JP5851134B2 - Sludge digester - Google Patents

Description

  The present invention relates to a sludge digester that is easy to maintain and repair and repair, in which sludge in a sludge digester is circulated (stirred) using a draft tube and a flow maker to anaerobically digest.

Conventionally, water treatment facilities such as sewage treatment plants, intensive treatment facilities for sludge, and organic waste treatment facilities such as human waste are subjected to anaerobic digestion treatment to reduce and stabilize sludge. An anaerobic digester is installed. This anaerobic digester is equipped with a stirring device for stirring sludge.
The stirring device employs a gas stirring method or a mechanical stirring method, and a two-stage paddle low-speed stirrer or a low-speed stirrer is used as the mechanical stirring method. For example, the gas agitation method is a method in which the digestion gas in the digestion tank is sucked into the draft tube and an upward flow is generated in the digestion tank by the air lift effect. The sludge is stirred at a low speed by a large two-stage paddle without providing a draft tube, and a circulating flow is generated in the anaerobic digester.

The digester tank of a conventional sludge digester is often large, and its vertical cross-sectional shape is a turtle shell or egg shape, and its height is generally several tens of meters.
In the digestion tank, sludge is treated by anaerobic digestion with microorganisms (methane fermentation using anaerobic methanogen), but the sludge in the digestion tank is efficiently treated (improves digestion efficiency) ) To maintain the sludge in the digestion tank at a constant temperature (medium-temperature digestion or high-temperature digestion), to promote the contact between the sludge in the digestion tank and to prevent the accumulation of sludge containing sand at the bottom of the digestion tank. The sludge must be circulated sufficiently in the tank. Normally, for the circulation of sludge in the digestion tank, the gas stirring method is adopted in the turtle shell shape, and the mechanical stirring method is adopted in the egg-shaped digestion vessel.

The digester that uses the gas agitation system has a gas extraction pipe for extracting the digestion gas from the digestion tank, a blower for increasing the pressure of the digestion gas from the gas extraction pipe, and boosting with this blower. A gas blowing pipe for blowing the digested gas into the sludge is provided, and the lower end of the gas blowing pipe is positioned at the bottom of the digestion tank.
When digestion gas is blown into the sludge from the gas blowing pipe, a vertical circulation flow is formed in the digestion tank, and the sludge is stirred.

On the other hand, as a relatively new digester using a mechanical stirring method, for example, a sludge digester of a sludge treatment system disclosed in Patent Document 1 below is known.
The cross-sectional shape of the sludge digestion tank is a turtle shell shape, and a draft tube is provided inside the sludge digestion tank. The draft tube is supported in a vertical state from the lower part of the inner wall of the sludge digestion tank via a support leg.
The draft tube has a relatively small inner / outer diameter small-diameter pipe portion disposed below, a large-diameter tube portion having an inner / outer diameter larger than the small-diameter tube portion disposed above, and the small-diameter tube portion and the large-diameter portion. It is comprised with the intermediate | middle pipe part which connects a pipe part.
The upper end portion of the large-diameter pipe portion disposed above extends to the through hole of the lid on the upper surface of the inspection port.

  Inside the draft tube, a stirrer for stirring the sludge in the sludge digestion tank is installed so that it can be inserted and removed. This stirrer includes a motor and a rotatable screw attached to a rotation shaft of the motor. Moreover, the convex taper ring fitted to the concave taper ring attached to the intermediate pipe part is attached to the upper outer side of the upper casing of the stirrer.

JP 2003-71498 A (left column, page 3, lines 9 to 14 and lines 34 to 40, and FIG. 1)

Although the conventional sludge digestion apparatus is comprised as mentioned above, there existed a subject as shown to following (1)-(8).
(1) In a gas agitating digester, the digested gas pressurized by a blower is blown into the sludge to circulate the sludge. However, since the circulating power (stirring power) is weak, the sludge is sufficiently circulated in the digester. In some cases, the sludge accumulates at the bottom of the digestion tank or interferes with anaerobic digestion, and the function of the digestion tank may not be exhibited (may result in malfunction).
(2) In recent years, the concentration of sludge introduced into the digestion tank by mechanical concentration has increased, making it difficult to circulate the sludge in the digestion tank.

(3) For the above reasons, there is a tendency to introduce a mechanical stirring method into a digester that employs a gas stirring method.
However, for example, when an underwater mechanical stirring system is introduced, sludge can be reliably circulated in the vertical direction in the digestion tank, but a large circulation facility (stirrer) is required to obtain a sufficient circulation flow. And a motor, etc.) are required, which increases the construction cost and operation cost.
In the apparatus disclosed in Patent Document 1, this circulation facility is installed in the draft tube (under the water surface), but not only the sludge circulation flow in the digestion tank or the draft tube is hindered. Therefore, it is difficult to maintain and manage the circulating equipment, which will hinder stable anaerobic digestion treatment. If maintenance and repair of the circulating equipment is to be performed, a large-scale work is required to remove these devices from the digestion tank, and depending on the situation, it is also necessary to empty the digestion tank. In addition to being expensive, the anaerobic digestion process cannot be performed, and the sludge must be separately treated.

(4) Since the apparatus disclosed in Patent Document 1 is provided with a plurality of “sludge inflow / outflow openings” below the digestion tank, a large facility (such as a stirrer or a motor) is provided. However, the discharge amount (force) and suction amount (force) at each opening are small (weak), especially at the bottom of the digestion tank, there is not enough circulation flow, and sludge accumulates at the bottom of the digestion tank. The efficiency of the anaerobic digestion process may deteriorate.
Furthermore, in the vicinity of the “sludge inflow / outlet opening 15” located above the draft tube, a large facility (such as a stirrer or a motor) may be provided so that the inflow and outflow of sludge cannot be performed smoothly. In addition, when scum is generated in the upper part of the digestion tank (near the water surface) and this scum is solidified and laminated, the “sludge inflow / outlet opening 15” is clogged or blocked, and sludge This will stop the circulation and cause a serious hindrance to the anaerobic digestion process.

(5) In the mechanical stirring method, when the rotating shaft of the stirrer is extended from the upper side to the lower side of the digester, vibration (resonance) and rotational blur may occur depending on the rotating speed and the thickness of the rotating shaft, which is It becomes impossible to form a circulating flow of sludge. If the vibration (resonance) or rotational vibration is large, the device may be damaged or destroyed, and the rotation must be stopped for inspection and repair. In particular, in an underwater type mechanical agitation method, when the rotating shaft is extended long in the draft tube, if the equipment is damaged due to vibration (resonance) or rotational blurring, the draft tube will also be damaged, and anaerobic digestion of sludge will occur. Processing may become impossible.
(6) The draft tube that extends vertically from the upper side to the lower side in the digestion tank is inherently unstable, and not only the vibration (resonance) and rotation blur of the rotating shaft of the stirrer, but also the quality of the circulating flow and sludge. Vibrate or swing under the influence of If the vibration or swing of the draft tube increases, it will not only affect the proper circulation of sludge, but may also be damaged by contact with the rotating shaft and blades of the agitator in the draft tube. is there.

(7) In the sludge treatment facility, depending on the quality of the wastewater flowing into the wastewater treatment facility where sludge is generated, the sludge to be treated contains a lot of magnesium (Mg), and this magnesium (Mg) is originally contained in the sludge. It reacts with phosphorus (P) and ammonia (NH 3), and insoluble magnesium ammonium phosphate (common name: struvite (MAP)) is produced. This is the same in organic waste processing facilities such as human waste (containing a large amount of Mg, P, and NH3). The struvite grows (thickens) by adhering to the inner wall or rotating shaft of the pipe, and hinders the flow in the pipe or prevents the operation of the equipment. Strabite is also generated in the digestion tank, and adheres to the sludge, such as a draft tube or circulation equipment, and thickens, which may cause problems with the circulation equipment or obstruct sludge circulation.
(8) In the digestion tank, when the anaerobic digestion process is started or when the digestion process is not smooth, foaming is likely to occur, and bubbles may flow out of the digestion tank. In such a case, even if the drive device (motor) of the stirrer is installed outside the digestion tank, bubbles may enter the motor, resulting in a malfunction and failing to form a sludge circulation flow. .

  This invention was made in order to solve the above problems, and efficiently and reliably circulates sludge in the digestion tank, improves the treatment function of anaerobic digestion, preserves various devices, and is good. An object is to provide a sludge digester capable of stably performing anaerobic digestion treatment of sludge and ensuring easy operation, maintenance and repair.

  The sludge digestion apparatus according to the present invention includes an anaerobic digester for anaerobically digesting sludge, a draft tube standing in the anaerobic digester and having openings at the upper and lower ends, and an upward flow in the draft tube Or a flow generator for generating a downward flow, wherein the flow generator includes a rotating shaft extending from an upper part of the anaerobic digester into the draft tube and a driving device for rotating the rotating shaft. The rotating shaft is provided with a spray disk, an upper rotating blade and a lower rotating blade, and a rod-shaped stabilizer is attached to the tip.

  In the sludge digestion apparatus according to the present invention, a tie rod fixed to the inner wall of the anaerobic digester is attached to the upper part of the draft tube, and is fixed to the inner wall of the anaerobic digester at the lower part of the draft tube. A support base is attached.

  In the sludge digestion apparatus according to the present invention, one or more of the upper part of the draft tube, the spray disk, the upper rotary blade, and the lower rotary blade are subjected to surface processing.

  In the sludge digestion apparatus according to the present invention, the drive machine is provided with a sealed bearing.

  According to the present invention, the rotating shaft is provided with the spray disk, the upper rotating blade, and the lower rotating blade, and the rod-shaped stabilizer is attached to the tip, so that an upward flow or a downward flow is generated in the draft tube. Since it is configured to have a flow machine, it can circulate (stir) the sludge reliably in the vertical direction even in deeply anaerobic digesters such as turtle shells and ovals, and even if the sludge is highly concentrated. In addition, it is possible to prevent the accumulation of sludge at the bottom of the anaerobic digestion tank and to perform the anaerobic digestion process efficiently and stably.

  In particular, the sludge rising by the spray disk can be uniformly diffused in the horizontal direction, and the upward spraying can be prevented, and the scum generated and laminated on the water surface by the upper rotating blades It is possible to prevent clogging by breaking, and to form and maintain a circulating flow in the vertical direction, and it is possible to reliably and stably generate an upward flow or a downward flow in the draft tube with the lower rotating blades. In addition, by attaching a rod-shaped stabilizer to the tip of the rotating shaft, the rotating shaft can be stably rotated, and resonance at the natural rotational speed can be prevented to prevent damage to equipment. .

  According to this invention, since the circulation flow is formed by the draft tube and the flow maker, the structure is simple, the circulation flow is not hindered, and the circulation flow in the vertical direction can be smoothly performed in the anaerobic digester. It can be formed and maintained, and construction costs and operating costs can be reduced. In addition, since the sludge can be reliably sucked or discharged at the top and bottom openings of the draft tube, a sufficient circulation flow can be obtained even at the bottom of the anaerobic digestion tank, preventing sludge accumulation and ensuring stable and efficient operation. There is an effect that anaerobic digestion treatment can be performed.

  According to the present invention, the structure is simple, and the length of the rotating shaft of the flow generator inserted in the draft tube is within a quarter of the total length of the draft tube. Maintenance and inspection are easy, and even if a device breaks down or malfunctions, it can be handled without requiring a large-scale work, and the cost and work can be reduced.

  According to the present invention, since the draft tube is fixed by the tie rod fixed to the inner wall of the anaerobic digestion tank and the support frame, vibration and oscillation due to the rotation of the rotating shaft of the flow generator and the circulating flow can be prevented. It has the effect of forming and maintaining a sludge circulation flow efficiently and stably.

  According to this invention, surface processing (polishing and lining) is applied to the upper portion of the draft tube (inner wall and outer wall such as a trumpet-shaped portion), spray disk, upper rotating blade, and lower rotating blade, so It is possible to suppress sticking and growth, and to prevent adhesion of foreign substances, so that the flow generator can be operated stably, and a circulating flow can be formed and maintained efficiently without receiving extra resistance, and a draft tube, etc. There is an effect that it is possible to suppress the blockage.

  According to the present invention, since the sealed bearing is provided in the driving device of the flow generator, it is possible to prevent the invasion of bubbles including corrosive gas and sludge particles generated in the anaerobic digestion tank. It is possible to maintain and prevent breakdowns and damages, and to operate the flow generator stably and satisfactorily. In particular, by providing a plurality of oil seals in the bearing, there is an effect that the intrusion of gas and bubbles into the bearing can be blocked.

It is sectional drawing which shows the structure of the sludge digestion apparatus by Embodiment 1 of this invention. It is a side view which shows the caster of the sludge treatment digester by Embodiment 1 of this invention. It is a side view which shows another form of the flow generator of the sludge treatment digester by Embodiment 1 of this invention. It is sectional drawing which shows the structure of the sludge digestion apparatus by Embodiment 2 of this invention. It is sectional drawing which shows the bearing of the flow generator of the sludge digestion apparatus by Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a sectional view showing a configuration of a sludge digesting apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a side view showing a flow generator of the sludge digesting apparatus according to Embodiment 1 of the present invention.
The sludge digester 1 according to the first embodiment includes an anaerobic digester 2, a draft tube 3, and a flow generator 4.
The anaerobic digestion tank 2 reduces the sludge generated from a sewage treatment facility or the like by anaerobic treatment, and simultaneously collects digestion gas.
The draft tube 3 has an upper end opening 31 and a lower end opening 32, and the flow is controlled in a certain direction by concentrating the flow produced by the flow generator 4 on the upper part or the lower part of the anaerobic digestion tank 2, and It creates an efficient stirring state without collision.
In order to keep the sludge (sludge in the tank) in an anaerobic state and a uniform state such as temperature, the flow generator 4 generates an upward flow or a downward flow in the draft tube 3, A necessary flow is created in the anaerobic digester 2.

Hereinafter, the structure of the anaerobic digester 2, the draft tube 3, and the flow generator 4 is demonstrated concretely.
In the example of FIG. 1, the anaerobic digestion tank 2 has a substantially oval shape, and the sludge in the tank in the anaerobic digestion tank 2 flows from the draft tube 3 disposed in the center of the inside. Depending on the direction, the structure is an upward flow or a downward flow.
When the sludge flow in the tank in the draft tube 3 is a downward flow, the sludge in the tank is blown to the bottom of the anaerobic digestion tank 2, so that the sludge in the tank is reflected on the bottom of the anaerobic digestion tank 2. And then uniformly flows upward through the inner wall of the anaerobic digester 2. In the vicinity of the liquid level in the anaerobic digestion tank 2, the flow of the sludge in the tank is sucked into the draft tube 3 by the flow generator 4.
On the other hand, when the flow of sludge in the tank in the draft tube 3 becomes an upward flow, the sludge in the tank sucked up from the bottom of the anaerobic digestion tank 2 is lifted to the top of the tank and overflows from the upper end opening 31 of the draft tube 3. The sludge in the tank becomes a flow descending outside the draft tube 3.
Therefore, the flow of the sludge in the tank in the anaerobic digestion tank 2 forms a uniform upward or downward flow around the draft tube 3.

  In the example of FIG. 1, the shape of the anaerobic digester 2 is substantially oval as described above, but the shape of the anaerobic digester 2 is not limited to this, for example, a spherical shape, a cylindrical shape, a turtle shell shape ( 4), a rectangular parallelepiped or the like, and the shape is not limited. However, it is preferable that each of the transverse section and the longitudinal section is symmetrical with respect to the draft tube 3.

The draft tube 3 is a long cylindrical member, is supported by a tie rod 21 and a support frame 22, and is erected at the center in the anaerobic digester 2.
The upper end opening 31 is provided in the upper part of the draft tube 3, and the lower end opening 32 is provided in the lower part. The upper end opening 31 and the lower end opening 32 of the draft tube 3 have a uniform flow direction when the sludge in the tank passes. In order to disperse into a trumpet, it has a structure that spreads in a trumpet shape (bell shape such as a trumpet).
Note that the draft tube 3 is entirely submerged below the liquid level. In the upper part of the draft tube 3, the spiral lower rotary blade 44 disposed on the rotary shaft 41 extending from the flow generator 4 into the draft tube 3 rotates, so that a flow is caused in the draft tube 3. It has become.
For this reason, the inside diameter of the draft tube 3 has a dimension that does not hinder the rotation of the lower rotary blade 44 of the flow generator 4.

  In the example of FIG. 1, the upper end opening 31 and the lower end opening 32 of the draft tube 3 have a trumpet-like structure, but the flow direction of the sludge in the tank when passing through the upper end opening 31 and the lower end opening 32 is changed. As long as it can be uniformly dispersed, the shape is not limited to the trumpet shape, and may be, for example, a funnel shape or a straight pipe.

The flow generator 4 has a structure extending from the upper part of the anaerobic digester 2 into the draft tube 3 (see FIG. 2), and includes a spray disk 42, an upper rotary blade 43, a lower rotary blade 44, and a rod-shaped stabilizer 45. The rotary shaft 41 includes a drive unit 46 that rotates the rotary shaft 41, and a bearing 47 that supports the rotary shaft 41.
The rotating shaft 41 of the flow generator 4 is a member that has one end connected to the drive unit 46 and the other end extended (inserted) into the draft tube 3 and rotated by the drive unit 46.

The spray disk 42 is a donut-shaped disk, and is disposed at a position above the draft tube 3 by inserting the rotating shaft 41 through a hole in the center.
Note that the lower side of the spray disk 42 has a shape in which the center gradually increases (expands) from the lower side toward the upper disk. For this reason, when the sludge in the tank pushed up by the upper rotary blade 43 hits the lower part of the spray disc 42, the sludge in the tank is placed on the liquid surface of the anaerobic digestion tank 2 along the surface shape of the spray disk 4. On the other hand, it is uniformly guided and dispersed in the horizontal direction.

The upper rotary blade 43 is spirally formed around the rotary shaft 41 at a position above the draft tube 3 and below the spray disk 42 and rotates as the rotary shaft 41 rotates. By this, it is a member which makes the sludge in the tank near the liquid level in the anaerobic digestion tank 2 flow upward or downward.
The lower rotary blade 44 is formed in a spiral shape around the rotating shaft 41 of the portion extending into the draft tube 3, and rotates along with the rotation of the rotating shaft 41, so that the tank in the draft tube 3. It is a member that allows the inner sludge to flow upward or downward.

  The rod-shaped stabilizer 45 is disposed at the tip of the rotating shaft 41, and the length thereof can be adjusted for the purpose of maintaining a stable rotating state of the rotating shaft 41.

The driving machine 46 is a motor such as a motor or an engine that rotates the rotary shaft 41, and the driving machine 46 is installed outside the anaerobic digester 2.
The bearing 47 is installed on the upper part of the anaerobic digester 2 adjacent to the drive unit 46, and incorporates a bearing 61 to support the rotating shaft 41.

Next, the process by the sludge digester 1 is demonstrated.
First, when the driving machine 46 rotates the rotating shaft 41, the upper rotating blade 43 and the lower rotating blade 44 fixed to the rotating shaft 41 rotate, and the sludge in the tank near the liquid surface in the anaerobic digestion tank 2 is rotated. And the sludge in the tank in the draft tube 3 flows upward or downward (the lower rotary blade 44 is in the draft tube 3, so the sludge in the tank in the draft tube 3 is surely upward or downward. Flow).

At this time, when the rotation direction of the rotary shaft 41 is a direction in which the lower rotary blade 44 is caused to flow downward in the tank sludge in the draft tube 3, the upper rotary blade 43 is a liquid in the anaerobic digester 2. Since the sludge in the tank in the vicinity of the surface flows so as to be pushed into the upper end opening 31 of the draft tube 3, the downward flow of the sludge in the tank in the draft tube 3 created by the lower rotary blade 44 is enhanced. become.
On the other hand, when the rotation direction of the rotary shaft 41 is a direction in which the lower rotary blade 44 flows upward in the tank sludge in the draft tube 3, the upper rotary blade 43 springs out from the upper end opening 31 of the draft tube 3. The sludge in the tank is made to flow toward the spray disc 42.

That is, since the upper rotary blade 43 and the lower rotary blade 44 are cut in the same direction, when the downward flow is formed in the draft tube 3, the upper rotary blade 43 opens the upper end opening of the draft tube 3. A flow is formed to push down the sludge in the tank in the direction of 31, and the lower rotary blade 44 in the draft tube 3 further lowers the sludge in the tank flowing into the draft tube 3 from the upper end opening 31 of the draft tube 3. Add a flow rate in the direction.
Thereby, the in-tank sludge in the draft tube 3 is uniformly blown and dispersed from the lower end opening 32 to the bottom of the anaerobic digestion tank 2, and the vertical flow rate of the anaerobic digestion tank 2 becomes uniform.

On the other hand, when the upward flow is formed in the draft tube 3, the rotating shaft 41 is rotated in the direction opposite to the case where the drive unit 46 forms the downward flow, and the lower rotary blade 44 is disposed in the draft tube 3. The flow of the sludge in the tank is flowed upward, and the upper rotary blade 43 applies a further upward flow rate to the sludge in the tank that has springed out from the upper end opening 31 of the draft tube 3.
Thereby, the in-tank sludge that has flowed out from the upper end opening 31 of the draft tube 3 is sprayed onto the spray disk 42 and dispersed.

When the upward flow is created in the draft tube 3, the spray disc 42 hits the lower part of the tank sludge that has spouted from the upper end opening 31 of the draft tube 3. Since it moves along the lower surface of the spray disk 42, the sludge in the tank pushed up by the upper rotary blade 43 is uniformly dispersed in the horizontal direction with respect to the liquid level of the anaerobic digester 2.
As described above, the spray disc 42 is disposed for the purpose of uniformly dispersing the sludge in the tank in the horizontal direction. However, the spray disc 42 is disposed so that the spray disc 42 is pushed up by the upper rotary blade 43. Therefore, the sludge in the tank is not directly blown onto the bearing 47 of the flow generator 4 and the sludge in the tank can be prevented from entering the bearing 47 of the flow generator 4.
Thus, since the viscous sludge in the tank is uniformly dispersed, so-called “water path” and “sludge pool” disappear, so that the vertical flow rate of the anaerobic digestion tank 2 becomes uniform, which is favorable. The stirring state can be maintained.

Although the sludge digester 1 of this Embodiment 1 employs a mechanical stirring method, as described above, when the rotating shaft of the stirrer extends from the upper side to the lower side of the digesting tank, the rotational speed and the rotating shaft Depending on the thickness, vibration (resonance) and rotation blur may occur, and a stable circulating flow of sludge in the tank may not be formed. In addition, when vibration (resonance) or rotational vibration is large, the device is damaged or destroyed, and thus it is necessary to stop the rotation for inspection and repair. In particular, when the rotating shaft 41 is elongated in the draft tube 3, if the device is damaged due to vibration (resonance) or rotational blurring, the draft tube 3 is also damaged, and anaerobic digestion of the sludge in the tank can be performed. It may disappear.
Therefore, in the first embodiment, a rod-shaped stabilizer 45 is disposed at the tip of the rotating shaft 41.

By adjusting or exchanging the length of the rod-shaped stabilizer 45, the rotational speed (inherent rotational speed) at which the rotary shaft 41 provided with the spray disc 45, the upper rotary blade 43 and the lower rotary blade 44 resonates is regularly used for the rotary shaft 41. It is possible to maintain the rotating shaft 41 in a stable rotating state by adjusting so as to be removed from the rotational speed.
In addition, the rod-shaped stabilizer 45 should be adjusted or replaced with respect to changes in the natural rotational speed caused by the balance between the rotating shaft 41, the spray disk 42, the upper rotating blade 43 and the lower rotating blade 44 caused by aging. Can respond.

Since the rod-shaped stabilizer 45 is designed as a separate part from the rotating shaft 41, the natural frequency can be moved, the stirring force can be adjusted in a wide range, and it is optimal for use conditions (rotation speed). The device can be easily manufactured.
For example, by adjusting the length of the rod-shaped stabilizer 45, the rotational speed at which the rotation shaft 41 resonates can be adjusted. Therefore, the rod-shaped stabilizer 45 has a structure whose length can be adjusted (for example, the rotation shaft 41 and the rotation shaft 41). If the rod-shaped stabilizer 45 is coupled by a screw structure, the length of the rod-shaped stabilizer 45 can be adjusted by changing the screwing condition.
Incidentally, by making the tip of the rod-shaped stabilizer 45 hemispherical, an effect of rectifying the flow around the rotary shaft 41 is produced, and the blockage in the draft tube 3 and the contamination to the rotary shaft 41 and the lower rotary blade 44 are generated. Entanglement of objects and pressure loss can be reduced.

  Although FIG. 1 shows an example in which the pitch of the upper rotary blade 43 and the lower rotary blade 44 is one pitch, it may be two pitches or more as shown in FIG. In this case, the change in the natural rotational speed can be dealt with by adjusting the length of the rod-shaped stabilizer 45. Further, the blade diameter and the width of one pitch of the upper rotating blade 43 and the lower rotating blade 44 may not be the same.

  As is apparent from the above, according to the first embodiment, the anaerobic digester 2 for anaerobically digesting the sludge in the tank, and the draft that is erected in the anaerobic digester 2 and has openings at the upper and lower ends. A tube 3 and a flow generator 4 for generating an upward flow or a downward flow in the draft tube 3 are provided, and the flow generator 4 is inserted into the draft tube 3 from the upper part of the anaerobic digester 2. A rotary shaft 41 extending to the rotary shaft 41 and a drive unit 46 for rotating the rotary shaft 41 are provided. The rotary shaft 41 is provided with a spray disk 42, an upper rotary blade 43 and a lower rotary blade 44, and has a rod shape at the tip. Since the stabilizer 45 is attached, the sludge in the anaerobic digestion tank 2 is efficiently and reliably circulated (stirred), the treatment function of the anaerobic digestion is improved, and various devices are maintained. Performing anaerobic digestion tank in the sludge stably by securing a good operation, the effect that can maintain and repair repair to provide easy sludge digester 1 is obtained.

Specifically, the following effects can be achieved.
According to the first embodiment, the rotating shaft 41 is provided with the spray disk 42, the upper rotating blade 43, and the lower rotating blade 44, and the rod-shaped stabilizer 45 is attached to the tip of the rotating shaft 41. 3 is provided with a flow generator 4 that generates an upward flow or a downward flow, so that the concentration of sludge in the tank is also high in the anaerobic digestion tank 2 having a deep water depth such as a turtle shell shape or an egg shape. The sludge in the tank can be reliably circulated (stirred) in the vertical direction even if it is converted, and the accumulation of sludge in the tank at the bottom of the anaerobic digester 2 can be prevented, and the anaerobic digestion process can be performed efficiently and stably. The effect which can be performed is produced.

  In particular, the spray disk 42 can uniformly diffuse the rising sludge in the tank in the horizontal direction, and can prevent the sludge in the tank from entering the jet bearing 47 upward, The scum generated and laminated on the water surface by the upper rotary blade 43 can be broken to prevent clogging, and a vertical circulation flow can be formed and maintained. Further, the lower rotary blade 44 can flow upward into the draft tube 3 or The downward flow can be generated reliably and stably. In addition, by attaching the rod-shaped stabilizer 45 to the tip of the rotating shaft 41, the rotating shaft 41 can be stably rotated, and resonance at the natural rotational speed can be prevented to prevent damage to equipment. There is an effect.

  According to the first embodiment, since the circulation flow is formed by the draft tube 3 and the flow maker 4, the structure is simple, and the circulation flow is not hindered. A circulating flow in the vertical direction can be formed and maintained, and construction costs and operation costs can be reduced. Further, since the sludge in the tank can be reliably sucked or discharged by the upper end opening 31 and the lower end opening 32 of the draft tube 3, a sufficient circulation flow can be obtained even at the bottom of the anaerobic digestion tank 2 to prevent accumulation of sludge in the tank. As a result, an anaerobic digestion process can be efficiently and stably performed.

  According to the first embodiment, the structure is simple, and the rotating shaft 41 of the flow generator 4 has a short length inserted into the draft tube 3 (fourths of the total length of the draft tube 3). Within 1), maintenance and inspection are easy, and even if a device breaks down or malfunctions, it can be handled without requiring large-scale work, and the cost and work can be reduced.

  According to the first embodiment, since the draft tube 3 is fixed by the tie rod 21 and the support frame 22 fixed to the inner wall of the anaerobic digestion tank 2, the rotation of the rotating shaft 41 of the circulating flow or the flow generator 4 is performed. It is possible to prevent vibrations and swinging due to the above, and to efficiently and stably form and maintain a circulating flow of sludge in the tank.

Embodiment 2. FIG.
In the second embodiment, as in the first embodiment, the draft tube 3 is supported by the tie rod 21 and the support frame 22, and a specific example will be described below.
Since the draft tube 3 has a long cylindrical shape, it receives various stresses caused by sludge in the tank flowing at different positions (heights). Therefore, the upper portion of the draft tube 3 is supported by the tie rod 21, the lower portion of the draft tube 3 is supported by the support base 22, one end of these is joined to the draft tube 3, and the other end is attached to the inner wall of the anaerobic digester 2. It is fixed.

4 is a cross-sectional view showing a configuration of a sludge digesting apparatus according to Embodiment 2 of the present invention.
In the example of FIG. 4, four tie rods 21 are disposed in the horizontal direction every 90 degrees on the upper portion of the draft tube 3 (for example, the four tie rods 21 are in the direction of 12 o'clock of the short hand of the watch). 3 o'clock direction, 6 o'clock direction, 9 o'clock position). The tie rod 21 is a rod-shaped connecting material that functions as a tensile material, and supports the upper portion of the draft tube 3 on the inner wall of the upper portion of the anaerobic digestion tank 2. The draft tube 3 holds four tie rods 21. And is fixed to the inner wall of the anaerobic digester 2 with an initial tension in the range of 10,000 N to 20000 N (N is Newton).

On the other hand, the support frame 22 for fixing the lower portion of the draft tube 3 includes three columns 23 that support the draft tube 3 obliquely from the inner wall at the bottom of the anaerobic digestion tank 2, and a horizontal direction from the middle portion of each column 23. And a horizontal column 24 disposed toward the draft tube 3. Due to the triangular structure formed by the draft tube 3, the support column 23 and the horizontal column 24, the position of the draft tube 3 is difficult to shift.
As described above, since the draft tube 3 is stably supported by the tie rod 21 and the support base 22 at the upper and lower sides thereof, the vibration (resonance) of the rotation shaft 41 and the occurrence of rotation blur are suppressed and stable. Rotation can be ensured.

In the second embodiment, an example in which four tie rods 21 are disposed is shown. However, any number of tie rods 21 may be used as long as the draft tube 3 can be fixed, for example, three or more than five. Good.
The number of the support columns 23 may be any number as long as the draft tube 3 can be supported, for example, two or four or more.

Embodiment 3 FIG.
In the sludge digesting apparatus 1 of the third embodiment, surface processing is performed on each of the rotating shaft 41, the spray disk 42, the upper rotating blade 43, the lower rotating blade 44, and the upper portion of the draft tube 3.
As the surface processing, an example in which the surface is smoothly finished by buffing # 320 can be considered.

The rotating shaft 41, spray disk 42, upper rotating blade 43, lower rotating blade 44, and upper portion of the draft tube disposed near the liquid surface of the anaerobic digester 2 are anaerobic digester desorbed liquid containing phosphorus. Stratabit (MAP) is likely to occur on these surfaces. If this adheres and grows, it may cause a malfunction in the function of the rotating body.
Therefore, in the third embodiment, the surface of the member is finished by buffing to eliminate fine unevenness on the surface of the member, thereby suppressing the attachment of struvite.

In the third embodiment, the surface of the member is finished by buffing # 320, but may be finished by buffing # 280 to # 1000. The polishing means may not be buffed as long as the surface roughness Ra (average roughness of the center line) is finished in the range of 1.6 μm to 0.013 μm .

  In the third embodiment, the example of finishing by buffing is shown as the surface processing. However, as described above, if the unevenness on the surface of the member can be eliminated to prevent the attachment of struvite, it is limited to the finishing by buffing. For example, the rotating shaft 41, the spray disk 42, the upper rotating blade 43, the lower rotating blade 44, and the upper portion of the draft tube 3 may be coated with a corrosion-resistant paint. This coating may be performed after the surface of the member is polished.

  As apparent from the above, according to the third embodiment, surface processing (polishing and lining) is performed on the upper part (inner wall and outer wall) of the draft tube 3, the spray disk 42, the upper rotary blade 43, and the lower rotary blade 44. Is to be applied. As a result, it is possible to suppress the adherence and growth of the strata and to prevent the adhesion of foreign matters, so that the flow generator can be operated stably, and the circulating flow can be efficiently formed and maintained without receiving excessive resistance. At the same time, there is an effect that blockage of the draft tube 3 and the like can be suppressed.

Embodiment 4 FIG.
In the fourth embodiment, as shown in FIG. 5, a bearing 47 that receives the rotating shaft 41 is sealed with an oil seal 62 that prevents foreign matters such as sludge in the tank from entering.
In the anaerobic digestion tank 2, a large amount of sludge bubbles are generated depending on the state of the sludge in the tank, or the upward flow of the sludge in the tank is generated depending on the rotation direction of the rotating shaft 41. In some cases, sludge in the tank is mixed into the bearing 47, and the bearing 61 is damaged or corroded to cause a problem.

  In addition, digestion gas is generated in the anaerobic digestion tank 2, and the pressure inside the tank is always positive, but since this digestion gas contains corrosive components such as hydrogen sulfide and organic acids, These may enter the bearing 47 and the bearing 61 and related equipment may corrode.

Therefore, in the fourth embodiment, as shown in FIG. 5, the oil seals 62 are arranged in quadruple at positions outside the position where the bearing 61 of the bearing 47 is installed.
In this way, by making the bearing 47 a sealed type that is not affected by the atmospheric pressure in the anaerobic digestion tank 2, intrusion of sludge and digestion gas in the tank is prevented, and damage and corrosion of the bearing 61 are prevented. Yes. The oil seal 62 can be, for example, an annular combination of a metal ring and a synthetic rubber, and the number of the oil seals 62 can be changed depending on the situation.

  As is clear from the above description, according to the fourth embodiment, since the sealed bearing 47 is provided in the drive unit 46 of the flow generator 4, the corrosive gas generated in the anaerobic digester 2 and Intrusion of bubbles containing sludge particles can be prevented, failure and damage of the drive unit 46 and the bearing 47 can be prevented, and the flow generator 4 can be maintained in a stable and good operating state.

  DESCRIPTION OF SYMBOLS 1 Sludge digester, 2 Anaerobic digester, 3 Draft tube, 4 Flow maker, 21 Tie rod, 22 Support frame, 23 Support column, 24 Horizontal column, 31 Upper end opening, 32 Lower end opening, 41 Rotating shaft, 42 Spray disk, 43 Upper rotary blade, 44 Lower rotary blade, 45 Bar stabilizer, 46 Drive, 47 Bearing, 61 Bearing, 62 Oil seal

Claims (3)

An anaerobic digester for anaerobically digesting sludge,
A draft tube standing in the anaerobic digester and having openings at the upper and lower ends;
And a sludge digester equipped with a flow generator for generating an upward flow or a downward flow in the draft tube,
The flow generator is
A rotating shaft extending from the upper part of the anaerobic digester into the draft tube and a driving device for rotating the rotating shaft;
The rotating shaft includes
A spray disc, upper rotary blade and lower rotary blade are provided,
A rod-shaped stabilizer is attached to the tip ,
From the upper end opening of the inner and / or outer wall of the draft tube to a position corresponding to the tip portion of the rod-shaped stabilizer over the rotary shaft, said spray disc, the surface roughness Ra of the upper rotating wing roots and the lower rotating wing The sludge digester characterized by being 1.6 micrometers-0.013 micrometers . At the top of the draft tube,
A tie rod fixed to the inner wall of the anaerobic digester is attached,
At the bottom of the draft tube,
The sludge digester according to claim 1, wherein a support frame fixed to an inner wall of the anaerobic digester is attached. In the drive machine,
An airtight bearing using an oil seal is provided. The sludge digester according to any one of claims 1 and 2 .

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