JP2014195775A - Hollow fiber membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an external pressure type hollow fiber membrane module capable of simultaneously performing drain reverse washing and air-scrubbing.SOLUTION: In an external pressure type hollow fiber membrane module 1 where: both ends of a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes 2 in which at least one end is open are bonded and fixed at the inside of a cylindrical container 3 by a resin partition wall 4; the resin partition wall 4 consists of an opening side resin partition wall 4a in which the open end part of the hollow fiber membrane 2 is fixed while keeping open and a sealed side resin partition wall 4b in which the end part of the hollow fiber membrane 2 is fixed at a sealed state; and a plurality of through holes are made at the sealed side resin partition wall 4b itself, at least one air introduction port 9 exists at a container side surface between the resin partition walls 4a and 4b of the cylindrical container 3.

Description

  The present invention relates to a hollow fiber membrane module used for membrane separation. More specifically, for example, the present invention relates to a hollow fiber membrane module used for water purification treatment such as river water, lake water, ground water, seawater, etc., or membrane separation treatment such as sewage and industrial wastewater.

  Membrane separation technology using hollow fiber membranes includes drinking water production in waterworks, industrial water, industrial ultrapure water, industrial water production such as food and medicine, sewage treatment such as municipal sewage purification and industrial wastewater treatment, etc. It is used in a wide range of fields. Generally, when raw water is filtered using a hollow fiber membrane module, the hollow fiber membrane stored in the container is supplied with a pressure type that supplies the raw water to the hollow fiber membrane using an external pressure such as a pump and a filtration tank. The pressure type hollow fiber membrane module is roughly divided into immersion types for immersing the hollow fiber membrane, and the pressure type hollow fiber membrane module supplies an external pressure type that supplies raw water to the outer surface of the hollow fiber membrane and obtains filtered water from the inside of the hollow fiber membrane, and raw water It is classified into an internal pressure type which supplies to the inner surface of the hollow fiber membrane and obtains filtered water from the outside of the hollow fiber membrane.

  Specifically, a pressurized external pressure hollow fiber membrane module is a hollow fiber membrane bundle in which hundreds to tens of thousands of hollow fiber membranes stored in a cylindrical container are bundled. The inner wall is bonded with resin to form a partition wall. The resin partition walls at both ends of this hollow fiber membrane bundle have one hollow fiber membrane end opened, the other hollow fiber membrane end sealed, and raw water is pumped into a region sandwiched between both resin partition walls, etc. The hollow fiber membrane is made to permeate by being pressurized and supplied, and the filtered water is taken out to the outside of the resin partition having the hollow fiber membrane end opened.

  Generally, in a pressurized external pressure hollow fiber membrane module, if filtration treatment is continued for a certain period of time, removal objects such as suspended substances in raw water accumulate on the outer surface of the hollow fiber membrane, which is due to the membrane clogging phenomenon. Induces a reduction in filtration flux. Therefore, in order to maintain membrane filtration performance, back pressure washing (hereinafter abbreviated as “back washing”) in which a part of the filtered water flows backward from the inside to the outside of the hollow fiber membrane, or compressive gas is allowed to flow through the hollow fiber membrane. There are used methods such as air scrubbing for supplying the outer surface to swing the hollow fiber membrane, and chemical cleaning for bringing a chemical solution into contact with the hollow fiber membrane. In particular, backwashing and air scrubbing are effective as physical removal methods for suspended solids accumulated between the membrane surface and between membranes. "Simultaneous cleaning" is also carried out (Patent Document 1).

  Normally, backwash wastewater containing raw water at the start of backwashing and suspended substances at the time of backwashing is discharged by overflow from a nozzle provided on the membrane primary side (raw water side) of the hollow fiber membrane module. At the end of backwashing, backwashing wastewater remains on the primary side of the hollow fiber membrane module. Thereafter, when the membrane is swung by air scrubbing, the outer surfaces of the membrane are abraded through suspended substances, the surface pores of the membrane are blocked, and the stability of the filtration operation may be impaired. This is the same in the idle reverse simultaneous cleaning. Moreover, in any cleaning, since the cleaning waste water containing the suspended material separated from the membrane after the cleaning is discharged at once, the suspended material remains in the vicinity of the resin partition wall on the discharge side of the hollow fiber membrane module. .

  Therefore, after the raw water remaining on the membrane primary side of the hollow fiber membrane module is discharged out of the module system before the start of backwashing, backwashing is started (Patent Document 2). It has been found that drain backwashing (Patent Document 3) in which backwashing is performed while discharging outside the module system is effective in removing suspended substances during backwashing.

Japanese Patent No. 3948593 JP 2007-289940 A JP-A-6-170364

  Drain backwashing is an effective cleaning means that can discharge the suspended substances separated during backwashing from the through hole of the lower resin partition wall as needed. In general hollow fiber membrane module structure, Since the drainage port for cleaning wastewater and the air introduction port are the same through-hole, the flow of cleaning wastewater that flows through the through-hole provided in the resin partition wall when air scrubbing is attempted during drain backwashing Since the direction is opposite, the air cannot flow into the module from the through hole, and it is impossible to perform air scrubbing while draining back. This invention solves this subject and provides the hollow fiber membrane module which makes it possible to perform drain backwashing and air scrubbing simultaneously.

  The hollow fiber membrane module of the present invention that solves the above-mentioned problems and achieves the object is such that both ends of a hollow fiber membrane bundle comprising a plurality of hollow fiber membranes having at least one open end are placed inside a cylindrical container by resin partition walls. Bonded and fixed, the resin partition is composed of an opening side resin partition that fixes the hollow fiber membrane with the open end of the hollow fiber membrane open, and a sealing side resin partition that fixes the end of the hollow fiber membrane in a sealed state. In the external pressure type hollow fiber membrane module in which a plurality of through-holes are provided in the sealing side resin partition wall itself, at least one air inlet is provided on the side surface of the container between the resin partition walls of the cylindrical container. .

  According to the hollow fiber membrane module of the present invention, when the external pressure type hollow fiber membrane module that supplies raw water, which is the water to be treated, to the outside of the hollow fiber membrane and performs the filtration process by the external pressure type is used upright, Since air is introduced from above the sealing-side resin partition at the bottom of the module during washing, the buoyancy of the air is not affected by the cleaning water discharged from the sealing-side resin partition at the bottom of the module. Therefore, air scrubbing can be carried out simultaneously with drain backwashing, and the suspendability of the suspended substances can be improved, and a hollow fiber membrane module excellent in stable filtration performance and excellent durability can be provided.

  A cylindrical air dispersion member having a plurality of air diffusion holes is disposed inside the cylindrical container so as to face the air inlet, and the air dispersion member wraps the outer periphery of the hollow fiber membrane bundle. Preferably they are arranged. Thereby, since the introduced air is dispersed around the hollow fiber membrane bundle by the cylindrical air dispersion member, the cleaning effect of the hollow fiber membrane bundle can be increased, and the effect obtained by the present invention is further increased. It is possible to provide a hollow fiber membrane module excellent in stable filtration performance and excellent durability.

  Moreover, it is preferable that the peripheral end portion on the upper end side of the air dispersion member is in contact with the inner peripheral surface of the cylindrical container, and the introduced air will pass only through the air diffusion holes of the air dispersion member, Air can be distributed and supplied around the hollow fiber membrane bundle, and a hollow fiber membrane module excellent in stable maintenance of filtration performance and durability can be provided.

  Furthermore, it is preferable that the peripheral end portion on the lower end side of the air dispersion member is bonded and fixed by the sealing-side resin partition wall, and it is possible to prevent the air dispersion member from rattling or breakage due to air flow, and the filtration performance. A hollow fiber membrane module excellent in stable maintenance and durability can be provided.

It is a schematic sectional drawing which shows an example of embodiment of the hollow fiber membrane module concerning this invention.

  Hereinafter, the hollow fiber membrane module of the present invention will be described with reference to FIG. In addition, this invention is not limited to the following embodiments.

  FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of an external pressure type hollow fiber membrane module according to the present invention. In the hollow fiber membrane module 1, hundreds to tens of thousands of hollow fiber membranes 2 are accommodated in a cylindrical container 3, and hollow fibers are formed by an opening side resin partition wall 4a and a sealing side resin partition wall 4b formed of an adhesive. The end face of the membrane is fixed in the cylindrical container 3. In the opening side resin partition 4a, the end of each hollow fiber membrane 2 is fixed in the cylindrical container 3 in a liquid-tight state in a state of opening toward the outside of the opening side resin partition 4a. On the other hand, in the sealing side resin partition 4b, the end surface of the hollow fiber membrane 2 is bonded and fixed in a sealed state. Further, the sealing side resin partition 4 b includes a plurality of through holes 5.

  The cylindrical container 3 includes at least a raw water supply / drain port 7, a filtrate outlet 6, an air vent 8 and an air inlet 9. The air introduction port 9 is arranged so that air is introduced between the resin partition walls 4a and 4b.

  A cylindrical air dispersion member 10 having a plurality of air diffusion holes 11 is provided inside the air introduction port 9 provided on the inner wall of the cylindrical container 3 so as to face the air introduction port 9. It is arranged to wrap up. Further, the peripheral end portion on the upper end side of the air dispersion member 10 is in liquid-tight contact with the inner peripheral surface of the cylindrical container 3, and the peripheral end portion on the lower end side is bonded and fixed to the sealing-side resin partition 4b. . The peripheral end portion on the lower end side of the air dispersion member 10 may be buried in the sealing-side resin partition 4b.

  Of the hollow fiber membrane 2 in the cylindrical container 3, a region sandwiched between the resin partition walls 4a and 4b is a filtration region. The material of the hollow fiber membrane 2 is not particularly limited, and polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, polyamide, polyetherketone, polyetheretherketone, polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, Examples thereof include cellulose, cellulose acetate, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, and composite materials thereof.

  The hollow fiber membrane 2 is open at least at one end in the length direction. The hollow fiber membrane 2 preferably has an outer diameter in the range of 0.3 to 3 mm. This is because if the outer diameter of the hollow fiber membrane is too small, the hollow fiber membrane may be removed during handling of the hollow fiber membrane when manufacturing the hollow fiber membrane module, or during filtration or washing when using the hollow fiber membrane module. This is because there are problems such as breakage and damage, and conversely, if the outer diameter is too large, the number of hollow fiber membranes that can be inserted into a cylindrical container of the same size is reduced and the filtration area is reduced. The hollow fiber membrane preferably has a thickness in the range of 0.1 to 1 mm. This is because, if the film thickness is too small, there is a problem that the film is broken by pressure, and conversely, if the film thickness is too large, there is a problem that it leads to pressure loss and an increase in raw material cost.

  Moreover, as resin which comprises the resin partition walls 4a and 4b, it is preferable to use polymer materials, such as an epoxy resin, a urethane resin, and an epoxy acrylate resin, which are general-purpose products and are inexpensive and have little influence on water quality.

  Next, as the material of the cylindrical container 3 and the air dispersion member 10, for example, polyolefin such as polyethylene, polypropylene, polybutene, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin (PFA) ), Tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), poly (trifluoroethylene chloride) (PCTFE), ethylene / trifluoroethylene trichloride copolymer Fluorine resins such as coalescence (ECTFE) and polyvinylidene fluoride (PVDF), and chlorine resins such as polyvinyl chloride and polyvinylidene chloride, as well as polysulfone resins, polyethersulfone resins, polyallylsulfone resins, polyphenylether resins, acrylonitrile -Butadiene-styrene copolymer (ABS), acrylonite Ryl-styrene copolymers, polyphenylene sulfide resins, polyamide resins, polycarbonate resins, polyether ketone resins, polyether ether ketone resins, and the like are used alone or in combination. Other than the resin, aluminum, stainless steel, and the like are preferable, and a composite material such as a resin-metal composite, a glass fiber reinforced resin, and a carbon fiber reinforced resin may be used. In production, the cylindrical container 3 is divided and formed into a pipe part and a head part.

  The air introduction port 9 constituting the present invention is provided between the resin partition walls 4a and 4b, and the air compressed for air scrubbing is a hollow fiber membrane through a pipe or tube connected to the air introduction port 9. Supplied in the module. The air inlet 9 is preferably installed in the vicinity of the sealing-side resin partition 4b, and the supplied air is supplied from the vicinity of the sealing-side resin partition 4b disposed on the lower side of the cylindrical container 3 to the cylinder. The entire hollow fiber membrane is swung by moving upward toward the opening-side resin partition 4a disposed on the upper side of the container 3. The degree of air compression is arbitrary, but if it is too high, the hollow fiber membrane will be rubbed and broken. If it is too low, the cleaning effect of air scrubbing will be reduced. The diameter of the air inlet 9 is not particularly limited as long as predetermined compressed air can be obtained, and is appropriately determined in consideration of air dispersibility in the hollow fiber membrane module. The air inlet 9 may be formed by integral molding with the cylindrical container 3 or by forming a screw hole in which a tap is cut in the cylindrical container 3 in advance and installing a nozzle later. Absent.

  The air dispersion member 10 has a plurality of air diffusion holes 11 penetrating the cylindrical side surface. The shape of the air diffuser 11 is arbitrary such as a circle, an ellipse, and a slit. Also, the size of the air diffuser 11 is arbitrary, but the size of about 2 to 10 mm is not easily blocked by the suspended substance, and the air pressure does not decrease during air scrubbing and the cleaning effect does not decrease. This is preferable. The air introduced into the cylindrical container 3 from the air introduction port 9 comes into contact with the hollow fiber membrane 2 through the plurality of air diffusion holes 11 while being dispersed over the outer peripheral surface of the air dispersion member 10. Thereby, air can be distributed and supplied around the hollow fiber membrane bundle, and stable maintenance of the filtration performance and durability can be further improved. Air or oxygen is generally used as air, but nitrogen gas or reaction gas is used when the raw water is a fermentation broth.

  It is preferable that the peripheral end portion on the upper opening side resin partition wall 4a side is liquid-tightly fixed to the inner peripheral surface of the cylindrical container 3. Thereby, the introduced air passes only through the air diffusion holes 11 of the air dispersion member, and the cleaning effect of the air scrubbing can be further enhanced.

  Moreover, it is preferable that the peripheral end part on the lower sealing side resin partition wall 4b side is bonded and fixed to the sealing side resin partition wall 4b, and more preferably buried and fixed. As a result, it is possible to prevent the air dispersion member from rattling or breaking due to air flow, and to maintain stable filtration performance and excellent durability.

  In the hollow fiber membrane module of the present invention, when the raw water is treated, the raw water pressurized from the through-hole 5 formed in the sealing-side resin partition 4b is closed with the air vent 8 and the air inlet 9 closed. , And supplied to the membrane primary side outside the hollow fiber membrane 2 between the resin partition walls 4a and 4b. The raw water is filtered by the hollow fiber membrane 2, the filtered water flows inside the hollow fiber membrane 2, and is sent out from the opening end of the opening-side resin partition 4 a to the outside of the hollow fiber module 1 through the filtered water outlet 6. Since objects to be removed such as suspended substances separated from the filtered water are accumulated outside the hollow fiber membrane 2 between the resin partition walls 4a and 4b, they are filtered out to some extent and then discharged out of the system by a cleaning process.

  Next, the method for cleaning the hollow fiber membrane module having the above-described configuration is performed as follows, for example.

  First, after the filtration step is stopped, the water on the primary side (raw water side) in the hollow fiber membrane module is discharged out of the membrane module system from the raw water supply / drain port 7, so that the water level in the membrane module is lowered, and the hollow fiber membrane The primary side of the film is filled with gas. The water on the primary side of the membrane in the membrane module may remain, but at least half of the hollow fiber membrane is in contact with the gas. Preferably, until the water level becomes 1/3 or less of the vertical length of the hollow fiber membrane, more preferably, the entire membrane is above the water surface, and water is discharged so that the entire membrane is in contact with gas.

  Thereafter, reverse pressure cleaning is performed in which the membrane filtrate is caused to flow backward from the filtrate outlet 6 from the membrane secondary side (filtration side). At this time, the back pressure washing wastewater in the membrane module is drained backwashed to sequentially discharge out of the module system from the through hole 5 formed in the sealing side resin partition wall 4b to the raw water supply / drainage port 7, thereby The suspended substance can be peeled off from the surface of the membrane without being disturbed. Thus, during drain backwashing, if the water pressure is not continuously applied to the primary side of the membrane, the effect of separating the suspended substance from the membrane surface is maintained. It is preferable to maintain the state where the periphery of the primary side of the membrane is in contact with the gas by appropriately controlling the backwash flow rate so as to maintain at least one third of the membrane length.

  The hollow fiber membrane module of the present invention can be subjected to air scrubbing during this drain backwashing, which can further improve the effect of separating suspended substances from the membrane surface. Conventionally, in a general membrane module structure, a plurality of small-diameter through holes 5 provided in the sealing-side resin partition wall 4b serve both as a drainage path for backwashing wastewater and an air introduction path. Even when air for air scrubbing was introduced, air could not be introduced into the membrane module due to backwash drainage flowing downward through the through-hole 5. Therefore, conventionally, after draining the drain backwash, stop the air scrubbing while supplying the raw water, or close the drain valve during the drain backwash and fill the membrane module with the backwash drainage. After scrubbing, the drainage valve was opened again, and the backwash wastewater was discharged out of the membrane module system.

  In the present invention, drain backwashing and air scrubbing are simultaneously performed, and then raw water is supplied to the membrane primary side of the membrane module to return to the normal filtration step. In order to shorten the cleaning time, drain scrubbing may be stopped first, and the air scrubbing may be continued while supplying the raw water with the drain valve closed. Alternatively, the backwash drainage may be discharged again after the drain valve is closed and air scrubbing is continued while the backwash drainage is filled in the membrane module.

  The above cleaning method may be performed every time after the filtration step is completed, or may be performed from time to time in combination with another cleaning method.

  As described above, the hollow fiber membrane module of the present invention can perform air scrubbing while draining back, and can effectively peel off suspended substances on the membrane surface. More stable than the prior art.

  Hereinafter, the present invention will be described with reference to specific examples and comparative examples, but the present invention is not limited to the examples.

Example 1
In a cylindrical container made of polyvinyl chloride having an inner diameter of 190 mm and an overall length of 1100 mm, about 8,000 porous hollow fiber membranes made of polyvinylidene fluoride having an outer diameter of 1.5 mm, an inner diameter of 0.9 mm and a length of about 930 mm are bundled. These hollow fiber membranes were bonded and fixed in a cylindrical container using urethane resin to form resin partition walls 4a and 4b. The hollow fiber membrane end on the opening side resin partition wall 4a side is in the open state, the hollow fiber membrane end on the sealing side resin partition wall 4b side is in the sealed state, and the sealing side resin partition wall 4b has 40 through-holes with an inner diameter of 8 mm. Formed. An air inlet 9 having an inner diameter of 8 mm was formed on the side surface of the cylindrical container at a position 10 mm away from the end surface on the hollow fiber membrane side of the sealing-side resin partition wall 4b toward the hollow fiber membrane side. A cylindrical air dispersion member 10 having an inner diameter of 180 mm and a height of 140 mm was disposed in the cylindrical container 3 in which the air introduction port 9 was formed, with an interval of about 5 mm from the inner wall of the cylindrical container 3. The lower peripheral end portion of the cylindrical air dispersion member 10 was disposed in a state of being buried in the resin partition wall 4b. The air dispersion member was made of polyvinyl chloride, and 30 diffused holes having an inner diameter of 4 mm were formed uniformly on the side surface of the cylinder in the circumferential direction to form one row, which was arranged in four rows in the axial direction.

(Comparative Example 1)
A hollow fiber membrane module having the same structure as that of Example 1 was used except that the air introduction port was provided in the vicinity of the raw water supply / drainage port 7 below the sealing-side resin partition wall 4b.

  Next, the following tests 1 and 2 were carried out for Example 1 and Comparative Example 1.

(Test 1)
Using the hollow fiber membrane module of Example 1 and Comparative Example 1, river water was filtered at a constant flow rate with a membrane filtration flux of 1.5 m ³ / (m ² · d), and 30 minutes after the start of filtration, All the water on the primary side of the membrane was discharged. After that, with the discharge valve communicating with the raw water supply / drain port 7 opened, back-pressure washing of a flux of 2 m ³ / (m ² · d) is started, and at the same time, 50 L / min of air from the air introduction port into the membrane module Introduced and air scrubbed. Back pressure washing and air scrubbing were carried out for 30 seconds and then stopped, and then a series of steps of returning to the filtration step by introducing raw water into the membrane module was repeated.

  As a result, the membrane filtration differential pressure of the membrane module of Example 1 and Comparative Example 1 was 15 kPa immediately after the start of operation, whereas the membrane filtration differential pressure of the membrane module of Comparative Example 1 after 120 months was 120 kPa. It was impossible to operate stably. On the other hand, the membrane module of Example 1 was able to stably operate with a membrane filtration differential pressure of 45 kPa even after 4 months. In the membrane module of Comparative Example 1, the air scrubbing air performed simultaneously with the back pressure cleaning from the beginning was not supplied into the membrane module.

(Test 2)
Next, raw water adjusted to a kaolin concentration of 50 mg / L as a suspended substance is filled into the membrane modules of Example 1 and Comparative Example 1, and the membrane filtration flux is 1.5 m ³ / (m ² · d) for 30 minutes. After performing the constant flow filtration, all the water on the membrane primary side in the membrane module was discharged. Thereafter, the membrane module of Example 1 started the back pressure cleaning of the flux 1.5 m ³ / (m ² · d) with the discharge valve communicating with the raw water supply / drain port 7 opened, and at the same time, 50 L from the air inlet port. / Min air was introduced into the membrane module for air scrubbing. Back pressure cleaning and air scrubbing were stopped 30 seconds after starting. On the other hand, the membrane module of Comparative Example 1 started back pressure washing with a flux of 1.5 m ³ / (m ² · d) with the discharge valve communicating with the raw water supply / drain port 7 open, and the back pressure was 30 seconds later. Washing was stopped. Thereafter, 50 L / min of air was introduced into the membrane module from the air inlet and air scrubbing was performed for 30 seconds. The backwash waste water obtained from Example 1 and Comparative Example 1 was stored in separate tanks in all amounts, and the turbidity exclusion rate was calculated by calculating the turbid mass from the amount of water and turbidity in each tank. The membrane module of 1 was about 95%, whereas the membrane module of Comparative Example 1 was about 80%.

  The hollow fiber membrane module of the present invention can be suitably used for, for example, water purification treatment such as river water, lake water, groundwater, seawater, or membrane separation treatment such as sewage and industrial wastewater.

DESCRIPTION OF SYMBOLS 1: Hollow fiber membrane module 2: Hollow fiber membrane 3: Cylindrical container 4a: Opening side resin partition 4b: Sealing side resin partition 5: Through-hole 6: Filtrated water outlet 7: Raw water supply / drainage port 8: Air venting port 9: Air inlet 10: Air dispersion member 11: Air diffusion hole of air dispersion member

Claims (4)

  Both ends of a hollow fiber membrane bundle composed of a plurality of hollow fiber membranes opened at least at one end are bonded and fixed to the inside of the cylindrical container by resin partition walls, and the resin partition walls open the open end portions of the hollow fiber membranes. It is composed of an opening-side resin partition that is fixed while being opened and a sealing-side resin partition that fixes the end of the hollow fiber membrane in a sealed state, and the sealing-side resin partition itself is provided with a plurality of through holes. In the pressure-type hollow fiber membrane module, the hollow fiber membrane module is characterized in that it has at least one air inlet on the side of the container between the resin partition walls of the cylindrical container.   A cylindrical air dispersion member having a plurality of air diffusion holes is disposed inside the cylindrical container so as to face the air inlet, and the air dispersion member wraps the outer periphery of the hollow fiber membrane bundle. The hollow fiber membrane module according to claim 1, wherein the hollow fiber membrane module is arranged.   The hollow fiber membrane module according to claim 2, wherein a peripheral end portion on an upper end side of the air dispersion member is in contact with an inner peripheral surface of the cylindrical container.   The hollow fiber membrane module according to claim 2 or 3, wherein a peripheral end portion on a lower end side of the air dispersion member is bonded and fixed by the sealing-side resin partition.

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