Membrane filtration system and membrane filtration method

Abstract

In the present invention, the concentration power of a cleaning solution is increased. A membrane filtration system comprises: a filtration body (32) for filtering, through a membrane, a cleaning solution (W0) from a scrubber that purifies exhaust gas from a ship's engine; and a cleaning means for cleaning the filtration body (32). The cleaning means executes cleaning by switching between: standard cleaning in which a pressurized liquid is supplied to the filtration body (32) and then discharged from the filtration body (32); and pulse cleaning in which the filtration body (32) is pressurized and then depressurized.

Description

Technical Field

[0001] The present invention relates to a membrane filtration system, a control device, a membrane filtration method, and a program.

Background Art

[0002] Exhaust gas from a marine engine contains harmful components such as NO

[0006] , , , , , ,

[0007] , and SO X etc. In order to clean the exhaust gas, a scrubber may be installed on the ship. Conventionally, the cleaning liquid obtained by cleaning the exhaust gas with a scrubber has been subjected to solid-liquid separation (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when solid-liquid separation is performed on the cleaning liquid of a marine scrubber, it is required to increase the concentration ratio of the cleaning liquid.

Means for Solving the Problems

[0005] The membrane filtration system of the present disclosure includes a filter body that membrane-filters the cleaning liquid from a scrubber that purifies the exhaust gas of a marine engine, and a cleaning means that cleans the filter body. The cleaning means switches between normal cleaning that cleans the filter body with pressurized liquid and pulse cleaning that pressurizes the filter body with gas and cleans the filter body, and executes them.

Effects of the Invention

[0006] According to the present disclosure, the concentration ratio of the cleaning liquid can be increased.

Brief Description of the Drawings

[0007] [Figure 1] Figure 1 is a schematic diagram of the exhaust gas treatment system according to this embodiment. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the membrane filtration apparatus according to this embodiment. [Figure 3] Figure 3 is a schematic block diagram of the control device according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating normal cleaning procedures. [Figure 5] Figure 5 illustrates pulse cleaning. [Figure 6] Figure 6 shows an example of the timing for performing pulsed cleaning and normal cleaning. [Figure 7] Figure 7 is a flowchart illustrating the flow for performing pulsed cleaning and normal cleaning. [Figure 8] Figure 8 is a schematic diagram showing another example of the configuration of a membrane filtration system. [Modes for carrying out the invention]

[0008] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[0009] Figure 1 is a schematic diagram of the exhaust gas treatment system according to this embodiment. As shown in Figure 1, in this embodiment, the ship S is equipped with an engine E and an exhaust gas treatment system 10 that treats exhaust gas G0 from the engine E. The exhaust gas treatment system 10 includes a scrubber 12 and a membrane filtration system 14. Exhaust gas G0 from the engine E is supplied to the scrubber 12. Inside the scrubber 12, a cleaning liquid W1 is sprayed from above and comes into contact with the exhaust gas G0 supplied into the scrubber 12, thereby removing NO from the exhaust gas G0. X , SO XHarmful components such as these are removed, and the exhaust gas G0 is purified. The purified exhaust gas G1 is returned to the engine E from the scrubber 12. Meanwhile, the cleaning fluid W1 absorbs harmful components and other substances by coming into contact with the exhaust gas G0 and is stored at the bottom of the scrubber 12 as cleaning fluid W0. The cleaning fluid W1 is, for example, water, but it can be any liquid with any properties as long as it can clean the exhaust gas G0.

[0010] The membrane filtration system 14 includes a membrane filtration device 20 for membrane filtration of the washing liquid W0 and a control device 22 for controlling the membrane filtration device 20. The membrane filtration device 20 includes a membrane filtration section 30 and piping L1 and L2. Piping L1 is connected to the primary side (raw water side) of the scrubber 12 and the membrane filtration section 30. The washing liquid W0 in the scrubber 12 is supplied to the primary side of the membrane filtration section 30 through piping L1. The washing liquid W0 is filtered through the membrane filtration section 30, removing solid components including absorbed harmful substances, and is discharged from the secondary side (filtration side) of the membrane filtration section 30 as filtered water, washing liquid W1. The washing liquid W1 discharged from the secondary side of the membrane filtration section 30 is returned to the scrubber 12 through piping L2, which is connected to the secondary side of the membrane filtration section 30 and the scrubber 12. The washing liquid W1 returned to the scrubber 12 is reused for purifying exhaust gas G0. The detailed configuration of the membrane filtration device 20 will be described later.

[0011] The exhaust gas treatment system 10 according to this embodiment is not limited to the configuration described above. For example, the exhaust gas treatment system 10 shown in Figure 1 is a so-called EGR (Exhaust Gas Recirculation) system that returns the exhaust gas G1 purified by the scrubber 12 to the intake side of the engine E, but it is not limited to that. The exhaust gas treatment system 10 may release the exhaust gas G1 purified by the scrubber 12 to the outside without returning it to the engine E, for example, it may be an EGCS (Exhaust Gas Cleaning System). Also, in the example of Figure 1, the cleaning liquid W0 from the scrubber 12 is supplied directly to the membrane filtration unit 30, but it is not limited to that, for example, a tank for primary storage of the cleaning liquid W0 from the scrubber 12 may be provided between the scrubber 12 and the membrane filtration unit 30, and the cleaning liquid W0 may be supplied from that tank to the membrane filtration unit 30. Furthermore, in the example shown in Figure 1, the washing solution W1 filtered through the membrane filtration unit 30 is returned directly to the scrubber 12, but this is not limited to this method. The washing solution W1 may also be returned to a tank for washing solution W0 or a tank specifically for washing solution W1.

[0012] The detailed configuration of the membrane filtration apparatus 20 will now be described. Figure 2 is a schematic diagram showing the configuration of the membrane filtration apparatus according to this embodiment. As shown in Figure 2, the membrane filtration apparatus 20 includes a membrane filtration section 30, a coagulant addition mechanism 40, a washing liquid storage tank 50, gas supply sections 60 and 62, a concentrated liquid storage tank 80, piping L1, L2, L3, and L4, a pump P, and valves V1, V2, V3, and V4.

[0013] The membrane filtration unit 30 performs membrane filtration using a dead-end method. The membrane filtration unit 30 includes a filter body 32 and a housing 34 that houses the filter body 32. The filter body 32 is a ceramic filter body. Examples of ceramics used for the filter body 32 include alumina, titania, zirconia, silica, mullite, spinel, or mixtures thereof. The filter body 32 has a plurality of holes extending from a first end 32A (hereinafter abbreviated as end 32A) to a second end 32B (hereinafter abbreviated as end 32B). The piping L1 is connected to end 32A. The coagulant addition mechanism 40 is a tank in which coagulant is stored and is connected to the piping L1 to add the coagulant to the cleaning liquid W0 flowing through the piping L1. Examples of coagulants include iron chloride. Furthermore, the piping L1 may be equipped with an in-line mixer for stirring the coagulant between the connection point of the coagulant addition mechanism 40 and the connection point of end 32A. However, the coagulant addition mechanism 40 and the in-line mixer are not essential components, and the washing liquid W0 may be free of coagulant. The material of the filter body 32 is not limited to ceramic and may be made of any material.

[0014] The piping L2 is connected to the side surface 34A of the housing 34. Since the side surface 34A of the housing 34 faces the side surface (outer surface) 32C of the filter body 32, it can also be said that the piping L2 is connected to the side surface 32C of the filter body 32. The cleaning liquid storage tank 50 and the gas supply unit 62 are connected to the piping L2. The cleaning liquid storage tank 50 stores a portion of the cleaning liquid W1 flowing through the piping L2. The gas supply unit 60 is connected to the cleaning liquid storage tank 50, and a valve V3 is provided between the cleaning liquid storage tank 50 and the piping L2. The gas supply unit 60 is a tank that stores gas, such as air, and supplies gas to the liquid surface of the cleaning liquid W1 in the cleaning liquid storage tank 50. The gas supply unit 62 is a tank that stores gas, such as air, and supplies gas to the piping L2.

[0015] The pipe L3 is connected to the pipe L1 and the concentrated liquid storage tank 80. The concentrated liquid storage tank 80 stores the concentrated liquid W2 generated by the backwashing of the filter element 32. A valve V4 is provided in the pipe L3. The pipe L4 is connected to the end 32B of the filter element 32 and the concentrated liquid storage tank 80. A valve V5 is provided in the pipe L4.

[0016] Figure 3 is a schematic block diagram of the control device according to the present embodiment. The control device 22 is a computer and includes a control unit 90 and a storage unit 100 as shown in Figure 3. The control unit 90 is a CPU (Central Processing Unit). The control device 22 executes the processes described below by reading a program (software) from the storage unit 100 and causing the control unit 90 to execute it. Note that the control unit 90 may execute these processes by one CPU, or may include a plurality of CPUs and execute these processes with those plurality of CPUs. Also, at least some of the subsequent processes may be realized by a hardware circuit or the like.

[0017] When performing membrane filtration, the control device 22 drives the pump P, opens the valves V1 and V2, and closes the valves V4 and V5. Thereby, the cleaning liquid W0 in the scrubber 12 is supplied to the end 32A which is the primary side of the filter element 32 through the pipe L1. The cleaning liquid W0 penetrates into the holes of the filter element 32 from the end 32A and is membrane-filtered. The cleaning liquid W0 is membrane-filtered by the holes of the filter element 32 and is discharged as the membrane-filtered cleaning liquid W1 from the side surface 32C which is the secondary side of the filter element 32. The cleaning liquid W1 discharged from the side surface 32C is returned to the scrubber 12 through the pipe L2. Note that the control device 22 may open the valve V3 for a predetermined time while performing membrane filtration to store a predetermined amount of the cleaning liquid W1 in the cleaning liquid storage tank 50. Also, the control device 22 may control the flocculant addition mechanism 40 while performing membrane filtration to add a flocculant to the cleaning liquid W1 before membrane filtration. In this case, the filter element 32 membrane-filters the cleaning liquid W1 to which the flocculant has been added.

[0018] Here, the membrane filtration device 20 performs a backwashing process on the filter element 32 in order to remove solid components clogged in the filter element 32 by membrane filtration. In the backwashing process, a concentrated liquid W2 containing solid components is generated. Particularly in ships, it is required to increase the concentration ratio of the cleaning liquid W1 and reduce the amount of the concentrated liquid W2. In response, the membrane filtration system 14 according to the present embodiment enables the reduction of the amount of the concentrated liquid W2 by devising the backwashing process. The membrane filtration system 14 alternately executes normal cleaning (back flush) and pulse cleaning (back blowing) as the backwashing process. That is, the membrane filtration system 14 alternately executes normal cleaning in which the filter element 32 is cleaned with a pressurized liquid by the cleaning means and pulse cleaning in which the filter element 32 is pressurized with a gas to clean the filter element 32. Specifically, the membrane filtration system 14 alternately executes normal cleaning in which a pressurized liquid is supplied to the filter element 32 by the cleaning means and discharged from the filter element 32 and pulse cleaning in which the filter element 32 is pressurized and then depressurized. The cleaning means here is the main body that executes the backwashing process in the membrane filtration system 14, and is realized by the control device 22, valves V1 to V5, and gas supply units 60 and 62, etc.

[0019] FIG. 4 is a diagram for explaining normal cleaning. As shown in FIG. 4, when performing normal cleaning, the control device 22 closes valves V1, V2, and V5, opens valves V3 and V4, and controls the gas supply unit 60 to supply gas A toward the liquid level of the cleaning liquid W1 in the cleaning liquid storage tank 50. The cleaning liquid W1 in the cleaning liquid storage tank 50 is pressurized by the gas A, supplied to the filter element 32 through the pipe L2, and discharged into the pipe L3 as the concentrated liquid W2 together with the solid components clogged in the filter element 32. The concentrated liquid W2 is supplied to the concentrated liquid storage tank 80 through the pipe L3. That is, the control device 22 controls the cleaning means to supply a pressurized liquid outside the filter element 32 to the filter element 32 to execute normal cleaning.Specifically, the control device 22 controls the cleaning means to supply the pressurized liquid to the filter element 32 from the second end 32B of the filter element 32 and discharge the pressurized liquid from the first end 32A of the filter element 32 to execute normal cleaning.

[0020] Figure 5 illustrates pulse cleaning. Here, the filter body 32 is housed in the housing 34. The housing 34 is also sealable to maintain a predetermined pressure state. As shown in Figure 5, when performing pulse cleaning, the control device 22 closes valves V1 to V5 and controls the gas supply unit 62 to supply gas A from piping L2 to the filter body 32. Gas A becomes pressurized. Then, the control device 22 opens valve V5 for a predetermined time and then closes it. As a result, the pressure of the pressurized gas A causes the cleaning liquid W1 remaining inside the housing 34 to be discharged into piping L4 as concentrated liquid W2, along with the solid components packed in the filter body 32. The concentrated liquid W2 is supplied to the concentrated liquid storage tank 80 through piping L4. In other words, the control device 22 performs pulse cleaning by controlling the cleaning means to discharge the liquid inside the filter body 32 to the outside of the filter body 32 by pressurizing and then depressurizing the remaining liquid inside the filter body 32 (housing 34). Specifically, the control device 22 controls the cleaning means to perform pulse cleaning by pressurizing the internal pressure inside the housing 34 to a pressure higher than the internal pressure inside the housing 34 when the cleaning liquid is filtered by the filter element 32, and then reducing the internal pressure inside the housing 34 after a predetermined time has elapsed, thereby discharging the liquid inside the housing 34 to the outside of the housing 34. In Figure 5, cleaning liquid W1 is shown as an example of the residual liquid remaining inside the housing 34. However, the residual liquid is not limited to cleaning liquid W1 and may also be cleaning liquid W0 from the scrubber.

[0021] In this case, while normal cleaning has strong cleaning power, it tends to increase the amount of concentrated solution W2 because it uses a large amount of cleaning solution W1. On the other hand, pulse cleaning has a shorter execution period and uses a small amount of cleaning solution W1, but tends to have weaker cleaning power compared to normal cleaning. In pulse cleaning, the cleaning solution W1 used is the liquid remaining in the housing 34, and this amount is less than the amount used in normal cleaning. In this embodiment, taking these characteristics into account, by performing both normal cleaning and pulse cleaning, it is possible to maintain cleaning power while suppressing the increase in the amount of concentrated solution W2. Furthermore, by performing pulse cleaning, it is possible to suppress clogging of the filter body 32 and maintain a constant membrane filtration area.

[0022] Furthermore, the control device 22 controls the number and timing of pulse washing and normal washing to more effectively suppress the increase in the amount of concentrated liquid W2 while maintaining cleaning power. The control device 22 sets at least one of the number of pulse washings and the number of normal washings based on the required processing flow rate of the washing liquid W0 and the target concentration ratio of the washing liquid W0. The required processing flow rate refers to the flow rate of the washing liquid W0 that requires membrane filtration treatment per unit time, and the target concentration ratio refers to the target value of the ratio of the flow rate of the generated concentrated liquid W2 to the flow rate of the washing liquid W0 to be subjected to membrane filtration treatment. The required processing flow rate and the target concentration ratio are set in advance. The control device 22 calculates the target flow rate of concentrated liquid W2 from the required processing flow rate and the target concentration ratio. The control device 22 also acquires information on the flow rate of concentrated liquid W2 generated in one pulse washing (hereinafter referred to as the first generated flow rate) and information on the flow rate of concentrated liquid W2 generated in one normal washing (hereinafter referred to as the second generated flow rate) in advance. The control device 22 sets at least one of the number of pulse washes and the number of normal washes based on the first and second generation flow rates, so that the total flow rate of the concentrated liquid W2 produced by pulse washing and normal washing is within the target flow rate of the concentrated liquid W2. For example, if the required processing flow rate is 200 l and the target concentration ratio is 100 times, the control device 22 calculates the target flow rate of the concentrated liquid W2 as 2 l. That is, the control device 22 calculates the target flow rate of the concentrated liquid W2 by dividing the required processing flow rate by the target concentration ratio. For example, if the first generation flow rate is 0.1 l and the second generation flow rate is 1 l, the control device 22 sets the number of pulse washes to 10 and the number of normal washes to 1 so that the total flow rate of the concentrated liquid W2 is within the target flow rate of the concentrated liquid W2 (in this case, 2 l). In other words, it is preferable that the control device 22 sets at least one of the number of pulse washings and the number of normal washings such that the total flow rate of the concentrated liquid W2 generated by pulse washing and normal washing is within the target flow rate of the concentrated liquid W2, and the number of pulse washings is greater than the number of normal washings.The control device 22 may, for example, set only the number of pulse washes based on the required processing flow rate and target concentration ratio if the number of normal washes is fixed, or it may set both the number of normal washes and the number of pulse washes based on the required processing flow rate and target concentration ratio without fixing the number of normal washes.

[0023] Figure 6 shows an example of the timing of pulse cleaning and normal cleaning. The horizontal axis in Figure 6 represents time, and the vertical axis represents the differential pressure between the primary and secondary sides of the filter body 32. As shown in Figure 6, as membrane filtration is performed, solid matter accumulates in the filter body 32, increasing the differential pressure. Backwashing removes the solid matter from the filter body 32, decreasing the differential pressure. The control device 22 sets the timing of pulse cleaning and normal cleaning so that, as shown in Figure 6, membrane filtration and pulse cleaning are repeated alternately multiple times (three times in the example in Figure 6) (in other words, after switching between them and performing them alternately), the control device switches from pulse cleaning to normal cleaning and performs normal cleaning once, repeating this cycle CY. That is, the control device 22 performs pulse cleaning multiple times before performing normal cleaning. It is preferable that the interval Δt1 for performing pulse cleaning is kept constant, and it is preferable that the interval Δt2 from the end of pulse cleaning to the start of normal cleaning is equal to the interval Δt1. The differential pressure waveform shown in Figure 6 is an example.

[0024] The control device 22 may set the timing for pulse cleaning and normal cleaning based on the filtration efficiency of the filter element 32. In this case, for example, a sensor is provided to detect the differential pressure between the primary and secondary sides of the filter element 32, and the control device 22 sequentially acquires the detected value from the sensor. If the differential pressure is below a threshold, the control device 22 determines that the filtration efficiency of the filter element 32 is appropriate and performs pulse cleaning and normal cleaning in the above cycle CY. On the other hand, if the differential pressure exceeds the threshold, the control device 22 determines that the filtration efficiency of the filter element 32 is inappropriate and performs normal cleaning regardless of the above cycle CY.

[0025] The number of pulse cleaning and normal cleaning cycles and their timings described above are merely examples, and the control device 22 may arbitrarily set the number of pulse cleaning and normal cleaning cycles and their timings.

[0026] Figure 7 is a flowchart illustrating the flow for performing pulse cleaning and normal cleaning. As shown in Figure 7, the control device 22 sets the timing for performing pulse cleaning and normal cleaning (step S10). Based on the required processing flow rate of the cleaning solution W0 and the target concentration ratio, the control device 22 sets at least one of the number of pulse cleanings and the number of normal cleanings, and sets the timing for performing pulse cleaning and normal cleaning so that pulse cleaning is performed multiple times before normal cleaning is performed once. The control device 22 performs pulse cleaning the set number of times and at the set timing (step S12; pulse cleaning execution step), and then performs normal cleaning the set number of times and at the set timing (step S14; normal cleaning execution step).

[0027] As described above, the membrane filtration system 14 according to this embodiment includes a filter body 32 that filters the cleaning liquid W0 from a scrubber 12 that purifies the exhaust gas G0 of the engine E of a ship S, and a cleaning means. The cleaning means cleans the filter body 32 by switching between normal cleaning, which cleans the filter body 32 with a pressurized liquid, and pulse cleaning, which cleans the filter body 32 by pressurizing it with gas. As mentioned above, in a ship S, it is required to increase the concentration ratio of the cleaning liquid W1 and decrease the amount of concentrated liquid W2. In contrast, with the membrane filtration system 14, since both pulse cleaning and normal cleaning are performed on the filter body 32, it is possible to maintain cleaning power with normal cleaning, suppress the increase in the amount of concentrated liquid W2, and increase the concentration ratio of the cleaning liquid W1.

[0028] Furthermore, the cleaning means performs pulse cleaning multiple times, followed by normal cleaning. According to the membrane filtration system 14 of this embodiment, by increasing the number of pulse cleanings compared to normal cleaning, the increase in the amount of concentrated liquid W2 can be appropriately suppressed.

[0029] Furthermore, the cleaning means sets at least one of the number of pulsed cleaning cycles and the number of normal cleaning cycles based on the flow rate of the cleaning solution W1 that requires membrane filtration (required processing flow rate) and the target concentration ratio of the cleaning solution W1. According to the membrane filtration system 14 of this embodiment, by setting at least one of the number of pulsed cleaning cycles and the number of normal cleaning cycles based on the required processing flow rate and the target concentration ratio, the target concentration ratio can be achieved while backwashing can be appropriately performed.

[0030] Furthermore, the filter body 32 may also perform membrane filtration of the washing solution W0 to which a coagulant has been added. According to the membrane filtration system 14 of this embodiment, the concentration ratio can be further increased by filtering the washing solution W0 to which a coagulant has been added.

[0031] Furthermore, the filter element 32 is made of ceramic. The ceramic filter element 32 has advantages in filtration efficiency compared to a centrifuge, such as not being affected by the difference in specific gravity between the solvent and the solid component, but it requires backwashing to remove the solid component. In contrast, the membrane filtration system 14 according to this embodiment uses the ceramic filter element 32 to achieve high filtration efficiency, and by switching between pulse washing and normal washing, it suppresses the increase in the concentrated liquid W2 generated by backwashing, making it possible to increase the concentration ratio when using a filter element 32 that requires backwashing. Also, since installation space is limited on ships, it is required to make the concentrated liquid storage tank 80 as small as possible. In contrast, the membrane filtration system 14 according to this embodiment suppresses the increase in the amount of concentrated liquid W2 by switching between pulse washing and normal washing to increase the concentration ratio, making it possible to reduce the size of the concentrated liquid storage tank 80 that stores the concentrated liquid W2. Furthermore, the membrane filtration system 14 performs membrane filtration using a dead-end method. By using a dead-end system, the circulation pump used in cross-flow systems and other methods becomes unnecessary, reducing initial costs and power consumption.

[0032] Furthermore, the control device 22 according to this embodiment is used in a membrane filtration device 20, and cleans the filter body 32 of the membrane filtration device 20 by switching between pulse washing and normal washing. With this control device 22, it is possible to maintain the washing power with normal washing while suppressing the increase in the amount of concentrated liquid W2, thereby increasing the concentration ratio of the washing liquid W1.

[0033] Figure 8 is a schematic diagram showing another example of the configuration of a membrane filtration device. In the above description, as shown in Figures 4 and 5, the flow direction of the cleaning liquid W1 for backwashing within the filter body 32 was reversed for pulse cleaning and normal cleaning in the membrane filtration device 20. However, as shown in the membrane filtration device 20a in Figure 8, the flow direction of the cleaning liquid W1 may be the same. In this case, for example, as shown in Figure 8, pipe L1 is connected to the end 32B of the filter body 32, and pipe L2 is connected to the end 32A side of pipe L1. Pipe L3 is connected to the end 32A of the filter body 32 and the concentrated liquid storage tank 80. In addition, pipe L5 is connected to the cleaning liquid storage tank 50 and the side 32C of the filter body 32 (side 34A of the housing 34). A gas supply unit 62 is also connected to pipe L5. Because the membrane filtration device 20a is configured in this way, the flow direction of the cleaning liquid W1 for backwashing within the filter body 32 is the same for pulse cleaning and normal cleaning.

[0034] Although embodiments of this disclosure have been described above, the embodiments are not limited by the content of these embodiments. Furthermore, the aforementioned components include those that can be easily conceived by a person skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above. [Explanation of Symbols]

[0035] 14 Membrane Filtration System 20 Membrane Filtration System 22 Control device 32 filter bodies

Claims

1. A filter body that uses a dead-end membrane filtration system to filter the cleaning fluid from a scrubber that purifies exhaust gas from a ship's engine, The system includes a cleaning means for cleaning the filter body, The filter body has a first primary side of the first end, a second primary side of the second end, and a secondary side of the side wall. When the cleaning solution is filtered through a membrane, the cleaning solution enters the filter body from the first primary side and is discharged from the secondary side. The aforementioned cleaning means is a membrane filtration system that switches between performing normal cleaning, in which the filter body is cleaned with a pressurized liquid, and pulse cleaning, in which the filter body is pressurized with gas to discharge the liquid inside the filter body from the second primary side and clean the filter body.

2. A filter body that uses a dead-end membrane filtration system to filter the cleaning fluid from a scrubber that purifies exhaust gas from a ship's engine, The system includes a cleaning means for cleaning the filter body, The filter body has a first primary side of the first end, a second primary side of the second end, and a secondary side of the side wall. When the cleaning solution is filtered through a membrane, the cleaning solution enters from the second primary side and is discharged from the secondary side. The aforementioned cleaning means is a membrane filtration system that switches between performing normal cleaning, in which the filter body is cleaned with a pressurized liquid, and pulse cleaning, in which the filter body is cleaned by pressurizing the filter body with gas and discharging the liquid inside the filter body from the first primary side.

3. The membrane filtration system according to claim 1 or 2, wherein the normal cleaning is performed by having the pressurized liquid enter the filter body from the secondary side and discharge it from the first primary side.

4. The membrane filtration system according to any one of claims 1 to 3, wherein the cleaning means switches between performing normal cleaning, in which pressurized liquid is supplied to the filter body and discharged from the filter body, and pulse cleaning, in which the filter body is pressurized and depressurized.

5. The membrane filtration system according to claim 4, wherein the cleaning means switches between performing normal cleaning, in which a pressurized liquid outside the filter body is supplied to the filter body and discharged from the filter body, and pulse cleaning, in which the residual liquid inside the housing housing the filter body is pressurized and then depressurized to discharge the liquid inside the filter body to the filter body.

6. The membrane filtration system according to claim 5, wherein the cleaning means switches between and performs normal cleaning, in which pressurized liquid is supplied to the filter body from the second end of the filter body and the supplied pressurized liquid is discharged from the first end of the filter body, and pulse cleaning, in which the internal pressure inside the housing is pressurized to a pressure higher than the internal pressure inside the housing during membrane filtration of the cleaning liquid, and after a predetermined time has elapsed, the internal pressure inside the housing is reduced to discharge the liquid inside the housing to the outside of the housing.

7. The membrane filtration system according to any one of claims 1 to 3, wherein the cleaning means switches from pulse cleaning to normal cleaning after performing pulse cleaning multiple times.

8. The membrane filtration system according to any one of claims 1 to 4, wherein the cleaning means sets at least one of the number of pulsed cleanings or the number of normal cleanings based on the flow rate of the cleaning solution that requires membrane filtration and the target concentration ratio of the cleaning solution.

9. A membrane filtration method for filtering a cleaning liquid from a scrubber that purifies exhaust gas from a ship's engine using a dead-end membrane filtration method, The filter body has a first primary side of the first end, a second primary side of the second end, and a secondary side of the side wall. When the cleaning solution is filtered through a membrane, the cleaning solution enters the filter body from the first primary side and is discharged from the secondary side. A membrane filtration method that switches between performing normal cleaning, in which the filter body is cleaned with a pressurized liquid, and pulse cleaning, in which the filter body is pressurized with gas to discharge the liquid inside the filter body from the second primary side and clean the filter body.

10. A membrane filtration method for filtering a cleaning liquid from a scrubber that purifies exhaust gas from a ship's engine using a dead-end membrane filtration method, The filter body has a first primary side of the first end, a second primary side of the second end, and a secondary side of the side wall. When the cleaning solution is filtered through a membrane, the cleaning solution enters from the second primary side and is discharged from the secondary side. A membrane filtration method that switches between performing normal cleaning, in which the filter body is cleaned with a pressurized liquid, and pulse cleaning, in which the filter body is cleaned by pressurizing the filter body with gas and discharging the liquid inside the filter body from the first primary side.

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