Position-retaining cage for draft tube of sludge digester and sludge digester equipped with same

Abstract

To provide a draft-tube posture holding cage used in a sludge digestion device, capable of maintaining the capability of holding a posture of a draft tube for a longer time.SOLUTION: A posture holding cage 40 used in a sludge digestion device 1 comprising a vertical digestion tank 10, a vertical axial flow pump 30 vertically hung in the center of the digestion tank 10, and a draft tube 20 covering the axial flow pump 30, is characterized by having a frame type cage body 41 interposed between a support part on the draft tube 20 side and a support part on an inner wall side of the digestion tank 10 in order to hold a posture of the draft tube 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sludge digester, and more particularly to a position maintaining member suitable for maintaining the position of a draft tube of a sludge digester. [Background technology]

[0002] As an example of a sludge digester, as shown in Figure 11, there is known a sludge digester 200 that comprises a digester tank 210, a draft tube 220 that is erected in the digester tank 210 and has openings at the upper and lower ends, and a vertical axial flow pump 230 that is positioned in the center of the top of the digester tank 210 and has a rotating shaft that hangs down so as to extend into the draft tube 220 (see, for example, Patent Document 1).

[0003] In this type of sludge digester 200, an axial flow pump 230 is placed in the center of the top of the digester tank 210, and a draft tube 220 is installed with its axis vertical to surround the agitator screw 232 at the tip of the rotating shaft of the axial flow pump 230. In this case, in a conventional sludge digester 200, as shown in an enlarged view of the main part in Figure 12, the upper opening 221 of the draft tube 220 is fixed to the inner wall surface of the digester tank 210 by a tie rod 240 having a turnbuckle 240t.

[0004] In the example shown in the figure, four tie rods 240 are arranged in a cross shape when viewed from above the digester tank 210, and tension is applied to each of the four tie rods 240 by tightening each turnbuckle 240t, so as to tautly support the upper opening 221 of the draft tube 220. This supports the draft tube 220 so that its inner surface does not come into contact with the mixing screw 232 of the axial flow pump 230 and so that the draft tube 220 itself does not vibrate due to the flow within the digester tank 210. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-314744 A (see FIG. 1) Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the draft tube's attitude-retaining member has an attitude-retaining structure in which tension is applied to the multiple tie rods 240 to tautly fix the upper opening 221 of the draft tube 220, the tie rods 240 may be fatigue-fractured during long-term use of the sludge digester 200 over several years to several decades. Therefore, the conventional tie rods 240 still have room for improvement in terms of maintaining the attitude-retaining performance of the draft tube 220 over a long period of time. Therefore, the present invention has been made with a focus on such problems, and it is an object of the present invention to provide a posture maintaining cage for a draft tube of a sludge digester, which can maintain the posture maintaining performance of the draft tube for a longer period of time, and a sludge digester equipped with the same. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one embodiment of the present invention provides a position-maintaining cage for a draft tube of a sludge digester, which is used in a sludge digester comprising a digestion tank, a draft tube erected in the digestion tank and having openings at its upper and lower ends, and a vertical axial flow pump positioned in the center of the top of the digestion tank and having a rotating shaft suspended down so as to extend into the draft tube, and is characterized in that it has a frame-type cage body that is fixed within the digestion tank in a suspended position with its upper part supported on the upper part of the inner wall of the digestion tank and its lower part is fixed to a support part on the upper side of the draft tube to maintain the upright position of the draft tube.

[0008] According to the attitude-maintaining cage for the draft tube of the sludge digester according to one embodiment of the present invention, unlike the conventional tie rod, which is tensioned by tightening a turnbuckle to provide tension, a frame-shaped cage body is interposed between the support part on the draft tube side and the support part on the inner wall side of the digester tank, so that the attitude of the draft tube can be fixed by a rigid joint. Therefore, according to the attitude-maintaining cage for the draft tube of the sludge digester according to one aspect of the present invention, fatigue breakage of the cage body having a rigid structure can be prevented or suppressed compared with a tie rod that is tightened by applying tension, and therefore the attitude-maintaining performance of the draft tube by the cage body can be maintained for a longer period of time.

[0009] Here, in a posture maintaining cage for a draft tube of a sludge digester according to one embodiment of the present invention, the cage body can be configured to have a plurality of arms which hang down with their base ends connected to a support part on the inner wall side of the digestion tank, a plurality of frame parts which are supported by the plurality of arms and are arranged at a distance in the vertical direction of the digestion tank, and a plurality of girders which are stretched between any one of the plurality of frame parts and the draft tube to support the draft tube. With this configuration, the length of the multiple beams that directly support the draft tube can be made relatively short, making this structure suitable for maintaining the position of the draft tube's core while fixing the orientation of the draft tube with rigid joints.

[0010] In order to solve the above problems, a sludge digester according to one embodiment of the present invention comprises a digestion tank, a draft tube erected in the digestion tank and having openings at an upper end and a lower end, a vertical axial flow pump disposed in the top center of the digestion tank and having a rotating shaft suspended so as to extend into the draft tube, and a posture maintaining member for maintaining the posture of the draft tube, wherein the posture maintaining member comprises a posture maintaining cage for the draft tube of the sludge digester according to one embodiment of the present invention.

[0011] According to one embodiment of the sludge digester of the present invention, a draft tube attitude maintaining cage for the sludge digester of one embodiment of the present invention is provided as an attitude maintaining member for maintaining the attitude of the draft tube, so that the attitude maintaining performance of the draft tube can be maintained for a longer period of time. Effect of the Invention

[0012] As described above, according to the present invention, the attitude retention performance of the draft tube of the sludge digester can be maintained for a longer period of time. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram of an embodiment of a sludge digester equipped with a draft tube attitude-maintaining cage according to one aspect of the present invention, in which a cross section along the axis is shown. [Diagram 2] FIG. 2 is an enlarged view of a portion of the attitude support cage in the sludge digestion apparatus of FIG. 1. [Diagram 3] 3A to 3C are explanatory views of the upper arm portion constituting the posture support cage of FIG. 2 ((a) front view, (b) side view, (c) top view). [Figure 4] 3A to 3C are explanatory views of the lower arm portion constituting the posture support cage of FIG. 2 ((a) front view, (b) side view, (c) top view). [Diagram 5] FIG. 3 is an explanatory diagram of an upper frame portion constituting the attitude support cage of FIG. 2, and also shows an exploded view of the cross beams and reinforcing beams, which are steel members. [Figure 6] FIG. 3 is an explanatory diagram of the middle frame portion constituting the attitude support cage of FIG. 2, and also shows an exploded view of the cross beams and reinforcing beams, which are steel members. [Figure 7] 3A and 3B are explanatory diagrams of the lower frame that constitutes the attitude holding cage in Fig. 2, and Fig. 3A also shows an exploded view of the cross beam, which is a steel member. Fig. 3B is an explanatory diagram of the clearance adjustment part, showing an enlarged view of the VV cross section in Fig. 3A. [Figure 8] 3A and 3B are explanatory views ((a) is a plan view, (b) is a front view) of an adjustment seat plate that constitutes the clearance adjustment portion of the attitude holding cage in FIG. 2. [Figure 9] 3A and 3B are explanatory views ((a) is a plan view, and (b) is a front view) of an adjustment bracket that constitutes the clearance adjustment portion of the attitude holding cage in FIG. 2. [Figure 10] FIG. 2 is a schematic diagram for explaining the process of installing the attitude-maintaining cage in the sludge digester of FIG. 1, and shows the state in which a scaffold for maintenance is provided. [Figure 11] FIG. 1 is an explanatory diagram of an example of a sludge digester equipped with a conventional tie rod, in which a cross section along the axis is shown. [Figure 12] FIG. 12 is an enlarged view of a portion of a conventional tie rod in the sludge digester of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship between thickness and planar dimensions, ratios, etc. are different from the actual ones, and the drawings also include parts where the relationship and ratio of dimensions differ from each other. Furthermore, the embodiments described below are merely examples of devices and methods for embodying the technical ideas of the present invention, and the technical ideas of the present invention do not limit the materials, shapes, structures, arrangements, etc. of the components to the embodiments described below.

[0015] As shown in Figure 1, the sludge digester 1 of this embodiment includes a digestion tank 10 for receiving sludge, a draft tube 20 arranged vertically in the digestion tank 10, and an axial pump 30 arranged in the center of the top of the digestion tank 10. The draft tube 20 is disposed vertically with its axis along the center of the digester tank 10, and the lower part of the draft tube 20 is fixed to the bottom 12 of the digester tank 10 by a plurality of support legs 15. In other words, since the lower part of the draft tube 20 is fixed to the bottom 12 by a plurality of support legs 15, the draft tube 20 forms a completely rigid support structure.

[0016] Axial flow pump 30 includes a motor unit 35 having a rotating shaft 31. Motor unit 35 is attached to the upper part of lid unit 13 provided at the center of the top of digester tank 10 and disposed outside digester tank 10, with rotating shaft 31 hanging down toward the inside of digester tank 10. An agitating screw 32 is provided at the tip of the rotating shaft 31. The agitating screw 32 is disposed so as to be located within the upper opening 21 of the draft tube 20. In the axial flow pump 30 of this embodiment, an upper screw 33 and a spray disk 34 are provided on the rotating shaft 31 at a position axially above the agitating screw 32.

[0017] In the sludge digester 1 of this embodiment, the axial pump 30 is capable of both forward and reverse rotation, and by operating the axial pump 30 in the forward direction, the agitating screw 32 creates a downward flow in which the sludge in the digestion tank 10 is introduced into the draft tube 20 from the upper opening 21 of the draft tube 20, and then discharged from the lower opening 22 of the draft tube 20 to circulate within the digestion tank 10. This causes the sludge in the digestion tank 10 to be agitated.

[0018] In the sludge digester 1 of this embodiment, as shown in an enlarged view of the main parts in Figure 2, the upper opening 21 of the draft tube 20 is also supported on the upper part 11 of the inner wall of the digester tank 10 by a posture maintaining cage 40. In this specification, the upper part 11 of the inner wall of the digester tank 10 refers to the part of the inner wall of the digester tank 10 that is higher than the upper opening 21 of the draft tube 20.

[0019] As a result, the attitude maintenance cage 40 of this embodiment can fix the attitude of the draft tube 20 by a rigid joint, without relying on tension support using tension, such as the above-mentioned turnbuckle-type tie rod 140. Therefore, fatigue failure of the attitude maintenance cage 40 is prevented, and the clearance adjustment function can be satisfied.

[0020] More specifically, the posture maintenance cage 40 of this embodiment includes a robust frame-shaped cage body 41. The frame-shaped cage body 41 includes an upper frame portion 70, a middle frame portion 80, and a lower frame portion 90, which are arranged horizontally in this order from the upper side of the digester tank 10, and multiple arms 50, 60 (four in this example) that connect these frame portions 70, 80, 90 to each other. In the posture holding cage 40 of this embodiment, the arms 50, 60 are arranged at an angle such that the horizontal distance between them decreases toward the bottom. Therefore, the frame members 70, 80, 90 are also configured so that the upper part is the largest and the frame members get smaller toward the bottom.

[0021] The arms 50, 60 and frame parts 70, 80, 90 of the cage body 41 in this embodiment are basically formed from cylindrical pipe material, and the connecting parts with other members are configured by welding annular connection flanges or plate-shaped joints. The connection flanges or joints have multiple through holes or female threads formed in appropriate positions to enable connection with the connection flanges or joints of other members with bolts and nuts. Note that the connection structure itself using bolts, nuts and welding for each part is performed by normal methods, so a detailed explanation will be omitted.

[0022] More specifically, the upper arm 50 is formed from a cylindrical pipe material, as shown in Figure 3, and a plate-shaped wall side connecting portion 52 is welded to its upper end, which is fixed to the upper inner wall 11 of the digester tank 10 by an anchor bolt. In addition, an annular connecting flange 51 is welded to the lower end thereof, so that it can be connected to the connecting flange 61 at the upper end of the lower arm portion 60. Furthermore, two connecting flanges 53 facing perpendicularly are welded to the middle portion of the cylindrical pipe material toward the sides, so that they can each be connected to a connecting flange 73 at the end of a cross beam 71 of the upper frame portion 70.

[0023] As shown in FIG. 4, the lower arm 60 is formed from a cylindrical pipe material, and has an annular connecting flange 61 welded to its upper end so as to be connectable to the connecting flange 51 at the lower end of the upper arm 50 . Two connecting flanges 64 facing perpendicularly are welded toward the side at the midpoint of the cylindrical pipe material, and each can be connected to a connecting flange 84 at the end of the cross beam 81 of the middle frame part 80. Furthermore, two connecting flanges 65 facing perpendicularly are welded toward the side near the lower end of the cylindrical pipe material, and each can be connected to a connecting flange 95 at the end of the cross beam 91 of the lower frame part 90.

[0024] As shown in FIG. 2, the upper frame portion 70 is the uppermost support portion of the digester tank 10, and by connecting the upper frame portion 70 to the middle portions of the arm portions 50, 60, the rigidity of the cage body 41 is further improved. The upper frame portion 70 has a rectangular frame structure that is the largest of the three frames, as shown in Fig. 5. The upper frame portion 70 has four cross beams 71 formed from cylindrical pipe material, and four reinforcing beams 76 that are also formed from cylindrical pipe material and connect adjacent cross beams 71 diagonally. Annular connection flanges 73 are welded to both ends of each cross beam 71, allowing connection to the connection flanges 53 of the upper arm portion 50. In addition, a reinforcing beam connection plate 72 is welded to the center of each cross beam 71 so as to protrude toward the draft tube 20, allowing connection plates 77 at both ends of the four reinforcing beams 76 to be connected.

[0025] As shown in FIG. 2, the middle frame portion 80 is a support portion between the upper frame portion 70 and the lower frame portion 90, and by connecting the middle frame portion 80 to the midpoints of the arm portions 50, 60, the rigidity of the cage body 41 is further improved. As shown in Fig. 6, the middle frame portion 80 has a rectangular frame structure that is medium in size among the three frame portions. Like the upper frame portion 70, the middle frame portion 80 has four cross beams 81 formed from cylindrical pipe material and four reinforcing beams 86 formed from cylindrical pipe material and connecting adjacent cross beams 81 diagonally. Annular connection flanges 84 are welded to both ends of each cross beam 81, making them connectable to the connection flanges 64 of the lower arm portion 60. In addition, a reinforcing beam connection plate 82 is welded to the center of each cross beam 81 so as to protrude toward the draft tube 20, making it possible to connect connection plates 87 at both ends of the four reinforcing beams 86.

[0026] 2, the lower frame 90 is the support part at the lowermost part of the digester tank 10 and has the smallest rectangular frame structure among the three frames. It is provided in the vicinity of the upper opening 21 of the draft tube 20 so as to surround the draft tube 20 around the agitating screw 32. As shown in FIG. 7, the lower frame portion 90 has four cross beams 91 formed from cylindrical pipe material and spaced at equal intervals in the circumferential direction, and support beams 92 formed from cylindrical pipe material and welded in an approximately T-shape so as to extend horizontally from the center of each cross beam 91 toward the draft tube 20.

[0027] An annular connection flange 95 is welded to both ends of each cross beam 91, so that the cross beams 91 can be connected to the connection flanges 65 of the lower arm portion 60. In addition, an annular support flange 93 is welded to the tip of the central support beam 92, so that the cross beams 91 can be connected to a clearance adjustment portion 100 provided between the tip of the support beam 92 and the draft tube 20 in the cross direction.

[0028] 2, the upper part of draft tube 20 has a hollow cylindrical opening casing 22 having an upper opening 21, and a hollow cylindrical upper casing 23 connected to the lower part of opening casing 22. Upper casing 23 is detachable from a flange portion facing the main body (lower portion) of draft tube 20 by bolts and nuts.

[0029] In addition, the opening casing 22 and the upper casing 23 are arranged to be easily disassembled, assembled, and maintained around the mixing screw 32 by means of bolts and nuts at their opposing flanges. The clearance adjustment part 100 of this embodiment is adapted to be attached to the lower flange of the upper casing 23. The clearance adjustment section 100 is provided with a clearance adjustment mechanism capable of adjusting the bridge state of each support girder 92 so as to maintain a predetermined opposing gap (clearance) between the mixing screw 32 of the axial pump 30 and the inner wall surface 20n of the draft tube 20.

[0030] As shown in Fig. 7(b), the clearance adjustment part 100 of this embodiment has an adjustment bracket 110 and an adjustment seat plate 120. As shown in Fig. 8, the adjustment seat plate 120 is a disk-shaped plate member having an insertion hole 121 for the draft tube 20 in the center and a plurality of adjustment holes 122 formed at intervals in the circumferential direction through the outer periphery. In addition, as shown in Fig. 9, the adjustment bracket 110 is a frame-shaped member formed in an octagonal shape in a plan view and having an insertion hole 111 for the draft tube 20 in the center. The four sides of the octagonal shape, top, bottom, left and right, serve as connecting parts 112 for the support girder 92.

[0031] As described in detail in the mounting method of the attitude holding cage 40 described later, this clearance adjustment section 100 is capable of adjusting the radial position of the fixing hole portion between the adjustment bracket 110 and the adjustment seat plate 120 within the range of the adjustment hole 122, thereby adjusting the misalignment between the mixing screw 32 of the axial pump 30 and the inner wall surface 20n of the draft tube 20. In the sludge digester 1 of this embodiment, the adjustment function of the clearance adjustment section 100 makes it possible to absorb misalignment between the mixing screw 32 of the axial pump 30 and the inner wall surface 20n of the draft tube 20, even in the case of a digester tank 10 having a large structure, and to maintain a stable supporting posture with the posture holding cage 40.

[0032] Next, we will explain how to attach the posture maintaining cage 40 of this embodiment to the sludge digester 1 of this embodiment, and how to use this posture maintaining cage 40 to maintain a predetermined opposing gap (clearance) between the mixing screw 32 of the axial pump 30 and the inner wall surface 20n of the draft tube 20.

[0033] As shown in the schematic diagram of Figure 10, when installing the posture maintenance cage 40 of this embodiment, a temporary scaffold S is assembled inside the digestion tank 10 for the sludge digestion apparatus 1. The temporary scaffold S is dismantled and removed after installation. According to the posture maintenance cage 40 of this embodiment, even if an existing tie rod is a tie rod 240 having a turnbuckle 240t as shown in Figure 11, the posture maintenance cage 40 can be installed in the same installation position, making replacement during maintenance easy.

[0034] Here, work inside the digestion tank 10 of the sludge digestion apparatus 1 involves loading and unloading through an opening in the lid 13 provided in the center of the top of the digestion tank 10. Therefore, it is desirable that the dimensions of the lid 13 are such that loading and unloading through the opening can be easily performed, and that the configuration is easy to install and disassemble. In contrast, the posture holding cage 40 of this embodiment has a two-part structure in which the arms 50 and 60 are split halfway in the axial direction, and the frames 70, 80, and 90 also have a three-stage structure spaced apart from each other above and below, and each of the frames 70, 80, and 90 can also be disassembled, making it easy to carry in and out through the narrow opening of the lid 13. In addition, the basic structures of the arms 50 and 60 and the frames 70, 80, and 90 are also the same, making it easy to disassemble and assemble.

[0035] The procedure for installing the posture maintenance cage 40 of this embodiment is as follows: for the cage body 41, the wall side connecting parts 52 of the four upper arms 50 are attached to the upper part 11 of the inner wall of the digester tank 10 with anchor bolts at a predetermined position facing the upper opening 21 of the draft tube 20. Next, the upper frame part 70 is assembled to the connection flanges 53 of the four upper arms 50 to more reliably construct a rigid structure.

[0036] Furthermore, the connecting flanges 61 of the lower arms 60 are connected to the connecting flanges 51 at the tips of the four upper arms 50, respectively, and then the middle frame 80 is attached to the connecting flanges 64 of the four lower arms 60 to construct a more rigid structure. Next, the lower frame portion 90 is attached to the connection flanges 65 on the tip sides of the four lower arm portions 60, and the adjustment bracket 110 is temporarily attached to the tip of the draft tube 20.

[0037] In this temporary hanging work, workers set up a gate-shaped structure on the temporary scaffolding S shown in Figure 10, and then suspend the components to be constructed using suspension equipment (not shown), assemble them so that the adjustment bracket 110 is positioned in the desired position while maintaining the desired posture. In the temporary hanging work, the opening casing 22 and upper casing 23 are removed in advance from the draft tube 20 side, and the upper end of the main body (lower part) of the draft tube 20 is inserted through the insertion hole 111 of the adjustment bracket 110 and through the insertion hole 121 of the adjustment seat plate 120, as shown in Figure 7 (b).

[0038] Next, an adjustable seat plate 120 is coaxially interposed between the flange at the upper end of the main body of the draft tube 20 and the lower flange of the upper casing 23, and the adjustable seat plate 120 is fixed to the draft tube 20 around its entire circumference with a plurality of flange connecting bolts and nuts 133 and a plurality of seat plate bolts and nuts 132. Then, a temporary installation work is performed by connecting the support flanges 93 at the tips of the four support beams 92 to the four connecting portions 112, respectively. As a result, the adjustment bracket 110 is temporarily fixed in place while also functioning as a support portion for the upper side of the draft tube 20.

[0039] Next, the clearance adjustment unit 100 adjusts the radial position within the sliding range of the fixing hole portion between the adjustment bracket 110 and the adjustment seat plate 120 on the adjustment bracket 110 so as to maintain a specified opposing gap (clearance) between the mixing screw 32 of the axial pump 30 and the inner wall surface 20n of the draft tube 20. Once the radial position is determined so that the opposing gap (clearance) can be maintained at a predetermined value, that position is fixed by multiple (six in this example) plate nuts 130 and adjustment bolts and nuts 131. At that time, the four support girders 92 are spanned without being subjected to tension in the axial direction thereof.

[0040] Once the clearance adjustment in the clearance adjustment part 100 has been completed, the adjustment bracket 110 and the adjustment seat plate 120 are welded on-site as necessary, thereby completely fixing the sliding position of the clearance adjustment part 100 and reliably maintaining the spanning state with the four support beams 92 after completing the axial clearance adjustment.

[0041] Next, the operation of the sludge digester 1 of this embodiment and the function and effect of the posture maintaining cage 40 will be described. Incidentally, in a sludge digestion facility such as the sludge digester 1 of this embodiment, a scum layer forms on the water surface of the sludge stored in the digestion tank 10. If the scum generated on the water surface in the digestion tank 10 solidifies and accumulates, not only will the sludge digestion process, which circulates the sludge, such as the inflow and outflow of sludge, not be able to proceed smoothly, but there is also a risk of the draft tube 20 being clogged and blocked, causing the circulation of the sludge to stop and causing serious problems in the anaerobic digestion process.

[0042] In contrast, in the sludge digester 1 of this embodiment, an upper screw 33 and a spray disk 34 are provided at a position axially above the mixing screw 32, so that the upper screw 33 can crush the scum layer in the water surface area (from HWL to LWL in Figure 2). Furthermore, by operating the axial flow pump 30 in reverse, the mixing screw 32 creates an upward flow in which the sludge in the digester tank 10 is introduced into the draft tube 20 through the lower opening 22 of the draft tube 20, and is then discharged from the upper opening 21.

[0043] Furthermore, during reverse operation, the upper screw 33 crushes the scum layer in the water surface area from HWL to HWL, while the spray disc 34 prevents the crushed scum from being sprayed upward and uniformly scatters the sludge in the water surface area from HWL to LWL around it, thereby reliably and stably generating an upward or downward flow in the draft tube 20, maintaining a good stirring state and enabling the sludge digestion process to continue stably.

[0044] Here, when the sludge digester is in operation, the draft tube 20 moves slightly. Therefore, if the attitude maintaining member for the upper part of the draft tube 20 is the tie rod 240 as described above, it is a tension support structure in which tension is applied to each by tightening the turnbuckle 240t. As a result, wear gradually progresses at the joint of the turnbuckle 240t, causing a loss of tension and increasing the rattle of the tie rod 240. Furthermore, since the conventional tie rod 240 is not designed to absorb the misalignment of the large-scale digester tank, there is a risk that fatigue failure of the tie rod 240 will progress more quickly due to the action of uneven force.

[0045] In contrast, the attitude holding cage 40 of this embodiment has a rigid fixed structure that does not rely on tension support using tension, such as the turnbuckle-type tie rod 240. That is, according to the attitude holding cage 40 of this embodiment, the frame-type cage main body 41 supports the draft tube 20 with a robust frame-type cage, so that fatigue failure of the attitude holding cage 40 is prevented and the clearance adjustment function can be satisfied.

[0046] Furthermore, according to the posture maintaining cage 40 of this embodiment, since the clearance adjustment section 100 is provided, even in the case of a digestion tank 10 having a large structure, the misalignment between the mixing screw 32 of the axial flow pump 30 and the inner wall surface 20n of the draft tube 20 can be absorbed and a stable supporting posture can be maintained.

[0047] In particular, according to the attitude maintaining cage 40 of this embodiment, the draft tube 20 to be constructed is supported in a surrounded state by the attitude maintaining cage 40, which is a rigid frame-type (cage-type) body, so as to maintain a clearance with the mixing screw 32. In particular, the cage body 41 of the posture holding cage 40 is firmly constructed by four arms 50, 60 via the inner wall and foundation of the digester tank 10 from a position higher than the water surface area HWL-HWL at the top of the draft tube 20, so that the cage body 41 is effectively prevented or suppressed from shaking due to the influence of water currents, etc., and the hanging posture of the draft tube 20 can be reliably maintained for a long period of time while maintaining an appropriate clearance between the draft tube 20 and the mixing screw 32.

[0048] Furthermore, in the configuration of this embodiment, four relatively short support girders 91 extend from the lower frame portion 90, which is the smallest of the frame portions, and these support girders 91 are suspended between the draft tube 20 to support the draft tube 20. Therefore, compared with tie rods that provide tension support, the support girders 91 can be configured over an extremely short distance, making this a particularly excellent structure for effectively preventing or suppressing the cage body 41 from shaking due to the effects of water currents, etc.

[0049] Here, in the operation of removing the scum layer as described above, if the posture maintaining member at the upper part of the draft tube 20 is structured in such a way as to hinder the flow of the agitated flow or the operation of removing the scum layer in the water surface area HWL to LWL at the upper part of the draft tube 20, this will be insufficient for continuing stable sludge digestion treatment. In contrast, the posture maintaining member of this embodiment, i.e., the posture maintaining cage 40, employs a cage-type frame support structure with a wide open area around the cage body 41, so that, like a tie rod that provides taut support by applying tension, it does not impede the flow of the agitating flow in the water surface area HWL to LWL, nor the function of the spray disk 34 to evenly scatter sludge in the water surface area HWL to LWL around it, or the function of the upper screw 33 to crush the scum layer in the water surface area.

[0050] Thus, according to the attitude holding cage 40 of this embodiment, compared to a tie rod that provides tension support by applying tension, it is possible to support the upper part of the draft tube 20 while surrounding it in a narrow area, thereby preventing or suppressing fatigue fracture of the attitude holding cage 40 itself. Therefore, according to the posture maintaining cage 40 of this embodiment, the flow of the agitating current and the operation of removing the scum layer in the water surface range from HWL to LWL are not hindered as with the conventional tie rods, and further, the problems with the conventional tie rods are eliminated and the posture maintaining performance of the draft tube 20 can be maintained for a longer period of time, so that it can be said to be extremely excellent as a posture maintaining member for the draft tube of a sludge digester.

[0051] The pump piping support cage according to the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. In other words, in the posture-maintaining cage of the present invention, the cage body 41 can be configured in various ways as long as it is interposed as a rigid frame-type structure between the support part on the draft tube 20 side and the support part on the inner wall side of the digester tank 10 in order to maintain the posture of the draft tube 20.

[0052] For example, in the above embodiment, as an example of constructing a sturdy frame-shaped cage body 41, an example was shown in which the cage body 41 has an upper frame portion 70, a middle frame portion 80 and a lower frame portion 90, which are arranged in order from the upper side of the digester tank 10, and multiple arm portions 50, 60 (four in this example) that connect these frame portions 70, 80, 90 to each other, but this is not limited to this. In other words, if the necessary rigidity can be ensured, for example, the upper frame portion 70 or the middle frame portion 80 can be omitted. However, in order to improve the rigidity of the cage body 41, it is preferable to further provide a frame portion other than the frame portion providing the girder connected to the draft tube 20.

[0053] Also, for example, if the clearance can be set without adjustment to an extent that clearance adjustment is not required when constructing the cage body on site, the clearance adjustment unit (clearance adjustment mechanism) can be omitted. However, since there is a high probability that clearance adjustment will be required when constructing the cage body on site, it is preferable to have a clearance adjustment unit. In addition, even when a clearance adjustment part is provided, the clearance adjustment part is not limited to being provided between the girder connected to the draft tube and the draft tube. However, a configuration in which the clearance adjustment part is provided between the girder connected to the draft tube is preferable for efficient clearance adjustment. [Explanation of symbols]

[0054] 1 Sludge digester (digestion equipment: agitator) 10 Digester 11 Upper part of inner wall 12 Bottom 13 Lid 15 Support legs 20 Draft tube (pump piping) 21 Upper opening 22 Opening casing 23 Upper casing 30 Axial flow pump 31 Rotation axis 32 Mixing screw 33 Upper screw 34 Spray Disc 35 Motor section 40 Posture-Maintaining Cage 41 Cage body 50 Upper arm (support part on the inner wall side of the digester) 51 Connecting flange 52 Wall side connection part 53 (Upper frame) connection flange 60 Lower arm 61 Connecting flange 64 (with inner frame) connection flange 65 (with lower frame) connection flange 70 Upper frame part 71 Crossbeam 72 Reinforcement girder connection plate 73 Connection flange 76 Reinforcement girder 77 Connection plate 80 Middle frame 81 Crossbeam 82 Reinforcement girder connection plate 84 Connection flange 86 Reinforcement girder 87 Connection plate 90 Lower frame part 91 Crossbeam 92 Support girder (girder that (directly) supports the draft tube) 93 Support flange 95 Connection flange 100 Clearance adjustment part 110 Adjustment bracket (upper support for draft tube) 120 Adjustment seat plate 130 Plate nut 131 Adjustment bolts and nuts 132 Seat bolts and nuts 133 Flange connection bolts and nuts S Temporary scaffolding

Claims

1. The present invention is used in a sludge digestion apparatus comprising a digestion tank, a draft tube vertically installed in the digestion tank and having openings at its upper and lower ends, and a vertical axial flow pump arranged in the center of the top of the digestion tank and having a rotating shaft suspended down so as to extend into the draft tube, a frame-shaped cage body that is fixed in the digestion tank in a hanging position with its upper portion supported by an upper portion of an inner wall of the digestion tank and has its lower portion fixed to a support portion on an upper side of the draft tube to maintain an upright position of the draft tube; The cage body includes: A plurality of arms that are suspended with their base ends connected to a support portion on the inner wall side of the digestion tank; A plurality of frame portions supported by the plurality of arm portions and arranged at a distance in the vertical direction of the digestion tank; a plurality of beams that are stretched between any one of the plurality of frame portions and the draft tube to support the draft tube; A posture-maintaining cage for a draft tube of a sludge digester, comprising:

2. 2. The attitude-maintaining cage for a draft tube of a sludge digester as described in claim 1, wherein a clearance adjustment section is provided between the plurality of girders and the draft tube, which can adjust the bridge state between the plurality of girders and the draft tube.

3. a digestion tank; a draft tube that is erected in the digestion tank and has openings at an upper end and a lower end; a vertical axial flow pump that is disposed in the center of the top of the digestion tank and has a rotating shaft that hangs down so as to extend into the draft tube; and an attitude maintaining member that maintains the attitude of the draft tube, 3. A sludge digester comprising a draft tube attitude maintaining cage for a sludge digester according to claim 1 or 2, as said attitude maintaining member.

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