JP2012139614A - Cleaning method for separation membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method for a separation membrane element capable of efficiently removing especially contamination adhered on a membrane surface near a raw water side by cleaning the separation membrane in the separation membrane element by flowing a cleaning liquid in a direction opposite to a raw water inflow direction in water production when a spiral type separation membrane element is loaded in a pressure vessel.SOLUTION: The cleaning method for a separation membrane element includes providing a raw water seal member mounted on the outer peripheral side of a telescope prevention plate of at least one end side which is a split-ring shaped seal member 14 made of a nonlinear elastic material, disposing a pressure resistance mechanism supporting a load of the separation membrane element in a raw water inflow side and a retentate discharge side in the cylindrical pressure vessel respectively, and flowing a cleaning liquid in the direction opposite to the raw water inflow direction in water production in the internal cleaning of the separation membrane element.

Description

  The present invention relates to a method of cleaning a spiral separation membrane element for separating and removing components present in a fluid to be treated in a pressure vessel.

  In recent years, fluid separation using a separation membrane such as a reverse osmosis membrane has been attracting attention as an energy-saving process, and its use is progressing. For example, in a reverse osmosis separation method using a reverse osmosis membrane, a solution containing a solute such as salt is permeated through the reverse osmosis membrane at a pressure higher than the osmotic pressure of the solution, thereby reducing the concentration of the solute such as salt. For example, it is used for desalination of seawater, desalination of brine, production of ultrapure water and wastewater treatment.

  In the case of a flat membrane, these separation membranes are often used in the form of spiral elements. As a structure of a conventional spiral separation membrane element, for example, as shown in FIG. 1, a single or plural laminates of a separation membrane 1, a supply-side flow path material 3 and a permeation-side flow path material 2 are formed with a perforated center. It is known that a telescope prevention plate 5 is installed around both ends of the tube 4 (see, for example, Patent Document 1).

  In this separation membrane element, the fluid to be treated 6 is supplied from one end surface, and the solvent component permeates the separation membrane 1 while flowing along the supply-side flow path material 3, whereby the solvent component is separated. Thereafter, the solvent component (permeating fluid 7 ′) that has permeated the separation membrane flows along the permeate-side flow path member 2, flows into the central tube 4 from the hole on the side surface, and flows in the central tube. The permeated fluid 7 is taken out from the other end face of the element. On the other hand, a processing fluid containing a high concentration of solute is taken out as a concentrated fluid 8 from the other end surface of the element.

  In the conventional separation membrane element described above, an elastic seal member is usually fitted in a circumferential groove on the outer peripheral side of the telescope prevention plate arranged on the raw water side, and the separation membrane element is a pressure vessel. A plurality of tubes are loaded and used in the vessel. The separation membrane element can seal the gap between the separation membrane element and the pressure vessel with the elastic material sealing member by fitting the elastic material sealing member in the circumferential groove on the outer peripheral side of the telescope prevention plate. In addition, since the flow of the liquid to be processed in the gap is prevented, the fluid to be processed can be efficiently processed by the separation membrane element. Conventionally, an elastic resin seal member such as an O-ring seal having an O-shaped cross section or a U-cup seal having a U-shaped cross section has been used. When an O-ring seal is used, the O-ring seal fitted in the circumferential groove on the outer peripheral side of the telescope prevention plate comes into contact with the inner wall of the pressure vessel, and the O-ring seal collapses and deforms. The gap between the separation membrane element and the pressure vessel is filled.

  FIG. 2 shows a state in which the separation membrane element having the O-ring seal 12 fitted to the outer peripheral portion 10 of the telescope prevention plate is loaded in the pressure vessel, and in the vicinity of the O-ring seal mounting portion. It is a partial expanded sectional view which expands and shows typically. In FIG. 2, the O-ring seal 12 is deformed at a portion in pressure contact with the inner wall 9 of the pressure vessel, and the contact area with the inner wall 9 of the pressure vessel is increased. Furthermore, since the O-ring seal 12 is made of an elastic resin, sliding friction with the inner wall 9 of the pressure vessel is large.

  Therefore, when the element is moved in the pressure vessel, a large load is required to resist the friction between the O-ring seal 12 and the inner wall 9 of the pressure vessel, and in particular, a plurality of separation membrane elements are pressurized. When moving in a container, since it becomes a big load and labor is applied, the operation | work which attaches / detaches a separation membrane element in a pressure vessel actually becomes inefficient.

  In order to eliminate such problems of the O-ring seal, a U-cup seal has been devised and widely used as a seal member for the separation membrane element. This U-cup seal is set on the telescope prevention plate of the separation membrane element so that the U-shaped open part faces the raw water side. The U-cup seal has a structure in which, when water is supplied from the raw water side, the U-shape is opened by the water pressure to fill the gap between the U-cup seal and the pressure vessel.

  FIG. 3 shows a state in which the separation membrane element in which the U-cup seal 13 is fitted to the outer peripheral portion 10 of the telescope prevention plate is loaded in the pressure vessel, and in the vicinity of the U-cup seal mounting portion. It is an expanded sectional view which expands and shows typically. In FIG. 3, the U-cup seal 13 has a relatively small contact area with the inner wall 9 of the pressure vessel, but as described above, a sealing function is exhibited for fluid flowing in the direction from right to left in the figure. The However, the sealing function is insufficient for fluid flowing from the left to the right in the figure.

  Due to such a U-cup seal structure, when the separation membrane element is moved from the raw water side to the concentrated water side, the end of the U-cup seal is in light contact with the inner wall of the pressure vessel, and the element is easily Can be moved. However, when moving from the concentrated water side to the raw water side, the end of the U-cup seal is in strong contact with the inner wall of the pressure vessel, and further, the end of the U-cup seal is warped, resulting in a gap between the separation membrane element and the pressure vessel. A very large load may be required to move the separation membrane element. Therefore, in an actual plant using an element in which a U-cup seal is used, the separation membrane element is detached from the pressure vessel by inserting the separation membrane element from the raw water side of the pressure vessel and pushing it into the concentrated water side. The element is extracted from the concentration side, or is extracted from the concentrated water side.

  When the separation membrane element loaded in the pressure vessel continues the membrane separation process that allows the raw water to pass through, the contaminants in the raw water adhere to and accumulate on the membrane surface of the separation membrane element. As a result, the volume and quality of the entire production water will decrease. The adhesion / deposition of dirt on the membrane surface is particularly large in the raw water side portion of the membrane surface in the separation membrane element closest to the raw water side.

  When dirt adheres to and accumulates on the membrane surface in the separation membrane element and the amount of water and quality of the production water decrease, the inside of the separation membrane element is washed with a cleaning solution in order to remove the dirt attached to the membrane surface. Is done. In the conventional cleaning of reverse osmosis membrane elements, a U-cup seal is used as a sealing material. Therefore, the cleaning liquid is flowed from the raw water side to the concentrated water side due to the structure of the sealing material.

  In the case of the U-cup seal, since the U-shaped open part is set on the telescope prevention plate of the separation membrane element so that it faces the raw water side, when the cleaning liquid flows from the raw water side to the concentration side, the U- Since the U-shaped open portion of the cup seal opens widely and seals the gap between the separation membrane element and the pressure vessel, the cleaning liquid can flow through the separation membrane element. However, although dirt attached to the raw water side of the membrane surface of the separation membrane element close to the raw water side is removed by the washing water, it is easily sent to the inside of the separation membrane element together with the washing water, and the dirt is sufficiently removed. It was difficult. Further, when the cleaning liquid is passed from the concentrated water side to the raw water side, the U-shaped open portion of the U-cup seal is crushed by the water flow of the cleaning water, and the gap between the separation membrane element and the pressure vessel increases. Therefore, the cleaning liquid does not pass through the separation membrane element, but passes through a large amount of gaps between the separation membrane element and the pressure vessel. As a result, the dirt adhering to the raw water side of the membrane surface in the separation membrane element is sufficient. Can not be removed.

  Furthermore, in the conventional apparatus, in order to support the load of the separation membrane element, a pressure-resistant member for supporting the load of the separation membrane element is installed on the concentrated water side, and the load of the separation membrane element is supported by the pressure-resistant member. This prevents damage to the separation membrane element. However, since such a pressure-resistant member is not provided on the raw water side, when the cleaning liquid is passed from the concentrated water side to the raw water side, the entire load of the element is applied in the vicinity of the permeate pipe. In the case of a reverse osmosis membrane element having a large diameter, the separation membrane element may be damaged.

  Further, as described in JP-A-11-104636 (Patent Document 2), in the case of a reverse osmosis membrane element using a hollow fiber membrane, from the concentrated water side to the raw water side, a washing liquid, Backflow cleaning is known in which cleaning is performed by passing a liquid / gas mixed fluid for cleaning. However, in the case of a spiral type separation membrane element, it has been considered that it is difficult to perform reverse flow cleaning for the reasons described above.

JP 10-137558 A JP-A-11-104636

  An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a method capable of performing efficient cleaning even when a spiral separation membrane element is loaded in a pressure vessel.

In order to achieve the above object, the present invention has any one of the following configurations.
(1) In the method of cleaning the inside of a separation membrane element loaded in a cylindrical pressure vessel with a liquid, the outer periphery of the membrane unit wound body in which the separation membrane element is wound with a membrane unit including the separation membrane is packaged Is a spiral separation membrane element that is covered with a body and is provided with a telescope prevention plate on both ends or one end of the membrane unit roll and exterior body, and is attached to the outer peripheral side of the telescope prevention plate on at least one end side The seal member is a split ring-shaped non-elastic seal member, and a pressure-resistant mechanism for supporting the load of the separation membrane element is disposed on each of the raw water inflow side and the concentrated water discharge side in the cylindrical pressure vessel, and A method for cleaning a separation membrane element, characterized by causing a cleaning liquid to flow in a direction opposite to the direction of inflow of raw water at the time of fresh water generation during internal cleaning of the separation membrane element.
(2) At the time of internal cleaning of the separation membrane element, after or before the cleaning operation in which the cleaning liquid flows in the direction opposite to the direction of the raw water inflow during the fresh water generation, the cleaning liquid flows in the direction of the raw water inflow during the fresh water generation. The separation membrane element cleaning method according to (1) above, wherein the cleaning operation is performed.
(3) When the spiral separation membrane element is loaded in the cylindrical pressure vessel, the inelastic material sealing member mounted on the outer peripheral side of the telescope prevention plate is in close contact with the inner wall of the pressure vessel. (1) The washing | cleaning method of the separation membrane element as described in (2).
(4) The separation membrane element according to any one of (1) to (3), wherein there is a circumferential groove on the outer peripheral side of the telescope prevention plate, and a non-elastic seal member is fitted in the circumferential groove. Cleaning method.
(5) The separation membrane element in which one or a plurality of inelastic material sealing members are mounted on the outer peripheral side of the telescope prevention plate, wherein the split end portions of the inelastic material sealing members are joined to each other. (1) The washing | cleaning method of the separation membrane element in any one of (4).
(6) A plurality of non-elastic seal members are mounted in parallel on the outer peripheral side of the telescope prevention plate, and the positions where the split ends of the non-elastic seal members are joined are a plurality of non-elastic seal members. The method for washing a separation membrane element according to (5), which is different from each other.
(7) The pressure-resistant mechanisms respectively arranged on the raw water inflow side and the concentrated water discharge side in the cylindrical pressure vessel are connected to the end of the cylindrical pressure vessel and the telescope prevention plate of the separation membrane element located on the end side. The method for cleaning a separation membrane element according to any one of the above (1) to (6), wherein the separation membrane element is a substantially conical or substantially cylindrical pressure-resistant member disposed therebetween.

  According to the method for cleaning a separation membrane element of the present invention, when the spiral type separation membrane element is loaded in the pressure vessel, the separation membrane in the element is flowed in a direction opposite to the direction of the raw water inflow during fresh water generation. The separation membrane element can be efficiently cleaned. In particular, it is possible to efficiently remove dirt adhering to the membrane surface near the raw water side. Further, even if the cleaning liquid is flowed in the direction opposite to the direction of the raw water inflow during the water preparation, the separation membrane element can be prevented from being damaged.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in these drawings.

  FIG. 1 is a partially broken perspective view showing an example of a spiral separation membrane element to which the method of the present invention is applied. As shown in FIG. 1, a typical example of a spiral separation membrane element is a spiral wound around a perforated central tube 4 in a state where a separation membrane 1, a supply-side flow channel material 3, and a permeation-side flow channel material 2 are laminated. The telescope prevention plate 5 is installed at both ends of the separation membrane wound body. The end of the separation membrane 1 is sealed to prevent mixing of the supply fluid and the permeated fluid.

  The separation membrane 1 is a flat membrane-like separation membrane, and a reverse osmosis membrane, an ultrafiltration membrane, a microfiltration membrane, a gas separation membrane, a degassing membrane or the like can be used. For the supply-side channel material 3, a net-like material, a mesh-like material, a grooved sheet, a corrugated sheet or the like can be used. For the permeate-side channel material 2, a net-like material, a mesh-like material, a grooved sheet, a corrugated sheet or the like can be used.

  The telescope prevention plate 5 is a plate-like object having a hole, which is installed in order to prevent deformation (telescope phenomenon) into a cylindrical shape due to the pressure of the fluid that the separation membrane winding passes through, It is preferable to have a circumferential groove for loading a sealing material. The telescope prevention plate 5 may be made of a resin material such as a thermoplastic resin, a thermosetting resin, or a heat resistant resin. Moreover, it is preferable that this telescope prevention board 5 is a spoke type structure which has an outer periphery annular part, an inner periphery annular part, and a radial spoke part.

  The central tube 4 has a plurality of holes on the side surface of the tube, and the material of the central tube 4 may be any of resin and metal, but plastics such as noryl resin and ABS resin are usually used.

  As a means for sealing the end of the separation membrane 1, an adhesion method is preferably used. As the adhesive, any conventionally known adhesives such as urethane adhesives, epoxy adhesives and hot melt adhesives can be used.

  In addition, the spiral separation membrane element preferably has a structure in which the outer peripheral portion of the separation membrane wound body is constrained by an exterior material and does not expand in diameter. The exterior material is a sheet made of polyester, polypropylene, polyethylene, polyvinyl chloride, or the like, or a glass fiber coated with a curable resin, and the sheet or fiber is wound around the outer peripheral surface of the separation membrane wound body. To restrain the element from expanding.

  In the spiral separation membrane element as described above, the method of the present invention is a split ring-like non-sealing material as a sealing material to be attached to the outer peripheral side of the telescope prevention plate at least one end of the telescope prevention plate at both ends or one end thereof. An elastic seal member (hereinafter referred to as a split ring seal) is used.

  The form of the split ring seal used in the present invention will be described with reference to FIG. The split ring seal has such a shape that the annular seal is cut and divided at one or more places. For example, the split ring seal has one split portion as shown in FIG. 4 (a) (plan view). Preferably, two semicircular arc split ring seals in which the annular seal is cut and divided at two locations may be used. The cross-sectional shape of the split ring seal is not particularly limited, and may be any structure that can fit in the groove on the outer peripheral portion of the telescope prevention plate 5 and does not move. For example, FIG. 4 (b) (bb) As shown in the cross-sectional view of FIG.

  Also, the length of the outer periphery of the split ring seal (outer peripheral length) is such that the outer diameter of the split ring seal when the split portions of the split ring seal are connected to form a ring is slightly larger than the diameter of the inner wall of the pressure vessel. When designed and actually mounted on the separation membrane element telescope prevention plate and loaded into the pressure vessel, the gap of the split part is reduced, so that the split ring seal is in close contact with the inner wall of the pressure vessel To do. Also, the inner ring length (inner circumference) of the split ring seal is such that when the split part of the split ring seal is connected into an annular shape, it fits in the circumferential groove of the outer periphery of the telescope prevention plate without any gap. If it is good. The size of the split ring seal may be optimized depending on the outer diameter and material of the element. For example, the radial width of the seal (that is, half of the difference between the outer diameter and the inner diameter) is about 5 to 10 mm. The thickness of the seal can be about 3 to 10 mm.

  The material of the split ring seal is not particularly limited as long as it is an inelastic material such as an inelastic resin or metal, but inelastic resin is preferable in consideration of resistance to seawater or separation membrane element cleaning liquid. Polyethylene, polypropylene, polyethylene terephthalate, nylon, noryl, ABS resin, polycarbonate, tetrafluoropolyethylene and the like are used.

  The shape of the split portion in the split ring seal is not particularly limited, but as an example, when it is cut at right angles to the seal longitudinal direction as shown in FIG. 5 (FIG. 5 (a)), On the other hand, there are a case where it is cut obliquely (FIG. 5B) and a case where it is cut stepwise with respect to the longitudinal direction of the seal (FIG. 5C).

  In particular, when the split ring seal is used when it is cut obliquely with respect to the longitudinal direction of the seal (FIG. 5 (b)) or when it is cut stepwise with respect to the longitudinal direction of the seal (FIG. 5 (c)). The split ring ends are pressed against each other with the pressure when the processing fluid flows through the pressure vessel, and there is almost no gap between the split ring ends. As a result, the sealing effect is substantially maintained even at the joint portion between the split ends, and the amount of the fluid to be treated bypassing the outside of the separation membrane element is considerably small, so that efficient water treatment can be performed.

  After the split ring seal is attached to the outer peripheral portion of the telescope prevention plate of the separation membrane element, the split portions may be disposed so as to contact each other, or the split portions may be joined. As a bonding method at that time, heat fusion bonding or strong bonding using an adhesive may be used, or bonding in which one piece of the split portion of the split ring seal and the other are combined by uneven fitting may be used. An example of the uneven fitting of the split part of the split ring seal is shown in FIG. As shown in FIG. 6, the split ring seals can be prevented from falling off due to an impact during handling by joining the split ends to a concave and convex shape.

  When the split ring seal is mounted on the outer periphery of the telescope prevention plate, one or a plurality of seal members may be mounted. When a plurality of seal members are mounted, it is preferable that the positions of the split portions are different from each other, thereby reducing the amount of raw water passing through the outside of the separation membrane element.

  The separation membrane element with the split ring seal mounted on the outer periphery of the telescope prevention plate can be moved with low load in the pressure vessel regardless of the moving direction due to the material and structure of the split ring seal. it can. In particular, even when a plurality of separation membrane elements are loaded in the pressure vessel, it is possible to easily move the separation membrane element from the raw water side to the concentrated water side or in the opposite direction. it can.

  Further, in the case of a separation membrane element having a large outer diameter, its own weight becomes heavy, so when a conventional elastic material sealing member is mounted, the elastic material sealing member is affected by the increased weight. However, because it deforms greatly and comes into contact with the inner wall of the pressure vessel, the load required to move the separation membrane element increases.However, when a split ring seal is installed, the seal member will The load required to move the separation membrane element does not increase so much because it hardly deforms. From this point, the split ring seal described above is very effective because it has a great advantage that the separation membrane element having a large outer diameter can be easily loaded and unloaded.

  On the other hand, in the case of an element equipped with an elastic O-ring seal used in the prior art, as described above, the movement of the element in the pressure vessel can be moved in either direction. There is a problem that a great load is required and a great amount of labor is required.

  In addition, in the case of an element equipped with a U-cup seal made of an elastic material used in the prior art, as described above, a cleaning method in which a cleaning solution is passed from the raw water side to the concentrating side, or from the concentrated water side to the raw water Even with the cleaning method in which the cleaning liquid is flowed to the side, it is difficult to sufficiently clean the film surface, and the cleaning effect is insufficient.

  However, when the separation membrane element with the above-mentioned split ring seal attached to the outer periphery of the telescope prevention plate is installed in the pressure vessel, reverse flow cleaning is performed to pass cleaning water from the concentrated water side to the raw water side. However, since the sealing member is not deformed by the supply pressure of the cleaning water, the gap between the separation membrane element and the pressure vessel is sufficiently sealed, and the cleaning liquid is allowed to pass through the membrane surface in the separation membrane element. The dirt can be removed, and the cleaning liquid can be washed out together with the dirt from the raw water side of the separation membrane element.

  When such backwashing is performed, the load in the pressure vessel is applied to the element in the pressure vessel from the concentrated water side to the raw water side, and the element load is applied to the raw water side. When the pressure-resistant mechanism is not disposed, the element on the raw water side is easily damaged during cleaning. However, in the present invention, since the pressure-resistant mechanism that supports the load of the separation membrane element is also arranged on the raw water side in the pressure vessel, the separation membrane element can be prevented from being damaged. As a specific example of the pressure-resistant mechanism, a pressure-resistant member similar to the pressure-resistant member arranged on the concentrated water side in the pressure vessel is also installed on the raw water side in the pressure vessel, and the load of the separation membrane element is For example, it can be supported by a sex member. In particular, in the case of a separation membrane element having a large element outer diameter, for example, an element having an outer diameter of 20 cm or more, the load of the separation membrane element becomes very large. Therefore, it is effective to install a pressure-resistant member also on the raw water side. Is.

  FIG. 7 is a schematic cross-sectional view illustrating when pressure-resistant members 33 and 36 are installed on both the raw water side and the concentrated water side in the pressure vessel 35 and a plurality of separation membrane elements 34 are loaded in the pressure vessel. In this figure, a conical pressure-resistant member is installed.

  The structure of the pressure-resistant member is not particularly limited, but the same pressure-resistant member that has been conventionally used on the concentrated water side of the pressure vessel may be used. The shape of the pressure-resistant member is not particularly limited, but since the shape of the end face of the separation membrane element is a circle, a cylindrical or conical shape with a circular contact surface is preferable. In order to prevent resistance during passage of raw water or concentrated water, it is preferable to provide a structure having a plurality of holes in the pressure-resistant member so as not to cause resistance to water flow while maintaining pressure resistance.

  The material of the pressure-resistant member is not particularly limited as long as it is a material that can obtain a desired pressure resistance, such as resin and metal, but is a material that is resistant to seawater and the cleaning liquid of the separation membrane element. Is preferable, and polyethylene, polypropylene, polyethylene terephthalate, nylon, noryl, ABS resin, polycarbonate, polyvinyl chloride, and the like are used.

  In this way, a pressure-resistant mechanism that supports the load of the separation membrane element is installed on both the raw water side and the concentrated water side in the pressure vessel. Even if the washing efficiency is increased by flowing, damage to the separation membrane element can be prevented, and contamination on the raw water side of the separation membrane element can be effectively removed.

  Further, in the cleaning method according to the present invention, it is important to perform a cleaning operation in which the cleaning liquid flows in a direction opposite to the direction of the raw water inflow during the fresh water generation when cleaning the separation membrane element. After or before, a cleaning operation for causing the cleaning liquid to flow in the direction of inflow of raw water at the time of fresh water may be supplementarily performed to further improve the cleaning performance. Further, the main cleaning operation and the auxiliary cleaning operation described above may be alternately repeated.

  Hereinafter, the present invention will be described with specific examples. However, the present invention is not limited to these examples.

<Example 1>
A split ring seal was attached to the outer peripheral groove of the telescope prevention plate on the raw water side of the spiral type reverse osmosis membrane element having a total length of 102 cm and a diameter of 40 cm. The split ring seal has a split ring shape shown in FIG. 4 having a split portion cut perpendicularly to the longitudinal direction of the seal, and uses a split ring seal made of polypropylene. The split parts were mounted in parallel so that the positions of the split parts were different. The radial width of the split ring seal was 8 mm, the thickness per piece was 3 mm, and the outer diameter was 40.5 cm.

  Six spiral reverse osmosis membrane elements were loaded in the same pressure vessel so that the telescope prevention plate equipped with the split ring seal was placed on the raw water side. At the time of this loading, a pressure-resistant member having a hole having a hole on the side surface is installed on both the concentrated water side and the raw water side in the pressure vessel with a cylinder having substantially the same outer shape as the separation membrane element. The load was supported by a pressure-resistant member.

  Next, brine water (salt concentration of 2500 mg / L) subjected to sand filtration treatment was supplied to five pressure vessels loaded with elements to perform desalting treatment and fresh water generation. The supplied water was adjusted to pH 6.5 and water temperature 25 ° C. and then supplied to the element. The operation was performed at an operation pressure of 0.8 MPa and a recovery rate of 50%. The evaporation residue concentration of the permeated water after continuing the operation for 24 hours was determined by measuring various ion concentrations by ion chromatography analysis, and found to be 26 mg / L.

  When the operation was continued for several months, the differential pressure (the value obtained by subtracting the pressure of the concentrated water from the pressure of the raw water) reached 2.0 times compared to the value immediately after the start of operation. did. When the separation membrane element in the pressure vessel was observed immediately after the operation was stopped, a large amount of dirt derived from the raw water was accumulated on the reverse osmosis membrane element closest to the raw water side.

  Therefore, in the separation membrane element loaded in the pressure vessel, a cleaning solution (sodium hydroxide aqueous solution) having a pH of 11 and 35 ° C. is fed from the concentrated water side to the raw water side at a supply rate of 200 L / min for 60 minutes per vessel. Water was passed through to remove the dirt adhering to the separation membrane element, and when the operation was started again, the differential pressure recovered to 1.1 times the value immediately after the start of the operation.

  When the end of both sides of the pressure vessel was opened at the completion of cleaning and the separation membrane element was confirmed, no abnormality was found in the shape of the element.

<Comparative Example 1>
The reverse osmosis membrane element was the same as in Example 1 except that one U-cup seal made of ethylene propylene rubber was attached as the seal material attached to the raw water side of the telescope prevention plate of the reverse osmosis membrane element. Six were loaded in the same pressure vessel.

  Next, brine water (salt concentration of 2500 mg / L) subjected to sand filtration treatment was supplied to five pressure vessels loaded with elements to perform desalting treatment and fresh water generation. The supplied water was adjusted to pH 6.5 and water temperature 25 ° C. and then supplied to the element. The operation was performed at an operation pressure of 0.8 MPa and a recovery rate of 50%. The evaporation residue concentration of the permeated water after the operation for 24 hours was determined by measuring various ion concentrations by ion chromatography analysis, and found to be 25 mg / L.

  When the operation was continued for several months, the differential pressure (the value obtained by subtracting the pressure of the concentrated water from the pressure of the raw water) reached 2.0 times compared to the value immediately after the start of operation. Then, the same cleaning as in Example 1 was performed and the operation was resumed. As a result, the differential pressure recovered only up to 1.5 times the value immediately after the start of operation, and the cleaning effect was clearly more than in the case of Example 1. It was inferior.

  When the end of both sides of the pressure vessel was opened at the completion of cleaning and the separation membrane element was confirmed, no abnormality was found in the shape of the element.

<Comparative example 2>
As in the case of Comparative Example 1, one U-cup seal made of ethylene propylene rubber was attached as a seal material attached to the raw water side of the telescope prevention plate of the reverse osmosis membrane element. The reverse osmosis membrane element was loaded into the pressure vessel in the same manner as in Example 1 except that the pressure-resistant member on the raw water side was not installed when the six reverse osmosis membrane elements were loaded into the same pressure vessel. did.

  Next, brine water (salt concentration of 2500 mg / L) subjected to sand filtration treatment was supplied to five pressure vessels loaded with elements to perform desalting treatment and fresh water generation. The supplied water was adjusted to pH 6.5 and water temperature 25 ° C. and then supplied to the element. The operation was performed at an operation pressure of 0.8 MPa and a recovery rate of 50%. The evaporation residue concentration of the permeated water after continuing the operation for 24 hours was determined by measuring various ion concentrations by ion chromatography analysis, and found to be 24 mg / L.

  When the operation was continued for several months, the differential pressure (the value obtained by subtracting the pressure of the concentrated water from the pressure of the raw water) reached 2.0 times compared to the value immediately after the start of operation. Then, the same cleaning as in Example 1 was performed and the operation was resumed. As a result, the differential pressure recovered only up to 1.4 times the value immediately after the start of operation, and the cleaning effect was clearly more than in the case of Example 1. It was inferior.

  Further, when the end of both sides of the pressure vessel was opened at the completion of cleaning and the separation membrane element was confirmed, the telescope prevention plate was detached by one element on the raw water side.

It is a partially broken perspective view which shows an example of the spiral-type separation membrane element to which this invention method is applied. A portion schematically showing the vicinity of the O-ring seal mounting portion in order to show a state in which the separation membrane element having the O-ring seal mounted on the telescope prevention plate is loaded in the pressure vessel (prior art) It is an expanded sectional view. A portion schematically showing the vicinity of the U-cup seal mounting portion in order to show a state in which the separation membrane element having the U-cup seal mounted on the telescope prevention plate is loaded in the pressure vessel (prior art) It is an expanded sectional view. FIG. 5 is a plan view (FIG. 4A) schematically showing a split ring-shaped non-elastic seal member used in the method of the present invention, and a sectional view taken along line bb (FIG. 4B). It is a schematic diagram which expands and shows the part near a split part when the split ring-shaped non-elastic seal member used in the method of the present invention is attached to the groove on the outer periphery of the telescope prevention plate of the separation membrane element. It is an enlarged schematic diagram of the vicinity of the split portion showing an example of joining one piece and the other of the split portion of the split ring-shaped non-elastic material sealing member by concave-convex fitting. It is a cross-sectional schematic diagram illustrating a case where pressure-resistant members are installed on both the raw water side and the concentrated water side in the pressure vessel, and a plurality of separation membrane elements are loaded in the pressure vessel.

1: Separation membrane 2: Permeation side channel material 3: Supply side channel material 4: Center tube 5: Telescope prevention plate 6, 6 ': Fluid to be treated (raw water)
7, 7 ': Permeated fluid (permeated water)
8: Concentrated fluid (concentrated water)
9: inner wall of cylindrical pressure vessel 10: outer peripheral portion of telescope prevention plate 11: outer peripheral surface of telescope prevention plate 12: O-ring seal 13: U-cup seal 14: non-elastic seal member in split ring shape 15: Split portion of split ring-shaped inelastic material seal member 16: Inner diameter of split ring-shaped inelastic material seal member 17: Outer diameter of split ring-shaped inelastic material seal member 18: Cut vertically Split portions 19 and 20: Seal member 21 near the vertically cut split portion 21: Both side portions of the circumferential groove of the telescope prevention plate 22: Diagonally cut split portions 23 and 24: Diagonally cut Seal member 25 in the vicinity of the split part: split part 26 cut in a staircase form, 27: a seal in the vicinity of the split part cut in a staircase form Seal member 28: non-elastic material seals member 29 having a split portion to fit the uneven: inelastic material seals member having a recess in an end face (one side)
30: Inelastic material sealing member having a convex portion on the end face (the other side)
31: Concave portion 32 on the end surface of the non-elastic seal member 32: Convex portion 33 on the end surface of the non-elastic seal member 33: Pressure-resistant member (raw water side)
34: separation membrane element 35: pressure vessel 36: pressure-resistant member (concentrated water side)

Claims (7)

In the method of washing the inside of a separation membrane element loaded in a cylindrical pressure vessel with a liquid, the outer periphery of the membrane unit wound body in which the separation membrane element is wound with a membrane unit including the separation membrane is covered with an exterior body. A spiral separation membrane element in which a telescope prevention plate is provided at both ends or one end of the membrane unit wound body and the exterior body, and a raw water seal member attached to the outer peripheral side of the telescope prevention plate at least at one end side , A split ring-shaped non-elastic seal member, and a pressure-resistant mechanism for supporting the load of the separation membrane element is disposed on each of the raw water inflow side and the concentrated water discharge side in the cylindrical pressure vessel, and the separation membrane A method for cleaning a separation membrane element, characterized by causing a cleaning liquid to flow in a direction opposite to a direction of inflow of raw water at the time of fresh water generation during internal cleaning of the element. When the separation membrane element is internally cleaned, after or before the cleaning operation that causes the cleaning liquid to flow in the direction opposite to the direction of the raw water inflow during the preparation, the cleaning operation that causes the cleaning liquid to flow in the direction of the raw water inflow during preparation The method for cleaning a separation membrane element according to claim 1, wherein the method is performed. When the spiral separation membrane element is loaded into the cylindrical pressure vessel, the non-elastic material sealing member mounted on the outer peripheral side of the telescope prevention plate is in close contact with the inner wall of the pressure vessel. The method for washing a separation membrane element according to claim 1 or 2. The separation membrane element according to any one of claims 1 to 3, wherein there is a circumferential groove on the outer peripheral side of the telescope prevention plate, and a sealing member made of an inelastic material is fitted into the circumferential groove. Method. A separation membrane element in which one or a plurality of inelastic material sealing members are mounted on the outer peripheral side of the telescope prevention plate, wherein split ends of the inelastic material sealing members are joined to each other. Item 5. A method for cleaning a separation membrane element according to any one of Items 1 to 4. A plurality of non-elastic seal members are mounted in parallel on the outer peripheral side of the telescope prevention plate, and the positions at which the split ends of the non-elastic seal members are joined to each other are a plurality of non-elastic seal members. The method for cleaning a separation membrane element according to claim 5, wherein: Pressure-resistant mechanisms arranged on the raw water inflow side and concentrated water discharge side in the cylindrical pressure vessel are arranged between the end of the cylindrical pressure vessel and the telescope prevention plate of the separation membrane element located on the end side. The method for cleaning a separation membrane element according to any one of claims 1 to 6, wherein the pressure-resistant member has a substantially conical or substantially cylindrical shape.

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