JP5869375B2 - Seawater infiltration device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a seawater infiltration water intake device that takes in seawater that permeates through a sand filtration layer on the seabed.

  In a seawater desalination plant, which is a representative plant for taking seawater, a reverse osmosis method using a reverse osmosis membrane has become the mainstream in recent years, instead of the evaporative fresh water generation method. In the case of this reverse osmosis method, in order to suppress performance deterioration due to fouling of the reverse osmosis membrane due to impurities, clean seawater with less impurities is required as a pretreatment for desalination.

  As a method for taking seawater, as shown in FIG. 10, for example, a direct water intake method in which seawater is taken from a water intake 1 provided on the seabed through a water conduit 2 is currently widely used. In addition, 3 in FIG. 10 is a pump for taking in seawater, 4 is a reverse osmosis membrane apparatus.

  However, the direct water intake method collects all waste, suspended matter, living organisms, etc. at the same time as seawater, so when the jellyfish or red tide is abnormal, when oil spills occur, or when turbidity increases due to high waves, the water intake is stopped. You may have to. In addition, since marine organisms such as barnacles and mussels are heavily attached to intakes and conduits, the pipe diameter should be taken into account for periodic cleaning, for example, addition of chemicals to prevent adhesion such as chlorine, and biological attachment charges in all pipes. Need to be increased. In addition, when chlorine is introduced into seawater to prevent the adhesion of marine organisms, there is a problem of biofouling in reverse osmosis membranes due to environmental pollution and chlorine. Furthermore, when processing the collected seawater with a reverse osmosis membrane, a sand filtration facility for filtering the seawater to which the flocculant has been added is necessary, and thus a facility for treating the sludge accumulated in the sand filtration facility is necessary.

  Therefore, in recent years, as a pretreatment of the seawater to be taken in, an indirect water intake method in which seawater permeating through the sand filtration layer 5 on the seabed is used as shown in FIG. 11 without using a chemical such as a flocculant. Has been.

  In this indirect water intake method, the seabed is excavated offshore several hundred meters from the shoreline and a depth of several tens of meters, and the excavation part is composed of supporting gravel layers 5a and 5b and filtered sand 5c as shown in FIG. This is a method of taking in the seawater that has been filtered and permeated and purified from the intake pipe 6 installed in the supporting gravel layer 5a by refilling the bottom of the seabed again while forming the sand filtration layer 5. As an example of such an indirect water intake method, the seawater infiltration flow rate expressed in the sand filtration layer on the seabed is 1 to 8 m / day, and the water depth of the sand filtration layer is 50 cm of the sand of the surface layer portion of the sand filtration layer. Patent Document 1 proposes an infiltration water intake method that is deeper than the complete movement limit water depth that moves above and shallower than the surface layer movement limit water depth that moves 1 cm or more.

  However, the osmotic water intake method proposed in Patent Document 1 does not cause the problems seen in the direct water intake method, but the osmotic water intake rate of seawater is a very slow filtration rate of 1 to 8 m / day. In order to take a large amount of seawater in a short period of time, a vast area is required, the construction scale is increased, and the initial cost is increased.

  In addition, the osmotic water intake method proposed in Patent Document 1 accumulates on the surface of the sand filtration layer and causes suspended substances such as silt (hereinafter simply referred to as “suspended substances”) that cause clogging of the filtered sand. )) Is removed using natural waves and currents, so the installation location of the infiltration water intake facilities was limited to sea areas where the flow of seawater due to tidal currents and waves was active.

  Therefore, in order to solve the former problem, the applicant increased the seawater permeation rate to as high as possible at 400 m / day or less, thereby increasing the amount of water intake in a short period of time, and taking water in comparison with the conventional method. A seawater osmotic filtration method was proposed that can significantly reduce the area and significantly reduce the construction scale.

  In addition, in order to solve the latter problem, the applicant stirs the suspended matter taken into the surface layer or the intermediate layer of the sand filtration layer by blowing air from the cleaning pipe embedded in the intermediate layer of the sand filtration layer. We proposed an infiltration unit that can be installed in calm waters where there are few tidal currents and waves.

  However, the high-speed osmotic water intake system provided with the above-described cleaning pipe has the following new problems.

  When the seawater permeation speed is increased to as high as possible at 400 m / day or less, clogging easily proceeds to the inside of the sand filtration layer, and the frequency of clogging increases. However, seawater cannot be taken while air is blown from the washing pipe to wash the sand filtration layer.Therefore, if clogging is prevented by simply increasing the washing frequency, the water intake volume will eventually be reduced. It will cause a decline. That is, in the high-speed osmotic water intake system, it is required to prevent clogging while reducing the frequency of cleaning by the cleaning pipe as much as possible so as not to cause a decrease in the water intake amount.

  Moreover, in the high-speed osmotic water intake system provided with the washing pipe, the suspended matter taken into the sand filtration layer is washed by ejecting air from the washing pipe. However, if the suspended matter rolled up above the sand filtration layer during this washing is quickly collected and discharged out of the system in the intake area, the suspended matter that causes clogging on the surface of the sand filtration layer Will accumulate again and will not be able to maintain a high penetration rate. Therefore, in the high-speed osmotic intake system provided with the washing pipe, a means for collecting the suspended matter rolled up above the sand filtration layer and discharging it out of the system is required.

Japanese Patent No. 3899788

  The problem to be solved by the present invention is that the seawater infiltration device equipped with a conventional cleaning pipe cannot increase the cleaning effect of the sand filtration layer at the time of water intake without increasing the frequency of air cleaning by the cleaning pipe. In addition, there is no means for efficiently collecting the suspended matter wound up above the sand filtration layer during air washing and quickly discharging it out of the system.

  The present invention is capable of generating an artificial seawater flow above the filtration surface, hardly causing clogging of the sand filtration layer, and suspended substances wound up above the filtration surface during air cleaning. An object of the present invention is to provide a seawater infiltration water intake device that can be easily and effectively discharged out of the system of the intake area.

The present invention has been made to achieve the above object,
A water intake pipe that takes in seawater that has permeated through the sand filtration layer on the seabed, and a washing pipe that jets air into the sand filtration layer to wash suspended substances that cause clogging of the sand filtration layer. In the seawater infiltration device provided, a baffle plate having an opening is disposed above the sand filtration layer, and a guide vane that causes a swirl flow on the surface of the sand filtration layer is attached to the baffle plate. Is the most important feature.

  According to the present invention, by arranging the baffle plate having an opening above the sand filtration layer, the flow downward in the vertical direction with respect to the filtration surface is blocked by the baffle plate at the time of water intake. After detouring, it is supplied to the surface of the sand filtration layer. At this time, since a shear flow in the horizontal direction is generated on the surface of the sand filtration layer and water is taken in while stirring the filtration surface, the effect of preventing clogging is enhanced as compared with the case where no baffle plate is provided.

  That is, the baffle plate generates a shear flow in the direction intersecting the seawater permeation direction on the surface of the sand filtration layer during intake of seawater.

  Further, according to the present invention, by disposing a baffle plate having an opening above the sand filtration layer, the suspended matter wound up above the sand filtration layer during air washing is ejected from the washing tube. The air can be forcibly raised in the direction of the opening with the air. Suspended substances can be collected by this air lift effect and discharged out of the system through the opening.

  That is, the baffle plate receives the suspended matter rolled up above the sand filtration layer at the time of washing the sand filtration layer on the lower surface of the baffle plate, and together with the air ejected from the washing pipe, Collecting in the direction of the opening and discharging upward from the opening.

  In the present invention, the baffle plate having the opening disposed above the sand filtration layer generates a shear flow in the direction intersecting the seawater infiltration direction on the surface of the sand filtration layer at the time of water intake. The effect of washing the surface of the sand filtration layer is obtained. Therefore, the seawater infiltration rate can be maintained at a high speed without increasing the frequency of air cleaning from the cleaning pipe.

  Further, in the present invention, a baffle plate having an opening disposed above the sand filtration layer captures suspended substances rolled up above the sand filtration layer and ejects them from the washing pipe when the sand filtration layer is washed. Since the air is raised in the direction of the opening by being accompanied by the air, it can be quickly discharged out of the system from the opening. Therefore, since the suspended matter wound up above the sand filtration layer does not accumulate again on the surface of the sand filtration layer, the seawater permeation rate can be maintained at a high speed.

  Since the present invention can maintain the seawater permeation speed at a high speed, the effect becomes remarkable when applied to a high-speed permeation water intake system. Specifically, the seawater permeation rate of the sand filtration layer is preferably higher than at least 8 m / day in the range of 400 m / day or less.

It is sectional drawing which looked at an example of the seawater penetration water intake device of the present invention from the direction of the side, (a) is a figure explaining the operation of a baffle plate at the time of water intake, (b) The operation of the baffle plate at the time of air washing is explained It is a figure to do. It is explanatory drawing of the analysis model which confirmed the effect of the baffle with the simulation by CFD (Computational Fluid Dynamics), (a) is the whole figure which arrange | positioned the baffle of the same size above the intake area of 4m x 4m, (b ) Is a diagram showing one of the analysis models of (a) divided into four equal parts. It is explanatory drawing of the Example which provided the check valve in the opening part of the baffle plate, (a) is a figure of the state by which the check valve was closed, (b) is the check valve open | released, and the osmosis | permeation direction of seawater It is a figure of the state in which the flow of water of the opposite direction has arisen. It is explanatory drawing of the Example which attached the guide vane to the baffle plate, (a) is a figure which shows the attachment position of the guide vane in the analysis model of CFD, (b) is the velocity vector of the filtration surface at the time of providing a guide vane. (C) is a figure explaining the attachment angle of a guide vane, (d) is a velocity vector figure in the case of not providing a guide vane. It is explanatory drawing of the Example which provided the air supply pipe which blows air in the lower surface side of a baffle plate, (a) is a figure explaining the effect | action of the air supply pipe at the time of water intake, (b) Air supply at the time of air washing It is a figure explaining the effect | action of a pipe | tube. It is explanatory drawing of the Example which provided the air supply pipe so that the inner surface of the cylinder which comprises an opening part may be followed, and is the figure which showed the cross section of the horizontal direction of a cylinder. (A) is explanatory drawing of the Example which provided the collecting pipe which takes in the suspended substance discharged | emitted upwards from an opening part at the time of air washing, (b) is an Example of the Example which combined the air supply pipe and the collecting pipe It is explanatory drawing. It is explanatory drawing of the Example which supports a baffle plate in the housing | casing of a unit type seawater osmosis intake device, (a) is the figure which showed the cross section in the AA 'line of a top view, (b) is a top view The figure which showed the cross section in the BB 'line, (c) is the figure seen from the direction of the plane. It is the figure which looked at the piping of the unit type seawater infiltration water intake device from the direction of a plane, (a) is a top view of a washing pipe, (b) is a top view of water intake piping. It is a schematic explanatory drawing of the conventional direct water intake method. It is a schematic explanatory drawing of the conventional indirect water intake method. It is explanatory drawing of the sand filtration layer formed in the excavation part of the seabed.

  The present invention is an air-washing type seawater infiltration device equipped with a washing pipe, which prevents clogging of the sand filtration layer even when the seawater infiltration rate is increased as high as possible, for example, 400 m / day or less. The purpose of maintaining the above was realized by arranging a baffle plate having an opening above the sand filtration layer.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS.
In FIG. 1, reference numeral 11 denotes an intake pipe 12 embedded in a supporting gravel layer of the sand filtration layer 31 for taking in seawater that has permeated the sand filtration layer 31 from the sea, and a filtration sand layer of the sand filtration layer 31. This is a seawater infiltration device of the present invention comprising a washing tube 13 for jetting air and washing suspended substances such as silt that cause clogging of the sand filtration layer 31, above the sand filtration layer 31. A baffle plate 14 having a plate member 14b that covers the upper side of the water intake area is disposed in the center portion with an opening portion 14a formed in the vertical direction by the cylindrical body 14c.

  The intake pipe 12 is composed of a main pipe and a branch pipe provided with a number of intake holes. By connecting the main pipe to a water collecting pump, the intake water is taken into the sand filtration layer 31 from the sea. is there.

  The cleaning pipe 13 is composed of a main pipe and a branch pipe provided with an air ejection hole. By connecting the main pipe with an air compressor, air is periodically ejected from the air ejection hole to The suspended matter taken in is stirred and rolled up into the sea above the sand filtration layer 31 and washed together with the suspended matter deposited on the surface of the sand filtration layer 31.

  The plate member 14b of the baffle plate 14 disposed above the sand filtration layer 31 is not disposed in parallel with the filtration surface of the sand filtration layer 31, but as shown in FIG. 1 (a), the position of the opening 14a. Is sloped so that is the highest. The inclination angle of the plate member 14b with respect to the horizontal plane is, for example, in the range of 1 to 5 °.

  As described above, the baffle plate 14 includes the plate member 14b having a shape in which the apex of the quadrangular pyramid is cut out (hereinafter, the shape in which the apex of the pyramid is cut out is not limited to the quadrangular pyramid is referred to as “a truncated pyramid”). In addition, an opening 14a is provided in the wharf portion of the plate member 14b (the portion in which the apex of the pyramid is cut off).

  In the present invention, the baffle plate 14 having such a shape is provided above the water intake area, so that the intake water is largely detoured so as to go around from the tip of the plate member 14b of the baffle plate 14 and supplied to the filtration surface of the filtration layer 31. Is done. Therefore, as shown to Fig.1 (a), the flow of a horizontal direction generate | occur | produces above the sand filtration layer 31, filtering is performed, giving a shear flow to the filtration surface and stirring.

  In other words, when the baffle plate 14 is not provided, the intake seawater flows downward in the vertical direction with respect to the filtration surface, and all components that cause clogging contained in the seawater are captured on the filtration surface. While clogging proceeds, in the present invention, the flow of horizontal seawater is generated above the sand filtration layer by the action of the baffle plate 14, so that the filtration surface can be obtained even during intake by performing this cross-flow filtration. Increases the cleaning effect.

  Therefore, in the present invention, even when performing high-speed filtration, it is not necessary to increase the frequency of air cleaning by the cleaning tube 13, and the cleaning interval can be extended.

  The position in the height direction of the baffle plate 14 is the same as the filtration surface at the end of the plate member 14b so that a shear flow is preferably generated in the direction intersecting the seawater infiltration direction on the surface of the sand filtration layer 31 at the time of water intake. The baffle plate 14 is arranged so that the height between them is in the range of 0.1 to 1 m, for example.

  But it is necessary to design the distance between filtration surfaces according to the conditions of a water intake area and the seawater penetration speed. As an example, when the intake area is 10 m × 10 m, the seawater infiltration rate is 100 m / day, and the shear inlet flow velocity is designed to be 0.5 m / second, filtration at the end of the plate member 14b is performed. The height between the surfaces is 0.139 m.

  Next, the operation of the baffle plate 14 during air cleaning will be described. As already described, the baffle plate 14 of this embodiment has a truncated pyramid-shaped plate member 14b, and an opening 14a is provided in the truncated portion of the plate member 14b.

  In the present invention, when the baffle plate 14 having the above-described shape is disposed above the water area, when the sand filtration layer 31 is air-washed by ejecting air from the cleaning pipe 13, the upper side of the sand filtration layer 31. The suspended matter S wound up is not diffused around the water intake area and can be received by the lower surface 14ba of the plate member 14b as shown in FIG. Further, the air A ejected from the cleaning tube 13 is also present below the plate member 14b.

  Since the baffle plate 14 has the highest shape where the opening 14a exists, the air A floats and gathers in the direction of the opening 14a. At this time, since the suspended matter S is also raised, the suspended matter S can also gather in the direction of the opening 14a and be discharged to the upper side of the baffle plate 14 together with the air A through the opening 14a.

  The suspended matter S discharged above the opening 14a in this way is shielded by the baffle plate 14 and therefore does not accumulate on the surface of the sand filtration layer 31 again. Therefore, in the present invention, the suspended matter S wound up above the sand filtration layer 31 during air cleaning can be efficiently collected by the baffle plate 14 and quickly discharged out of the system from the opening 14a.

  The size of the opening 14a needs to be designed according to the size of the water intake area and the amount of air ejected from the cleaning tube 13 so that the suspended matter S is smoothly discharged upward from the opening 14a during air cleaning. However, if an example in the case where a water intake area is 10m x 10m is given, it can be set as the range of (phi) 100-200cm.

  In addition to suspended substances that cause clogging during air cleaning, there are some substances that do not cause clogging, but rather have a large particle size necessary to maintain the filtration effect of the sand filtration layer 31. include. However, such a substance having a large particle size does not rise with the air A, and deposits on the sand filtration layer 31 after a predetermined time. Therefore, in the present invention, a substance having a large particle size necessary for maintaining the filtration effect can be left in the sand filtration layer 31.

  FIG. 2 is an explanatory diagram of an analysis model when the effect at the time of water intake by the baffle plate 14 is confirmed by simulation using CFD (Computational Fluid Dynamics). In the analysis model, as shown in FIG. 2A, the length of the side of the water intake area 32 is L1 and L2 are 4 m × 4 m in size, and the baffle plate 14 of the same size is disposed above the side.

  As shown in FIG. 2 (b), the height between the baffle plate 14 and the surface of the water intake area 32 is 1.2m at the position of the opening 14a, and the height at the end of the plate member 14b. H2 was set to 1 m. The seawater penetration rate was 100 m / day.

  Using this analysis model, the results of CFD simulations of the flow of seawater above the filtration surface with and without the baffle 14 are compared. When the baffle 14 is provided, the horizontal direction is above the filtration surface. It was confirmed that an effect of stirring the filtration surface was obtained.

  FIG. 3 is an explanatory diagram of an embodiment in which a check valve 15 is provided in the opening 14 a of the baffle plate 14. In the present invention, the intake seawater should be detoured around the end of the baffle plate 14 and flow in the horizontal direction above the filtration surface. Therefore, the intake seawater flows downward from above the opening 14a in the vertical direction. It is more preferable to provide means for preventing this.

  Therefore, in the embodiment of FIG. 3, a check valve 15 that allows only the flow of water in the direction opposite to the infiltration direction of seawater is provided in the opening 14a. The check valve 15 may be provided at the upper end of the cylindrical body 14c of the embodiment of FIG.

  Therefore, in the embodiment of FIG. 3, even when a flow of seawater that attempts to flow backward through the opening 14 a temporarily occurs during intake, as shown in FIG. Since the reverse flow is interrupted by closing, the horizontal shear flow is not disturbed below the baffle plate 14. Further, while the horizontal flow is favorably generated below the baffle plate 14, as shown in FIG. 3B, a part of the seawater that has not been taken up pushes the check valve 15 to open the opening. It flows above 14a and circulates.

  FIG. 4 is an explanatory diagram of an embodiment in which the guide vanes 16 are attached to the baffle plate 14. In the present invention, the seawater that flows from the end of the baffle plate 14 and flows in the horizontal direction above the filtration surface is swirled in either the left or right direction so as not to interfere with each other. Rise.

  Therefore, in the embodiment of FIG. 4, guide vanes 16 that cause a swirl flow on the surface of the sand filtration layer 31 are attached to the baffle plate 14. If the guide vane 16 is, for example, a baffle quadrangular pyramid-shaped baffle plate 14, as shown in FIG. 4A, the guide vane 16 intersects the surface of the plate member 14 b inward from the corner of the plate member 14 b. Install. Moreover, as shown in FIG.4 (b), it attaches to all the four corner | angular parts of the board member 14b.

  The effect when this guide vane 16 was provided was confirmed by CFD simulation. 4 (b) and 4 (d) are velocity vector diagrams. In FIG. 4 (b) where the guide vane 16 is provided, the shear flow swirls in the central portion of the filtration surface, and the guide vane 16 is not provided. It was also confirmed that the stirring effect is enhanced.

  FIG. 4C is a view for explaining the mounting angle of the guide vane 16 at the corner of the baffle plate 14. Since the guide vanes 16 generate a swirling flow in either the left or right direction on the filtration surface, the angles θ1 and θ2 formed with the sides of the baffle plate 14 are not equal angles but are provided with a difference. Is preferred.

  Specifically, as a condition for generating a swirling flow of seawater above the filtration surface, the smaller angle θ1 is in the range of 0 to 40 °. In addition, θ1 is more preferably in the range of 20 to 30 ° in order to further enhance the stirring effect.

  FIGS. 5 and 6 are explanatory views of an embodiment in which an air supply pipe 17 for blowing air is provided on the lower surface 14ba side of the baffle plate 14. In the present embodiment, the air supply pipe 17 is provided at a position below the opening 14a so that air can be directly blown into the opening 14a, and the air A is supplied even during water intake. The air supplied from the air supply pipe 17 is branched from the cleaning pipe 13 and supplied.

  In the case of such a configuration, as shown in FIG. 5A, the air A supplied from the air supply pipe 17 immediately rises inside the cylindrical body 17c, and air bubbles are generated in the opening 14a even during water intake. Ascending seawater flow is generated. Therefore, the flow of the horizontal seawater at the time of water intake above the sand filtration layer 31 becomes smooth, and a part of suspended matter generated when the filtration surface is stirred and washed by the shear flow is discharged from the opening 14a. You can also

  Further, according to the present invention, the suspended substance S is raised by being accompanied by the air ejected from the cleaning tube 13 during cleaning. As shown in FIG. 5B, the air is supplied from the air supply tube 17 during cleaning. Since the air lift effect is promoted by supplying A, the discharge capacity of the suspended solid S is further improved.

  When the air supply pipe 17 is provided, the cylindrical body 14c having a required length in the seawater infiltration direction constitutes the opening 14a, and the air supply pipe 17 is supplied as shown in FIG. It is preferable to provide the air along the inner surface of the cylindrical body 14c so that the air rises while turning in the cylindrical body 14c, because the seawater rising effect associated with the rising of the bubbles increases.

  FIG. 7A is an explanatory diagram of an embodiment in which a collecting pipe 18 that takes in the suspended matter S discharged upward from the opening 14a when the sand filtration layer 31 is washed is provided. In the present invention, during air cleaning, the suspended matter S wound up above the sand filtration layer 31 is discharged upward from the opening of the baffle plate 14 by the air lift effect.

  Since the suspended matter S discharged from the opening 14a is collected by the baffle plate 14 and the suspended components are concentrated, the cylindrical body 14c does not adversely affect the environment around the water intake area. It is desirable to collect by the collecting pipe 18 connected to and transport to the sea surface for separation and recovery. In addition, if such a collecting pipe 18 is provided, it is easy to install the sand filtration layer 31 even in a sea area where the flow rate of the seawater in which the suspension material S is not expected to diffuse due to tidal currents or waves is low.

  Further, the configuration using the collecting pipe 18 may be combined with the configuration using the air supply pipe 17 as shown in FIG.

  8 and 9 are explanatory views of an embodiment in which the seawater infiltration water intake device 11 is unitized. 8 (a) and 8 (b), a reference numeral 12 includes a main pipe 12a and a plurality of branch pipes 12b branched in a direction intersecting the main pipe 12a, and a supporting gravel layer 34 for forming a deep layer of the sand filtration layer. The intake pipe embedded in is shown. The filtration sand layers 33a to 33c for forming the intermediate layer and the surface layer of the sand filtration layer are embedded with a main pipe 13a and a cleaning pipe 13 composed of a plurality of branch pipes 13b branched in a direction intersecting the main pipe 13a. .

  This seawater infiltration device 11 is formed in advance with a unit type seawater infiltration device 11 in which an intake pipe 12 is embedded in a supporting gravel layer 34, a cleaning pipe 13 is embedded in a filtration sand layer 33, and is required at an installation location on the seabed. The sand filtration layer is formed by combining the number of unit type seawater infiltration water intake devices 11, and the seawater that has permeated the sand filtration layer from the sea is taken in by the water intake pipe 12. An opening portion 14a is formed in the vertical direction by a cylindrical body 14c at the center, and the baffle plate 14 having a truncated pyramid-like plate member 14b is disposed above the surface layer 33a of the filtration sand layer 33 so as to be unit type. It is supported by the corners 19 a to 19 d of the casing of the seawater infiltration device 11. Therefore, a gap exists between the uppermost part of the side surface of the housing and the baffle plate 14 as shown in FIGS.

  In the branch pipe 13b of the cleaning pipe 13, as shown in FIG. 9A, a large number of ejection holes 13ba are arranged in a row at a position on the top side when installed on site. In the present embodiment, the ejection angle of the ejection hole 13ba is set to be 90 degrees with respect to the horizontal plane. The land side of the main pipe 13 is connected to an air compressor of a seawater desalination plant. The air supplied from the main pipe 13a to each branch pipe 13b is ejected in the vertical direction from the ejection hole 13ba to the top side. In the present embodiment, as an example, the ejection hole 13ba is provided in the direction toward the top when installed on site, but the ejection hole 13ba of the cleaning tube 13 is, for example, downward when installed on site. It may be configured.

    FIG. 9B is a plan view of the intake pipe 12, and the branch pipe 12b is provided with a large number of intake holes over the entire surface. The land side of the main pipe 12a is connected to a water collection pump of a seawater desalination plant. Seawater that has naturally permeated through the sand filtration layer is introduced into the branch pipe 12b through the water intake hole, and taken into the seawater desalination plant through the main pipe 12a.

  The present invention prevents clogging by the action of the baffle plate 14 and can maintain the seawater infiltration rate at a high speed, so that the seawater infiltration rate is higher than that of a conventional infiltration water intake system of 8 m / day. The effect becomes remarkable when applied to the system.

  However, according to the results of the inventors conducting a test using groundwater having higher permeability than seawater, it was possible to continuously operate normally up to 600 m / day, but the penetration rate was 700 m / day. In the case of the day, the required amount of purified water was larger than the amount of water taken, and water could not flow continuously in the sand filtration layer, and normal water intake was not possible. Therefore, in the present invention intended for infiltration of seawater, it is preferable that the safety factor is about 1.5 and the upper limit of the seawater infiltration rate is 400 m / day.

  In the present invention, when the seawater infiltration rate is 400 m / day, for example, the amount of water intake is 50 times that of the conventional seawater infiltration rate of 8 m / day, so the area of the intake area can be reduced to 1/50. it can. In addition, since the sand filtration layer can be installed in the sea area where the flow of seawater is small, the present invention can install an infiltration water intake facility near the seawater desalination plant. As a result, the scale of construction and water intake facilities can be reduced, and the impact on the surrounding environment during construction can be alleviated.

Specifically, for example, when the seawater permeation rate is 100 m / day and the permeation area per unit of the unit-type seawater permeation intake device 11 is 30 m ² (10 m × 3 m), the water collection amount per unit is 3000 m. ³ / day. For example, when 35 such unit-type seawater infiltration devices 11 are arranged in the lateral direction, a water intake of about 100,000 t / day is obtained in a water intake area of 10 m × 105 m which is much more compact than before. It is done.

  The present invention is not limited to the above examples, and it is needless to say that the embodiments may be changed as appropriate within the scope of the technical idea described in each claim.

  For example, the shape of the baffle plate is not limited to the truncated pyramid shape as shown in the embodiment, but may be a truncated cone shape as necessary.

  Moreover, although the example which provides an opening part in the center part of a baffle plate was disclosed in said Example, the position which provides an opening part is not restricted to this. Moreover, although the example which provides one opening part in a baffle plate was disclosed in said Example, you may provide a some opening part in one baffle plate.

DESCRIPTION OF SYMBOLS 11 Seawater infiltration water intake device 12 Water intake piping 13 Washing pipe 14 Baffle plate 14a Opening part 14b Plate member 14ba Lower surface 14c Cylindrical body 15 Check valve 16 Guide vane 17 Air supply pipe 18 Collecting pipe 31 Sand filtration layer A Air S Suspension material

Claims (10)

A water intake pipe that takes in seawater that has permeated through the sand filtration layer on the seabed, and a washing pipe that jets air into the sand filtration layer to wash suspended substances that cause clogging of the sand filtration layer. In the seawater infiltration device provided, a baffle plate having an opening is disposed above the sand filtration layer, and a guide vane that causes a swirl flow on the surface of the sand filtration layer is attached to the baffle plate. Seawater infiltration water intake device characterized by   2. The seawater infiltration device according to claim 1, wherein the baffle plate generates a shear flow in a direction intersecting a seawater infiltration direction on the surface of the sand filtration layer when intake of seawater.   The baffle plate receives the suspended matter rolled up above the sand filtration layer at the time of washing the sand filtration layer on the lower surface of the baffle plate, and the opening portion together with the air blown from the washing pipe The seawater infiltration water intake device according to claim 1 or 2, wherein the seawater infiltration water intake device is configured to be gathered in the direction of and discharged upward from the opening.   The seawater infiltration water intake device according to any one of claims 1 to 3, wherein the seawater infiltration rate of the sand filtration layer is higher than at least 8 m / day in a range of 400 m / day or less.   5. The baffle plate according to claim 1, wherein the baffle plate has a truncated pyramid-shaped or truncated-cone-shaped plate member, and the opening is provided in the truncated portion of the plate member. Seawater infiltration water intake device. The seawater infiltration water intake device according to any one of claims 1 to 5 , wherein an air supply pipe for blowing air is provided on a lower surface side of the baffle plate. The seawater infiltration water intake device according to claim 6 , wherein the air supply pipe is provided at a position where air can be directly blown into the opening. The cylindrical portion having a required length in the seawater infiltration direction constitutes the opening, and the air supply pipe is arranged so that the supplied air rises while turning in the cylindrical body. The seawater infiltration water intake device according to claim 7 , wherein the seawater infiltration water intake device is provided so as to be along the inner surface. The seawater infiltration water intake device according to any one of claims 1 to 8 , further comprising a collecting pipe that takes in the suspended matter discharged upward from the opening when the sand filtration layer is washed. The seawater infiltration water intake device according to any one of claims 1 to 9 , wherein a check valve that allows only a flow of water in a direction opposite to a seawater infiltration direction is provided in the opening.

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