Filter press filter cloth diagnosis method

Abstract

To provide a filter cloth diagnostic method for a filter press that allows continued operation while maintaining high filtration performance by detecting abnormalities such as clogging or tearing of the filter cloth and responding to them at an early stage.SOLUTION: In a filter press in which a raw liquid is supplied to a filter chamber formed between filter plates on which a filter cloth is stretched to perform dehydration, the filter plates are opened to discharge a dehydrated cake, and then the filter plates are closed to supply a cleaning liquid to the filter chamber to perform immersion cleaning of the filter cloth, a reference pressure of the filter chamber with respect to the supply amount of the cleaning liquid is set in advance and a pressure P of the cleaning liquid supplied to the filter chamber is measured. When the measurement value P is within a reference value P0, the operation of each apparatus is continued; when the measurement value P is larger than the reference value P0, it is determined that clogging of the filter cloth is progressing and an alarm is issued; and when the measurement value P is smaller than the reference value P0, it is determined that breakage of the filter cloth is occurring and an alarm is issued, with the result that the filter cloth can be replaced at an appropriate timing to prevent the dehydration efficiency from decreasing.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a filter cloth diagnosis method for a filter press that detects clogging, damage, etc. of a filter cloth according to the water passing pressure into a filtration chamber.

Background Art

[0002] Conventionally, in a filter press, a stock solution is supplied to each filtration chamber, and solid-liquid separation is performed by a filter cloth. Since solids adhere to the filter cloth due to the dehydration process and the dehydration performance deteriorates, the filter cloth is regularly washed. However, if the dehydration process continues, the solids may penetrate deeply into the gaps of the filter cloth, and the clogging may not be eliminated even after washing. In addition, by repeating the plate opening / closing process and the dehydration process of the filter plates, excessive force may act on the filter cloth and cause damage.

[0003] Patent Document 1 discloses a technique for stopping an electric motor that supplies a slurry in response to an abnormal pressure because the slurry supply pressure changes according to clogging or damage of a filter cloth when the slurry is press-fitted into a filtration chamber.

[0004] Patent Document 2 discloses a technique for measuring the degree of clogging of a filter cloth from changes in the flow rate and pressure of air or water passing through the filter cloth while running an endless filter cloth and sandwiching the filter cloth to send air or water from one side during washing of the filter cloth.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In Patent Document 1, since it is detected at the supply pressure of a slurry with unstable properties, when the properties of the slurry change, the filtration resistance and the like change, and it becomes difficult to determine whether the change in the supply pressure is due to clogging or damage of the filter cloth. Further, when the slurry is press-fitted, a cake layer is immediately formed on the surface of the filter cloth, resulting in cake filtration. The resistance of the filter cloth is extremely small compared to the resistance of the cake layer, and it is difficult to determine the clogging or damage of the filter cloth based on the resistance value of the press-fitted slurry. Furthermore, even when abnormal pressure is frequently detected during slurry press-fitting, it is necessary to continue the filtration operation, and problems such as a decrease in the filtration rate and poor peeling occur due to continuing the filtration operation without replacing the filter cloth. The slurry pump that supplies the slurry to the dehydrator undergoes wear of the impeller and the like as the press-fitting operation progresses, and the pump performance deteriorates. Therefore, it is difficult to determine whether the pressure change is due to clogging of the filter cloth or a decrease in pump performance.

[0007] In Patent Document 2, since each filtration chamber of the filter press is covered with an endless filter cloth stretched in a zigzag shape, a pressure detector may be provided at an arbitrary position on the travel path. However, in order to adopt a separate method in which a pair of independent filter cloths are provided for each filtration chamber, it is necessary to provide a pressure detector for each filter cloth. Further, it is necessary to prepare detection water or air separately from the fluid used in the filtration process and the cleaning process.

[0008] The present invention provides a method for diagnosing a filter cloth of a filter press that uses a cleaning liquid during a cleaning process of the filter cloth and detects clogging, damage, etc. of the filter cloth according to the cleaning pressure.

Means for Solving the Problems

[0009] In a filter press in which a stock solution is supplied to a filtration chamber formed between filter plates with a filter cloth stretched, dehydrated, the filter plates are opened to discharge the dehydrated cake, and then the filter plates are closed and a cleaning liquid is supplied to the filtration chamber to immerse and clean the filter cloth, a reference pressure P0 of the filtration chamber with respect to the supply amount of the cleaning liquid is set in advance, and During immersion cleaning, in a full water stateMeasure the pressure P of the cleaning liquid supplied to the filtration chamber. When the measured value P is within the reference pressure P0, continue the operation of each device. When the measured value P is greater than the reference pressure P0, it is determined that the clogging of the filter cloth is progressing and an alarm is issued. When the measured value P is less than the reference pressure P0, it is determined that the filter cloth is damaged and an alarm is issued. By detecting abnormalities such as clogging and tearing of the filter cloth and being able to respond promptly when there is an abnormality, normal filtration operation can be carried out.

[0010] Further divide step by step a value exceeding the upper limit value Pmax of the reference pressure P0 and determine the degree of clogging of the filter cloth according to each division. When the measured value P is greater than the reference pressure P0, identify the corresponding division and warn of the degree of clogging of the filter cloth. Even when clogging of the filter cloth occurs, it becomes possible to use it up to the life of the filter cloth, and the filter cloth can be replaced at an appropriate timing.

[0011] After correcting the measured value P based on at least one of the measured temperature and water level values, compare it with the reference pressure P0. Since control can be performed based on the corrected measured value P, abnormalities of the filter cloth can be detected with high accuracy.

Advantages of the Invention

[0012] The filter cloth diagnosis method of the filter press according to the present invention diagnoses abnormalities of the filter cloth by detecting the pressure in the filtration chamber while supplying the cleaning liquid into the filtration chamber after closing the filter plates again after discharging the dewatered cake. Since it is possible to take measures such as replacing the filter cloth before the start of the next filtration operation, the filtration operation can always be carried out efficiently. Foreign matter mixing in the inflowing stock solution and sudden filter cloth breakage can also be detected, so appropriate filtration performance can be ensured. Since the filter cloth diagnosis is carried out within the process of immersion cleaning, there is no need to newly provide a process called filter cloth diagnosis, and the operation time will not be prolonged. In addition, since the water passage of the cleaning liquid does not change and water, chemical liquid, etc. with stable properties are used as the cleaning liquid, the pressure change during water passage is caused only by clogging and tearing of the filter cloth, and the state of the filter cloth can be accurately diagnosed by pressure measurement. Furthermore, since it can be carried out using conventional equipment, there is no need to newly install equipment, and no installation area or installation cost is required.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Figure 1 is a schematic side view of a filter press according to the present invention. The filter press 1 has a large number of filter plates 5... supported on guide rails 4 bridged between a front frame 2 and a rear frame 3 so as to be openable and closable. A clamping cylinder 6 disposed on the rear frame 3 is connected to a movable head 7, and the filter plates 5... are closed by moving the movable head 7 toward the front frame 2 side. On the other hand, the filter plates 5... are opened by moving the movable head 7 toward the rear frame 3 side.

[0015] Above the closed filter plates 5..., a supply passage 8 is formed, and a supply pipe 9 with a valve V1 interposed is connected to one end of the supply passage 8. Below the filter plates 5..., a discharge passage 11 is formed, and a discharge pipe 12 with a valve V3 interposed is connected to the discharge passage 11. The supply passage 8 and the discharge passage 11 are formed by the communication of supply ports and discharge ports (not shown) opened in each filter plate 5.

[0016] Between adjacent filter plates 5, 5, a filtration chamber 13 communicating with the supply passage 8 and the discharge passage 11 is formed. Inside the filtration chamber 13, a pair of filter cloths 21, 21 (shown in Figure 3) are stretched so as to cover the filter beds 20, 20 of the filter plates 5. Each filter cloth 21... is generally cleaned after the filtration process in order to eliminate clogging and the like caused by solids generated in the solid-liquid separation process.

[0017] Figure 2 is a flow diagram of a filter press during the cleaning process according to the present invention. The cleaning liquid storage tank 14 is connected to a cleaning liquid supply pipe 10 whose other end is connected to a supply path 8. A valve V2 and a cleaning liquid supply pump 15 are installed in the cleaning liquid supply pipe 10. By opening the valve V2 and driving the pump, the cleaning liquid in the cleaning liquid storage tank 14 can be supplied into the supply path 8. The cleaning liquid supplied into the supply path 8 flows into each filtration chamber 13 and performs cleaning while immersing the filter cloth 21. A discharge pipe 12 with a valve V3 is connected to the discharge path 11, and the cleaning liquid can be filled into each filtration chamber 13 by operating the valve V3.

[0018] A pressure gauge 16 is arranged in the cleaning liquid supply pipe 10 and is configured to measure the water flow pressure of the cleaning liquid supplied into each filtration chamber 13. The pressure P measured by the pressure gauge 16 is transmitted to the control device 17 and compared with a predetermined reference pressure P0 for judgment.

[0019] Although the specific control method will be described later, since the cleaning liquid supply pipe 10 communicates with the filtration chamber 13 via the supply path 8, by measuring the pressure of the cleaning liquid supply pipe 10, the pressure in the filtration chamber 13 can be grasped and the state of the filter cloth 21 in the filtration chamber 13 can be diagnosed.

[0020] When the filter cloth 21 is torn, the supplied cleaning liquid is discharged from the damaged part, and the pressure in the filtration chamber 13 decreases, so the measured value of the pressure P becomes smaller. When the filter cloth 21 is clogged and the flow resistance of the cleaning liquid increases, the pressure in the filtration chamber 13 increases, so the measured value of the pressure P becomes larger. In this way, by utilizing the phenomenon that the pressure in the filtration chamber 13 changes according to the state of the filter cloth 21 in the filtration chamber 13, the state of the filter cloth 21 can be diagnosed by measuring the pressure P of the cleaning liquid supply pipe 10 communicating with the filtration chamber 13.

[0021] In this embodiment, the pressure gauge 16 is provided in the cleaning liquid supply pipe 10. However, the location is not limited to this as long as it can measure the water passing pressure P of the cleaning liquid supplied into the filtration chamber 13. Further, in order to correct the actual lift of the cleaning liquid stored in the cleaning liquid storage tank 14, a water level gauge 18 may be installed in the cleaning liquid storage tank 14. Similarly, in order to correct the viscosity of the cleaning liquid that changes due to temperature changes, a thermometer 19 may be installed in the cleaning liquid supply pipe 10. By correcting the actual lift and viscosity of the cleaning liquid based on the values of the water level gauge 18 and the thermometer 19, the measurement error of the measured pressure P can be corrected. Therefore, the value of the measured pressure P is caused only by the state of the filter cloth 21, and it becomes possible to more accurately diagnose the state of the filter cloth 21.

Example

[0022] Hereinafter, examples of the present invention will be described in detail with reference to FIGS. 1 to 3. <Initial setting> In advance, when there are no abnormalities such as clogging or damage in the filter cloth 21, the pressure of the filtration chamber 13 with respect to the supply amount of the cleaning liquid supplied is set as the reference pressure P0. It is desirable to set the reference pressure P0 with a certain width. At the same time as setting the reference pressure P0, values higher than the upper limit value Pmax of the reference pressure P0 are further set in stages. According to each set section, the degree of clogging of the filter cloth 21 is defined as slight clogging, moderate clogging, and severe clogging.

[0023] <Closing plate and press-fitting process> As shown in FIG. 1, the parallel filter plates 5... are closed by a clamping cylinder 6, a supply path 8 is formed above the filter plates 5..., and a discharge path 11 is formed below. A filtration chamber 13 is formed between adjacent filter plates 5.

[0024] The stock solution press-fed from the supply pipe 9 flows into each filtration chamber 13 via the supply passage 8. The inflowing stock solution spreads evenly within each filtration chamber 13 and is subjected to solid-liquid separation by a pair of filter cloths 21, 21 stretched within the filtration chamber 13. As a result, a dewatered cake is formed between the filter cloths 21, 21. On the other hand, the separated filtrate permeates through the filter cloth 21 and is then discharged from the discharge pipe 12 via the discharge passage 11 formed below the filter plate 5.... At this time, the valve V1 installed in the supply pipe 9 and the valve V3 installed in the discharge pipe 12 are open.

[0025] <Pressing Process> If necessary, a pressing process may be performed after the press-fitting process is completed. When performing the pressing process, filter plates with diaphragms stretched on their surfaces 5 are arranged in parallel in large numbers to form the filter press 1, and the diaphragm is expanded by a fluid to apply a pressing pressure to the dewatered cake in the filtration chamber 13. In this case, the pressing fluid supply pump can be diverted and used as the cleaning fluid supply pump 15.

[0026] <Plate Opening and Cake Discharging Process> After a dewatered cake is formed in the filtration chamber 13, the clamping cylinder 6 is driven to open a large number of filter plates 5.... By opening the filter plates 5..., the dewatered cake falls outside the machine due to its own weight, vibration of the filter cloth 21 and so on.

[0027] <Plate Closing and Cleaning Process> As shown in FIG. 2, after discharging the dewatered cake, the filter plates 5... are closed again to form filtration chambers 13... between adjacent filter plates 5, 5. Subsequently, the cleaning fluid supply pump 15 is driven to supply the cleaning fluid in the cleaning fluid storage tank 14 to the filtration chamber 13. At this time, the valve V1 installed in the supply pipe 9 and the valve V3 installed in the discharge pipe 12 are closed, and the valve V2 installed in the cleaning fluid supply pipe 10 is open.

[0028] Start the immersion cleaning in this state. Since valve V3 is closed, the water level in the filtration chamber 13 gradually rises due to the supplied cleaning liquid, filling the filtration chamber 13 and immersing the filter cloth 21. Then, stop the supply of the cleaning liquid, close valve V2, and perform immersion cleaning for a predetermined time. Immersion cleaning prevents the drying of the filter cloth 21 by immersing it. As a result, the mother liquor adhering to the filter cloth 21 does not evaporate, preventing clogging of the filter cloth 21 due to precipitation and crystallization of dissolved components such as calcium carbonate and calcium sulfate. In this embodiment, water is filled as the cleaning liquid, but it may also be filled with an acidic chemical solution to remove the dissolved components.

[0029] After performing immersion cleaning for a predetermined time with the filtration chamber 13 in a sealed state, as shown in FIG. 3, open valves V2 and V3 and start supplying the cleaning liquid again. Adjust the opening degree of valve V3 to adjust the discharge amount and keep the filtration chamber 13 in a full-water state while continuously supplying the cleaning liquid at a constant pressure. Depending on the implementation conditions, the discharge pipe 12 may be used as a riser pipe, and the filtration chamber 13 may be kept in a full-water state. After the filtration chamber 13 is in a full-water state, measure the press-in pressure P of the cleaning liquid supplied from the cleaning liquid supply pipe 10 with the pressure gauge 16 to grasp the pressure P in the filtration chamber 13. Since the filtration chamber 13 is in a full-water state, if there are no abnormalities such as clogging or tearing of the filter cloth 21, the water flow resistance does not change and the pressure P does not change. On the other hand, if an abnormality occurs, the water flow resistance changes and the pressure in the filtration chamber 13 changes, so the measured pressure value P changes. When the pressure value P changes in this way, it is determined that there is an abnormality in the filter cloth 21 in the filtration chamber 13, and the state of the filter cloth 21 is diagnosed. In this embodiment, while immersing and cleaning the filter cloth 21 in the full-water filtration chamber 13, the state of the filter cloth 21 can be diagnosed at the same time. Note that the discharged cleaning waste liquid is discharged to the outside through the discharge pipe 12.

[0030] Regarding immersion cleaning, as another embodiment, as shown in FIG. 4, after closing valve V1 at the start of cleaning, valves V2 and V3 are opened to start the supply of the cleaning liquid, and while continuously supplying the cleaning liquid, the filter cloth 21 may be immersed for cleaning. Between the filter cloths 21, 21, after a predetermined time has elapsed since the start of cleaning, it is filled with the cleaning liquid due to the water flow resistance. By filling the space between the filter cloths 21, 21 with the cleaning liquid, when there is no abnormality in the filter cloth 21, the water flow resistance does not change and the measured pressure P does not change. On the other hand, when an abnormality occurs in the filter cloth 21, the water flow resistance changes and the pressure in the filtration chamber 13 changes, so the value of the measured value P changes. When the pressure value P changes in this way, it is determined that there is an abnormality in the filter cloth 21 in the filtration chamber 13. In this mode, by measuring the press-fitting pressure P when the space between the filter cloths 21, 21 is filled with the cleaning liquid after a predetermined time has elapsed since the start of cleaning, an abnormality in the filter cloth 21 can be detected. Note that the timing of starting the measurement of the press-fitting pressure P in the present embodiment and another embodiment is appropriately determined according to the implementation conditions.

[0031] When measuring the pressure with the pressure gauge 16, it is conceivable that a measurement error may occur due to the air leaking from the filtrate discharge pipe 12. Therefore, a siphon breaker may be provided in the filtrate discharge pipe 12 as necessary. Also, as another embodiment, the pressure gauge 16 may also be provided in the discharge pipe 12, and the pressure in the filtration chamber 13 may be grasped based on the differential pressure from the pressure P measured by the cleaning liquid supply pipe 10, and the state of the filter cloth 21 may be diagnosed.

[0032] The cleaning pressure at the start of cleaning increases, but the solid matter adhering to the surface of the filter cloth 21 is peeled off by the immersion cleaning, and the water flow resistance of the filter cloth 21 decreases, so the permeation amount of the cleaning liquid increases, and gradually the cleaning pressure decreases to a predetermined value. Therefore, if solid-liquid matter enters the gaps of the filter cloth 21 and clogging that cannot be removed by cleaning occurs, the water flow resistance of the filter cloth 21 does not decrease, so the cleaning pressure does not decrease much from the start of cleaning. Also, if the filter cloth 21 is damaged, a large amount of the cleaning liquid leaks from the damaged part, so the water flow resistance decreases. Therefore, the cleaning pressure becomes low from the start of cleaning.

[0033] The following describes in detail the filter cloth diagnosis method performed during immersion cleaning. The reference pressure P0 determined in advance in the initial settings is stored in the control device 17 in advance, and the state of the filter cloth 21 is diagnosed by comparing it with the measured value P of the pressure measured during cleaning. Specifically, as shown in FIG. 2, the measured value P of the pressure of the cleaning liquid measured by the pressure gauge 16 installed in the cleaning liquid supply pipe 10 is transmitted to the control device 17, and the control device 17 compares the measured value P with the reference pressure P0. As a result of the comparison by the control device 17, when the measured value P is within the reference pressure P0, the operation of each device is continued with the current settings. Also, when the measured value P is greater than the reference pressure P0, it is determined that the clogging of the filter cloth 21 is progressing and an alarm is issued. Further, when the measured value P is less than the reference pressure P0, it is determined that the filter cloth 21 is damaged and an alarm is issued.

[0034] In order to accurately compare the measured value P of the pressure of the cleaning liquid with the reference pressure P0, the measured value P may be corrected under conditions equivalent to the conditions for setting the reference pressure P0 based on at least one of the value of the temperature measured by the thermometer 19 and the water level measured by the water level gauge 18. By performing the correction, it becomes possible to perform the control accurately and diagnose the state of the filter cloth 21 with high precision.

[0035] When the measured value P is greater than the reference pressure P0, the degree of clogging may be determined step by step using a pressure range obtained by further stepwise dividing the value exceeding the upper limit value Pmax of the predetermined reference pressure P0. Even when the measured value P is greater than the reference pressure P0, for example, if it is within 10% of the upper limit value Pmax, it is a mild clogging with a low risk of solid-liquid separation, and if it is within 10 - 30% of the upper limit value Pmax, it is a moderate clogging with a risk of solid-liquid separation. When it exceeds 30% of the upper limit value Pmax, it is a severe clogging at the immediate replacement level with a high risk of solid-liquid separation, and warnings may be issued according to each classification. By performing filter cloth replacement when a warning of severe clogging is displayed, the dehydration efficiency in the next filtration process will not decrease.

[0036] In this embodiment, the cleaning liquid is supplied to the rear frame of the supply path 8 3Although it is configured to supply from the side, it can be appropriately modified and implemented, such as a configuration that supplies from the stock solution supply side or a configuration that supplies from the discharge pipe 12. Further, the cleaning drainage discharged from the discharge pipe 12 may be returned and reused.

[0037] It is not limited to the present embodiment described above and shown in the drawings, and can be modified and implemented without departing from the gist of the invention described in the claims.

Industrial Applicability

[0038] The filter cloth diagnosis method of the filter press of the present invention can diagnose the state of the filter cloth while performing immersion cleaning of the filter cloth, and does not require special equipment or the like, so it can be applied to existing filter presses. Further, based on the detected clogging or damage of the filter cloth, etc., the inspection and repair timing can be accurately predicted, so highly reliable maintenance management becomes possible. By detecting abnormalities of the filter cloth at an early stage, stable dehydration operation can also be realized, so it becomes a useful detection system in various industrial and infrastructure fields.

Explanation of Signs

[0039] 21 Filter cloth 5 Filter plate 13 Filtration chamber P0 reference pressure P measured value Upper limit value of Pmax reference pressure

Claims

1. In a filter press that supplies a stock solution to a filtration chamber (13) formed between filter plates (5) with a filter cloth (21) stretched therebetween for dehydration, opens the filter plates (5) to discharge the dewatered cake, and then closes the filter plates (5) to supply a cleaning liquid to the filtration chamber (13) to immerse and clean the filter cloth (21), a reference pressure (P0) of the filtration chamber (13) with respect to the supply amount of the cleaning liquid is set in advance, and during immersion cleaning, the pressure (P) of the cleaning liquid supplied to the full water state filtration chamber (13) is measured, when the measured value (P) is within the reference pressure (P0), the operation of each device is continued, when the measured value (P) is greater than the reference pressure (P0), it is determined that the clogging of the filter cloth (21) is progressing and an alarm is issued, when the measured value (P) is less than the reference pressure (P0), it is determined that the filter cloth (21) is damaged and an alarm is issued A method for diagnosing a filter cloth of a filter press, characterized in that.

2. The value exceeding the upper limit value (Pmax) of the reference pressure (P0) is further divided step by step, and the degree of clogging of the filter cloth (21) corresponding to each division is determined, when the measured value (P) is greater than the reference pressure (P0), the corresponding division is specified and the degree of clogging of the filter cloth (21) is warned The method for diagnosing a filter cloth of a filter press according to claim 1, characterized in that.

3. The measured value (P) is corrected based on at least one of the measured temperature and water level values and then compared with the reference pressure (P0) The method for diagnosing a filter cloth of a filter press according to claim 1 or claim 2, characterized in that.

Images