Flocculator

Abstract

To provide a flocculator which achieves reduction of the number of brackets by fixing arms of adjacent stirring blades through a common bracket to a rotary shaft of the flocculator and thereby achieves reduction of the weight.SOLUTION: In order to achieve the above object, a flocculator includes: a rotary shaft; brackets provided at the rotary shaft; and at least two or more stirring blades fixed to the brackets through arms. An end of one arm and an end of the other arm located at the adjacent side of the stirring blades, provided in a line in an axial direction of the rotary shaft and located adjacent to each other, are fixed to the same bracket.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flocculator.

Background Art

[0002] Most of the colloidal particles present in natural water such as river water are negatively charged and repel each other due to their mutual charges, forming a stable dispersion system. Such particles do not settle as they are. Therefore, it is necessary to change the properties of the colloidal turbidity through the processes of aggregation and floc formation so that it can be removed by sedimentation and filtration operations. For example, in water purification facilities, a flocculant is added to raw water such as river water, and an aggregation treatment is performed to make the turbidity into minute flocs by rapid stirring. The minute flocs that have undergone the aggregation treatment grow into large flocs by repeatedly colliding with each other by applying slow stirring. This process is called floc formation. The raw water containing such minute flocs is slowly stirred by a slow stirrer called a flocculator to grow the flocs into coarse flocs, and the raw water is purified by separating the coarse flocs from the raw water by, for example, sedimentation separation.

[0003] As a flocculator, a configuration is widely used in which a plurality of rotating shafts provided with a large number of paddles are arranged side by side on the same axis horizontally in a floc formation tank for growing flocs, and these rotating shafts are connected and rotated by a connecting mechanism, and the raw water is slowly stirred by the paddles. The slow stirring by the flocculator must be operated so as not to break the grown flocs and not to cause sedimentation. As such a flocculator, one described in Patent Document 1 is disclosed. Generally, paddles having a rectangular cross-sectional shape are used, including the flocculator disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] A flocculator is required to have a performance of efficiently performing slow stirring in order to grow fine flocs into coarse flocs suitable for sedimentation separation. However, in a stirrer having a horizontal rotation axis like the above-described flocculator, since the circumferential flow becomes dominant, it cannot be said that the mixing and diffusion in the transverse direction of the floc formation tank are sufficient. In addition, it is desirable for the flocculator that the load on the bearing supporting the rotation axis is small in terms of construction cost and maintenance cost, and it is required to reduce the self-weight of the flocculator. On the other hand, since the flocculator needs to have a function of stirring while resisting the resistance of water, there is a limit in weight reduction when considering the balance with the mechanical strength of each member of the flocculator.

[0006] Therefore, an object of the present invention is to provide a flocculator that is lightweight by reducing the number of brackets by fixing the arms of adjacent stirring blades to the rotation axis of the flocculator while sharing the brackets.

MEANS FOR SOLVING THE PROBLEMS

[0007] As a result of intensive studies on the above problems, the present inventor has found that it is possible to reduce the number of members by sharing the same bracket for the arms of adjacent stirring blades, and to reduce the weight of the flocculator. That is, the present invention is the following flocculator.

[0008] In order to solve the above problems, a flocculator according to an embodiment of the present invention includes a rotating shaft rotatably supported by bearings, two or more brackets fixed to the peripheral wall surface with a space in the axial direction of the rotating shaft, and a paddle horizontally mounted and fixed between rod-shaped arms whose ends are fixed to the brackets and extend in the axial diameter direction of the rotating shaft. In the flocculator, the ends of one arm and the other arm located on the adjacent side of the adjacent stirring blades arranged in the axial direction of the rotating shaft are fixed to the same bracket.

[0009] According to this flocculator, in the paddles and arms constituting the stirring blades arranged in the axial direction of the rotating shaft, the adjacent arms are not fixed to their respective brackets, but are fixed to the same bracket, so the number of brackets can be reduced. As a result, the flocculator can be lightened by the amount corresponding to the reduced number of members.

[0010] Further, as an embodiment of the flocculator of the present invention, the ends of one of the arms and the ends of the other arm located on the adjacent side of the adjacent stirring blades arranged in the axial direction of the rotating shaft are alternately fixed to the same bracket at a predetermined interval in the rotational direction of the rotating shaft. According to this feature, the plurality of arranged stirring blades do not form a structure that crosses and continues across the flocculation tank on the same plane, and both ends of each stirring blade are open. For this reason, there is room for the water pushed by the paddle to escape to both ends of the stirring blade, generating a flow in the axial direction of the rotating shaft and promoting the turbulent diffusion of water. Thereby, the stirring efficiency of the flocculator can be improved.

[0011] Furthermore, as an embodiment of the flocculator of the present invention, the paddle has a substantially U-shaped cross-sectional shape, and the distance between one horizontal portion and the other horizontal portion increases as the distance from the vertical portion increases. According to this feature, in the stirring blade, the paddle that directly receives water pressure can increase the longitudinal rigidity while keeping the plate thickness thin, so that the paddle can be lightened. Also, when the rigidity of the paddle is increased, the deflection of the paddle during stirring is reduced compared to the conventional case, so the number of arms for fixing the paddle is reduced. As a result, the flocculator is lightened as a whole. Further, since the shape is such that the distance between the upper horizontal part and the lower horizontal part increases as it moves away from the vertical part, even when storing the paddle as a spare part, it can be compactly stacked and put together.

Effects of the Invention

[0012] According to the present invention, by alternately shifting the arrangement of adjacent stirring blades, it is possible to provide a flocculator that creates a flow in the rotational axis direction of the flocculator and is lightened while ensuring strength by reducing the number of members.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] The present invention will be described below with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted. Also, for the sake of illustration, the dimensional ratios in the drawings do not necessarily match those in the description. In the first embodiment, the case where the flocculator according to the present invention is applied to the floc formation tank of the water purification facility will be described.

[0015] FIG. 1 is a plan view showing the flocculator of the floc formation tank according to the first embodiment of the present invention. In a water purification facility or the like, a coagulant is added to raw water such as river water, and a coagulation treatment is performed to make turbidity into flocs. In the coagulation treatment, after adding a coagulant to the raw water and rapidly stirring it, slow stirring is performed to gradually make the turbidity in the raw water into larger flocs, making it easier to remove the flocs in the post-treatment. The flocculator is a device for gently stirring the raw water to be treated in order to grow flocs in the floc formation tank. Hereinafter, the raw water to be subjected to the coagulation treatment is referred to as water to be treated.

[0016] 〔First Embodiment〕 The configuration of the flocculator 10 according to the first embodiment will be described. FIG. 1 is a plan view showing the flocculator of the floc formation tank according to the first embodiment of the present invention. FIG. 2 is a side view taken along line a-a of the main part of the flocculator shown in FIG. 1. Referring to FIG. 1, the flocculator 10 is configured to include a submerged bearing 41, a support base 42, a rotating shaft 21, and stirring blades 11a, 11b, and 11c in the floc formation tank 32. In the example of FIG. 1, for example, four stirring blades 11a are arranged along the peripheral wall surface of the rotating shaft 21 with a central angle of, for example, 90° as viewed around the axis X. Hereinafter, for the sake of convenience of description, the stirring blades 11a, 11b, and 11c shown in FIG. 1 will be described as representatives.

[0017] In the water purification facility, an inflow channel 31 for supplying raw water to be treated is provided upstream of the flocculation tank 32, and a sedimentation tank 33 for promoting sedimentation of the formed flocs is provided downstream of the flocculation tank 32. Although not shown in FIG. 1, usually, a plurality of flocculation tanks 32 are provided in parallel between the inflow channel 31 and the sedimentation tank 33, and the respective flocculation tanks are connected via water passing holes (not shown).

[0018] The raw water to be treated in a state where turbidity has become minute flocs by rapid agitation flows into the flocculation tank 32 via the inflow channel 31. Inside the flocculation tank 32, the flocculator 10 gently rotates around the axis X of the rotary shaft 21, and accordingly, the agitation blades 11a, 11b, and 11c scrape the raw water to be treated in the flocculation tank 32, thereby agitating the raw water to be treated. By the slow agitation due to the rotation of the flocculator 10 in the flocculation tank 32, the minute flocs in the raw water to be treated collide with each other by turbulent diffusion and grow into coarse flocs. The raw water to be treated containing the coarse flocs grown to a size suitable for sedimentation is discharged to the sedimentation tank 33. The rate of aggregation, which is a factor in floc formation, increases as the particle concentration of the flocs is higher and the particle diameter is larger, so appropriate agitation is necessary. After the flocs have become in a property suitable for sedimentation, they are discharged from the floc formation layer 32 to the sedimentation tank 33. The flocculator 10 is a device that rotates around a rotary shaft perpendicular to the horizontal with respect to the streamline of the raw water to be treated flowing into the flocculation tank 32 via the inflow channel 31 and gently agitates the raw water to be treated in the flocculation tank 32. By this slow agitation, the flocs are coarsened.

[0019] The flocculator 10 includes a rotary shaft 21 rotatably supported by a pair of underwater bearings 41 and a support base 42 provided in the flocculation tank 32, two or more brackets 14 fixed to the peripheral wall surface with a space in the axial direction X of the rotary shaft, and agitation blades 11a, 11b, and 11c. A representative example of the structure of the stirring blade 11a shown in Fig. 1 will be described. The stirring blade 11a includes three arms 13a1, 13a2, and 13a3 provided at a predetermined interval in the axial direction X of the rotation axis, and four paddles 12. The stirring blade 11a has its ends fixed to the bracket 14 via the arms 13a1, 13a2, and 13a3, and has a structure in which rod-shaped arms 13a1, 13a2, and 13a3 extending in the radial direction of the shaft diameter of the rotation axis and four paddles 12 are horizontally fixed between the arms 13a1, 13a2, and 13a3. The number of arms and the number of paddles are not limited to the quantities illustrated in Fig. 1.

[0020] The rotating shaft 21 is a hollow cylindrical body made of stainless steel or the like, and the wall thickness forming this hollow cylindrical body is formed as thin as possible within a range where the necessary strength can be maintained. Thereby, during the operation of the flocculation tank 32, the flocculator 10 is configured to generate buoyancy by being entirely submerged, thereby reducing the self-weight of the entire flocculator 10. When the diameter of the rotating shaft 21 is, for example, 250 mm to 600 mm, it is within a range suitable for operation as a flocculator and sufficient buoyancy can be obtained. As other materials for the rotating shaft 21, those obtained by extrusion molding steel materials such as SS400 and STPG (Steel Tube Pipe General), or resin materials such as FRP (Fiber Reinforced Plastics) may be used. As long as the required strength in design can be obtained, it has an advantage in terms of weight reduction of the flocculator. Also, it is more excellent than metal materials in terms of durability in an environment where water splashes.

[0021] On the rotating shaft 21, brackets 14 are fixedly attached to the peripheral wall surface of the rotating shaft 21 at predetermined intervals along the axis X direction. The bracket 14 is a plate-shaped member made of stainless steel or the like, and is a member for fixedly attaching the ends of the arms 13a1, 13a2, and 13a3 which are constituent members of the stirring blade 11a. Similarly, the ends of the arms 13b1, 13b2, and 13b3 which are constituent members of the stirring blade 11b, and the ends of the arms 13c1, 13c2, and 13c3 which are constituent members of the stirring blade 11c are fixedly attached to the bracket 14. As a method for fixing the bracket 14 to the peripheral wall surface of the rotating shaft 21, bolt tightening, welding, etc. are suitable.

[0022] The mounting interval of the bracket 14 along the axis X direction of the rotating shaft 21 is adjusted according to the mounting intervals of the arms 13a1, 13a2, 13a3, 13b1, 13b2, 13b3, 13c1, 13c2, and 13c3. In the stirring blades 11a and 11b arranged adjacent to each other, the adjacent arms 13a3 and 13b1 are fixedly attached so as to share the same bracket 14. Similarly, in the stirring blades 11b and 11c arranged adjacent to each other, the adjacent arms 13b3 and 13c1 are fixedly attached so as to share the same bracket 14. As a method for fixing the arms 13a1, 13a2, and 13a3 to the bracket 14, bolt tightening, welding, etc. are suitable. As shown in FIG. 2, the arms 13a1, 13a2, and 13a3 are arranged so as to extend in a cross shape in the axial diameter direction of the rotating shaft 21, for example, when viewed from the axis X direction of the rotating shaft 21, and are fixedly attached to the rotating shaft 21 via the bracket 14.

[0023] The stirring blade 11a is formed by horizontally fixing four paddles 12 between three arms 13a1, 13a2, and 13a3. For example, as shown in FIG. 1, the three arms 13 are arranged in parallel, and the four paddles 12 are arranged in a basket shape at regular intervals on these arms 13. FIG. 1 shows a case where three stirring blades 11a, 11b, and 11c are arranged adjacent to each other on the same plane in the axial direction X of the rotating shaft 21.

[0024] The paddle 12 is a paddle-shaped plate member. When the stirring blade 11a scrapes the water in the flocculation tank 32 in the rotation direction as the rotating shaft 21 rotates around the axis X, the paddle 12 becomes the main member having the function of pushing out the water facing the water. The material of the paddle 12 may be any material that can obtain the strength against the reaction force due to the water resistance generated in the direction opposite to the rotation direction of the stirring blade 11a with the arms 13a1 and 13a2, or 13a2 and 13a3 as fulcrums. For example, the paddle 12 may be formed by pressing a metal material such as SUS (Steel Use Stainless) or aluminum, or may be formed by extrusion molding a resin material such as FRP or PVC (Polyvinyl Chrolide).

[0025] As shown in FIG. 2, the paddle 12 is a flat plate member having a water scraping surface facing the rotation direction Y of the rotating shaft 21. The water scraping surface is composed of, for example, a surface having a normal line in the rotation direction Y of the arm 13a3. During the operation of the flocculator 10, the water scraping surface stirs the water to be treated while receiving the reaction force due to the water resistance from the water to be treated. The paddle 12 is fixed to the arm 13a3 by bolting, for example, through a fastening hole (not shown) provided through the water scraping surface.

[0026] The operation and effect of the flocculator 10 according to the first embodiment will be described. In this embodiment, the arm 13a3 of the stirring blade 11a and the arm 13b1 of the stirring blade 11b, which are adjacent to each other, have their respective ends fixed to the same bracket 14. Similarly, the arm 13b3 of the stirring blade 11b and the arm 13c1 of the stirring blade 11c, which are adjacent to each other, have their respective ends fixed to the same bracket 14.

[0027] When the arm 13a3 and the arm 13b1 are fixed and attached to different brackets 14 individually, it is desirable that the two brackets 14 are as close as possible in the axial direction X of the rotation axis 21. The distance between the two brackets 14 is also the distance between the arm 13a3 and the arm 13b1, and the distance between the arm 13a3 and the arm 13b1 becomes the gap at the adjacent ends of the stirring blades 11a and 11b. The gaps at the ends of the stirring blades 11a, 11b, and 11c are desirably made small to avoid impairing the stirring effect. On the other hand, when bolting or welding is required for fixing the bracket 14, a minimum space for bolt placement or welding work is necessary, so there is a limit to reducing the clearance. As in the present embodiment, if the arm 13a3 and the arm 13b1 at adjacent positions have their respective ends fixed to the same bracket 14, the gap between the stirring blades 11a and 11b is only the thickness of the bracket 14. Also, since the arm 13a3 and the arm 13b1 can be fixed with one bracket 14, the number of parts can be reduced, which also contributes to reducing the weight of the entire flocculator 10.

[0028] 〔Second Embodiment〕 The configuration of the flocculator 10 according to the second embodiment will be described. In the description of the embodiments other than the first embodiment described below, the members that are the same as or equivalent to the members described in the first embodiment are given the same reference numerals, the description is omitted, and only the different parts will be described.

[0029] FIG. 3 is a plan view showing a flocculator of a floc formation tank according to the second embodiment of the present invention. FIG. 4 is a side view taken along line b-b of the main part of the flocculator shown in FIG. 3. The flocculator 10 is configured to include a rotary shaft 21 rotatably supported by a submerged bearing 41 and a support base 42 provided in the floc formation tank 32, two or more brackets 15 fixed to the peripheral wall surface with a space in the axial direction X of the rotary shaft, and stirring blades 11a, 11b, and 11c, which is the same as in the first embodiment. Further, the arm 13a3 of the stirring blade 11a and the arm 13b1 of the stirring blade 11b, which are adjacent to each other, have their respective ends fixed to the same bracket 15. Similarly, the arm 13b3 of the stirring blade 11b and the arm 13c1 of the stirring blade 11c, which are adjacent to each other, have their respective ends fixed to the same bracket 15. However, it is different from the first embodiment in that the stirring blades 11a, 11b, and 11c are not arranged on the same plane.

[0030] In the second embodiment, the stirring blade 11a and the stirring blade 11b, which share the rotary shaft 21 and are adjacent to each other in the axial direction X, are arranged at a predetermined angle when viewed from the axial direction X. That is, for example, the surface of the paddle 12 of the stirring blade 11a facing the water to be treated and the surface of the paddle 12 of the stirring blade 11b facing the water to be treated are not on the same plane but are arranged at a predetermined angle. The predetermined angle is, for example, 45° as shown in FIG. 4. In the first embodiment, the stirring blades 11a, 11b, and 11c are substantially continuously connected on the same plane. However, in the second embodiment, different from the first embodiment, the stirring blade 11b is not substantially continuously connected to the stirring blade 11a at the end on the stirring blade 11a side but is interrupted at the end of the stirring blade 11b. Similarly, the stirring blade 11b is not substantially continuously connected to the stirring blade 11c at the end on the stirring blade 11c side but is interrupted at the end of the stirring blade 11b.

[0031] Similar to the first embodiment, in the second embodiment, the mounting interval of the bracket 15 along the axial direction X of the rotary shaft 21 is adjusted according to the mounting intervals of the arms 13a1, 13a2, 13a3, 13b1, 13b2, 13b3, 13c1, 13c2, and 13c3. In the case of the stirring blades 11a and 11b arranged adjacent to each other, the arms 13a3 and 13b1 are not adjacent to each other and have a positional relationship with a predetermined angle in the rotational direction Y of the rotating shaft 21, but are fixedly attached so as to share the same bracket 15. Similarly, in the case of the stirring blades 11b and 11c arranged adjacent to each other, the arms 13b3 and 13c1 having a positional relationship with a predetermined angle in the rotational direction Y of the rotating shaft 21 are fixedly attached so as to share the same bracket 15.

[0032] The operation and effect of the flocculator 10 according to the second embodiment will be described. In the present embodiment, the arm 13a3 of the stirring blade 11a and the arm 13b1 of the stirring blade 11b, which are at adjacent positions of the stirring blades 11a and 11b, have their respective ends fixed to the same bracket 15. Similarly, the arm 13b3 of the stirring blade 11b and the arm 13c1 of the stirring blade 11c, which are at adjacent positions of the stirring blades 11b and 11c, have their respective ends fixed to the same bracket 15, which is the same as in the first embodiment. In addition to this, in the second embodiment, the stirring blade 11b is disconnected at the end of the stirring blade 11b without being substantially continuous with the stirring blade 11a at the end on the stirring blade 11a side. Similarly, the stirring blade 11b is disconnected at the end of the stirring blade 11b without being substantially continuous with the stirring blade 11c at the end on the stirring blade 11c side. Thus, both ends of the diffusion blade 11b viewed from the axial direction X are not substantially continuous with the ends of the adjacent stirring blades 11a and 11c and are disconnected. Therefore, the water to be treated pushed by the diffusion blade 11b forms a flow in the axial direction of the rotating shaft 21 in addition to the flow in the radial direction of the rotating shaft 21. By this action, the stirring effect is enhanced.

[0033] In the stirring operation, it is required that the water to be treated containing flocs be uniformly dispersed. By the rotation of the flocculator equipped with paddles, forced convection is imparted to the water in the floc formation tank 32. As a result, since a part of the water moves at a different speed from the surrounding water, turbulent overflows are generated by shear forces. Due to the turbulent diffusion caused by this forced convection, local mixing is performed. At the same time, since the forced convection moves the water throughout the floc formation tank, overall mixing also progresses. The flow pattern in a fluid state formed in the water throughout the floc formation tank by the rotation of the flocculator can be classified into three types: circumferential flow, axial flow, and radial flow.

[0034] The flow formed by the rotation of the stirring blades 11a, 11b, 11c composed of paddle-shaped paddles 12 is mainly the circumferential flow around the rotation axis 21. The flow state of the water to be treated formed throughout the floc formation tank 32 by the stirring blades 11a, 11b, 11c is roughly divided into three types: circumferential flow, axial flow, and radial flow, depending on the shape of the paddle 12, the shape and arrangement of the stirring blades 11a, 11b, 11c, etc. When the stirring blades 11a, 11b, 11c are arranged in a substantially continuous manner on the same plane, the circumferential flow and the radial flow become dominant as the flow pattern. This is because there is not much room for the axial flow viewed from the rotation axis 21 to flow out from the respective ends of the stirring blades 11a, 11b, 11c.

[0035] In this embodiment, since a stirring state is achieved by combining three types of flow patterns: circumferential flow, axial flow, and radial flow, more effective stirring is enabled.

[0036] 〔Third Embodiment〕 The configuration of the flocculator 10 according to the third embodiment will be described. FIG. 5 is a side view showing the arrangement of the paddles and arms of the third embodiment of the present invention. FIG. 6 is a cross-sectional view of the paddle of the third embodiment of the present invention. The paddle 12a included in the flocculator 10 of the present embodiment is characterized by having a substantially U-shaped cross-sectional shape. When viewed in FIG. 6, it includes a flange 12a1 which is a pair of horizontal members vertically, and a web 12a1 which is a vertical member connecting the pair of flanges 12a1. The mutual distance between the upper flange 12a1 and the lower horizontal flange 12a1 has a cross-sectional shape that becomes larger as it moves away from the web 12a1. With such a cross-sectional shape, the bending rigidity of the paddle 12a can be increased, and the wall thickness of the member can be made thinner. Therefore, the weight can be reduced while maintaining the strength of the member. Also, while being substantially U-shaped, the upper flange 12a1 and the lower horizontal flange 12a1 have a cross-sectional shape that opens outward from the web 12a1. For example, when using the web 12a1 as the bottom surface and stacking a plurality of paddles 12a, the lower surfaces of the pair of flanges 12a1 of the upper paddle 12a can be substantially fitted onto the upper surfaces of the pair of flanges 12a1 of the lower paddle 12a for stacking. Therefore, a plurality of paddles 12a can be stacked and stored in a non-bulky and stable state. Also, it contributes to efficient transportation.

Explanation of Reference Numerals

[0037] 10…Flocculator, 11a, 11b, 11c…Agitating vane, 12, 12a…Paddle, 12a1…Flange, 12a2…Web, 13a1, 13a2, 13a3, 13b1, 13b2, 13b3, 13c1, 13c2, 13c3…Arm, 14, 15…Bracket, 21…Rotating shaft, 31…Inflow channel, 32…Floc formation tank, 33…Sedimentation tank, 41…Submerged bearing, 42…Support base, 51…Drive source

Claims

1. A rotating shaft, a bracket provided on the rotating shaft, and at least two or more stirring blades fixed to the bracket via arms, characterized in that: the ends of one of the arms and the ends of the other arms, which are located on adjacent sides of the adjacent stirring blades arranged in a row in the axial direction of the rotating shaft, are fixed to the same bracket. A flocculator.

2. The flocculator according to claim 1, characterized in that the ends of one of the arms and the ends of the other arms, which are located on adjacent sides of the adjacent stirring blades arranged in a row in the axial direction of the rotating shaft, are alternately fixed to the same bracket at a predetermined interval in the rotation direction of the rotating shaft.

3. The flocculator according to claim 1 or 2, characterized in that the paddle has a substantially U-shaped cross-sectional shape, and the distance between one horizontal portion and the other horizontal portion increases as the distance from the vertical portion increases.

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