JP2007113295A - Air lift pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air lift pump which exerts its ability of excavating ballast, sediment, sludge, etc. that are deposited and hardened on a subaqueous bottom over a long time. <P>SOLUTION: The air lift pump 10 is formed of: a riser pipe 11 whose lower-end header 12 reaches as far as the subaqueous bottom 2; a nozzle 14 which is enclosed by the header 12 and sprays high-pressure fluid containing air at least as part of the fluid, to the subaqueous bottom; a compressor 15 and a high-pressure water pump 16 for feeding compressed air and high-pressure water to the nozzle 14, respectively; and a rotary blade 20 which receives a turning force from a fluid turbine 30 rotated by the high-pressure fluid, and cuts away a subaqueous bottom forming material. The rotary blade 20 is arranged at the center of the header 12, and carries out excavation of a central area. Then rotating flow is formed around the rotary blade by the high-pressure fluid from the nozzle 14, and the rotating flow carries out excavation of an area other than the central area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air lift pump that collects sand and sludge from the bottom of the water.

One type of device used to drown the bottom of seas, lakes, rivers, etc. is an air lift pump. This is because a nozzle is placed at the tip of the pipe lowered to the bottom of the water and high pressure compressed air is blown into the pipe from this nozzle to excavate the bottom of the water. Is collected on the surface of the water. Examples of air lift pumps can be found in Patent Documents 1 and 2.
Japanese Patent Laid-Open No. 5-311695 (page 2 to page 3, FIG. 1 to FIG. 2) JP 2001-162109 A (page 3 to page 4, FIGS. 1 to 7)

  In an air lift pump, a plurality of nozzles are usually arranged in a bowl shape to form a swirling flow of air and water, thereby increasing the excavation capacity. The air lift pump described in Patent Document 1 does not leak to that example. However, even with such ingenuity, the appropriate excavation capability can be expected only at the location where the air jet ejected from the nozzle directly hits and at the location where the swirling flow formed by the air jet has a high flow velocity, and is long on the bottom of the water. It was difficult to say that it had sufficient excavation capacity for gravel sand and mud that had accumulated and solidified for a period of time.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an air lift pump that exhibits excavation ability even for gravel sand, mud, sludge and the like that have accumulated and solidified on the bottom of the water for a long time.

  (1) In order to achieve the above object, the present invention provides a riser pipe whose lower end reaches the bottom of the water, a nozzle for supplying a high pressure fluid at least part of which is air to the bottom of the water surrounded by the riser pipe, A high-pressure fluid source for supplying a high-pressure fluid, an air lift pump that separates a water bottom constituent material from the water bottom with a high-pressure fluid and raises the inside of the riser pipe together with air and collects it on the water surface. It is characterized by arranging a rotating blade that is rotated by the step of scraping off the water bottom constituent material.

  According to this configuration, the rotating blade that mechanically scrapes the bottom material, such as gravel sand, mud, sludge, etc., is arranged in the riser pipe, so even if the bottom material is solidified, it is surely stripped. And can be collected.

  (2) Further, the present invention is characterized in that, in the air lift pump having the above-described configuration, the rotating blade is given a rotational force from a fluid turbine rotating with a high-pressure fluid.

  According to this configuration, since the fluid turbine is used as the power source of the rotating blade, the high-pressure fluid can be used for driving the fluid turbine, the configuration is simplified, and it is exceptionally suitable for power supply in water like an electric motor. This makes it suitable for underwater use.

  (3) Further, the present invention is characterized in that, in the air lift pump configured as described above, the rotating blade is disposed in a central portion of the riser pipe, and a swirling flow is formed around the periphery by the high-pressure fluid from the nozzle. .

  According to this configuration, excavation of the central portion of the riser pipe is handled by the rotating blade, and excavation other than the central portion is handled by the swirling flow by the high-pressure fluid, so that the entire excavation of the riser pipe can be reliably performed.

  (4) Further, the present invention is characterized in that, in the air lift pump configured as described above, the rotating blade is rotated by being pushed by a high-pressure fluid ejected from the nozzle.

  According to this configuration, the rotating blade can be rotated without using a complicated drive mechanism. Since the mechanism is simple, there are few failures even when used for excavation of gravel sand, mud, sludge, etc.

  (5) Further, in the air lift pump having the above configuration according to the present invention, the rotary blade has a flange portion protruding rearward in the rotation direction, and air in the high-pressure fluid is contained in the flange portion with a bubble of a certain size or less. A plurality of through-holes that are allowed to pass through in the form are formed.

  According to this configuration, when the air separated from the high-pressure fluid rises following the rotating blade, it passes through the through hole of the flange and becomes a bubble of a certain size or less. By generating a large number of such small air bubbles, the water in the riser pipe can be pushed up steadily at a constant pace.

  (6) Further, the present invention is characterized in that, in the air lift pump configured as described above, a flange portion for preventing burial is formed on the outer periphery of the lower end of the riser pipe.

  According to this configuration, the riser pipe is not excessively buried in the water bottom constituent material, and excavation at an appropriate depth can be performed.

  (7) Moreover, the present invention is characterized in that, in the air lift pump configured as described above, a peripheral edge of the flange portion is raised.

  According to this configuration, the riser pipe can be smoothly moved in the horizontal direction because the peripheral edge of the flange portion is hardly caught by the unevenness of the water bottom.

  (8) Further, the present invention is characterized in that, in the air lift pump having the above configuration, the flange portion is connected to the riser pipe via a flexible portion.

  According to this configuration, the flange portion changes its inclination according to the undulation of the bottom of the water, so that the flange portion is always in close contact with the bottom of the water and rarely leaks the vortex of the high-pressure fluid to the outside.

  (9) Further, the present invention is characterized in that, in the air lift pump configured as described above, a side opening for taking in the water bottom constituent material is formed at the lower end of the riser pipe.

  According to this configuration, the water bottom constituent material can be taken in from the side opening of the riser pipe, and it can be shredded by the rotating blade, and then collected.

  (10) In the air lift pump having the above-described configuration, the present invention is characterized in that a shutter that closes the side opening for a specific period during rotation is formed on the outer peripheral portion of the rotating blade.

  If there is a side opening in the riser pipe, it is inevitable that high pressure fluid or air bubbles will leak from it. According to this configuration, the side opening is closed by the shutter for a specific period during the rotation of the rotary blade, so that the high-pressure fluid and the air bubbles can be fully utilized for rolling up and floating the bottom material.

  (11) The present invention is also characterized in that, in the air lift pump configured as described above, the rotating blade protrudes downward from the lower end of the riser pipe by a predetermined length.

  According to this configuration, the flatness of the bottom of the water is high, and even when the bottom of the water does not enter the riser pipe, the bottom can be reliably excavated with the rotating blade.

  According to the present invention, the water bottom constituent material can be reliably subdivided and collected by the rotating blade. Further, since the rotary blade is rotated by the high pressure fluid, the high pressure fluid source for the nozzle can be used also as the power source of the rotary blade, and the configuration is simplified. Further, the excavation of the central portion of the riser pipe is handled by the rotating blade, and the excavation other than the central portion is handled by the swirling flow by the high-pressure fluid from the nozzle, so that the excavation can be reliably performed on the entire surface of the riser pipe.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 is a vertical sectional view showing a schematic configuration of an air lift pump, FIG. 2 is a horizontal sectional view of a lower end portion of the air lift pump, and FIG. 3 is an effect of a combination of a type of fluid ejected from a nozzle and a type of fluid for rotating a turbine. It is a table | surface which shows a difference.

  The air lift pump 10 includes a riser pipe 11 that is vertically lowered from the top of the water surface 1 toward the bottom 2. The material constituting the bottom 2 is assumed to be sludge. The lower end of the riser pipe 11 reaches the water bottom 2, and the lower end portion is a header portion 12 that extends downward in a tapered shape. A flange portion 13 is formed on the outer periphery of the lower end of the header portion 12. The flange portion 13 is for increasing the ground contact area to the water bottom 2 to prevent burial.

  A nozzle 14 is disposed in the header portion 12. The nozzle 14 is used for excavation by blowing a high-pressure fluid to the bottom 2. As seen in FIG. 2, the nozzle 14 is arranged so as to eject a high-pressure fluid in the tangential direction of the inner peripheral surface of the header portion 12 and form a swirling flow along the inner peripheral surface of the header portion 12. A plurality of nozzles 14 are arranged around the center of the header portion 12 to generate a powerful swirling flow. In the first embodiment, two nozzles 14 which are the minimum unit are arranged.

  The high pressure fluid supplied to the nozzle 14 must be at least partially air. Needless to say, this is to produce an airlift effect. Therefore, a compressor 15 and a high-pressure water pump 16 are prepared as high-pressure fluid sources. The compressor 15 pumps compressed air to the nozzle 14 through the air pipe 17, and the high-pressure water pump 16 pumps high-pressure water to the nozzle 14 through the water pipe 18.

  A rotating blade 20 is disposed at the lower center of the header portion 12. The rotary blade 20 is formed by arranging the excavating blades 22 radially on the lower surface of a horizontally arranged disc 21. The lower end of the excavation blade 22 protrudes downward by a predetermined length h from the lower end of the riser pipe 11, that is, the lower end of the header portion 12.

  The rotating blade 20 is rotated by a fluid turbine 30 disposed at the center of the riser pipe 11. The fluid turbine 30 is fixed to the housing 32 supported by the riser pipe 11 by a hollow strut 31, a vertical hollow rotating shaft 33 rotatably supported in the housing 32, and the outside of the hollow rotating shaft 33. It consists of a rotor 34. A sheath shaft 35 protrudes downward from the lower end of the housing 32. The hollow rotary shaft 33 extends downward through the sheath shaft 35, and is connected to the rotary blade 20 when it exits the sheath shaft 35. It is the compressed air supplied through the air pipe 17 that rotates the rotor 34. Note that the rotor 34 may be rotated by high-pressure water supplied through the water pipe 18.

  The operation of the air lift pump 10 is as follows. When the header portion 12 of the riser pipe 11 is placed on the bottom 2 as shown in FIG. 1 and the compressor 15 and / or the high-pressure water pump 16 is driven, only compressed air, only high-pressure water, or compressed air and high-pressure water are discharged from the nozzle 14. Mixed high-pressure fluid is ejected. A compressed air nozzle and a high-pressure water nozzle that are independent of each other may be provided, and the compressed air and the high-pressure water may be ejected independently. The jetted high-pressure fluid forms a swirling flow as shown by an arrow in FIG. Thereby, a peripheral part is excavated among the circular water bottoms surrounded by the header part 12. The air that has finished the role of excavation becomes an air bubble 4 and rises in the riser pipe 11. As the water pressure increases, the volume of air bubbles gradually increases.

  On the other hand, the compressed air from the compressor 15 or the high-pressure water from the high-pressure water pump 16 collides with the rotor 34 of the fluid turbine 30 and rotates it. As a result, the hollow rotary shaft 33 rotates and the rotary blade 20 also rotates. The compressed air or high-pressure water that gives energy to the rotor 34 passes through the hollow rotary shaft 33 and is diffused into the water from the center of the rotary blade 20. The rotary blade 20 excavates the central part of the water bottom surrounded by the header portion 12 with the excavation blade 22. Since the excavation blade 22 protrudes downward by a length h from the lower end of the header portion 12, the flatness of the bottom 2 is high, and even when the sludge does not enter the header portion 12, the sludge is reliably excavated. Can do.

  Thus, the sludge pieces 3 excavated by the rotary blade 20 in the central portion of the header portion 12 and excavated by the swirling flow of the high-pressure fluid around the header portion 12 rise in the riser pipe 11. Ascends in an updraft mixed with air bubbles 4. Then, after overflowing from the upper end of the riser pipe 11, it is recovered by an appropriate recovery device. In the first embodiment, the trough 40 constitutes a collection device.

  In the first embodiment, the rotary blade 20 and the rotor 34 of the fluid turbine 30 are directly connected. However, an appropriate speed reducer is used to reduce the rotation of the rotor 34 and transmit it to the rotary blade 20. May be. Alternatively, the fluid turbine 30 may be placed outside the riser pipe 11 and the rotational force may be transmitted to the rotary blade 20 via an appropriate transmission mechanism.

  The effect of rolling up sludge underwater, excavating sludge, or raising sludge pieces by air lift action depends on the combination of the type of high-pressure fluid supplied to the nozzle 14 and the high-pressure fluid supplied to the fluid turbine 30. It changes variously. FIG. 3 shows four types of high pressure fluid supplied to the nozzle 14: “none”, “compressed air”, “high pressure water”, “compressed air & high pressure water”, and “high” fluid supplied to the fluid turbine 30 “none” and “compression”. It is the table | surface which showed what becomes "the sludge rolling-up effect", "sludge excavation effect", and "air lift effect" by combining those as three types of "air" and "high pressure water".

  A second embodiment of the present invention is shown in FIGS. 4 is a vertical sectional view showing a schematic configuration of the air lift pump, FIG. 5 is a perspective view of the rotating blade, and FIG. 6 is a sectional view of the rotating blade. The second embodiment has many components in common with the first embodiment. In order to avoid duplication of description, the same components as those in the first embodiment are denoted by the same reference numerals as those used in the description of the first embodiment, and the description thereof is omitted.

  Also in the second embodiment, a rotating blade is arranged at the lower center of the header portion 12 of the riser pipe 11. In the rotary blade 50 of the second embodiment, four vertical excavation blades 52 are radially arranged at the lower end of the vertical rotary shaft 51. A bearing portion 54 supported by struts 53 on the inner surface of the riser pipe 11 rotatably supports the vertical rotation shaft 51. Similar to the excavation blade 20 of the first embodiment, the lower end of the vertical excavation blade 52 protrudes downward from the lower end of the header portion 12 by a predetermined length h. In addition, although the vertical rotating shaft 51 is cantilevered by the bearing part 54, you may strengthen the support by forming in the bearing part 54 the same sheath axis | shaft as 1st Embodiment. Alternatively, the lower end of the vertical rotation shaft 51 may be extended below the vertical excavation blade 52 and received by a stay extending from the riser pipe 11. In short, as long as the holding structure can hold the rotating blade 50 firmly, any structure may be used.

  The cross-sectional shape of the vertical excavation blade 52 is a wedge shape, and the inside is a hollow portion 52a. The hollow portion 52a has an opening 52b on the surface opposite to the traveling direction. The rotating blade 50 is rotated by the high-pressure fluid ejected from the driving nozzle 55. A plurality of drive nozzles 55 (four in the figure) are arranged around the center of the header portion 12 so as to blow high-pressure fluid into the hollow portion 52a of the vertical excavation blade 52 through the opening 52b. What is ejected from the drive nozzle 55 is compressed air supplied from the compressor 15 or a mixed fluid supplied from the compressor 15 and high-pressure water supplied from the high-pressure water pump 16.

  A levitation nozzle 56 is arranged in line with the drive nozzle 55. Compressed air is supplied from the compressor 15 to the levitation nozzle 56.

  The operation of the air lift pump 10 is as follows. When the header portion 12 of the riser pipe 11 is placed on the water bottom 2 as shown in FIG. 4 and the compressor 15 is driven, compressed air is ejected from the driving nozzle 55 and the levitation nozzle 56. When the high-pressure water pump 16 is driven, a mixed fluid of compressed air and high-pressure water is ejected from the driving nozzle 55. The high-pressure fluid ejected from the driving nozzle 55 pushes the vertical excavation blade 52 later, and the vertical excavation blade 52 advances while lifting the water bottom 2.

  The vertical excavation blade 52 continuously rotates while receiving high-speed fluid one after another from the drive nozzles 55 arranged at intervals of 90 °. The number of drive nozzles 55 may be further increased so that the transfer from one drive nozzle 55 to the next drive nozzle 55 is performed more smoothly.

  The compressed air ejected from the levitation nozzle 56 becomes the air bubble 4, and an upward flow in which water and the air bubble 4 are mixed is formed inside the riser pipe 11. The sludge pieces 3 that have been rolled up by the vertical excavation blade 52 and are chopped up are lifted by the upward flow, overflow from the upper end of the riser pipe 11, and then collected by the trough 40.

  According to the second embodiment, the rotating blade can be rotated without using a complicated drive mechanism such as a fluid turbine. Since the mechanism is simple, there are few failures even when used for excavation of gravel sand, mud, sludge, etc.

  A third embodiment of the present invention is shown in FIG. FIG. 7 is a sectional view of the rotating blade.

  The third embodiment relates to an improvement of the rotary blade 50 of the second embodiment. That is, in the third embodiment, a large number of through-holes 52c that pass from the hollow portion 52a of the vertical excavation blade 52 to the upper surface are formed. When compressed air or a mixed fluid of compressed air and high-pressure water is ejected from the drive nozzle 55, the high-pressure fluid pushes the vertical excavation blade 52 later and simultaneously ejects it from the through hole 52c to the upper surface. The high-pressure fluid ejected from the through hole 52 c helps the sludge piece 3 to be separated from the vertical excavation blade 52. As a result, the resistance received by the rotating blade 50 is reduced, and the rotating blade 50 rotates more smoothly. Moreover, when the high-pressure fluid spouts the sludge piece 3 upward, the sludge piece 3 is easily caught in the upward flow.

  A fourth embodiment of the present invention is shown in FIG. FIG. 8 is a sectional view of the rotating blade.

  The fourth embodiment relates to an improvement of the rotary blade 50 of the third embodiment. That is, in the fourth embodiment, a hook portion 52 d that protrudes rearward in the rotational direction is formed at the upper rear end of the vertical excavation blade 52. A plurality of through holes 52e are formed in the flange portion 52d.

  Air is separated from the high-pressure fluid that has pushed the vertical drilling blade 52. Of course, air is separated from the high-pressure fluid ejected from the through-hole 52c, and air is also separated from the high-pressure fluid that could not be ejected from the through-hole 52c. The latter air tends to rise while following the vertical drilling blade 52. This air passes through the through hole 52e of the flange 52d, and at that time, bubbles of a certain size or less are formed. Since the air that has passed through the through-hole 52c also becomes air bubbles of a certain size or less, a large number of air bubbles having a size of less than a certain size are generated as a whole, and the water in the riser pipe 11 is steadily maintained at a constant pace. Push up.

  If the air rising while following the vertical excavation blade 52 is left as it is, the tendency of bubbles to coalesce and the air bubbles become too large and only the air bubbles rise is increased. As a result, the push-up of water exhibits a pulsating flow or intermittent flow, and the air lift effect is reduced. By taking a measure to reduce the size of the air bubble in the through hole 52e of the flange 52d, such a problem is eliminated and a certain air lift effect can be secured.

  About the angle which the collar part 52d extends backward, an optimal angle is calculated | required by experiment. In FIG. 8, a state in which the angle of the flange portion 52d is changed is illustrated by a virtual line. Further, it is preferable that the flange portion 52d has a shape like a trough turned inside out to prevent escape of air.

  FIG. 9 shows a fifth embodiment of the present invention. FIG. 9 is a sectional view of the riser pipe.

  The riser pipe 11 of FIG. 9 has a shape in which the cross section of the flange portion 13 is curved in an arc shape and the periphery is raised. For this reason, since the periphery of the flange part 13 is hardly caught by the unevenness | corrugation of a water bottom, the riser pipe 11 can be moved to a horizontal direction smoothly. Needless to say, the riser pipe 11 having this shape can be used in the first embodiment and the second embodiment.

  A sixth embodiment of the present invention is shown in FIG. FIG. 10 is a cross-sectional view of the riser pipe.

  The sixth embodiment relates to an improvement of the riser pipe 11 of the fifth embodiment. That is, in 6th Embodiment, the flange part 13 is connected to the riser pipe 11 via a flexible part. Specifically, the riser pipe 11 is cut off immediately above the header portion 12, and the cut portions are connected by a bellows tube 58 made of rubber or soft synthetic resin to form the flexible portion 57.

  By being connected to the riser pipe 11 through the flexible portion 57 in this way, the flange portion 13 changes its inclination according to the undulation of the water bottom. For this reason, the flange portion 13 is always in close contact with the bottom of the water, and the vortex or air bubble of the high-pressure fluid rarely leaks to the outside through the gap between the flange portion 13 and the bottom of the water. Therefore, the energy of the high-pressure fluid and the buoyancy of the air bubbles can be concentrated in the riser pipe 11 and the header portion 12 so that the water bottom constituent material can be collected efficiently.

  A seventh embodiment of the present invention is shown in FIGS. FIG. 11 is a perspective view of the header portion of the riser pipe, and FIGS. 12 and 13 are horizontal sectional views of the header portion, showing different states.

  The seventh embodiment is premised on the use of the vertical excavation blade 52. Here, a side opening 59 is formed in the outer peripheral portion of the header portion 12 of the riser pipe 11. As can be seen in FIGS. 12 and 13, the side openings are provided at two locations so as to be symmetric with respect to the vertical rotation axis 51. The number of vertical drill blades 52 is also two. The vertical excavation blade 52 is the same as that of the fourth embodiment.

  A shutter 60 is provided on the outer periphery of the vertical excavation blade 52. The shutter 60 has a flat circular arc shape and faces the inner peripheral surface of the header portion 12 with a predetermined interval. The shutter 60 has a length and height that can sufficiently close the side opening 59. The shutter 60 is not depicted in FIG.

  When the rotary blade 50 rotates, the side opening 59 opens as shown in FIG. 12 for a specific period. At this time, the water bottom constituent material can be taken in from the side opening 59, and it can be shredded by the vertical excavation blade 52 and collected. During another specific period, the side opening 59 is closed by the shutter 60 as shown in FIG. At this time, since the high-pressure fluid and air bubbles do not leak from the side opening 59, the high-pressure fluid and air bubbles can be fully utilized for winding and floating of the bottom material.

  A flange portion 13 may be formed on the outer periphery of the lower end of the header portion 12. In this case, the flange portion 13 is provided with a notch continuous to the side opening 59.

    As mentioned above, although each embodiment of the present invention was described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

    The present invention is widely applicable to air lift pumps used for collecting water bottom constituent materials.

The vertical sectional view showing the schematic structure of the air lift pump concerning a 1st embodiment of the present invention. Horizontal sectional view of the lower end of the air lift pump Table showing the difference in the effect of the combination of the type of fluid ejected from the nozzle and the type of fluid that rotates the turbine The vertical sectional view showing the schematic structure of the air lift pump concerning a 2nd embodiment of the present invention. Perspective view of rotating blade Cross section of rotating blade Sectional drawing of the rotary blade of the air lift pump which concerns on 3rd Embodiment of this invention. Sectional drawing of the rotary blade of the air lift pump which concerns on 4th Embodiment of this invention. Sectional drawing of the riser pipe of the air lift pump which concerns on 5th Embodiment of this invention. Sectional drawing of the riser pipe of the air lift pump which concerns on 6th Embodiment of this invention. The perspective view of the riser pipe of the air lift pump concerning a 7th embodiment of the present invention. Horizontal sectional view of the riser pipe of the seventh embodiment FIG. 12 is a horizontal sectional view of a riser pipe according to a seventh embodiment, showing a state different from FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water surface 2 Water bottom 10 Air lift pump 11 Riser pipe 12 Header part 13 Flange part 14 Nozzle 15 Compressor (high pressure fluid source)
16 High pressure water pump (high pressure fluid source)
DESCRIPTION OF SYMBOLS 20 Rotating blade 30 Fluid turbine 50 Rotating blade 52 Vertical drilling blade 52d Steel plate 52e Through hole 57 Flexible part 59 Side opening 60 Shutter

Claims (11)

A bottom structure comprising a riser pipe having a lower end reaching the bottom of the water, a nozzle for supplying a high pressure fluid, at least part of which is air, to the bottom of the water surrounded by the riser pipe, and a high pressure fluid source for supplying the high pressure fluid to the nozzle In an air lift pump that peels material from the bottom of the water with a high-pressure fluid and raises the inside of the riser pipe together with air and collects it on the water surface.
An air lift pump characterized in that a rotating blade that is rotated by the high-pressure fluid and scrapes off the water bottom constituent material is disposed in the riser pipe.   The air lift pump according to claim 1, wherein the rotary blade is given a rotational force from a fluid turbine rotating with the high-pressure fluid.   The air lift pump according to claim 2, wherein the rotating blade is disposed in a central portion of the riser pipe, and a swirling flow is formed around the rotating blade by the high pressure fluid from the nozzle.   The air lift pump according to claim 1, wherein the rotating blade is rotated by being pushed by a high-pressure fluid ejected from the nozzle.   The rotating blade has a flange protruding rearward in the rotation direction, and the flange has a plurality of through holes through which air in the high-pressure fluid passes in the form of bubbles of a certain size or less. The air lift pump according to claim 4.   The air lift pump according to any one of claims 1 to 5, wherein a flange portion for preventing burial is formed on an outer periphery of a lower end of the riser pipe.   The air lift pump according to claim 6, wherein a peripheral edge of the flange portion is raised.   The air lift pump according to claim 6 or 7, wherein the flange portion is connected to the riser pipe via a flexible portion.   The air lift pump according to any one of claims 1 to 5, wherein a side opening for taking in a water bottom constituent material is formed at a lower end of the riser pipe.   The air lift pump according to claim 9, wherein a shutter that closes the side opening for a specific period during rotation is formed on an outer peripheral portion of the rotating blade.   The air lift pump according to any one of claims 1 to 10, wherein the rotating blade protrudes downward by a predetermined length from a lower end of the riser pipe.

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