CLEANING-IN-PLACE METHOD AND FILTER DEVICE

Abstract

A cleaning-in-place method includes terminating a cleaning-in-place cycle if a deviation of a currently detected value of a backwash hydraulic parameter (P) from a value of the same backwash hydraulic parameter (P) detected in a previous backwash cycle (32, 34, 36 38) in the same cleaning-in-place cycle exceeds a predefined deviation limit value. A filter device is provided having a control device for carrying out a respective cleaning-in-place method.

Claims

1. A cleaning-in-place method for cleaning a membrane filter system having a membrane filter, the method comprising the steps of: starting a cleaning-in-place cycle for cleaning the membrane filter; providing intervals carrying out backwash cycles during the cleaning-in-place cycle; determining, during the backwash cycles, at least one backwash hydraulic parameter of the filter; and terminating the cleaning-in-place cycle when the determined backwash hydraulic parameter for the backwash cycles meets a certain criterion.

2. A cleaning-in-place method according to claim 1, in which the cleaning-in-place cycle comprises a chemical cleaning using at least one cleaning agent.

3. A cleaning-in-place method according to claim 1, wherein the cleaning-in-place cycle uses a crossflow flowing along a feed side of the membrane filter.

4. A cleaning-in-place method according to claim 1, wherein the backwash cycle comprises passing a backwash flow through the filter membrane.

5. A cleaning-in-place method according to claim 1, wherein for determining the backwash hydraulic parameter a backwash variable is measured for a period of time and the backwash hydraulic parameter is sampled when the parameter has stabilized.

6. A cleaning-in-place method according to claim 1, wherein the cleaning-in-place cycle is terminated, if a deviation of a currently determined value of the backwash hydraulic parameter from a value of the same backwash hydraulic parameter determined in a previous backwash cycle in the same cleaning-in-place cycle exceeds a predefined deviation limit value.

7. A cleaning-in-place method according to claim 1, wherein during the cleaning-in-place cycle at least one characteristic value characterizing the efficiency of the cleaning-in-place process is determined.

8. A cleaning-in-place method according to claim 1, wherein the backwash hydraulic parameter is a parameter characterizing permeability of the membrane filter.

9. A cleaning-in-place method according to claim 1, wherein the backwash hydraulic parameter is determined at least based on flow and/or transmembrane pressure measured during the backwash cycle in the membrane filter system.

10. A cleaning-in-place method according to claim 1, wherein during the backwash cycle the flow is ramped to a certain value and then ramped back to zero.

11. A cleaning-in-place method according to claim 1, wherein the intervals between two backwash cycles in the cleaning-in-place cycle are predefined.

12. A cleaning-in-place method according to claim 1, wherein the intervals between two backwash cycles in the cleaning-in-place cycle are variable and are adjusted based on the change of the hydraulic parameter in previous backwash cycles during the cleaning-in-place cycle.

13. A cleaning-in-place method according to claim 1, wherein several cleaning-in-place cycles are carried out with changing at least one setting of a cleaning-in-place recipe used in the cleaning-in-place cycles to determine a most economic recipe for the cleaning-in-place cycles.

14. A filter device comprising: at least one filter membrane; a backwashing configuration for backwashing the filter membrane and a cleaning-in-place configuration for cleaning-in-place of the filter membrane; and a control device controlling the cleaning-in-place configuration and the backwash configuration, wherein the control device is configured to control a cleaning-in-place cycle with the steps comprising: starting the cleaning-in-place cycle for cleaning the filter membrane; carrying out a backwash cycle in intervals during this cleaning-in-place cycle; determining at least one backwash hydraulic parameter of the filter membrane during the backwash cycle; and terminating the cleaning-in-place cycle, when the determined backwash hydraulic parameter meets a certain criterion.

15. A filter device according to claim 14, further comprising at least one sensor element connected to the control device, the at least one sensor element detecting the at least one backwash hydraulic parameter or at least one value on a basis of which the backwash hydraulic parameter is determined.

16. A filter device according to claim 15, wherein the at least one sensor element is a pressure sensor arranged to detect a transmembrane pressure and/or said at least one sensor element is a flow sensor arranged to detect the flow during the backwash cycle.

17. A filter device according to claim 14, wherein: the backwashing configuration comprises a backwash pump controlled by said control device; and a backwash flow provided by said backwash pump is set by said control device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the drawings:

[0030] FIG. 1 is a schematic view showing a filter device according to the invention; and

[0031] FIG. 2 is a graph showing the change of membrane permeability during the cleaning in place cycle.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0032] Referring to the drawings, the filter device as shown in FIG. 1 comprises a membrane 2 having a feed side 4 and a filtrate or permeate side 6. For the filtering process there is provided a feed pump 8 arranged to feed raw water from a water source 10, for example a raw water tank or well to the feed side 4 of the membrane 2. The device as shown in FIG. 1 is provided for crossflow filtration. This means the feed pump 8 provides a feed flow along the entrance of feed side 4 of the membrane 2. The water is leaving the filter via a retentate outlet 12, for example to a drain. The permeate passing the membrane 2, i.e. the clean water is flowing out of the filter via a filtrate or permeate outlet 14 into a filtrate tank 16. The method according to the invention may, however, also be carried out analogously in dead-end-filtration.

[0033] The filter device as shown in FIG. 1, furthermore, is provided for carrying out a backwash. For backwashing there is provided a backwash pump 18 arranged to pump clean water from the filtrate tank 16 towards the permeate side 6 of the membrane 2. The clean water can pass the membrane 2 from the permeate side 6 to the feed side 4 and flowing out of the filter via the retentate outlet 12. Thus, by activating the backwash pump 18 the membrane 2 can be backwashed by the clean water produced before.

[0034] Additionally, the filter device shown in FIG. 1 is equipped with means for cleaning-in-place. The cleaning-in-place equipment comprises a cleaning-in-place pump 20 or CIP pump 20, respectively. The CIP pump 20 is connected to the feed side 4 of the membrane 2. The filter further comprises a cleaning-in-place or CIP outlet 22 connected to a cleaning-in-place tank or CIP tank 24. The suction side of the CIP pump is also connected to the CIP tank 24 so that a closed cleaning-in-place circuit is provided. The CIP pump 20 pumps a cleaning-in-place agent or solution from the CIP tank 24 into the filter arrangement such that the cleaning-in-place agent flows in a cross flow along the feed side 4 of the membrane 2 and, then, back to the CIP tank via the CIP outlet 22. Furthermore, there may be provided means for dosing cleaning-in-place agents or chemicals and/or means for heating the cleaning-in-place solution which are not shown in FIG. 1. The retentate outlet 12, preferably, is provided with a controllable valve by which the retentate outlet 12 is closed during the cleaning-in-place cycle.

[0035] The filter device furthermore comprises a control device 26. The control device 26 is connected to the CIP pump 20 and the backwash pump 18 and in this example also to the feed pump 8. The control device 26 controls the backwash pump 18, the CIP pump 20 and the feed pump 8, by switching the pumps on and off and, preferably, also speed regulation to ensure the desired flows and/or pressures on the outlet side of the respective pump. Furthermore, in the filter there are provided two pressure sensors 28 and 30 on both sides of the membrane 2, i.e. the pressure sensor 28 is arranged on the permeate side 6 and the pressure sensor 30 is arranged on the feed side 4 of the membrane 2 such that by the pressure sensors 28 and 30 a transmembrane pressure TMP can be detected. Furthermore, in this example the backwash pump 18 detects the backwash flow, i.e. acts as a flow sensor. Instead of the flow detection by the backwash pump 18 there may be provided a separate flow sensor in the backwash line connecting the filtrate tank 16 and the permeate side 6 of the membrane 2.

[0036] During production the CIP pump 20 and the backwash pump 18 are switched off and the feed pump 8 feeds raw water 10 through the feed side 4 of the membrane 2 and the clean water passing through the membrane 2, i.e. the permeate flows into the filtrate tank 16 via the permeate outlet 14.

[0037] Over time, the membrane fouls and the hydraulic resistance increases. Thus, in intervals either a backwash, and/or a cleaning-in-place (CIP) is necessary to bring the performance back to the membrane. In a backwash cycle the membrane is flushed with produced water in reverse direction. In the cleaning-in-place cycle the membrane 2 is cleaned by a cleaning solution or agent in a cross flow on the feed side 4 as mentioned above. The need for such backwash or cleaning-in-place may be detected by the control device 26 in conventional manner, for example as known from EP 2 985 069 B1.

[0038] The method according to the invention now described by an example refers to the cleaning-in-place cycle. To start the cleaning-in-place cycle (CIP-cycle) the control device 26 switches off the feed pump 8 and starts the operation of the CIP pump 20. Furthermore, cleaning chemicals or agents may be added into the CIP tank or the CIP circuit via a suitable dosing means, not shown in FIG. 1. According to the invention, in intervals simultaneously to the CIP-cycle a backwash cycle is started by switching on the backwash pump 18. The backwash pump 18 is activated by the control device 26 in predefined or varying intervals. Furthermore, the control device 26 may carry out a speed control of the backwash pump 18, for example to ramp up and down the backwash flow, and/or control a preheating of the cleaning-in-place fluid and/or control a valve at the retentate outlet 12.

[0039] During these backwash cycles the transmembrane pressure is detected via the pressure sensors 28 and 30. Furthermore, the flow is detected via the backwash pump 18 itself. The control device 26 is provided to calculate a characteristic value on basis of those detected values, i.e. to calculate a backwash hydraulic parameter forming this characteristic value. In this example, this backwash hydraulic parameter is the permeability of the membrane. Alternatively, the backwash hydraulic parameter may for example be the hydraulic resistance of the membrane 2 or a characteristic value derived from the hydraulic resistance. Both, the hydraulic resistance or the permeability of the membrane, can be calculated by use of Darcy-law. For the Darcy equation also the surface of the membrane 2 and/or the temperature may be taken into consideration. The temperature may be detected by an additional temperature sensor connected to the control device 26. The surface size of the membrane 2 may be stored in the control device 26. Alternatively, for example a parameter reflecting the position of the pump's duty point can be calculated which does not require the knowledge of the membrane surface area. For each backwash cycle carried out during the CIP-cycle the respective backwash hydraulic parameter, i.e. preferably the permeability P of the membrane is detected or sampled. The backwash hydraulic parameter is sampled when the parameter has stabilized and the respective backwash cycle 32, 34, 36 and 38 is terminated. During the CIP-cycle 24 several backwash cycles are carried out and the detected values for the permeability P are compared as shown in FIG. 2.

[0040] In FIG. 2 the permeability P over time t is shown. FIG. 2 shows four backwash cycles 32, 34, 36 and 38 during a single CIP-cycle. As can be seen the four backwash cycles 32, 34, 36 and 38 are carried out in intervals. Between those backwash cycles 32, 34, 36 and 38 no permeability P is detected since the backwash pump 18 is switched off and no flow detection takes place. As can be seen for the backwash cycles 32, 34 and 36 the maximum of the permeability P determined during the respective backwash cycles increases. This shows that in this time a cleaning effect is achieved by the running CIP-cycle. In backwash cycle 38 no further increase of the permeability P can be detected, the permeability detected in the backwash cycles 36 and 38 is the same, i.e. the permeability stays constant. This shows that no further cleaning effect is achieved by the running CIP-cycle. If the control device 26 does not detect a further increase in permeability, the CIP-cycle is terminated, in this example at the point in time t1. Thus, an unnecessary long CIP-cycle can be avoided and the production can be started again by starting the feed pump 8.

[0041] According to the invention, the backwash cycle carried out simultaneously during the CIP-cycle is used to determine a characteristic backwash hydraulic parameter to monitor the cleaning result achieved by the CIP-cycle. Thus, according to the invention a real time measurement of the cleaning result by determining the backwash hydraulic parameter is possible and the CIP-cycle can be terminated if the maximum possible cleaning result is detected. The maximum possible cleaning result is achieved when no further increase of permeability can be detected or no further decrease of the hydraulic resistance can be detected, respectively. The method according to the invention, therefore, allows to speed up the CIP-cycle and at the same time to ensure the maximum possible cleaning result. By reducing the time for the CIP-cycle the production time can be increased allowing a smaller dimension of the entire filter device, resulting in reduced energy consumption and costs.

[0042] Furthermore, it is possible to detect further characteristic parameters being characteristic for the efficiency of the cleaning-in-place cycle during the cleaning-in-place cycle. In particular, the required time, energy consumption and/or consumption of chemicals for the cleaning-in-place cycle can be detected. This allows to optimize the cleaning-in-place cycles for example by adjusting or changing the recipes to find the most efficient recipe for the CIP-cycle. A recipe for the CIP-cycle may be defined by the composition of the CIP solution or agent and/or temperature of the cleaning-in-place fluid.

[0043] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

LIST OF REFERENCE CHARACTERS

[0044] 2 membrane
4 feed side
6 permeate side
8 feed pump
10 raw water source
12 retentate outlet
14 permeate outlet
16 filtrate tank
18 backwash pump
20 cleaning-in-place pump, CIP pump
22 cleaning-in-place outlet, CIP outlet
24 cleaning-in-place tank, CIP tank
26 control device
28, 30 pressure sensors
32, 34, 36, 38 backwash cycles
t1 point in time
t time
P permeability