JP5684368B2 - Flat membrane element and submerged membrane separation apparatus using the same - Google Patents

Description

  The present invention relates to a flat membrane element that is immersed in a liquid to be filtered stored in a processing tank and used for filtration, and an immersion membrane separation apparatus using the flat membrane element.

  A submerged membrane separation apparatus is known as equipment for filtering treatment target liquids such as septic tank sludge, domestic wastewater sludge, human waste, and facility wastewater. Such a submerged membrane separator generally includes a membrane unit in which a plurality of flat membrane elements are assembled as described in Patent Document 1 (Japanese Patent Laid-Open No. 2003-117358). Is immersed in the liquid to be treated and filtered.

  Further, as described in Patent Document 1 and Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-212436), the flat membrane element constituting the membrane unit is applied to the surface of a rectangular flat plate-shaped filter plate. The filter membrane sheet is formed by superimposing a slightly smaller rectangular thin-film filter membrane and welding the peripheral edge of the filter membrane sheet to the filter plate. It is said that.

  By the way, the filtration membrane sheet in such a flat membrane element is subjected to a negative pressure from the outside for suctioning the filtrate, and also causes a fluid flow in the treatment tank to prevent stagnation and preserve the microbial environment. In order to prevent clogging of the filtration membrane, fluid flow pressure and vibration are exerted by aeration exerted from below. In addition, a positive pressure supplied from the outside may be applied to physically eliminate clogging of the filtration membrane, and an ultrasonic generation means is installed in the treatment tank to apply ultrasonic vibration. (See Patent Documents 3 to 5).

  On the other hand, in order to take out the liquid filtered by the flat membrane element through the outer tube, conventionally, as shown in Patent Documents 1 and 2, the outer opening portion of the filtrate flow path has been It is comprised by the nozzle part which protrudes upwards from a board, and an external pipe | tube body is connected with respect to this nozzle part.

  However, as a result of investigation by the present inventor, as described above, fluid flow pressure and vibration are exerted on the plate-like membrane element in the operating state of the submerged membrane separator, so that the external tube body is connected to the nozzle portion. It has been found that there are cases where it is not yet sufficient to keep the state stable. That is, the magnitude of the actual external force exerted by negative pressure, positive pressure, fluid pressure, vibration, etc. as described above varies depending on the state of the viscosity of the liquid to be filtered, the magnitude of the applied pressure, etc. There was a possibility that the external tube would be easily detached from the nozzle portion due to the external force acting.

JP 2003-117358 A JP 2001-212436 A JP-A-3-213128 JP 2007-111623 A Japanese Patent Laid-Open No. 9-103791

  The present invention has been made in the background of the above-mentioned circumstances, and the problem to be solved is that the nozzle portion protruding upward from the filter plate has a disconnection that acts on the external tube to be connected. It is an object of the present invention to provide a flat membrane element having a novel structure that can achieve the effect of reducing the directional fluid pressure with a simple structure without an increase in the size of manufacturing equipment and a significant increase in manufacturing cost.

  In addition, the present invention provides a submerged membrane separator having a novel structure that is configured using such a flat membrane element and that can stably exert its intended filtration function over a long period of time. Also aimed.

  Hereinafter, the aspect of this invention made | formed in order to solve such a subject is described. In addition, the component employ | adopted in each aspect as described below is employable by arbitrary combinations as much as possible.

First, a feature of the present invention relating to a flat membrane element is that a planar polygonal filtration membrane sheet is superimposed on the surface of a synthetic resin filter plate, and the periphery of the filtration membrane sheet is fixed to the filter plate. In addition, in the flat plate membrane element formed in the filter plate, the filtrate channel that guides the filtrate that has passed through the filter membrane sheet to the outside, the outer opening portion of the filtrate channel is the upper edge of the filter plate. A cylindrical nozzle part projecting upward from the part, and an external tube body can be connected to the nozzle part, and the base of the nozzle part at the upper edge of the filter plate On the lower side of the end, it protrudes outward on both sides of the filter plate, and gradually protrudes outward from the lower side upwards, so that it rises from below along the surface of the flat membrane element. Filtration target liquid In flat membrane element proximal side projection which forms an inclined surface for guiding in a direction away from the nozzle portion.

  In the flat membrane element having a structure according to the present invention, the end of the external tube is extrapolated to the nozzle portion, but below the tip surface of the external tube connected to the nozzle portion. In this case, a proximal end side protruding portion is provided. And since this base end side protrusion part is equipped with the outer periphery inclined surface which expands, for example in a taper shape toward the upper direction from the downward direction, it is made to flow upward from the bottom along the surface of a flat membrane element. The liquid to be filtered is guided in a direction away from the nozzle portion by the outer peripheral inclined surface of the base end side protruding portion.

  As a result, by forming the proximal-side protruding portion as described above, the fluid pressure directly exerted on the distal end surface of the external tube connected to the nozzle portion is also inclined with respect to the filtration target liquid that flows upward from below. Since it is reduced by the guiding action of the surface, an effect of preventing the outer tube body from coming out from the nozzle portion can be expected.

  Further, in the present invention relating to the flat membrane element, the lower end edge of the filter plate has a tapered cross-sectional shape that gradually decreases in thickness toward the lower side, and both side surfaces in the plate thickness direction at the lower end edge are The inclined surface gradually protrudes outward in the plate thickness direction as it goes upward, and the upper end of the inclined surface protrudes outward in the plate thickness direction from the overlapping surface of the filtration membrane sheets on the filter plate. The aspect made into the direction protrusion is employ | adopted suitably.

  By adopting such a specific structure at the lower edge of the filter plate, the flow of the liquid to be filtered, which is guided from below to the space between the filter plates (cross flow region) based on aeration, etc. It can be guided by the inclined surface of the protrusion and allowed to flow in between the filter plates. As a result, rectification of the liquid to be filtered on the filtration membrane sheet is achieved, local fluctuations in the fluid pressure exerted on the filtration membrane sheet are suppressed, and damage to the filtration membrane sheet is avoided and durability is improved. The above object of the present invention can be realized more effectively.

  In addition, since the upper end of the inclined surface at the lower edge of the filter plate is an outward protrusion protruding outward from the overlapping surface of the filtration membrane sheet, the filtration target guided from below the filter plate It is also prevented that the fluid pressure of the liquid acts directly on the lower end surface of the filtration membrane sheet. This prevents the filter membrane sheet from peeling off the filter plate at the lower edge of the filtration membrane sheet due to the action of the fluid pressure of the liquid to be filtered, and more effectively prevents damage to the target filtration membrane sheet and improves durability. It becomes possible.

  By the way, in the present invention relating to the flat membrane element, for example, the filter plate made of a thermoplastic synthetic resin is used as the welded structure of the filter membrane sheet to the filter plate surface, and the filter membrane sheet is overlapped on the surface of the filter plate. A plurality of welding ridges that are located in the peripheral portion of the joining region and extend linearly in the circumferential direction are formed in parallel, and the welding adjacent to each corner of the planar membrane-shaped filtration membrane sheet A corner auxiliary protrusion is formed between the protrusions, and the welding protrusion and the corner auxiliary protrusion are welded and fixed to the filtration membrane sheet, thereby reducing the welding area to the filter plate at the periphery of the filtration membrane sheet. A structure that is larger at the corner than at the corner is preferably employed.

  If such a welding structure is adopted, the filtration membrane sheet is efficiently welded to the filter plate without significantly increasing the welding area to the filter plate at the periphery of the filtration membrane sheet, and its spreading tension and durability Can be improved effectively. That is, when welding a flat polygonal filter membrane sheet to the filter plate at the periphery, the entire filtration membrane sheet can be efficiently held in a stretched state with a small number of points by exerting a tension on each diagonal line. It becomes. Here, in the present invention, a large tensile force can be exerted on the filtration membrane sheet in the diagonal direction by welding each corner of the filtration membrane sheet to the filter plate with the corner auxiliary projections. As a result, compared with the case where each side portion of the filtration membrane sheet has a tensile tension, the tensile strength of the filtration membrane sheet is efficiently increased while suppressing an increase in the welding area by providing the tensile tension at each corner. It can be made.

  In addition, by adopting such a welding structure, the welding area can be increased by the corner reinforcing protrusions only at each corner of the filtration membrane sheet that bears a large spreading tension. There is no need to increase the weld area over the circumference. Therefore, the energy required for welding (such as the horn output of ultrasonic welding and the amount of heat generated by heat welding) does not need to be significantly increased. The increase can be suppressed as much as possible.

  Furthermore, when adopting the welding structure as described above, for example, it is located on the outer peripheral side of the welding protrusion, and extends to the entire circumference in the circumferential direction with a width extending over both the inner and outer circumferences including the outer peripheral edge of the filtration membrane sheet. A mode in which mesh-like projections are formed in the fixed outer edge region and the outer peripheral edge of the filtration membrane sheet is welded to the mesh-like projections is suitably employed together.

  In other words, by welding the outer peripheral edge of the filtration membrane sheet to the filter plate, it is possible to prevent the outer peripheral edge of the filtration membrane sheet from curling up, and the filtration membrane sheet is damaged and durable due to such curling up. It is also possible to avoid the occurrence of problems such as deterioration.

  Further, the present invention relating to the submerged membrane separation apparatus is characterized in that a plurality of plate-like membrane elements having a structure according to the present invention as described above are spread in the vertical direction and spaced apart from each other in the horizontal direction. A membrane unit that is positioned and supported so as to overlap with each other is placed in a treatment tank in which the liquid to be filtered is stored and immersed in the liquid to be filtered, and a cross flow region is formed between the opposing surfaces of the adjacent flat membrane elements. The submerged membrane separation apparatus is provided with an aeration means below the flat membrane element and an ultrasonic generator for applying ultrasonic vibration to the filtration membrane sheet of the flat membrane element. It is in the mold membrane separator.

  In such a submerged membrane separator having a structure according to the present invention, by adopting a flat membrane element having a structure according to the present invention, a stable connection state of the external pipe as described above can be obtained. Yes, especially in an environment where a special fluid pressure in the removal direction is exerted on the external conduit by the aeration means or ultrasonic generation means, the initial filtration performance should be demonstrated with excellent durability over a long period of time. Is possible.

BRIEF DESCRIPTION OF THE DRAWINGS The front view which shows the general | schematic whole structure of the immersion type membrane separator as embodiment of this invention. The side view which shows the general | schematic whole structure of the immersion type membrane separation apparatus shown by FIG. The elements on larger scale of the membrane unit which comprises the immersion type membrane separator shown by FIG. IV-IV sectional drawing in FIG. The single-piece front view of the flat membrane element used for the membrane unit which comprises the immersion type membrane separator shown by FIG. The elements on larger scale of the flat membrane element shown by FIG. FIG. 6 is a partially enlarged plan view of the flat membrane element shown in FIG. 5. VIII-VIII sectional drawing in FIG. The elements on larger scale of the flat membrane element shown by FIG. IX-IX sectional drawing in FIG. FIG. 6 is a partially enlarged bottom view of the flat membrane element shown in FIG. 5. The single article front view of the filter plate which comprises the flat membrane element shown by FIG. The elements on larger scale of the filter plate shown by FIG. The enlarged view of the XIV-XIV cross section in FIG.

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

  1 and 2 show an outline of a submerged membrane separation apparatus 2 as an embodiment of the present invention. The submerged membrane separation device 2 includes a treatment tank 4 in which a liquid to be filtered is introduced and stored, and a membrane unit 10 that is a filtration device is installed in the treatment tank 4 in an accommodated state. . The membrane unit 10 has a structure in which a plurality of flat plate membrane elements 14 are mounted in a housing state on a case frame 12 having a rectangular tower-shaped skeleton structure. It is immersed and operated. In the following description, the vertical direction means the vertical direction in FIGS. 1 and 2 which is the vertical vertical direction in the installed state of the membrane unit 10 in principle.

  More specifically, the case frame 12 is formed by connecting and combining a plurality of appropriate rigid members such as extruded profiles with welding or bolts. A plurality of flat membrane elements 14 are mounted inside the case frame 12 having a hollow structure.

  In the case frame 12, the peripheral wall is opened outward, and the flat membrane element 14 mounted inside is exposed to the outside. The case frame 12 is opened up and down, and aeration tubes 16 and 16 are piped below the case frame 12. These aeration pipes 16, 16 are connected to an external air pump or the like (not shown) so that compressed gas is supplied, and the compressed gas is formed on the peripheral walls of the aeration pipes 16, 16. It is ejected from the ejection hole into the liquid to be filtered.

  Then, the air or the like ejected from the aeration pipes 16, 16 is floated upward through gaps (cross flow regions) between the opposing surfaces of the plurality of flat membrane elements 14 mounted in the case frame 12. Thus, the flow of air or the like causes a fluid flow from the lower side to the upper side with respect to the liquid to be filtered existing in the cross flow region. In the case frame 12, the region from the aeration pipes 16, 16 to the lower end edge of the flat membrane element 14 is covered with a peripheral wall plate 17 and is ejected from the aeration pipes 16, 16. Air (for example, nitrogen as well as air can be used as the aeration gas depending on the required conditions) is efficiently guided to the crossflow region without unnecessary diffusion. It is like that.

  Further, below the case frame 12, an ultrasonic transducer 18 as an ultrasonic wave generating unit is mounted and disposed between the aeration pipes 16 and 16. The ultrasonic transducer 18 is configured to generate ultrasonic vibrations when supplied with power from the outside. The ultrasonic vibrations are applied to the plate-like membrane element 14 using the case frame 12 and the liquid to be filtered as a transmission medium. It has become.

  Here, the flat membrane element 14 of the present embodiment includes a filter plate 20 having a substantially rectangular flat plate shape. The filter plate 20 is integrally formed of a hard resin material such as ABS. In particular, in the present embodiment, a pair of ear portions 22 projecting to the left and right sides at the upper end portion of the main body portion having a rectangular flat plate shape, 22 are integrally formed with each strip shape. Then, as shown in FIGS. 3 to 4, the pair of left and right ear portions 22, 22 are fixedly held by the case frame 12, so that the flat membrane element 14 becomes the case frame. It is positioned and assembled in 12.

  Each ear 22 has a service hole 23 formed through the substantially central portion in the thickness direction, and the flat membrane element 14 can be lifted using these service holes 23, 23. It can be done. Each ear portion 22 is covered with a bag-like protective cover 24 formed of a rubber elastic body or the like. Then, the tabular membrane element 14 is positioned with respect to the case frame 12 by sandwiching the ear portion 22 via the protective cover 24 by the structural members 26 and 28 constituting the case frame 12. .

  As described above, the plurality of flat membrane elements 14 attached to the case frame 12 are positioned with respect to each other in a state where they are overlapped in parallel with each other at a minute interval in the thickness direction. In addition, the distance between the opposing surfaces of the flat membrane elements 14 and 14 arranged adjacent to each other is not particularly limited, but is set to be approximately the same as the thickness dimension of the filter plate 20, for example.

  Further, filtration membrane sheets 30 are respectively superimposed on the both side surfaces of the filter plate 20 in the flat membrane element 14, and the filtration function is exhibited by utilizing the filtration action of the filtration membrane sheet 30. Yes. In short, in this embodiment, as shown in FIGS. 5 to 11, flat membrane elements 14 in which both side surfaces of the filter plate 20 have the same structure are used, and on both side surfaces of the filter plate 20. Each of the filtration membrane surfaces 30 is overlaid and arranged so as to cover substantially the entire surface, whereby the filtration treatment surface 34 is configured.

  Further, the filter plate 20 is integrally formed with a substantially cylindrical nozzle portion 40 that protrudes upward from the upper end surface at both the left and right side portions. A suction hole 42 penetrating on the central axis of the nozzle portion 40 is opened at a portion covered with the filtration membrane sheet 30 on the surface 43 of the filter plate 20. As a result, one end of an external tube body 44 such as a resin tube is externally connected to the nozzle portion 40, and a negative pressure such as an external suction pump is applied through the external tube body 44, whereby the flat membrane element 14 is The filtration target liquid to be immersed is allowed to permeate the filtration membrane sheet 30, filtered and sucked from the suction hole 42 of the nozzle portion 40, and discharged through the external tube body 44. As is clear from this, in this embodiment, the opening portion of the suction hole 42 at the tip of the nozzle portion 40 constitutes the outward opening portion of the filtrate flow path filtered by the filtration membrane sheet 30. Yes.

  In addition, in the upper edge part of the filter plate 20 of this embodiment, in the part located in the lower part of the base end side of the nozzle part 40, the base end side protrusion parts 46 and 46 which protrude on both the front and back surfaces of the filter plate 20 are formed. Has been. These front and rear base-end-side protrusions 46 and 46 have a shape in which a hemisphere is embedded in the upper end edge of the filter plate 20 as a whole, and swell and expand outward from the bottom upward. ing.

  In addition, inclined surfaces 48 and 48 that gradually protrude outward from the lower side of the filter plate 20 toward the upper side are formed by the outer peripheral surfaces of the base end side protruding portions 46 and 46. That is, as shown in FIG. 8, these inclined surfaces 48, 48 have an inverted skirt shape that expands toward the nozzle portion 40 immediately below the proximal end side of the nozzle portion 40.

  In addition, the protrusion height of the base end side protrusions 46 and 46 is the distance between the tops of the base end side protrusions 46 and 46 on both the front and back sides of the filter plate 20 at the maximum protrusion portion at the upper end (L in FIG. 8). Is preferably set to be equal to or larger than the outer diameter of the lower end (D in FIG. 8) of the external tube body 44 extrapolated to the nozzle portion 40. Thereby, as shown by an arrow in FIG. 8, the base-end-side protruding portion with respect to the filtration target liquid that flows from below to above along the surface 43 of the filter plate 20 in the treatment layer. The rectifying action (guide action) by the inclined surfaces 48 and 48 of 46 and 46 is more effectively exhibited. That is, by the rectifying action of the inclined surfaces 48, 48, the liquid to be filtered that flows upward from the bottom toward the nozzle portion 40 is guided in a direction away from the nozzle portion 40 toward the outer peripheral side, and is extrapolated to the nozzle portion 40. In addition, the action of the fluid pressure on the lower end surface and the like of the outer tube 44 can be more effectively reduced.

  Further, on the upper edge of the filter plate 20 of the present embodiment, on both sides in the left-right direction (the left-right direction in FIGS. 6 and 7 which is the length direction of the upper edge of the filter plate 20) sandwiching the nozzle portion 40. The rectifying protrusions 50 and 50 that are positioned and protrude upward are integrally formed. In particular, in this embodiment, the rectifying protrusions 50 and 50 on both sides are symmetrical with respect to the nozzle part 40, and the protruding tip edge part upward is the distal end from the nozzle part 40. An inclined upper side 52 that gradually increases in protruding height from the proximal end toward the proximal end.

  In particular, in the present embodiment, the rectifying protrusion 50 is formed into a right-angled triangular shape with unequal sides formed with substantially the same thickness as the outer peripheral edge of the filter plate 20. Then, a right-angled corner is directed to the nozzle portion 40 side, and the oblique side is formed as an inclined upper side 52. Further, the maximum protruding height (in other words, the length of the side facing the nozzle portion 40) from the upper edge of the filter plate 20 in the inclined upper side 52 is substantially the same as the protruding height of the nozzle portion 40, or It is desirable to make it slightly larger.

  These rectifying protrusions 50, 50 are nozzles that protrude from the upper end of the filter plate 20 against the fluid flow of the liquid to be filtered that flows from below to above along the both side surfaces of the filter plate 20. A rectifying effect is exhibited in the vicinity of the portion 40. In addition, the rectifying protrusions 50 and 50 also exhibit a function of protecting both sides of the nozzle portion 40. That is, when the filter plate 20 is transported, or when the filter plate 20 is attached to or detached from the case frame 12, when the nozzle portion 40 hits another member, the rectifying protrusion 50 is in front of the nozzle member 40. It is easy to hit other members. Therefore, it is possible to prevent the nozzle portion 40 from being damaged due to the nozzle portion 40 unexpectedly hitting another member.

  In addition, in the present embodiment, since the rectifying protrusion 50 includes the inclined upper side 52, the liquid to be filtered that is caused to flow upward from below along the surface 43 of the filter plate 20 in the treatment layer. The rectifying action (guide action) by the inclined upper side 52 is also exhibited. That is, at the upper edge of the filter plate 20, a vortex flow is generated due to the absence of the filter plate 20 immediately above the filter plate 20 with respect to the upward fluid flow, and a local pressure drop occurs. The pressure drop position is on an inclined line along the inclined upper side 52. As a result, as the pressure gradient increases in a direction substantially orthogonal to the inclined upper side 52, the rectifying effect by the inclined upper side 52 is exerted as shown by the arrows in FIG. The liquid to be filtered that flows upward toward the nozzle 40 is guided in a direction away from the nozzle portion 40 toward the outer peripheral side, and the effect of the fluid pressure on the lower end surface of the external tube body 44 extrapolated to the nozzle portion 40 is further effective. Can be reduced.

  On the other hand, in the filter plate 20, a welding allowance 54 extending along the outer peripheral edge is formed on the surface 43 on which the filtration membrane sheet 30 is superimposed, as shown in FIGS. The welding allowance 54 is formed with a substantially rectangular frame shape as a whole so as to continuously extend over the entire circumference in the circumferential direction. Then, the filtration membrane sheet 30 is welded and fixed at the welding allowance 54 using a known appropriate welding device such as an ultrasonic welding device having an ultrasonic welding horn or a heating welding device having a heating welding head. As a result, the peripheral edge of the filtration membrane sheet 30 is continuously fixed to the filter plate 20 in close contact with the entire periphery. Moreover, in the wide area | region of the center part of the filtration membrane sheet 30 enclosed by the welding allowance 54, the internal area | region which spreads over the whole is formed between the overlapping surfaces of the filtration membrane sheet 30 and the filter plate 20. ing. A suction force (negative pressure) exerted from the outer tubular body 44 through the suction hole 42 of the nozzle portion 40 is exerted on the substantially entire surface of the filtration membrane sheet 30 through the inner region.

  Here, in this embodiment, the welding allowance 54 includes two parallel rib-like welding protrusions 56 and 58 extending continuously in the circumferential direction with a constant chevron cross section. Further, the grid-shaped welding projections 60 as the mesh-shaped projections extending in the circumferential direction so as to surround the outer circumferential sides of the welding projections 56 and 58 with a predetermined width, and the two inner circumferential welding projections 56 and the outer circumferential side. In the square portions between the welding ridges 58, the welding margins 54 are configured including the corner welding ridges 62 extending in a key shape as the corner auxiliary projections.

  As shown in the enlarged cross section of FIG. 14, the inner circumferential welding ridge 56, the outer circumferential welding ridge 58, and the corner welding ridge 62 are all protruding from the proximal end portion. This has a substantially constant chevron cross-section with a narrow width and extends in the circumferential direction. Further, the grid-like welding projections 60 (not clearly shown in the drawing) are a plurality of straight ridges intersecting in a grid shape with a cross-sectional shape tapered in the protruding direction in the same manner as the above-mentioned ridges 56, 58, 62. It is desirable to be formed as an aggregate. Thus, it becomes possible to weld each protrusion 56,58,62 and the grid | lattice-like welding protrusion 60 to the filtration membrane sheet 30 efficiently and stably by setting it as a tapered cross-sectional shape.

  Moreover, it is desirable that the inner circumferential welding projection 56, the outer circumferential welding projection 58, and the corner welding projection 62 are formed with substantially the same projection height. On the other hand, the lattice-shaped welding projections 60 may have the same projecting height as compared with the projections 56, 58, and 62, but it is preferable that the lattice-shaped welding projections 60 have a lower projecting height. Accordingly, as described in, for example, Patent Document 2, only the inner circumferential welding projection 56, the outer circumferential welding projection 58, and the corner welding projection 62 are used by using the up / down horn of the ultrasonic welding apparatus. It is also possible to weld the lattice-shaped welding projections 60 to the filtration membrane sheet 30 in the same manner using an up / down horn in a separate step after the welding to the filtration membrane sheet 30 first. Alternatively, using the up / down horn of the ultrasonic welding apparatus, the grid-like welding projections 60 and the filtration membrane sheet 30 are simultaneously formed together with the inner circumferential welding projections 56, the outer circumferential welding projections 58, and the corner welding projections 62. Even if it is made to weld, each protrusion 56,58,62 with large protrusion height is contact | abutted by the up-down horn ahead of the grid | lattice-like welding protrusion 60, is fuse | melted, and is welded to the filtration membrane sheet 30 As a result, it is possible to effectively ensure the reliability of welding of the protrusions 56, 58, 62, which have the role of ensuring the sealing performance and the stretching strength, to the filtration membrane sheet 30.

  In particular, the peripheral edge of the filtration membrane sheet 30 is provided with two parallel inner and outer circumferential welded protrusions 56 and 58, and in addition to ensuring a high and reliable sealing performance in the circumferential direction, Further, the corner welding ridge 62 is welded to the filtration membrane sheet 30 to increase the welding area. Thereby, especially in the square part, the filter membrane sheet 30 is applied in a state where the large stretch tension is efficiently applied to the entire surface of the filter membrane sheet 30 by applying a large stretch tension to the filter membrane sheet 30 in the diagonal direction. The filter plate 20 can be attached. Moreover, the fixed supporting force by the filter plate 20 exerted on each corner of the filtration membrane sheet 30 by the corner welding protrusions 62, 62, 62, 62 is the tension between the corners over the entire length of each side. As a result, an adhering state without slack due to a large tension with respect to the entire circumference of the peripheral edge portion of the filtration membrane sheet 30 is efficiently realized.

  Moreover, the corner-welding projection 62 that applies an effective spreading tension to the entire filtration membrane sheet 30 in this way is only provided partially only at the corners at the peripheral edge of the filtration membrane sheet 30. Therefore, the increase in the welding energy associated with the addition of the corner welding projections 62, 62, 62, 62 is hardly regarded as a problem, and the welding margin in a mode in which the corner welding projection 62 is not provided. It is possible to perform welding using substantially the same welding apparatus required for welding 54 to the filtration membrane sheet 30. Therefore, there is no need for significant expansion or modification of equipment, and the intended flat membrane element 14 can be produced economically.

  In the present embodiment, a concave groove 64 that extends in a branch shape is formed over substantially the entire center portion of the surface 43 surrounded by the welding allowance 54. Specifically, the concave groove 64 includes a lateral groove portion 64a extending left and right at the upper portion of the surface 43, and a plurality of vertical groove portions 64b extending in the vertical direction at predetermined intervals in the width direction of the surface 43. The upper end of each vertical groove 64b is connected to the horizontal groove 64a. Further, a connection groove 66 extending upward to the vicinity of the welding allowance 54 is formed on both side portions in the lengthwise direction of the lateral groove portion 64 a, and the upper end portion of the connection groove 66 is penetrating the nozzle portion 40. The suction hole 42 communicates with the inner end portion. Thereby, the suction force exerted from the outer tube 44 through the nozzle portion 40 is exerted over the entire concave groove 64 formed in the surface 43 of the filter plate 20.

  And the filtration membrane sheet 30 is piled up and attached with respect to the surface 43 of the filter plate 20 in which such a ditch | groove 64 was formed. The filtration membrane sheet 30 has a membrane shape having a size that allows the outer peripheral portion to overlap the welding allowance 54. In particular, in this embodiment, the outer peripheral edge of the filtration membrane sheet 30 is the welding protrusion 60. The rectangular flat film shape is one size larger than the inner peripheral edge and one size smaller than the outer peripheral edge of the lattice-shaped welding projection 60.

  As described above, the filtration membrane sheet 30 is welded to the welding allowance 54 in a state where the filtration membrane sheet 30 is overlaid on the surface 43 of the filter plate 20 by using an appropriate mounting device. 11 to 11, the welding protrusions 56, 58, the corner portion welding protrusions 62, and the grid-shaped welding protrusions 60 constituting the welding allowance 54 are integrated and fixed by welding. Yes. In addition, the welding protrusions 56 and 58 and the corner | angular part welding protrusion 62 shown by FIG.5, 6,9 can permeate | transmit this filtration membrane sheet 30 after welding of the filtration membrane sheet 30, and can be visually recognized from the surface. Represents a state. In short, the inner and outer circumferential welding ridges 56 and 58 and the corner portion welding ridge 62 are fused and integrated with the thermoplastic resin of the filtration membrane sheet 30 by welding, and this integrated portion is the filtration membrane sheet 30. It is in a state where it can be visually recognized from the surface.

  As the filter membrane sheet 30, conventionally known ones can be used. For example, PTFE is used as a porous filter material, and the whole is formed of PTFE alone, and is reinforced. For this purpose, an integrated composite structure or a laminated structure with other materials is preferably employed. Specifically, for example, a polyethylene terephthalate substrate (base film) coated with polytetrafluoroethylene is preferably employed.

  Here, the base material functioning as the reinforcing material is not particularly limited as long as it is a porous body having a larger pore diameter than that of a PTFE porous membrane and has excellent water permeability. For example, felt, non-woven fabric, woven fabric, mesh (mesh-like sheet) or the like can be used, but non-woven fabric is desirable from the viewpoint of strength, collection property, flexibility and the like. In addition, as the fiber material of the reinforcing material, polyolefin (polyethylene, polypropylene, etc.), polyamide, polyester (polyethylene terephthalate, etc.), aromatic polyamide, or a composite of these is particularly preferably employed.

  In addition, as a method for producing a laminate of a base material and a PTFE porous membrane as a reinforcing material or the like, for example, they may be simply overlapped (heated as necessary) and bonded, A method such as thermal lamination may be used. Alternatively, adhesive lamination such as hot melt powder may be interposed.

  In the present invention, in addition to the double-sided filtration layer type filtration membrane sheet 30 in which the PTFE separation membrane is formed on both sides of the substrate, the single-side filtration layer type filtration in which the PTFE separation membrane is formed on one side of the substrate. The membrane sheet 30 is also preferably employed. Such a single-side filtration layer type filtration membrane sheet 30 can be obtained by, for example, melt casting by casting a polymer material solution, which is a PTFE membrane material, on one surface of a substrate and forming a PTFE membrane on the substrate. In addition to being able to be formed, it can be manufactured by a known method such as forming a PTFE film formed by melt extrusion on one surface of a base material by welding or the like.

  And the single-side filtration layer type filtration membrane sheet 30 in which the PTFE separation membrane is deposited on one side of the base material in this way has a PTFE membrane formed only on one side of the base material, In combination with the fact that the PTFE membrane is not impregnated, compared with the double-sided filtration layer type ethylene-based filtration membrane sheet that has been conventionally used as a filtration membrane, It becomes possible to suppress the sheet filtration resistance to about half. Therefore, it is possible to reduce the acting force of the negative pressure and the positive pressure exerted on the filtration membrane sheet 30, which contributes to the improvement of durability intended by the present invention. When the single-side filtration layer type filtration membrane sheet 30 is employed, it is desirable to overlap the filter plate 20 so that the film formation side of PTFE becomes the outer surface, and thereby the filtration membrane sheet of the welding allowance 54. The welding strength to 30 can be ensured more effectively.

  Moreover, in this invention, it is desirable that the thickness dimension of the filtration membrane sheet 30 is 0.1 mm-0.3 mm. Thereby, the adhering strength and durability to the filter plate 20 can be obtained more advantageously. That is, when the thickness dimension of the separation membrane is smaller than 0.1 mm, it is difficult to give sufficient durability to the separation membrane. When the thickness dimension of the separation membrane is larger than 0.3 mm, the module body It may be difficult to obtain sufficient fixing strength.

  In the filter plate 20 of the present embodiment, fine irregularities are given to the region surrounded by the welding allowance 54 on the surface 43 on which the filtration membrane sheet 30 is overlaid and covered. This prevents the filtration membrane sheet 30 from adhering to the surface 43 of the filter plate 20 at the time of negative pressure suction or the like.

  Further, if necessary, between the surface 43 of the filter plate 20 and the filtration membrane sheet 30, adhesion to the surface 43 of the filtration membrane sheet 30 can be prevented to ensure a stable effective filtration area, or the filtration membrane sheet 30. A film-like spacer can be provided for the purpose of, for example, improving the durability by carrying from the back surface. For example, a membrane spacer made of polyethylene terephthalate or the like and made of a porous membrane having a pore size sufficiently larger than the filtration membrane sheet 30 is overlapped between the surface 43 of the filter plate 20 and the filtration membrane sheet 30. It is also possible to weld the outer peripheral edge of the membrane spacer together with the outer peripheral edge of the filtration membrane sheet 30 to the welding allowance 54.

  Thus, in the filtration processing surface 34 formed by superimposing the filtration membrane sheet 30 on the surface 43 of the filter plate 20, the suction force exerted from the nozzle portion 40 passes through the concave groove 64 and the surface 43. It extends over substantially the entire inner region defined between the membrane sheet 30 and the filter membrane 30 above. As a result, a suction force through the filtration membrane sheet 30 is exerted on the liquid to be treated to which the outer surface of the filtration membrane sheet 30 is exposed. From the region, the filtration process is performed through the suction hole 42 of the nozzle unit 40 to be discharged from the external tube body 44 to the outside. Note that the filtration and suction direction of the liquid to be treated by the filtration membrane sheet 30 is a direction orthogonal to the upward fluid flow direction in which the inside of the treatment tank is caused to flow by the aeration air action. The fluid flow region between the provided filter plates 20 and 20 is also referred to as a cross flow region.

  By the way, in the filter plate 20 of the present embodiment, as shown in FIG. 10, as shown in FIG. 10, an outward protrusion having a tapered cross-sectional shape that gradually decreases toward the bottom, over the substantially entire length of the lower edge. A portion 72 is formed. The outward projections 72 are inclined surfaces 74 and 74 that gradually protrude outward in the thickness direction as both side surfaces in the thickness direction go upward. As a result, the inclined surfaces 74 and 74 guide the flow of the liquid to be processed that rises from below to above, thereby suppressing disturbance of the fluid flow when entering the cross flow region. .

  As a result, the local pressure fluctuation exerted on the filtration membrane sheet 30 disposed on the surface 43 of the filter plate 20 and the action of the large pressure associated therewith are reduced or avoided, and the durability of the filtration membrane sheet 30 is improved. Damage avoidance can be achieved more effectively. In particular, the maximum thickness dimension of the uppermost end of the outward protrusion 72 is slightly larger than the thickness dimension of the outer peripheral portion 76 of the filter plate 20 and slightly protrudes from both the front and back surfaces of the filter plate 20. As a result, the fluid pressure of the liquid to be treated that is caused to flow upward from below is reduced from acting directly on the edge portion of the filtration membrane sheet 30 welded to the surface 43 of the filter plate 20. Durability and peeling durability are also improved.

  In addition, since the liquid to be filtered introduced into the cross flow region is rectified, vibration due to the fluid pressure exerted on the filter plate 20 is also reduced or prevented, resulting in vibration of the filter plate 20. It is also possible to reduce the wear of the support portion, reduce abnormal noise, and the like.

  The flat membrane elements 14 having the above-described structure are positioned and arranged so as to overlap each other at a predetermined interval in the horizontal direction in the membrane units 10 arranged in parallel with a predetermined cross-flow region. At that time, the filtration membrane sheets 30, 30 disposed on the opposing surfaces are firmly and largely spread on the peripheral edge with respect to the filter plate 20 by the welding allowance 54 having a specific structure including the corner welding protrusions 62. Since it is fixedly supported with tension, problems such as damage due to mutual interference and deterioration in durability can be effectively prevented. That is, the filtration membrane sheets 30 and 30 disposed on the opposing surfaces of the filter plates 20 and 20 adjacent to each other are physically supplied with positive pressure during maintenance such as on / off of the suction pump and prevention of clogging. Due to the action or the like, it may swell locally or as a whole due to fluid pressure fluctuation or aeration pressure fluctuation of the liquid to be filtered that is caused to flow further from below, or an excitation force action by ultrasonic waves. However, as described above, each filtration membrane sheet 30 is stretched and attached with a sufficiently large tension, and the working pressure is locally increased by the rectifying action of the inclined surface 48, the rectifying protrusion 50, the inclined surface 74, and the like. Therefore, such swelling can be suppressed as much as possible. As a result, it is exerted by contact between the filter membrane sheets 30 and 30 arranged opposite to each other and contact with the surface 43 of the filter plate 20. Friction is reduced and excellent durability is exhibited.

  The embodiments of the present invention have been described in detail above. However, the present invention can be implemented in a mode in which various changes, corrections, improvements, and the like are added based on the knowledge of those skilled in the art. It goes without saying that any aspect is included in the scope of the present invention as long as it does not depart from the spirit of the present invention.

  For example, in the welding allowance 54, the welding protrusions extending continuously in the circumferential direction are not limited to two as illustrated, but three or more are formed in parallel or substantially in parallel to the extent that equipment and the like correspond. You may do it. In the case where three or more strips are formed, it is only necessary that corner auxiliary projections positioned at each corner are formed between at least two adjacent welding projections.

  Further, the corner auxiliary protrusions employed in the present invention are, for example, a “<” shape or “L” shape extending at a predetermined length toward both sides in the circumferential direction with the corner vertex as the center. However, the present invention is not limited thereto, and any material may be used as long as it is formed at the corner portion and exhibits a reinforcing welding action to the filtration membrane sheet 30 at the corner portion. For example, the corner auxiliary protrusions can be configured by a plurality of dot-like protrusions protruding at the corners, divided linear protrusions, or the like.

  Furthermore, within a range that does not cause a problem in the welding apparatus, the length extending to each side of the corner auxiliary protrusion is appropriately adjusted, and the cross-sectional shape such as the width dimension and the protrusion height of the corner auxiliary protrusion is set in the circumferential direction. It is also possible to make it different from the extending welding ridge, and it is also possible to add auxiliary welding points scattered in the middle part of each side part.

  In addition, the inclined surfaces 48 and 48 by the base end side protrusion parts 46 and 46 below the nozzle part 40 described in this specification, the rectifying protrusions 50 and 50 on both the left and right sides of the nozzle part 40, and the inclined upper sides 52 and 52 thereof. Furthermore, the outwardly projecting portion 72 having a tapered surface at the lower end edge of the filter plate 20 and the like can each independently constitute the invention independently of the present invention. Thereby, special technical effects such as the rectification effect of the liquid to be filtered and the protection effect of the nozzle portion 40 can be effectively exhibited by each. However, in the present application, each of the inventions has the same object as the invention described in claim 1 of the present invention, and has the technical effect of solving the common problem. In order to satisfy the formal requirement of unity of application and for the purpose of satisfying the above, it is dependently described in the claims. That is, any of the following inventions can be technically recognized independently, but in the present application, no right is claimed alone for the above-mentioned formal reasons.

  Filtrate flow path for superposing a filtration membrane sheet on at least one surface of a rigid filter plate and fixing the periphery of the filtration membrane sheet to the filter plate, and guiding the filtrate that has passed through the filtration membrane sheet to the outside Is a flat membrane element that is disposed in a vertical direction in a treatment tank and is immersed in a liquid to be filtered, wherein a filtration treatment surface is formed on at least one surface side of the filtration plate. The outer opening portion of the filtrate flow path is constituted by a cylindrical nozzle portion protruding upward from the upper edge of the filter plate, and an external tube is connected to the nozzle portion. The upper end edge of the filter plate protrudes outwardly on both sides of the filter plate and gradually increases outward from the bottom upward. Protrusion on the base end side that forms a protruding inclined surface Flat membrane element arrangement is provided.

  Filtrate flow path for superposing a filtration membrane sheet on at least one surface of a rigid filter plate and fixing the periphery of the filtration membrane sheet to the filter plate, and guiding the filtrate that has passed through the filtration membrane sheet to the outside Is a flat membrane element that is disposed in a vertical direction in a treatment tank and is immersed in a liquid to be filtered, wherein a filtration treatment surface is formed on at least one surface side of the filtration plate. The outer opening portion of the filtrate flow path is constituted by a cylindrical nozzle portion protruding upward from the upper edge of the filter plate, and an external tube is connected to the nozzle portion. The rectifying protrusions that are located on both sides of the filter plate at the upper end edge of the filter plate and that protrude in the upward direction from the upper end edge of the filter plate. The flat membrane element of the structure provided with. In addition, it is preferable that at least one of the rectifying protrusions provided on both sides of the nozzle part includes an inclined upper side that gradually protrudes upward from the distal side to the proximal side with respect to the nozzle part. It is.

2: Submerged membrane separator, 10: Membrane unit, 14: Flat membrane element, 16: Aeration pipe (aeration means), 18: Ultrasonic vibrator (ultrasonic generation means), 20: Filter plate, 30: Filtration membrane sheet, 40 Nozzle part (filtrate flow path) 43: Surface, 44: External tube, 46: Protruding part on the base end side, 48: Inclined surface, 50: Rectifying protrusion, 52: Inclined upper side, 56: Inside Circumferential welding projection (welding projection), 58: Outer circumferential welding projection (welding projection), 60: Lattice welding projection (mesh projection), 62: Corner welding projection (corner auxiliary projection), 72: outward projection, 74: inclined surface

Claims (4)

A filtrate that guides the filtrate that has permeated through the filter membrane sheet to the outside while the perimeter of the filter membrane sheet is fixed to the filter plate by superimposing a plane polygonal filter membrane sheet on the surface of a synthetic resin filter plate In a flat membrane element having a flow path formed in the filter plate,
An outward opening portion of the filtrate flow path is configured by a cylindrical nozzle portion protruding upward from an upper end edge of the filter plate, and an external tube body can be connected to the nozzle portion. As well as
By projecting outwardly on both sides of the filter plate on the lower side of the base end side of the nozzle portion at the upper edge of the filter plate, and gradually projecting outward from the lower side upward, the flat plate A flat membrane having a base-end-side protruding portion that forms an inclined surface that guides the liquid to be filtered, which is caused to flow upward from below along the surface of the membrane element, in a direction away from the nozzle portion. element. The flat membrane element according to claim 1, wherein an outer peripheral surface shape of the cylindrical nozzle portion protruding upward from an upper end edge portion of the filter plate has a small diameter upward. The lower end edge of the filter plate has a tapered cross-sectional shape that gradually decreases in thickness toward the lower side, and outwards in the thickness direction as both side surfaces in the thickness direction at the lower end edge go upward. And an upper end of the inclined surface that is an outward protrusion that protrudes outward in the thickness direction from the overlapping surface of the filtration membrane sheets on the filter plate. Item 3. The flat membrane element according to item 1 or 2 . A membrane unit in which a plurality of the flat membrane elements according to any one of claims 1 to 3 are positioned and supported so as to spread in the vertical direction and to overlap each other at a predetermined interval in the horizontal direction is filtered. An immersion type membrane separation apparatus that is installed in a treatment tank in which a target liquid is stored and immersed in the target liquid for filtration, and that forms a cross flow region between opposing surfaces of the adjacent flat plate membrane elements, A submerged membrane separation apparatus, wherein aeration means is provided below the flat membrane element, and ultrasonic generation means for applying ultrasonic vibration to the filtration membrane sheet of the flat membrane element is provided.

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