Self-emptying separator

Abstract

The invention relates to a self-emptying separator which has a rotatable centrifugal drum (1) with a vertical axis of rotation D, which is provided with an inlet for a suspension to be processed in the centrifugal area and with at least one outlet for a liquid phase and with solids-discharging openings (12) to which an emptying system with a piston slide valve (11) is assigned, wherein the emptying system furthermore has a control fluid system (11) assigned to the piston slide valve (11) for controlling its opening and closing movements, wherein at least fluid for activating closing movements of the piston slide valve (11) can be directed in a closed conduit system as far as a closing chamber, wherein, in order to supply the closing chamber (103) with the fluid for activating closing movements of the piston slide valve (11), a pressure vessel (118) is provided which is arranged upstream of the closing fluid valve (107) and which can be acted upon and can be preloaded with a defined pressure via an additional valve (119), and wherein the control device (101) is furthermore provided at least for determining a drop in pressure in the pressure vessel (118) when the solids-discharging openings (12) are closed.

Description

[0001] Self-draining separator

[0002] The invention relates to a self-emptying separator according to the preamble of claim 1 and to a method for processing a centrifuged material according to claim 9.

[0003] Discontinuously discharging separators as defined in this document have, in addition to one or more outlets for one or more liquid phases, a discharge system with a piston valve that can be moved alternately into an open and a closed position by a fluid, particularly with liquid as the fluid. The piston valve opens solids discharge openings in the drum wall (open position) and closes them again (closed position). In the open position, a solid phase is discharged from the centrifuge drum.

[0004] To ensure precise operation of such a drum emptying system of a self-emptying separator, it can be equipped with a control fluid system with a piston valve. This serves to fill a chamber on the piston slide with fluid – preferably a liquid – and it serves to allow fluid to escape from a chamber on the piston slide for the emptying of solids, so that the piston slide can move. For example, in a separator with a vertical axis of rotation, fluid can escape from beneath a piston slide, causing the product in the drum to push it vertically downwards. The aim is to supply the most precisely measured volume of liquid possible to the control fluid system of the centrifugal drum in a short time during emptying ("opening fluid"). The volume of the opening fluid therefore determines the emptying quantity.

[0005] Currently, the control fluid systems of most self-draining separators are designed “open”, i.e. both closing fluid and opening fluid are sprayed into the rotating drum via control water sprays.

[0006] For example, DE 31 15 875 C1 discloses an open control fluid system in which both closing fluid and opening fluid are sprayed into the rotating centrifuge drum via control water sprays. DE 28 22 478 describes a self-draining separator with a control fluid system in which the control fluid is fed under pressure through a pipe that initially runs centrally in a rotating drive spindle and then radially through the drive spindle into the centrifuge drum.

[0007] EP 3 207 995 B1, like DE 28 22 478, also discloses a self-draining separator with a control fluid system in which the control fluid is guided through the rotating drive spindle. The feed channel is arranged in a ring around a feed channel for the suspension to be processed, also to cool the mechanical seal. The opening fluid is discharged through a line that passes axially off-center through the rotor or the centrifugal drum rotating during operation and is then guided axially further, which is structurally difficult to implement due to the rotation of the drum.

[0008] State-of-the-art control fluid systems have proven themselves well in practice. The disadvantage of this system is that leaks in this hydraulic system cannot be easily detected.

[0009] The object of the invention is to solve this problem.

[0010] The invention achieves this object by the subject matter of claim 1. It further provides the method of claim 9.

[0011] A self-emptying separator is provided which comprises a rotatable centrifugal drum with a vertical axis of rotation, wherein the centrifugal drum is provided with solids discharge openings, to which a discharge system is assigned, comprising a piston valve which is fluid-actuated, in particular by means of fluid, and movable into an open and a closed position. The discharge system further comprises a control fluid system assigned to the piston valve for controlling its opening and closing movements. This control fluid system, in turn, comprises the following:

[0012] - a control device designed at least to control the opening and closing movements,

[0013] - an opening fluid line in the drum, to which the fluid for activating opening movements of the piston slide (11) can be supplied from a stationary location which does not rotate during operation via an opening fluid supply in which an opening fluid valve is arranged,

[0014] - a closing chamber to which the fluid for activating closing movements of the piston slide can be supplied via a closing fluid supply in which a closing fluid valve is arranged,

[0015] - wherein at least the fluid for activating closing movements of the piston valve can be conducted in a closed line system into the closing chamber,

[0016] - furthermore, a pressure vessel is provided to supply the closing chamber with the fluid for activating closing movements of the piston slide, which is arranged in front of the closing fluid valve and which can be pressurised and prestressed with a defined pressure via an additional valve, and

[0017] - that the control device is further provided at least for determining a pressure drop in the pressure vessel when the solids openings are closed.

[0018] Such a self-draining separator has a whole range of advantages.

[0019] The opening and closing fluid (i.e. the fluid which is then used for opening or closing, i.e. the fluid for activating the respective opening or closing movements of the piston valve) can be, for example, water or, for example, the product or the flowable suspension to be processed.

[0020] The pressure drop measured in the pressure vessel when closing the solids discharge openings allows a relatively accurate determination of the discharge volume. The discharge volume can then be increased or decreased as needed using the opening water metering device to achieve the preselected discharge volume. The preselected discharge volume depends on the bowl geometry and the process requirements of the centrifuge.

[0021] Therefore, if the actual volume of discharged solids does not match a target value, the amount of opening water in the dosing device can be adjusted—increased or decreased—for the next discharge. During total discharges, the closing water valve is closed, so the drum remains open until it is completely empty.

[0022] A pressure drop in the pre-loaded pressure vessel between two partial discharges can be used as an indicator of a seal defect in the piston valve or drum valve and can be used for leak monitoring. This is particularly possible because, unlike injecting the closing water with a type of shower into the rotating centrifuge drum, no volume of the closing fluid can be lost when filling the closing chamber in the rotating system.

[0023] According to an optional and advantageous further development, it can be provided that the volume of the opening fluid required for opening can be dosed with a dosing device.

[0024] It is advantageous if both the closing fluid and the opening fluid are fed, preferably in a closed and hermetic hydraulic system (lines, valves, etc.), from a location outside the separator's rotating system via a rotary union into the drive spindle and from there into the rotating drum, into the opening fluid line in the drum, or the closing chamber. Injection from a non-rotating location into an injection chamber of the rotating centrifuge drum is not required. The supply line in the closed system enables the precise delivery of a defined fluid volume to the respective chamber. Fluid losses during injection are avoided.

[0025] The invention accordingly also provides the following method: A method for carrying out a partial emptying of solids when processing a flowable product with a separator according to one of the preceding claims, characterized by the following method steps:

[0026] Step a): Providing a self-emptying separator according to any one of claims 1 to 8 related thereto,

[0027] Step b): continuously rotating the centrifugal drum and continuously processing a flowable suspension, wherein the suspension is centrifugally separated into at least a liquid phase and a solid phase; step c) at intervals - repeated during step b) - emptying of solids by the following sub-steps:

[0028] Sub-step i): Opening the opening fluid valve so that an opening fluid volume metered by the metering device is admitted into the opening fluid line in the drum, whereby the piston slide moves into an open position and the solids openings are released and thereby opened by the piston slide, whereby the solids of the centrifuge drum are emptied;

[0029] Sub-step ii): Terminating the solids discharge by closing the opening fluid valve and opening the closing fluid valve, whereby closing fluid is refilled from the pressure vessel into the closing chamber via the opened closing fluid valve until it is filled and the piston valve covers the solids openings of the centrifuge drum and the solids openings are thereby closed; and

[0030] Substep iii): Determine the pressure drop in the pressure vessel when the solids openings are closed.

[0031] A change in the pressure drop in sub-step iii) between two partial discharges, which should in themselves lead to the same pressure drop, can in turn be easily used as an indicator of a seal defect, thus easily monitoring a leak in the rotating system.

[0032] It is also possible to determine the volume of solid discharged based on the pressure drop determined in step iii) and / or to adjust the discharge quantity for the next discharge based on a variation of the pressure in the pressure vessel.

[0033] The pressure vessel is pre-pressurized to a predetermined pressure, for example, between two emptying steps (i), (ii), and (iii) by filling it with a fluid. Further advantageous embodiments of the invention can be found in the remaining subclaims.

[0034] The invention is described in more detail below using exemplary embodiments with reference to the drawing. The invention is not limited to these exemplary embodiments, but can also be implemented in other ways, either literally or in other equivalent ways. It shows:

[0035] Figure 1: a schematic sectional view of a separator with a control fluid system according to the invention, as well as a block diagram of the control fluid system;

[0036] Figure 2: an enlarged detail of a rotary feedthrough of the separator from Fig. 1;

[0037] The following description of the figures describes an exemplary embodiment. Individual features of this exemplary embodiment can also be combined with exemplary embodiments not shown and are also suitable as advantageous embodiments of the subject matter described in one or more of the main and subclaims.

[0038] Fig. 1 shows a rotatable centrifuge drum 1 of a centrifuge designed as a self-emptying separator. The centrifuge drum 1 can have a vertical axis of rotation D.

[0039] A drive spindle SP for rotating the centrifugal drum 1 is rotatably mounted in a machine frame G. It supports the centrifugal drum 1, which is mounted on a free end of the drive spindle SP. The drive spindle SP is rotated by a motor 14. Other drive variants are also possible.

[0040] The centrifugal drum 1 can be single-conical and / or, as in this case, double-conical (bottom and / or top, and especially inside). The centrifugal drum 1 is preferably designed for continuous operation, i.e., for continuous, non-batch centrifugal processing of a flowable suspension. The centrifugal drum 1 can have an upper drum section 2 and a lower drum section 3. These drum sections 2, 3 can be connected to one another in various ways, for example, with a locking ring 4.

[0041] A distributor 5 is formed in the centrifugal drum 1 for supplying the product from a product inlet pipe 6 into a separation chamber 7. In the distributor 5, the product P is transferred into the rotating system. The product inlet pipe 6 is guided into the centrifugal drum 1 from above, or from the end opposite the drive spindle SP.

[0042] Fig.1 shows an example of a so-called clarification separator, which is designed to clarify a product P to be processed (a flowable suspension) in the centrifugal field or to separate it into a solid phase S and a single liquid phase L.

[0043] The actual centrifugal separation of the product P into different phases takes place in the separation chamber 7. The separation chamber 7 preferably comprises a disk stack 8 of separation disks. It also has a solids collection chamber 9 radially outwardly, in which the solid phase S separated from the suspension or the flowable product P collects during the separation and / or clarification process.

[0044] Furthermore, the separator here has a single liquid discharge 10, via which a liquid phase L can be discharged from the centrifugal drum 1. The liquid discharge 10 is designed here as a so-called peeling disc, which operates as a centripetal pump. The liquid discharge 10 can also be implemented in another way. Furthermore, several liquid phases can also be discharged, for which purpose the centrifugal drum 1 must be provided with a corresponding additional discharge system (e.g., with another peeling disc and a separating plate for feeding another liquid phase to this peeling disc, neither of which is shown). The separator is then designed as a so-called separation separator, in which two liquid phases and one solid phase are separated from one another.

[0045] A fluid-operated discharge system is used to discharge the solid phase S from the solid collection chamber 9 of the centrifugal drum 1. The system has a piston valve 11 for opening and closing several solid discharge openings 12, which can be circumferentially distributed in the region of the largest diameter of the centrifugal drum 1. The discharge system further comprises a control fluid system 100 associated with the piston valve 11 for controlling its opening and closing movements.

[0046] The control fluid system 100 has a control device 101. This can be embodied as a higher-level control computer of the separator. The control fluid system 100 further comprises, in the centrifugal drum 1, an opening fluid line in the drum 102 and a closing chamber 103, to which a fluid, in particular water, for activating the opening and closing movements can be supplied via an opening fluid supply 104 and a closing fluid supply 105, in each of which an opening fluid valve 106 and a closing fluid valve 107 can be arranged.

[0047] It is advantageous if both the closing fluid and preferably the opening fluid are preferably guided in a closed and hermetic hydraulic system (lines, valves and the like) from a location outside the rotating system of the separator via a sealed rotary feedthrough 13 (see also Fig. 2) into the drive spindle SP and from there into the rotating centrifugal drum 1 into the opening fluid line in the drum 102 or the closing chamber 103.

[0048] Injection from a non-rotating location into an injection chamber of the rotating centrifugal drum 1 is therefore not necessary.

[0049] The opening fluid supply 104 and a closing fluid supply 105 each take place from a stationary location outside the elements of the separator rotating during operation - such as the centrifugal drum 1 and the drive spindle SP - through the rotary union 13 through the drive spindle SP rotating during operation of the separator and then through radial line sections 1043, 1053 into the centrifugal drum 1 rotating at the speed of the drive spindle SP.

[0050] The rotary union 13 advantageously makes it possible to realize a sealed transition of a fluid from stationary supply lines—such as the opening fluid supply 104 and the closing fluid supply 105 here—into / out of or through a rotating separator element, such as the drive spindle SP, into the centrifuge drum 2, which rotates at the same speed. Figure 2 shows an enlarged detail of an exemplary rotary union 13 for the separator from Figure 1.

[0051] The rotary union 13 is designed here as a two-line rotary union.

[0052] The opening fluid supply 104 and the closing fluid supply 105 into the rotary feedthrough 13 preferably takes place in the radial direction through radial feed sections 1041, 1051 into a tubular section 17 of the rotary feedthrough 13 which is aligned with the drive spindle SP and does not rotate during operation of the separator.

[0053] After entering the radial supply sections 1041, 1051, the opening fluid and the closing fluid are guided separately from one another in the tubular section 17, each in an axially arranged fluid channel 1042, 1052. The fluid channels 1042, 1052 are designed coaxially here.

[0054] This tubular section 17 axially adjoins the drive spindle SP, which rotates during operation and in which the fluid channels 1042, 1052 continue axially or coaxially to one another as fluid channels 1042-1, 1052-1. The respective fluid channel 1042-1, 1052-1 of the drive spindle SP opens into the respective corresponding radial line section 1043, 1053, which each exits the drive spindle SP in the radial direction.

[0055] The transition of the fluid channels 1042, 1042-1 and 1052, 1052-1 between the non-rotating tubular section 17 and the rotating drive spindle SP can be sealed by means of seals 16. The drive spindle SP can in turn be driven, for example, by a drive 14. Here, the rotor 14-1 of the drive 14 is firmly connected to the drive spindle SP, and the stator 14-2 of the drive 14 is firmly connected to the housing G.

[0056] The opening fluid supply 104 is assigned a metering device 108 which is connected upstream of the opening fluid valve 106.

[0057] The dosing device 108 has a dosing element 110 that is movable, in particular displaceable, within a dosing chamber 109, which divides the dosing chamber 109 into a fluid chamber 111 and a pressure chamber 112 for the application of fluid, in particular a gas such as compressed air. The dosing element 110 is designed here as a movable, in particular deformable, membrane. The dosing element 110 can also be designed differently.

[0058] The fluid chamber 111 is formed between a filling valve 113 and the opening fluid valve 106 as well as an adjusting element 114.

[0059] A compressed air line 115, into which a valve 116 is connected, also opens into the pressure chamber 112. A respective control input of all controllable valves can be connected to the control device 101.

[0060] A piston valve 117, which is inserted into a wall of the centrifugal drum 1, can serve to discharge the closing fluid (and the opening fluid), here controlled by the opening fluid.

[0061] In order to keep the solids discharge openings 12 of the centrifugal drum 1 closed during operation, as shown on the right-hand side of Fig. 1, the closing fluid valve 107 is opened. The closing chamber 103 in the centrifugal drum 1 is supplied with closing fluid via a pressure vessel 118 containing pressurized closing fluid, which is pre-tensioned during filling via an additional valve 119 and a fluid source (not shown here), such as a pump, connected upstream of the valve, so that a defined pressure prevails in the closing fluid system.

[0062] The term "pre-loaded" can mean that the pressure vessel 118 is provided with a defined (over)pressure via the valve 119 by keeping the valve 119 open during filling until the defined pressure is detected by a suitable measuring device M, whereby the valve 119 is closed. This can occur, for example, in the period between two solids discharges—i.e., partial discharges.

[0063] If a partial emptying is performed to empty the solids S from the solids chamber 9 of the centrifugal drum 1, the opening fluid valve 106 is first opened, so that an opening fluid volume metered by the metering device 108 is admitted into the opening fluid line 102 in the drum. The opening fluid overcomes the locking force of the piston valve 117, thereby discharging the closing fluid, so that the piston slide 11 moves into the open position and the solids openings 12 are released by the piston slide 11 and thereby opened.

[0064] When the partial emptying is to be terminated, the opening fluid valve 106 is closed and the closing fluid valve 107 is opened. This pushes closing fluid from the pressure vessel 118 into the closing chamber 103 via the opened closing fluid valve 107 until it is filled and the piston slide 11 covers the solids openings 12 of the centrifuge drum 1, closing the solids openings 12.

[0065] This creates a pressure drop in the pressure vessel 118, which can be determined, in particular, measured by the measuring device M. The magnitude of the pressure drop in the pressure vessel 118 allows a conclusion to be drawn about how much closing fluid was consumed and thus allows a precise statement about the volume of solids emptied during the partial emptying. For the next emptying, the pressure vessel 118 is pre-pressurized again via the valve 119 and supplied with the defined pressure, which can be detected or measured by the measuring device M.

[0066] By comparing the opening fluid metering device 108 with the discharged solid volume determined by the pressure drop in the pressure vessel 118, the solid volume to be discharged during the next solid discharge process can be increased or decreased as needed to achieve a preselected solid volume to be discharged. Accordingly, the metering device 108 pre-meters a larger or smaller opening fluid volume in the metering device 108 than for the previous partial discharge.

[0067] The preselected solid volume depends on the geometry of the centrifugal drum 1 and the process requirements of the separator.

[0068] During a total emptying, the closing fluid valve 107 is closed so that the centrifugal drum 1 remains open until the centrifugal drum 1 is completely emptied.

[0069] A pressure drop occurring in the pre-stressed pressure vessel 118 between two partial discharges can be used as an indicator of a sealing defect on the piston slide 11 or the piston valve 117 and can be used for leakage monitoring.

[0070] Both the closing fluid and the opening fluid are preferably conveyed in a closed and hermetic hydraulic system from a location outside the rotating system of the separator via the rotary union 13 into the drive spindle SP and from there into the rotating centrifugal drum 1 into the opening fluid line in the drum 12 or the closing chamber 13. For example, using the measuring device M, which can be designed as a pressure monitoring device, it can be determined whether a leak exists in this closed system, e.g., in the piston slide seal or in the piston valve 117 for discharging the closing fluid. The pressure drop during a separator emptying process can also be used to determine the volume of solids emptied.

[0071] The control device 101 can be controlled with a computer program product in the form of a control program, which also takes over the separator control and / or regulation and thus can also control and / or regulate the actuation of the piston slide 11, in particular also the metering of the opening fluid in the metering device 108 and the preload of the pressure vessel 118 as well as the implementation and execution of the measurements.

[0072] Reference symbol

[0073] 1 centrifugal drum

[0074] 2 drum top

[0075] 3 Drum base

[0076] 4 locking ring

[0077] 5 distributors

[0078] 6 Product inlet pipe

[0079] 7 Separation room

[0080] 8 plate pack

[0081] 9 Solids collection chamber

[0082] 10 Liquid discharge

[0083] 11 piston valves

[0084] 12 Solids discharge opening

[0085] 13 Rotary union

[0086] 14 Drive

[0087] 14-1 Rotor

[0088] 14-2 Stator

[0089] 16 seals

[0090] 17 Pipe section

[0091] 100 Control fluid system

[0092] 101 Control device

[0093] 102 Opening fluid line in the drum

[0094] 103 Locking chamber

[0095] 104 Opening fluid supply

[0096] 1041 radial supply line section

[0097] 1042 Fluid channel

[0098] 1042-1 Fluid channel

[0099] 1043 radial line section

[0100] 105 Closing fluid supply

[0101] 1051 radial supply line section

[0102] 1052 Fluid channel

[0103] 1052-1 Fluid channel

[0104] 1053 radial line section

[0105] 106 Opening fluid valve 107 Closing fluid valve

[0106] 108 Dosing device

[0107] 109 Dosing room

[0108] 110 Dosing element

[0109] 111 Fluid chamber

[0110] 112 Printing room

[0111] 113 Filling valve

[0112] 114 Adjustment element

[0113] 115 Compressed air line

[0114] 116 Valve

[0115] 117 Piston valve

[0116] 118 pressure vessels

[0117] 119 Valve

[0118] G Machine frame

[0119] D axis of rotation

[0120] L Liquid phase

[0121] S solid

[0122] SP drive spindle

[0123] P Product

[0124] M measuring device

Claims

Claims: A self-emptying separator comprising a rotatable centrifugal drum (1) with a vertical axis of rotation D, which is provided with an inlet for suspension to be processed in the centrifugal field, with at least one outlet for a liquid phase, and with solid discharge openings (12) to which a discharge system with a piston valve (11) is assigned, which is fluid-actuated, in particular by means of fluid, and can be moved into an open and a closed position, wherein the discharge system further comprises a control fluid system (100) assigned to the piston valve (11) for controlling its opening and closing movements, wherein the control fluid system (100) in turn comprises: a) a control device (101) which is designed at least for controlling the opening and closing movements, b) an opening fluid line in the drum (102) which is supplied via an opening fluid supply (104) in which an opening fluid valve (106) is arranged,the fluid for activating opening movements of the piston valve (11) can be supplied from a stationary location that does not rotate during operation, c) a closing chamber (103) to which the fluid for activating closing movements of the piston valve (11) can be supplied via a closing fluid supply (105) in which a closing fluid valve (106) is arranged, characterized in that d) at least the fluid for activating closing movements of the piston valve (11) can be conveyed in a closed piping system up to the closing chamber, e) a pressure vessel (118) is provided for supplying the closing chamber (103) with the fluid for activating closing movements of the piston valve (11), which is arranged upstream of the closing fluid valve (107) and which can be pressurized and pre-tensioned with a defined pressure via an additional valve (119),and f) that the control device (101) is further provided at least for determining a pressure drop in the pressure vessel (118) when the solid openings (12) are closed. Self-emptying separator according to claim 1, characterized in that the volume of fluid required for opening to activate opening, The movement of the piston slide (11) can be metered by means of a metering device (108).

3. Self-emptying separator according to one of the preceding claims, characterized in that both the fluid for activating opening movements and the fluid for activating closing movements are or can be supplied in a closed piping system up to the opening fluid line in the drum (102) or up to the closing chamber (103).

4. Self-emptying separator according to one of the preceding claims, characterized in that the pressure in the pressure vessel (118) can be determined via a measuring device M.

5. Self-emptying separator according to one of the preceding claims, characterized in that the metering device (108) has a metering element (110) movable in a metering chamber (109) and an adjustment element (114) for metering the amount of fluid required for opening.

6. Self-emptying separator according to one of the preceding claims, characterized in that the opening fluid supply (104) and the closing fluid supply (105) are provided at least sectionally through a sealed rotary feedthrough (13) through the drive spindle SP rotating during operation of the separator.

7. Self-emptying separator according to claim 6, characterized in that the rotary feedthrough (13) is designed as a two-line rotary feedthrough.

8. Self-emptying separator according to one of the preceding claims, characterized in that the control device (101) has a computer control program that takes over the separator control and regulation and also controls the actuation of the piston valve (11), in particular also the metering of the opening fluid in the metering device (108) and the actuation of the valve (119) for pre-tensioning the pressure vessel (118) as well as the execution and performance of measurements. A method for performing partial solid emptying during the processing of a free-flowing product with a separator according to one of the preceding claims, characterized by the following process steps: a) providing a self-emptying separator according to one of the preceding claims; b) rotating the centrifugal drum (1) and continuously processing a free-flowing suspension, wherein the suspension is centrifugally separated at least into a liquid phase F and a solid phase S; c) repeatedly emptying solid S at intervals during step b) by the following sub-steps: i.Opening of the opening fluid valve (106), so that a volume of opening fluid metered by the metering device (108) is admitted into the opening fluid line in the drum (102), whereby the piston slide (11 ) moves into an open position and the solid openings (12) are released and thereby opened by the piston slide (11 ), resulting in the emptying of the solid from the centrifugal drum (1 ); ii. Terminating the solids discharge by closing the opening fluid valve (106) and opening the closing fluid valve (107), whereby closing fluid is replenished from the pre-pressurized pressure vessel (118) into the closing chamber (103) via the open closing fluid valve (107) until it is filled and the piston slide (11) covers the solids openings (12) of the centrifugal drum (1) and the solids openings (12) are thereby closed; iii. Determining a pressure drop in the pressure vessel (118) when the solids openings (12) are closed.Method according to claim 9, characterized in that a change in the pressure drop in step iii) between two partial emptyings is used as an indicator of a sealing defect on the piston slide (11 ) or on the piston valve (117), thereby realizing leakage monitoring.

11. A method according to claim 9 or 10, characterized in that the volume of emptied solid is determined as an actual value based on the pressure drop determined in step iii).

12. A method according to claim 10 or 11, characterized in that the actual value is compared with a target value and that, if the actual value of the volume of emptied solid does not correspond to a predetermined target value, the amount of opening water in the metering device (108) is adjusted for the subsequent emptying.

13. Method according to one of claims 9 to 12, characterized in that the pressure vessel (118) is pre-pressurized to a predetermined pressure by filling it with a fluid.

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