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] The invention relates to a self-emptying separator according to claim 1 and a method for processing centrifugal material according to claim 9.

[0002] Discontinuously emptying separators, as defined in this document, have, in addition to one or more outlets for one or more liquid phases, an emptying system with a piston valve that is fluid-actuated, in particular with liquid as the fluid, and can be moved alternately into an open and a closed position, whereby the piston valve opens (open position) and closes (closed position) solid discharge openings in the drum wall. In the open position, a solid phase is discharged from the centrifugal drum.

[0003] To ensure precise operation of such a drum emptying system in a self-emptying separator, it can incorporate a control fluid system with a piston valve. This system serves to fill a chamber on the piston valve with fluid—preferably a liquid—and to allow fluid to escape from a chamber on the piston valve during the emptying of solids, thus enabling the piston valve to move. For example, in a separator with a vertical axis of rotation, fluid can escape below a piston valve, causing the product in the drum to push it vertically downwards. The aim is to supply the control fluid system of the centrifugal drum with the most precisely measured volume of liquid possible in a short time during emptying ("opening fluid"). The volume of the opening fluid thus determines the emptying quantity.

[0004] Currently, the control fluid systems of most self-emptying separators are designed "open", meaning that both closing fluid and opening fluid are injected into the rotating drum via control water jets.

[0005] For example, DE 31 15 875 C1 discloses an open control fluid system in which both closing fluid and opening fluid are injected into the rotating centrifugal drum via control water jets.

[0006] DE 28 22 478 describes a self-emptying separator with a control fluid system in which the control fluid is guided under pressure through the drive spindle into the centrifugal drum via a pipeline that is initially centrally located in a rotating drive spindle and then radially extending through the drive spindle.

[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 annularly around a feed channel for the suspension to be processed, also to cool the mechanical seal. The opening fluid is drained through a line that passes axially off-center through the rotor or the centrifugal drum rotating during operation and is then continued axially. This is practically impossible to implement due to the rotation of the drum.

[0008] US4401429 discloses a solid-bowl centrifuge with a self-emptying function, in which an annular gap is controlled by an annular slide valve. The prior art control fluid systems have proven effective in practice. A disadvantage of this system is that leaks in this hydraulic system cannot be easily detected.

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

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

[0011] A self-emptying separator is provided, comprising a rotatable centrifugal drum with a vertical axis of rotation. The centrifugal drum is provided with solid discharge openings, to which a discharge system with a piston valve is associated. The piston valve is fluid-actuated, in particular by means of fluid, and can be moved into an open and a closed position. The discharge system further comprises a control fluid system associated with the piston valve for controlling its opening and closing movements. This control fluid system, in turn, has the following features: a control device designed at least for controlling the opening and closing movements, 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 that does not rotate during operation via an opening fluid supply in which an opening fluid valve is arranged, a closing chamber to which the fluid for activating closing movements of the piston valve can be supplied via a closing fluid supply in which a closing fluid valve is arranged, wherein at least the fluid for activating closing movements of the piston valve can be guided in a closed piping system up to the closing chamber, wherein furthermore a pressure vessel is provided for supplying the closing chamber with the fluid for activating closing movements of the piston valve, which is arranged upstream of the closing fluid valve and which can be pressurized and pre-tensioned via an additional valve with a defined pressure, and that the control device is furthermore provided at least for determining a pressure drop in the pressure vessel when the solid openings are closed.

[0012] Such a self-emptying separator has a whole range of advantages.

[0013] The opening and closing fluid (i.e., the fluid 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.

[0014] The measured pressure drop in the pressure vessel when closing fluid is introduced to close the solids discharge openings allows for a relatively accurate estimation of the discharge volume. The dosing system for the opening fluid can then be used to increase or decrease the discharge volume as needed to achieve the pre-selected discharge quantity. The pre-selected discharge quantity depends on the drum geometry and the process requirements of the centrifuge.

[0015] Therefore, if the actual volume of emptied solid does not match a target value, the amount of opening water in the dosing device can be adjusted – increased or decreased – for the next emptying.

[0016] During complete emptying, the shut-off water valve is closed, so that the drum remains open until it is completely empty.

[0017] A pressure drop occurring in the pre-pressurized pressure vessel between two partial emptying cycles can be used as an indicator of a sealing defect in the piston valve or drum valve and for leakage monitoring. This is particularly possible because, unlike when the closing water is injected into the rotating centrifugal drum using a type of nozzle, no volume of the closing fluid can be lost during filling of the closing chamber in the rotating system.

[0018] It may be provided, after optional and advantageous further training, that the volume of opening fluid required for opening can be dosed using a dosing device.

[0019] It is advantageous if both the closing fluid and the opening fluid are preferably routed in a closed and hermetic hydraulic system (lines, valves, etc.) from a location outside the rotating separator system via a rotary feedthrough into the drive spindle and from there into the opening fluid line in the rotating drum or the closing chamber. Injection from a non-rotating location into an injection chamber of the rotating centrifugal drum is not required. The closed system allows for the precise delivery of a defined fluid volume into the respective chamber. Fluid losses during injection are avoided.

[0020] The invention also provides the following method: A method for carrying out a partial solids emptying during the processing of a flowable product with a separator according to one of the preceding claims, characterized by the following method steps: Step a): Providing a self-emptying separator according to any one of claims 1 to 8 relating thereto, Step b): continuous rotation of the centrifugal drum and continuous processing of a free-flowing 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 through the following sub-steps: Substep i): Opening the opening fluid valve so that a volume of opening fluid metered by the metering device is admitted into the opening fluid line in the drum, causing the piston slide to move into an open position and the solid openings to be released and opened by the piston slide, thereby emptying the solid from the centrifugal drum; Partial step ii): The solids discharge is terminated 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 open closing fluid valve until it is full and the piston slide covers the solids openings of the centrifugal drum, thereby closing the solids openings; and Part iii): Determining the pressure drop in the pressure vessel when the solid openings are closed.

[0021] A change in the pressure drop in sub-step iii) between two partial emptyings, which should in themselves lead to the same pressure drop, can in turn be easily used as an indicator of a sealing defect, thus enabling simple monitoring of a leak in the rotating system.

[0022] It is also possible to determine the volume of emptied solid based on the pressure drop determined in step iii), and / or to adjust the amount of emptying for the next emptying based on a variation of the pressure in the pressure vessel.

[0023] The pressure vessel is, for example, pre-pressurized between two emptying processes with the sub-steps i), ii) and iii) by refilling it with a fluid to a predetermined pressure.

[0024] Further advantageous embodiments of the invention can be found in the remaining dependent claims.

[0025] The invention is described in more detail below with reference to exemplary embodiments and the drawing. The invention is not limited to these exemplary embodiments, but can also be realized in other ways, either literally or equivalently. The drawing shows: 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; Figure 2: a close-up of a rotary feedthrough of the separator made of Fig. 1 ;

[0026] 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 each also suitable as advantageous embodiments of the objects described in one or more of the main and dependent claims.

[0027] Fig. 1 Figure 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.

[0028] 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. Alternatively, other drive configurations are also possible.

[0029] The centrifugal drum 1 can be designed with a single conical shape and / or, as shown here, a double conical shape (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 free-flowing suspension.

[0030] The centrifugal drum 1 can have a drum upper part 2 and a drum lower part 3. These drum parts 2, 3 can be connected to each other in various ways, for example with a locking ring 4.

[0031] In the centrifugal drum 1, a distributor 5 is formed for the product feed from a product feed pipe 6 into a separation chamber 7. In the distributor 5, the product P is transferred into the rotating system. The product feed pipe 6 is led into the centrifugal drum 1 from above, i.e., from the end opposite the drive spindle SP.

[0032] Fig. 1 Figure 1 shows an example of a so-called clarification separator, which is designed to clarify a product P (a free-flowing suspension) to be processed in a centrifugal field or to separate it into a solid phase S and a single liquid phase L.

[0033] In the separation chamber 7, the actual centrifugal separation of product P into different phases takes place. The separation chamber 7 preferably comprises a tray stack 8 consisting of separation trays. It also has a solids collection chamber 9 radially outside this, in which the solid phase S separated from the suspension or the free-flowing product P collects during the separation and / or clarification process.

[0034] Furthermore, the separator here has a single liquid discharge 10 through which a liquid phase L can be discharged from the centrifugal drum 1. The liquid discharge 10 is designed here as a so-called skimming disc, which operates as a centripetal pump. The liquid discharge 10 can also be implemented in other ways. Multiple liquid phases can also be discharged, for which the centrifugal drum 1 must then be equipped with a corresponding additional discharge system (e.g., with another skimming disc and a separating plate for feeding another liquid phase to this skimming disc; neither of these are shown). The separator is then designed as a so-called separation separator, in which two liquid phases and one solid phase are separated from each other.

[0035] A fluid-operated discharge system serves to remove the solid phase S from the solids collection chamber 9 of the centrifugal drum 1. This system includes a piston valve 11 for opening and closing several solids discharge openings 12, which can be distributed circumferentially in the region of the largest diameter of the centrifugal drum 1. The discharge system also comprises a control fluid system 100 associated with the piston valve 11 for controlling its opening and closing movements.

[0036] The control fluid system 100 comprises a control device 101. This can be configured as a higher-level control computer for the separator. The control fluid system 100 further includes, within the centrifugal drum 1, an opening fluid line in the drum 102 and a closing chamber 103, to which a fluid, in particular water, 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, to activate the opening and closing movements.

[0037] It is advantageous if both the closing fluid and preferably also the opening fluid are preferably supplied 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.

[0038] Therefore, it is not necessary to inject from a non-rotating location into an injection chamber of the rotating centrifugal drum 1.

[0039] The opening fluid supply 104 and a closing fluid supply 105 each originate from a stationary location outside the rotating elements of the separator during operation – such as the centrifugal drum 1 and the drive spindle SP – through the rotary feedthrough 13, through the drive spindle SP rotating during operation of the separator, and then through radial line sections 1043, 1053 to the centrifugal drum 1 rotating at the speed of the drive spindle SP.

[0040] The rotary feedthrough 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 - in / out or through a rotating separator element, such as the drive spindle SP, to the centrifugal drum 2, which rotates at the same speed.

[0041] In Fig 2 is a close-up of an exemplary rotary feedthrough 13 for the separator made of Fig. 1 depicted.

[0042] The rotary feedthrough 13 is designed here as a two-wire rotary feedthrough.

[0043] The opening fluid supply 104 and the closing fluid supply 105 into the rotary feedthrough 13 preferably take place in a radial direction through radial supply 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.

[0044] After entering the radial supply sections 1041 and 1051, the opening fluid and the closing fluid are guided separately from each other in axially arranged fluid channels 1042 and 1052 within the tubular section 17. The fluid channels 1042 and 1052 are coaxially arranged.

[0045] This tubular section 17 is axially adjacent to the drive spindle SP, which rotates during operation and in which the fluid channels 1042, 1052 continue axially and coaxially to each other 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 conduit section 1043, 1053, which exits the drive spindle SP in a radial direction.

[0046] The transition between 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, for example, be driven by a drive 14. In this case, the rotor 14-1 of the drive 14 is fixedly connected to the drive spindle SP, and the stator 14-2 of the drive 14 is fixedly connected to the housing G.

[0047] The opening fluid supply 104 is associated with a metering device 108, which is located upstream of the opening fluid valve 106.

[0048] The metering device 108 has a metering element 110 that is movable, in particular displaceable, within a metering chamber 109 and that divides the metering chamber 109 into a fluid chamber 111 and a pressure chamber 112 for pressurizing with fluid, in particular a gas such as compressed air. Here, the metering element 110 is designed as a movable, in particular deformable, diaphragm. The metering element 110 can also be designed differently.

[0049] The fluid chamber 111 is formed between a filling valve 113 and the opening fluid valve 106 as well as an adjusting element 114.

[0050] A compressed air line 115, into which a valve 116 is connected, also leads into the pressure chamber 112. A control input for each controllable valve can be connected to the control device 101.

[0051] A piston valve 117, which is inserted into a wall of the centrifugal drum 1, can serve to drain the closing fluid (and the opening fluid), here controlled by the opening fluid.

[0052] To keep the solids discharge openings 12 of the centrifugal drum 1 closed during operation, as shown on the right side of Fig. 1 As shown, the closing fluid valve 107 is open. The closing chamber 103 in the centrifugal drum 1 is supplied with closing fluid via a pressure vessel 118, which contains closing fluid under pressure. This vessel is pressurized during filling via an additional valve 119 and a fluid source upstream of it (not shown here), such as a pump, so that a defined pressure prevails in the closing fluid system.

[0053] The term "pre-pressurized" can mean that the pressure vessel 118 is pressurized to 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, at which point the valve 119 closes. This can occur, for example, during the period between two solids emptying operations – i.e., partial emptying operations.

[0054] When a partial emptying is carried out to remove the solid S from the solids chamber 9 of the centrifugal drum 1, the opening fluid valve 106 is first opened, allowing a volume of opening fluid metered by the metering device 108 to enter the opening fluid line 102 in the drum. The opening fluid overcomes the holding force of the piston valve 117, causing the closing fluid to be released, so that the piston slide 11 moves into the open position and the solids openings 12 are released and thus opened by the piston slide 11.

[0055] When partial emptying is to be completed, the opening fluid valve 106 is closed and the closing fluid valve 107 is opened. This allows closing fluid from the pressure vessel 118 to flow into the closing chamber 103 via the open closing fluid valve 107 until it is filled and the piston slide 11 covers the solid openings 12 of the centrifugal drum 1 and the solid openings 12 are closed.

[0056] This results in a pressure drop in pressure vessel 118, which can be determined, in particular measured by the measuring device M. The magnitude of the pressure drop in pressure vessel 118 allows conclusions to be drawn about how much sealing fluid was consumed and thus enables a precise statement about the volume of solids emptied by the partial emptying. For the next emptying, pressure vessel 118 is repressurized via valve 119 and pressurized to the defined pressure, which can be detected or measured by the measuring device M.

[0057] The metering device 108 of the opening fluid allows the volume of solids to be emptied during the next solids emptying process to be increased or decreased as needed by comparing it with the volume of solids emptied, determined by the amount of the pressure drop in the pressure vessel 118, in order to achieve a preselected solids volume to be emptied. Accordingly, the metering device 108 pre-meters a larger or smaller volume of opening fluid into the metering device 108 than was used for the previous partial emptying.

[0058] The preselected solids volume depends on the geometry of the centrifugal drum 1 and the process engineering requirements of the separator.

[0059] During total emptying, the closing fluid valve 107 is closed, so that the spin drum 1 remains open until the spin drum 1 is completely empty.

[0060] A pressure drop occurring in the pre-pressurized pressure vessel 118 between two partial emptying operations can be used as an indicator of a sealing defect on the piston slide 11 or on the piston valve 117 and can be used for leakage monitoring.

[0061] In this system, both the closing fluid and the opening fluid are preferably guided in a closed and hermetic hydraulic system from a location outside the rotating separator system via the rotary feedthrough 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, respectively. For example, the measuring device M, which can be designed as a pressure monitoring device, can be used to determine whether a leak exists in this closed system, e.g., in the piston valve seal or in the piston valve 117 for draining the closing fluid. The volume of solids discharged can also be inferred from the pressure drop during an emptying process of the separator.

[0062] The control device 101 can be controlled by a computer program product in the form of a control program, which also takes over the separator control and / or regulation and can thus also control and / or regulate the actuation of the piston valve 11, in particular the metering of the opening fluid in the metering device 108 and the pre-tensioning of the pressure vessel 118 as well as the execution and performance of the measurements. Reference sign

[0063] 1 Centrifugal drum 2 Drum upper part 3 Drum lower part 4 Locking ring 5 Distributor 6 Product feed pipe 7 Separation chamber 8 Disc pack 9 Solids collection chamber 10 Liquid discharge 11 Piston valve 12 Solids discharge opening 13 Rotary feedthrough 14 Drive 14-1 Rotor 14-2 Stator 16 Seals 17 Pipe section 100 Control fluid system 101 Control device 102 Opening fluid line in the drum 103 Closing chamber 104 Opening fluid supply 1041 Radial supply section 1042 Fluid channel 1042-1 Fluid channel 1043 Radial line section 105 Closing fluid supply 1051 Radial supply section 1052 Fluid channel 1052-1 Fluid channel 1053 Radial line section 106 Opening fluid valve 107 Closing fluid valve 108 Metering device 109 Metering chamber 110 Metering element 111 Fluid chamber 112 Pressure chamber 113 Filling valve 114 Adjusting element 115 Compressed air line 116 Valve 117 Piston valve 118 Pressure vessel 119 Valve GMachine frame DRotary axis LLiquid phase SSolid SPDrive spindle PProduct MMeasuring device

Claims

1. Self-emptying separator, which has 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 and with at least one outlet for a liquid phase and with solids-discharge openings (12) to which an emptying system with a piston slide valve (11) is assigned, which can be moved in a fluid-actuated manner, in particular by means of fluid, into an open position and into a closed position, wherein the emptying system furthermore has a control fluid system (100) assigned to the piston slide valve (11) for controlling its opening and closing movements, wherein the control fluid system (100) in turn has the following: 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), to which the fluid for activating opening movements of the piston slide valve (11) can be fed from a stationary location which does not rotate during operation via an opening fluid supply (104) in which an opening fluid valve (106) is arranged, c) a closing chamber (103), to which the fluid for activating closing movements of the piston slide valve (11) can be fed via a closing fluid supply (105), in which a closing fluid valve (106) is arranged, d) wherein at least the fluid for activating closing movements of the piston slide valve (11) can be conducted into the closing chamber in a closed conduit system, e) wherein 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 subjected to a defined pressure and preloaded via an additional valve (119), and f) wherein the control device (101) is furthermore provided at least for determining a pressure drop in the pressure vessel (118) when the solids openings (12) are closed.

2. Self-emptying separator according to claim 1, wherein the volume of fluid required for opening can be metered with a dosing device (108) to activate opening movements of the piston slide valve (11).

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

4. Self-emptying separator according to one of the preceding claims, wherein 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, wherein the dosing device (108) has a dosing element (110) displaceable in a dosing chamber (109) and an adjusting element (114) for dosing the quantity of fluid required for opening.

6. Self-emptying separator according to one of the preceding claims, wherein the opening fluid supply (104) and the closing fluid supply (105) take place, at least in sections, 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, wherein the rotary feedthrough (13) is designed as a two-line rotary feedthrough.

8. Self-emptying separator according to one of the preceding claims, wherein the control device (101) has a computer control program which takes over the separator control and regulation and also controls the actuation of the piston slide valve (11), in particular also the dosing of the opening fluid in the dosing device (108) and the actuation of the valve (119) for preloading the pressure vessel (118) and also the performance and execution of measurements.

9. Method for carrying out a partial discharge of solids when processing a flowable product with a separator according to one of the preceding claims, comprising the following method steps of: a) providing a self-emptying separator according to one of the preceding claims, b) rotation of the centrifugal drum (1) and continuous processing of a flowable suspension, wherein the suspension is separated centrifugally into at least a liquid phase F and a solid phase S; c) at intervals during step b) repeatedly emptying solid S through the following sub-steps: i. opening of the opening fluid valve (106), so that an opening fluid volume metered by the dosing device (108) is admitted into the opening fluid line in the drum (102), causing the piston slide valve (11) to move into an opening position and the solids openings (12) to be released by the piston slide valve (11) and thereby opened, causing the solids of the centrifugal drum (1) to be emptied; ii. terminating the emptying of solids by closing the opening fluid valve (106) and opening the closing fluid valve (107), whereby closing fluid is replenished from the preloaded pressure vessel (118) into the closing chamber (103) via the open closing fluid valve (107) until it is filled and the piston slide valve (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.

10. Method according to claim 9, wherein a change in the pressure drop in step iii) between two partial drains is used as an indicator for a sealing defect on the piston slide valve (11) or on the piston valve (117), whereby leakage monitoring is implemented.

11. Method according to claim 9 or 10, wherein the volume of emptied solids is determined as an actual value using the pressure drop determined in step iii).

12. Method according to claim 10 or 11, wherein the actual value is compared with a target value and in that, in the event that the actual value of the volume of discharged solid does not correspond to a predetermined target value, the quantity of opening water in the dosing device (108) is adjusted for the subsequent emptying.

13. Method according to one of claims 9 to 12, wherein the pressure vessel (118) is preloaded to a predetermined pressure by filling it with a fluid.

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