtrate side behind the filter medium, according to the preamble of claim 1.

[0002] The invention further relates to a device for washing a filter cake on a filter medium, wherein the filter cake, consisting of a suspension, is infiltrated onto the filter medium as a clump of solid particles with remaining mother liquid, and a feed device for supplying a washing fluid for washing at least a region of the filter cake is provided on a top side facing away from the filter medium, wherein a pressure differential is set on the filter medium, due to which the washing fluid passes through the filter cake from the top side towards the filter medium, thereby driving off remaining mother liquid towards the filter medium, and the wash filtrate can be discharged by means of a discharge line on a filtrate side behind the filter medium, according to the preamble of claim 7.

[0003] A generic method and a generic device are disclosed, for example, in EP 3 098 215 A1 or EP 3 556 447 A1. A similar device is also known from US 3 943 233 A.

[0004] The washing of a filter cake is usually carried out by spraying a washing liquid onto the cake surface after a partially filtered filter cake emerges from a filtration area. Due to a pressure differential, liquid is drawn towards an inner filter cell. The pore fluid, also called mother fluid, is partially forced out by the sprayed washing liquid in a piston-like motion. As the washing process continues, the washing liquid mixes with the mother fluid, resulting in a mixture of washing liquid and pore filtrate. Between cake formation and washing, and in the case of multiple washings between washings, the cake pores are usually emptied by the ingress of gas – typically air – before the next washing process begins. This partial emptying of the cake pores is often desirable and can improve the washing effect.

[0005] The economic efficiency of the washing process depends on various aspects, such as the successful completion of the washing task, i.e., achieving the washing goal, saving washing liquid to achieve the required purity, and / or minimizing the mixing of washing liquid and mother liquid, because otherwise the filtrates will require extensive post-treatment.

[0006] The invention is based on the Auf G abe The aim is to specify a particularly efficient method and a particularly efficient device for washing a filter cake on a filter medium.

[0007] The problem is solved, firstly, by a method having the features of claim 1 and, secondly, by a device having the features of claim 7. Preferred embodiments of the invention are specified in the dependent claims.

[0008] The method according to the invention is characterized in that that the filter medium is driven continuously and a continuous filtration and washing process is carried out, that the washing area is divided into several separate sections and arranged in a pressure-tight housing, that during washing, a volume flow of the wash filtrate (30) and / or a gas penetration through the filter cake (5) are detected as a control variable by the measuring device, wherein a filter cell filling or a filter cell emptying is controlled via a mass balance and the washing is regulated in such a way that an undersaturation of the filter cake is achieved, wherein previously measured filtration data determine how much filtrate the filter cake can hold at maximum saturation.

[0009] One aspect of the invention lies in the controlled or regulated washing of the filter cake on the filter medium. For control purposes, a measured variable, which can be measured with sufficient accuracy, is provided as the controlled variable. For control or monitoring, at least one measured variable is acquired as the controlled variable from the outflowing wash filtrate via at least one measuring device. The wash filtrate represents the filtrate displaced during washing, which comprises displaced mother liquid from the pores of the filter cake and optionally washing fluid, in particular washing liquid, or a mixture of mother liquid and washing fluid, flowing out of the cake. Depending on this at least one measured controlled variable, at least one washing parameter can be changed and set as a reference variable in the process via the control device. This allows for a particularly efficient washing result.According to the invention, the washing process is regulated in such a way that a certain undersaturation of the filter cake of about 5 to 10% is achieved.

[0010] According to a further development of the invention, it is particularly preferred that, during washing, the measuring device detects a quantity of the washing filtrate, a volume flow rate of the washing filtrate, a composition of the washing filtrate and / or a gas penetration through the filter cake as a control variable.

[0011] According to one aspect of the invention, the filtrate quantity in individual process zones, the washing liquid quantity, the drum speed, and the pressure difference in the individual washing zones can be measured relatively accurately. However, measuring the residual cake moisture, the degree of filter cell filling, and analyzing the cake surface is problematic. Nevertheless, the quantity of the wash filtrate and the volumetric flow rate of the outgoing wash filtrate can be measured very accurately using appropriate measuring devices, such as a flow meter, including any changes to the flow rate.

[0012] The composition of a wash filtrate, consisting of the mother liquid and the washing fluid, especially the washing liquid, can be determined quickly and accurately using appropriate analytical equipment. This also allows for the precise determination of the proportion of gas present in the washing fluid and thus of any gas penetration through the filter cake.

[0013] Various washing parameters can be adjusted as control variables to regulate the washing process. According to a further development of the invention, it is particularly advantageous to use a pressure differential across the filter medium and / or a supply of washing fluid as control variables during washing. These two washing parameters can be adjusted quickly and very precisely.

[0014] A pressure differential across the filter medium, i.e., a pressure difference between the top and bottom surfaces, can be directly set using a suitable compression and / or vacuum device and reliably determined via a pressure measuring device. The supply of washing fluid can also be precisely controlled, with the amount of washing fluid to be sprayed and / or the activation or deactivation of additional washing fluid supply devices being quickly and accurately adjusted by the control unit.

[0015] Regarding changes and adjustments to the pressure differential, a further development of the invention provides that the pressure differential at the filter medium is set on a top side and / or a filtrate side. When using a pressure filter with a surrounding pressure housing, the ambient pressure in the filter cake area can be freely adjusted. Alternatively or additionally, a vacuum can be applied to the filtrate side, i.e., in a filter cell of the filtration device, using a vacuum device, such as a vacuum pump.

[0016] A preferred embodiment of the invention further consists in using a control variable for adjusting the pressure differential: the output of a pump for conveying the wash filtrate and / or a throttle valve on a discharge line for the wash filtrate. By changing the output of a pump for conveying the wash filtrate, the pressure differential across the filter medium can be specifically altered. Alternatively or additionally to changing the pump output, a throttle valve can also be provided on a discharge line for the wash filtrate leading from a filter cell, which can be adjusted by means of an actuating device. This allows a pressure drop across the throttle valve and thus also an adjustment of the pressure differential across the filter medium.

[0017] In an advantageous embodiment, a particularly good washing result can be achieved by repeatedly carrying out the washing on the filter cake.

[0018] A particular advantage is that the repeated washing is carried out as a counterflow wash, in which the wash filtrate from a subsequent wash cycle is used as the washing fluid for the preceding wash cycle. This allows for particularly economical and efficient use of the washing fluid. Control can be implemented for each individual wash cycle, only for specific wash cycles, especially the final wash cycle, or for the entire washing process.

[0019] The device according to the invention for washing the filter cake is characterized in that a control device for controlled washing is provided depending on the outflowing wash filtrate, wherein a measured variable can be detected as a control variable for controlled washing by means of a measuring device and supplied to the control device, and that the control device is designed to change at least one washing parameter as a reference variable depending on the measured control variable of the wash filtrate.

[0020] The device according to the invention is particularly suitable for carrying out the method described above. The advantages outlined above can be achieved in this process.

[0021] According to the invention, it is particularly advantageous that the filter medium is driven in a continuous loop. This allows, in particular, a continuous filtration and washing process to be carried out.

[0022] Furthermore, according to one embodiment of the invention, it is particularly advantageous that the device has a pressure-tight housing in which a filtration area and a washing area are arranged. In particular, the washing area can be divided into several separate sections. These sections can be separated from one another by appropriate airlocks or partitions. In the pressure-tight housing, an overpressure can be set, either overall or in specific sections. This allows for the particularly efficient setting of pressure differentials for carrying out the filtration process and, in particular, the washing processes.

[0023] The device according to the invention has a drum filter.

[0024] According to the invention, the control / monitoring of cell filling and emptying is achieved via a mass balance. From the amount of suspension, its concentration, and the filter speed, it is known how much filter cake lies on a filter area of ​​less than 1 m², or how thick the filter cake is (cake height in mm). With the previously measured filtration data (for example, the specific cake density or porosity from the laboratory), the pore volume fraction of the filter cake is known with sufficient accuracy. This means it is known how much filtrate a fully saturated filter cake can hold at maximum capacity.

[0025] Numerical example (all figures are illustrative and naturally dependent on the material system and operating mode): One ton of filter cake is conveyed through the washing zone per unit of time (for simplicity, this refers to dry solids). The solids content can be determined from the suspension volume flow rate, the suspension concentration, and the filter rotation speed. This filter cake can, for example, contain a maximum of 400 kg of filtrate (which corresponds to a pore saturation S of 100%). By dehumidifying the cake, the saturation can be reduced to S = 40–90%, depending on the duration; let's simply assume S = 60%. S = 60% then corresponds to 240 kg of pore filtrate (remaining in the cake) and 160 kg of liquid flowing out of the filter cell.

[0026] A washing liquid quantity of 500 kg is added to this filter cake from the undersaturated stage (washing ratio 0.5 = 500 kg / 1,000 kg solids). The filtrate thus contains 500 kg of wash filtrate without dehumidification, and 660 kg with dehumidification (S = 60%) (i.e., 500 kg + 160 kg). The dehumidified filtrate (at 160 kg) represents a significant portion that can be measured with sufficient accuracy.

[0027] It should be noted that the focus here is less on achieving precise saturation down to the last percent, but rather on ensuring that undersaturation occurs, predictable to within 5-10%. For example, S = 60 or 80% would be sufficient in this case. The main thing is that adequate pore emptying occurs; this ensures that the washing liquid actually penetrates the cake instead of simply running off the surface. The resulting gas flow can aid in partial cell emptying (note: the cell can be partially emptied by the gas flow, but it could also be emptied with a separate gas stream introduced directly via the filter's control head).

[0028] This ensures (partial) pore emptying without excessive gas flow.

[0029] The invention is further described below with reference to preferred embodiments, which are schematically illustrated in the accompanying drawings. The drawings show: Fig. 1 a side view of a first device according to the invention; Fig. 2 a representation of a second device according to the invention; Fig. 3 a representation of a third device according to the invention; Fig. 4 an alternative control arrangement for the device of Fig. 3 Fig. 5 a schematic representation of a fourth device according to the invention; Fig. 6 a schematic representation of a fifth embodiment of a device according to the invention in a first operating state; Fig. 7 a representation of the device of Fig. 6 in a second operating state; and Fig. 8 a schematic representation of a sixth embodiment of a device according to the invention.

[0030] According to Fig. 1 A first device 10 according to the invention is designed as a drum filter with a suspension trough 12, into which a rotating drum with a cylindrically arranged filter medium 14 is partially immersed in a known manner. The filter medium 14 can be surrounded by a housing 11, which can be designed as a pressure housing.

[0031] In a generally known manner, a filter cake 5 is partially filtered through the filter medium 14 as it passes through the suspension trough 12, which is filled with a suspension, i.e., a mother liquid containing solid particles, due to a pressure differential applied to it. After the filter medium 14 with the partially filtered filter cake 5 exits the suspension, the filter cake 5 is optionally subjected to washing after intermediate dehumidification.

[0032] In the illustrated embodiment according to Fig. 1 Two washing stages are arranged, comprising a first feed device 22a with nozzles 24 for spraying a washing fluid 20 onto the filter cake 5 on the filter medium 14 and a second feed device 22b, which is also equipped with nozzles 24 for spraying the washing fluid 20. The washing areas between the two feed devices 22a, 22b, as well as to adjacent areas, can be separated by partitions 28 (not shown).

[0033] In the illustrated embodiment, the washing fluid 20, due to an applied pressure differential at the filter medium 14, penetrates the filter cake 5 on the filter medium 14 and thereby drives mother liquid out of the filter cake 5 to an inner filtrate side, whereby washing filtrate 30, which can be a mixture of mother liquid and washing fluid 20, is discharged via a discharge line 16. Gas 29 can also penetrate the filter cake 5 with the washing fluid 20.

[0034] In a further washing stage, which can generally precede or follow the first washing stage, washing fluid 20 is sprayed onto the filter cake 5 via the second feed device 22b, whereby the resulting wash filtrate 30 is conveyed via a return line 17 to the first feed device 22a as washing fluid 20 for a counter-current washing process. This arrangement of a counter-current washing process is particularly advantageous for the highly efficient removal of any remaining mother liquid from the solid particles, whereby the dehumidified filter cake 5 is removed from the filter medium 14 in a removal section 15 in a generally known manner.

[0035] The amount of liquid and solids is known from the amount of suspension (from the volume flow rate and solids concentration). A portion of the liquid (pore fluid as saturation) remains in the filter cake 5. This portion can be determined with sufficient accuracy by indirect measurement. Thus, if the emerging cake has a saturation of 100%, the filter cake 5 is reduced to a lower saturation of less than 100% by means of an initial pre-dehumidification. It is irrelevant whether the filtrate is discharged via several or a single filtrate collection line, as only the combined volume flow rate of the parent liquid is required for the calculation. Furthermore, when measuring the liquid difference, it is helpful if the filter cake 5 contains a large amount of pore filtrate, i.e., is sufficiently thick and / or has a higher porosity. This increases the reliability of the measurement.

[0036] In device 10 after Fig. 1 After each washing step, a certain degree of undersaturation of the filter cake 5 is generally desirable. Depending on the degree, this undersaturation can lead to a gas flow. This gas flow can also facilitate the emptying of the filter cell and the internal filtrate piping. However, a gas flow is only an optional process variant and in Fig. 1 not shown.

[0037] It is possible that a certain gas flow rate or pore undersaturation is not desired and set in every washing zone. In particular, undersaturation may be undesirable for cake removal after the final wash.

[0038] In connection with a second device 10 according to Fig. 2 A possible control or regulation of the washing process according to the invention is explained. The device 10 features, according to... Fig. 2 accordingly Fig. 1 a suspension trough 12 with a drum-shaped filter medium 14, wherein, for the sake of simplicity, only a single washing area with a feed device 22 for spraying washing fluid 20 is shown. In addition, according to Fig. 2 The schematic also indicates the supply of gas 29, which penetrates the filter cake 5 (not shown) on the filter medium 14.

[0039] In the device 10 according to Fig. 2 Wash filtrate 30 is pumped out via the discharge line 16 by means of a pump 32. A first measuring device 40a is arranged in a first section, with which the pressure in the filtrate line 16 and – if the pressure above the filter medium 14 is known – also the pressure difference across the filter medium 14 can be determined. A separator 18 is connected upstream of the pump 32, which is designed to separate gas from the flow of wash filtrate 30. Gas can be discharged via a vent 19. The wash filtrate 30 in the separator 18 is drawn in by the pump 32. A second measuring device 40b can detect and monitor the fill level in the separator 18. A control device is designed such that the second measuring device 40b is operatively connected to a controllable throttle valve 34, which is connected upstream of the separator 18.If the fill level in the separator 18 falls, the throttle valve 34 opens slightly, causing the pressure differential across the filter cake to increase. This occurs because the pressure differential across the throttle valve 34 decreases, or rather because the overall pressure differential remains constant and shifts towards the filter cake. This results in a greater undersaturation of the filter cake on the filter medium 14. Conversely, if the fill level rises, the throttle valve 34 closes slightly. Accordingly, the pressure differential across the filter cake on the filter medium 14 decreases, thus reducing the undersaturation of the filter cake.

[0040] Furthermore, a third measuring device 40c is assigned to the pump 32, which can be a volume measuring device or a flow meter. The control device is designed such that the pump 32 is controlled in such a way as to generate a flow of wash filtrate 30 that is as constant as possible.

[0041] If the saturation of the filter cake is determined with sufficient accuracy before washing, sufficiently precise control of the pore emptying within the filter cake can be achieved. A defined and measurable quantity of washing fluid is applied to the filter cake. The potentially undersaturated pores in the filter cake fill at least partially, and some of the washing fluid permeates the filter cake. Subsequent pore emptying can also occur. The total quantity of wash filtrate 30 is derived from the quantity of washing fluid 20 and the quantity of pore filtrate or mother liquid. The latter results from the difference in the saturation of the filter cake before and after washing. This difference in saturation could be zero, positive, or negative.Since the required parameters are known, i.e., the saturation of the filter cake before washing, the maximum amount of mother liquid known from the solids throughput, and the amount of washing fluid 20 added, the desired amount of washing filtrate 30 can be determined or specified as a target or control parameter.

[0042] As a result, a desired flow rate of wash filtrate 30 can be set by controlling the pressure differential at the filter cake on the filter medium 14. Since all controls and measurements are subject to minor errors, the entire balance of all incoming and outgoing liquid flows from all washing areas can preferably be additionally monitored and balanced in the background as a second control variable.

[0043] According to Fig. 3 The flow rate of the wash filtrate 30 can also be controlled in another way. A third measuring device 40c, designed to measure a volume flow rate or quantity of wash filtrate 30, is configured to control the inlet throttle valve 34. By appropriately controlling the throttle valve 34a, the volume flow rate of wash filtrate 30 can be increased or decreased. Alternatively, the following arrangement can be used to control the fill level in the separator 18: Fig. 2 The second measuring device 40b, which determines a fill level, controls a second throttle valve 34b at the outlet of the separator 18. By opening and closing the second throttle valve 34b accordingly, the liquid level in the separator 18 can be raised or lowered. The other components of the design of Fig. 3 correspond to those of Fig. 2 , whereby a regulated pump 32 can be dispensed with if a sufficient pressure difference is present.

[0044] Alternatively, as shown in the box in Fig. 3 As shown, an unregulated pump 32 with a fixed speed is also provided for the removal of the washing filtrate 30, whereby the liquid quantity is then regulated by the control device via the second downstream throttle valve 34b.

[0045] According to the alternative control device Fig. 4 The fill level in the separator 18 can also be regulated by means of the second measuring device 40b, which determines a fill level, by the second measuring device 40b acting directly on a controlled pump 32 with a control element 33. As with the other embodiments, the components of the device 10 not described in detail can be designed according to the preceding descriptions.

[0046] In these design variants, the target flow rate of wash filtrate 30 is known by calculation, and a control measure can be implemented by the control unit by comparing the actual flow rate of wash filtrate 30 or a fill level. The flow rate of wash filtrate 30 can be further regulated by means of the pressure differential across the first adjustable throttle valve 34.

[0047] According to Fig. 5 A further embodiment of the device 10 according to the invention is shown, wherein a pressure measuring device is connected upstream and downstream of the throttle valve 34 on the filtrate line 16 as a first measuring device 40a.

[0048] If the gas content in the wash filtrate 30 increases, the flow velocity also typically increases significantly. The amount of wash filtrate 30 can be regulated using a known Kv value of the valve, which corresponds to the pressure loss coefficient or flow resistance. If gas breaks through the filter cake, the pressure drop at the throttle valve 34 will increase abruptly – with the same amount of wash filtrate 30 – meaning the pressure upstream of the throttle valve 34 will rise. In this case, the control unit can slightly close the throttle valve 34 upstream of the separator 18, thus reducing the gas flow and consequently the pressure differential across the filter cake on the filter medium 14.Thus, a pressure difference at the throttle valve 34, which is determined via the two measuring devices 40a, can be used as the actual control variable for controlling the throttle valve 34 if a flow rate of gas 29 is specifically set and therefore expected during the washing process.

[0049] It should be noted that the pressure increase due to gas flow can also be used to adjust the calculated undersaturation of the pores in the filter cake according to the solutions described above. Therefore, in addition to balancing the mass flows, gas flow can also be recorded.

[0050] A further embodiment of the invention will be discussed in connection with the Figuren 6 und 7 This further embodiment relates to the possibility of connecting additional feeding devices 22, whereby for illustrative purposes only a first feeding device 22a and a second feeding device 22b are shown. However, virtually any number of further feeding devices 22 can be provided. This embodiment can be used as an alternative to, or in particular as a supplement to, the previously described embodiments of a device 10 according to the invention.

[0051] The filter cake can initially be washed using a first feed device 22a, through which washing fluid 20 is sprayed onto the filter cake. At least one further feed device 22b is not yet switched on. If an excessively high throughput of gas 29 is detected during the washing process, for example due to the arrangement according to Fig. 5 , to reduce the flow of gas 29, the additional supply device 22b for washing fluid 20 can be activated, which in Fig. 7 The liquid washing fluid 20 has a higher viscosity than the gas 29. Therefore, the washing fluid 20 acts as a brake on the volumetric flow rate of the gas 29 within the filter cake. A wider distribution of the washing fluid 20 prevents excessive or premature throughput of gas 29. It is understandable that if the same amount of washing fluid is applied over a larger area, gas 29 will flow into a wider area. However, due to the parallel flow of washing fluid 20, the flow of gas 29 is still slowed or impeded.

[0052] According to Fig. 8Figure 10 shows a further embodiment of the device 10 for measuring the flow rate of gas 29. In this embodiment, the gas discharged via the exhaust vent 19 from the separator 18 on the discharge line 16 can be measured by means of a fourth measuring device 40d. In particular, the fourth measuring device 40d can be configured as a volumetric or flow meter for determining the gas flow. The fourth measuring device 40d is connected to the adjustable throttle valve 34 to adjust the pressure differential across the filter medium 14. By appropriately controlling the throttle valve 34, the flow rate of gas 29 can be increased or decreased.

[0053] This design can also be used, in particular, in combination with one of the devices 10 described above.

[0054] The described embodiment of a device 10 is based on the core concept of controlled washing of a filter cake on the filter medium 14. For this purpose, properties of the wash filtrate 30 can be used to ensure a controlled flow of wash fluid 20 through the filter cake on the filter medium 14. The key means of achieving this controlled washing, with or without changing the residual moisture content of the cake (i.e., saturation of the filter cake), is the pressure differential. The pressure differential controls whether the available washing time is sufficient to guide the wash fluid 20 through the filter cake and, if necessary, to force or limit gas flow.

[0055] Preferably, the filter cake on the filter medium 14 has a certain thickness, which is preferably greater than 40 mm. This minimum cake thickness ensures a sufficient amount of pore filtrate so that it can be measured with sufficient accuracy.

[0056] It is still preferable that the filter cake can actually undergo pore emptying at the applied pressure differential. The capillary inlet pressure of the filter cake should be lower than the applied pressure differential, for example, less than 0.5 bar, which generally applies to all particle layers that can be filtered onto a continuous filter with a greater cake thickness.

Claims

1. Method for washing a filter cake (5) with a drum filter on a filter medium (14), onto which the filter cake is filtered from a suspension, wherein the filter cake (5) forms an aggregate of solid particles with residual mother liquid and, for washing, at least one area of the filter cake (5) on an upper side facing away from the filter medium (14) is acted upon by a washing fluid (20) which, due to an applied pressure difference, traverses the filter cake (5) from the upper side towards the filter medium (14) and thereby expels residual mother liquid towards the filter medium (14) and flows out as washing filtrate (30) on a filtrate side behind the filter medium (14), wherein a control means is used for the regulated control of the washing depending on the outflowing washing filtrate (30), for which at least one measured variable is detected by means of at least one measuring means (40) as regulating variable for regulated washing, and wherein depending on the measured regulating variable of the washing filtrate (30) at least one washing parameter is changed as reference variable by the control means, characterized in that the filter medium (14) is driven in rotation and a continuous filtration and washing process is carried out, in that a washing area is divided into several separate sections and arranged in a pressure-tight housing, in that during washing a volume flow of the washing filtrate (30) and / or a gas breakthrough through the filter cake (5) are detected by the measuring means as regulating variable, and in that a control of filter cell filling or filter cell emptying is carried out via a mass balance, and in that the washing is regulated in such a way that an undersaturation of the filter cake is achieved, wherein it is determined by previously measured filtration data, how much filtrate the filter cake can hold maximum at complete saturation.

2. Method according to claim 1, characterized in that during washing a pressure difference on the filter medium (14) and / or a supply of washing fluid (20) are provided as reference variable.

3. Method according to any one of claims 1 to 2, characterized in that the pressure difference on the filter medium (14) is set on an upper side and / or a filtrate side.

4. Method according to any one of claims 1 to 3, characterized in that as reference variable for setting the pressure difference a capacity of a pump (22) for conveying away the washing filtrate (30) and / or a throttle valve (34) on a discharge line (16) for the washing filtrate (30) are adjusted.

5. Method according to any one of claims 1 to 4, characterized in that the washing is carried out repeatedly on the filter cake (5).

6. Method according to claim 5, characterized in that the repeated washing is carried out as countercurrent washing, in which the washing filtrate (30) of a subsequent washing process is used as a washing fluid (20) to carry out the washing in a preceding washing process.

7. Device for washing a filter cake (5) on a filter medium (14), in particular pursuant to a method according to any one of claims 1 to 6, wherein the filter cake (5) is filtered onto the filter medium (14) from a suspension as an aggregate of solid particles with residual mother liquid and a supply means (22) is provided for supplying a washing fluid (20) to wash at least one area of the filter cake (5) on an upper side facing away from the filter medium (14), wherein on the filter medium (14) a pressure difference is set, due to which the washing fluid (20) traverses the filter cake (5) from the upper side towards the filter medium (14) and thereby expels residual mother liquid towards the filter medium (14) and by means of a discharge line (16) washing filtrate (30) can be discharged on a filtrate side behind the filter medium (14), wherein a control means is provided for the regulated control of the washing depending on the outflowing washing filtrate (30), wherein by means of at least one measuring means (40) at least one measured variable can be detected as regulating variable for regulated washing and can be forwarded to the control means, and wherein depending on the measured regulating variable of the washing filtrate (30) the control means is designed to change at least one washing parameter as reference variable wherein the device (10) comprises a drum filter, and characterized in that the filter medium (14) is driven in a circulating manner and a continuous filtration and washing process is carried out, in that the washing area is divided into several separate sections and arranged in a pressure-tight housing, in that during washing, a volume flow of the washing filtrate (30) and / or a gas breakthrough through the filter cake (5) are recorded as a controlled variable by the measuring device, and in that the control device is designed in such a way that a control of a filter cell filling or a filter cell emptying takes place via a quantity balance and the washing is regulated in such a way that an undersaturation of the filter cake is achieved, wherein it is determined by previously measured filtration data how much filtrate the filter cake can hold maximum at complete saturation.

8. Device according to claim 7, characterized in that in the pressure-sealed housing (11) a filtration area and the washing area are arranged.