JP7734316B2 - Dehydration aid adding device and dehydration aid adding method - Google Patents

Description

The present invention relates to a dehydration aid addition device and method for effectively dehydrating difficult-to-dehydrate sludge generated at sewage treatment plants.

Traditionally, difficult-to-dewater sludge, such as excess sludge and digested sludge, generated at wastewater treatment plants has low fiber content and poor dewaterability. Excess sludge is produced by biological treatment, where organic matter (e.g., fiber) in the sludge is converted by microorganisms. Digested sludge is produced by anaerobic digestion, where the organic matter (e.g., fiber) in the sludge is decomposed by anaerobic bacteria. Therefore, difficult-to-dewater sludge before dewatering contains only a small amount of fiber. Fiber in sludge functions as agglomeration nuclei and also has the effect of forming water channels within the flocculated flocs during dewatering. Therefore, sludge with reduced fiber content cannot be properly flocculated or dewatered, resulting in poor dewaterability. Therefore, a dewatering method has been proposed in which fibrous materials or plant materials such as sawdust and rice husks are mixed in as dewatering aids to compensate for the reduced fiber content. The use of fibrous materials as dewatering aids consistently produces dewatered cakes with low moisture content with the addition of small amounts, and is known to improve the peelability of the dewatered cakes in the case of pressurized dewatering.

Patent Document 1 discloses a technology in which a fibrous dewatering aid, such as a material used to manufacture nonwoven fabric, is fed into a hopper using compressed air, and then supplied to a treatment tank such as a sludge storage tank, where it is mixed with the sludge inside the tank.

Patent Document 2 discloses a technology in which powdered or granular materials such as dewatering aids are pressure-fed using the ejector action of pressurized air, and then the powdered or granular materials and pressurized air are pressurized and sprayed through a nozzle, and mixed with the supplied sludge in a mixing section.

Patent document 3 discloses a technology in which waste paper is dry-defibered, then transported with air and mixed with sludge incineration ash.

Japanese Patent Application Laid-Open No. 2020-179336 Special Publication No. 01-10255 Japanese Patent Application Publication No. 06-63528

When using conventional plant materials as dehydration aids, the dehydration aids are lightweight, so a mixing device is required to mix them with the sludge, which contains a lot of moisture before dehydration. In particular, when supplying them to a large sludge storage tank, a large mixing device is required, and when mixing in a separate mixing tank, a dedicated mixing tank, mixing and transport equipment, and installation space are required. Another issue is that sludge remaining in the sludge storage tank can rot, reducing the dehydration efficiency of the dehydration equipment installed downstream.

In Patent Document 1, the hopper is a cyclone type, so the dewatering aid inside the hopper settles downward and is then supplied to a treatment tank such as a sludge storage tank. However, because the compressed air that has delivered the dewatering aid is discharged upward from a central separator, only the dewatering aid is supplied to the treatment tank, and the energy of the compressed air is not used to agitate the dewatering aid.

In Patent Document 2, a nozzle is provided to supply powder and granular material into the mixing section, which can cause the supplied sludge to flow back into the nozzle and block the sealed transport pipe. Furthermore, in addition to the nozzle, a turbulence generator with a variable cross-sectional area is also provided inside the mixing tank, making the device structure complex.

Patent Document 3 describes a technology in which defibrated fibers are mixed with sludge incineration ash, then supplied to a mixing tank and mixed using a mixing blade; it does not use air obtained from a blower blade built into the defibrator to mix the fibers.

The present invention provides a dewatering aid addition device and method that defibrates waste materials (fibrous materials) generated during the manufacturing process of nonwoven fabrics and other materials, reuses the defibrated material as a dewatering aid, and adds the defibrated material, which is pumped by compressed air, to sludge and mixes it uniformly.

The present invention is an apparatus for adding and mixing dehydration aids to sludge, and is equipped with a defibrator that defibrates fibrous material to form dehydration aids, a communication part connected to the defibrator and pressurizing the dehydration aids using compressed air, and a sludge mixing tank connected to the communication part and mixing and stirring the sludge, which is fluidized by the supplied compressed air, together with the dehydration aids.This allows the sludge and dehydration aids to be mixed efficiently, and therefore makes it possible to produce mixed sludge in which the dehydration aids are uniformly mixed.

The defibrator is a dry-type defibrator, and its other end is connected to a communication section connected to the bottom of the sludge mixing tank. It is equipped with a blower blade that generates compressed air to supply to the communication section. This allows the compressed air generated within the defibrator to be used to pressurize the dewatering aid and mix and stir the sludge and dewatering aid, eliminating the need for a separate compressed air supply source.

The sludge mixing tank is equipped with an aeration pipe installed internally at the bottom and communicating with the communication section, a partition plate extending upward with a specified gap at the bottom and top, and a sludge supply section to which circulating sludge is supplied by compressed air supplied from the aeration pipe.By forming the aeration pipe outlet hole in a position not facing the sludge supply section, sludge and dewatering aid can be mixed by air lift within the sludge mixing tank, improving the miscibility of the dewatering aid and sludge and increasing the dewaterability of the sludge.

By connecting a return section that returns a portion of the dewatering aid to the defibrator to the communication section, the dewatering aid can be repeatedly defibrated, improving defibration efficiency, and by circulating compressed air, excessive supply of compressed air to downstream equipment can be prevented, ensuring that an appropriate amount is always supplied.

In a method for adding a dehydration aid to sludge, the fiber material is defibrated to form a dehydration aid, and then the dehydration aid is pumped into a sludge mixing tank using compressed air. The sludge, which is fluidized by the compressed air supplied to the sludge mixing tank, is mixed and stirred with the dehydration aid, thereby producing mixed sludge in which the dehydration aid is uniformly mixed in the early stages of the dehydration process, thereby improving the dehydration efficiency in the dehydrator.

The dewatering aid adding device and dewatering aid adding method of the present invention mix and agitate dewatering aids formed by defibrating fibrous materials with sludge in a sludge mixing tank to produce mixed sludge. The sludge in the tank is fluidized using compressed air obtained from the defibrator, eliminating the need for a large mixing tank equipped with an agitator. This reduces installation space and running costs, resulting in a compact and inexpensive device. Furthermore, the dewatering aids are continuously pumped using compressed air after defibration, preventing clumping and preventing blockage of the communication section, allowing for continuous supply of dewatering aids to the sludge mixing tank. The communication section is equipped with a check valve to maintain a constant fluid flow, preventing backflow of sludge and enabling continuous operation. Furthermore, the sludge in the sludge mixing tank is constantly fluidized by the supplied compressed air, preventing sludge from accumulating at the bottom. The sludge mixing tank functions as an aeration tank due to the intake of oxygen when compressed air is supplied, preventing sludge from decaying. The microorganisms in the sludge that have absorbed oxygen then absorb phosphorus, preventing it from being re-eluted, which also reduces the phosphorus concentration in the dehydrated filtrate discharged from the dehydrator.Furthermore, the fibers used for defibration are those that would otherwise be discarded, such as scraps of nonwoven fabric, which also contributes to resource recycling.

1 is a flow diagram of a sludge treatment method according to the present invention. FIG. 2 is a schematic diagram of a dehydration aid adding device. FIG. FIG. FIG. 10 is an explanatory view showing the sludge mixing tank as viewed from the front. FIG. 6 is an explanatory view showing the sludge mixing tank as viewed from the direction of the arrow shown in FIG. 5 .

FIG. 1 is a flow diagram of the sludge treatment method according to the present invention.
In this embodiment, the system comprises a reaction tank 1 in which influent water flowing into a sewage treatment plant is circulated in an endless circulating water channel while being aerated and stirred for biological treatment, a final sedimentation tank 2 in which treated water supplied from the reaction tank 1 is separated by settling and the supernatant is disinfected before being discharged into a river or the like, a dehydration aid adding device 3 that adds and mixes a dehydration aid with the excess sludge supplied from the final sedimentation tank 2, and a dehydrator 4 that dehydrates the mixed sludge to which the dehydration aid has been added and produces dehydrated cake. Note that, as shown by the dashed line, the dehydration aid adding device 3 is also provided upstream of the dehydrator 4 when the activated sludge in the reaction tank 1 is directly supplied to the dehydrator 4 using the direct dehydration method.

In this embodiment, the dewatering aid is added to and mixed with excess sludge generated at a treatment plant that uses the oxidation ditch (OD) method, in which influent water and activated sludge are mixed and circulated using an aeration device in a reaction tank 1 shaped like an endless channel. However, the method can also be applied to difficult-to-dewater sludge such as digested sludge, and easily dewaterable sludge such as mixed raw sludge.

FIG. 2 is a schematic diagram of the dehydration aid adding device.
The dewatering aid adding device 3 is composed of a defibrator 5, a sludge mixing tank 6, and a communication part 7 that connects them. The defibrator 5 defibrates clumped fibrous material and forms defibrated material that is in a state similar to untangled short fibers. In this embodiment, scraps (fibrous material) generated during the manufacturing process of nonwoven fabrics, etc. are defibrated to form defibrated material, and the formed defibrated material is used as the dewatering aid. In order to improve the defibration efficiency of the fibrous material, it is desirable to install a constant volume feeder (not shown) upstream of the defibrator 5 and feed a constant volume of fibrous material to the defibrator 5.

The sludge mixing tank 6 mixes and agitates the dewatering aid (defibrated material) formed by the defibrator 5 with excess sludge and activated sludge, etc., shown in Figure 1, to produce mixed sludge. An air diffuser 9 with multiple jetting holes 20 is provided below the sludge mixing tank 6, so that the sludge and dewatering aid supplied to the tank can be mixed and agitated by the air jetted from the jetting holes 20. The sludge mixing tank 6 uses a conventional sludge storage tank and stores and mixes the sludge.

A supply pipe (communication part 7) is provided between the defibrator 5 and the sludge mixing tank 6, with one end connected to the defibrator 5 and the other end connected to the sludge mixing tank 6, allowing the dewatering aid formed by the defibrator 5 to be supplied to the sludge mixing tank 6. A check valve 10 is installed in the communication part 7 to prevent backflow from within the sludge mixing tank 6.

The other end of the communication part 7, which is connected to the sludge mixing tank 6, is connected to an air diffuser 9 inside the tank, and the dewatering aid supplied from the communication part 7 and compressed air for pressurizing the dewatering aid are supplied from the nozzle 20.

The communication section 7 is connected to a return section 12, one end of which is connected to the fiber supply section 11, so that the defibrated fiber can be returned to the defibrator 5. This allows the fiber to be repeatedly defibrated, forming dewatering aids of the desired size and improving their mixability with the sludge in the sludge mixing tank 6. As a result, the flocculation of the sludge in the flocculation mixing tank (not shown) located upstream of the dehydrator and the dehydration efficiency in the dehydrator can be improved.

In this embodiment, the communication section 7 uses a supply pipe connected to the defibrator 5 and the sludge mixing tank 6, respectively. However, the defibrator 5 and sludge mixing tank 6 may be unitized and connected to each other without a supply pipe. Furthermore, the fibrous material that is defibrated to form the dewatering aid is not limited to scraps of nonwoven fabric, but may also be scraps of old clothing, used filter cloth, or scraps of automobile skin materials. Reusing items that would normally be discarded is generally environmentally friendly, so it is desirable to make effective use of waste materials.

FIG. 3 is a partial cross-sectional front view of the fiberizer, and FIG. 4 is a vertical cross-sectional side view of the fiberizer.
As shown in Figure 3, the defibrator 5 has a defibrating chamber 13 inside a rectangular casing 14, and is configured so that after the fibers supplied from a supply port 22 (at the back side of Figure 3 and on the right side of Figure 4) of the defibrating chamber 13 are defibrated in the defibrating chamber 13, the dewatering aid (defibrated material) is discharged from a communication part 7 connected to the side of the casing 14. A blower blade 17 driven by a driver 16 is housed inside the defibrating chamber 13, and by driving the driver 16, the blower blade 17 can be rotated at high speed.

The inner wall of the defibrating chamber 13 is continuously formed in the circumferential direction, and when the blower blades 17 are rotated at high speed, a high-speed jet air stream (compressed air) is generated in the rotational direction, causing the fibrous material to come into contact with the defibrating teeth 18 and defibrate. As shown in Figure 4, the defibrating teeth 18 have a sawtooth shape, and the high-speed jet air stream (compressed air) collides with the clumps of fibrous material swirling inside the defibrating chamber 13, cutting the long fibers and defibrating them to a state close to short fibers. The dewatering aid formed in the defibrating chamber 13 is pressurized by the high-speed jet air stream (compressed air) toward the communicating section 7 and supplied into the air diffuser pipe 9 connected to the communicating section 7. The desired dewatering aid can be obtained by appropriately changing the shape of the defibrating teeth and adjusting the degree of defibration depending on the operating conditions.

The defibrator 5 used in this embodiment is a dry-type defibrator that uses the airflow it generates to physically impact the fibrous material supplied from the supply port 22, defibrating it and then pressurizing the resulting dewatering aid toward the communication section 7. However, the mechanism is not limited to this embodiment as long as it is capable of defibrating and pressurizing the fibrous material. In other embodiments, for example, the fibrous material may be defibrated using a defibrator that does not have an internal wind generating mechanism, and then the dewatering aid may be transported using a wind generating mechanism such as a blower connected to the fibrous material supply section 11. If the wind generating mechanism is installed externally, the compressed air obtained from the wind generating mechanism can also be used in processes such as squeezing and cake blowing.

FIG. 5 is an explanatory diagram showing the sludge mixing tank as seen from the front, and FIG. 6 is an explanatory diagram showing the sludge mixing tank as seen from the direction of the arrow shown in FIG.
As shown in Figure 5, the sludge mixing tank 6 is connected to a sludge supply unit 15 at its lower end and to a sludge discharge unit 19 at its upper end. In this embodiment, the sludge is supplied from below, mixed and stirred in the tank, and then discharged from above.

The sludge mixing tank 6 has an air diffuser 9 extending into the tank so that it is located below the connection 21 (sludge supply port) of the sludge supply unit 15. The air diffuser 9 has multiple spray holes 20 formed in it and is connected to the communication unit 7, allowing the dewatering aid and compressed air pressure-fed from the communication unit 7 to be sprayed out of the spray holes 20.

As shown in Figure 6, the nozzle holes 20 are openings formed in the lower part of the air diffuser pipe 9, and the dewatering aid and compressed air supplied into the air diffuser pipe 9 are sprayed downward. By arranging the air diffuser pipe 9 below the connection part 21 of the sludge supply part 15 and by directing the nozzle holes 20 formed in the air diffuser pipe 9 downward, sludge is not supplied toward the nozzle holes 20, and therefore the nozzle holes 20 are not clogged with sludge supplied from the sludge supply part 15. In this way, it is desirable to form the nozzle holes 20 of the air diffuser pipe 9 at a position not facing the sludge supply part 15.

The dewatering aid and compressed air are sprayed downward and then flow upward. At this time, the sludge supplied from above the air diffuser 9 is mixed and stirred with the dewatering aid as it flows upward due to the compressed air supplied from below. After the sludge is uniformly mixed with the dewatering aid, it becomes mixed sludge and is discharged from the sludge discharge section 19.

In this embodiment, a partition plate 8 having a predetermined thickness is installed in the sludge mixing tank 6 to increase the fluidity of the sludge in the tank. This allows compressed air supplied from an air diffuser 9 installed below to agitate the sludge in the tank by airlift. Specifically, the partition plate 8 is installed at the bottom and top of the sludge mixing tank 6 with predetermined gaps so that it extends upward. Sludge supplied from the sludge supply unit 15 can circulate around the partition plate 8 through the predetermined gaps at the bottom and top. In other words, the installation of the partition plate 8 in the tank allows sludge to circulate vertically within the tank. As the supplied sludge flows around the partition plate 8 (in the direction of the arrow), the dewatering aid supplied from below is incorporated into and mixed with the flowing sludge, producing mixed sludge with a uniformly mixed dewatering aid. In this embodiment, the supplied excess sludge, which has a low concentration and high fluidity obtained by the OD method, can be efficiently circulated around the partition plate 8 without accumulating at the bottom of the tank.

The interior of the sludge mixing tank 6, which is provided with a partition plate 8, is divided into zones A and B by the partition plate 8. Zone A is the zone to which sludge is supplied from the sludge supply section 15 and dewatering aid and compressed air are supplied from the communication section 7. On the other hand, zone B , which is divided by the partition plate 8, is the zone to which mixed sludge produced by the air lift action occurring within the tank is discharged.

By configuring the system so that the supplied sludge can be mixed and stirred together with the dewatering aid, the sludge does not remain at the bottom of the tank for long periods of time, preventing it from decaying. The compressed air sprayed out along with the dewatering aid is generated by the rotation of the blower blades 17 inside the fiberizer 5, so there is no need to install a separate external wind generating mechanism such as a blower, nor is there any need to install a large mechanical stirring device.

The position, number, and shape of the ejection holes 20 and the partition plate 8 are determined appropriately according to the design conditions. The connection position between the sludge supply unit 15 and the sludge discharge unit 19 is also not limited. The sludge supply unit 15 may be connected to the upper part of the tank, and the sludge discharge unit 19 may be connected to the lower part of the tank, so that sludge is supplied from above and discharged from below. To prevent clogging of the ejection holes 20, the sludge supply unit 15 may be connected to the lower part of the tank, and an air diffuser 9 with ejection holes 20 formed on its upper part may be disposed above the connection part 21 of the sludge supply unit 15. Similarly, the connection position of the communication unit 7 may be appropriately determined according to the configuration of the sludge mixing tank 6. For efficient airlift mixing, a compressed air supply pipe may be separately connected to the sludge mixing tank 6 to increase the amount of compressed air supplied.

The present invention is not limited to the embodiments described above. Modifications and variations are possible without departing from the spirit of the present invention.

The dewatering aid adding device and dewatering aid adding method of the present invention uses a defibrator to defibrate fibrous materials that would otherwise be discarded, such as scraps generated during the manufacturing process of nonwoven fabrics, and uses the defibrated materials as dewatering aid, thereby making effective use of fibrous materials that would otherwise be discarded. By effectively utilizing waste generated in the area where this product is operated as dewatering aid, it is possible to solve the waste disposal problems facing the area. The dewatering aid defibrated by the defibrator is compressed and transported using compressed air generated by the blower blades inside the defibrator, eliminating the need for a separate energy source such as a wind generating mechanism, making this an environmentally friendly device.

5 defibrator 6 sludge mixing tank 7 communication section 8 partition plate 9 air diffuser 12 return section 15 sludge supply section 17 blower blade 20 ejection hole

Claims (5)

In a device that adds and mixes dewatering aids to sludge,
A defibrator (5) that defibrates fibrous materials to form a dewatering aid;
a communication section (7) connected to the defibrator (5) and for pressure-feeding the dewatering aid with compressed air;
a sludge mixing tank (6) connected to a communication part (7) for mixing and stirring the sludge fluidized by the supplied compressed air together with a dewatering aid;
A dehydration aid adding device comprising: The defibrator (5) is a dry type defibrator,
The other end is connected to a communication part (7) connected to the lower part of the sludge mixing tank (6),
2. The dewatering aid adding device according to claim 1, further comprising a blower blade (17) for generating compressed air to be supplied to the communication section (7). The sludge mixing tank (6) includes an aeration pipe (9) disposed below and communicating with the communication part (7);
A partition plate (8) extending upward with a predetermined gap provided at the bottom and top;
a sludge supply unit (15) to which circulating sludge is supplied by compressed air supplied from an air diffuser pipe (9),
3. The dewatering aid adding device according to claim 1, wherein the air diffuser pipe has a nozzle hole formed at a position not facing the sludge supply section. 4. The dewatering aid adding device according to claim 3, wherein a return section (12) for returning a part of the dewatering aid to the defibrator (5) is connected to the communication section (7). In a dewatering aid addition method in which a dewatering aid is added and mixed with sludge,
After defibrating the fiber material to form a dewatering aid,
The dewatering aid is pressure-fed to the sludge mixing tank (6) using compressed air,
A method for adding a dewatering aid, characterized in that the sludge fluidized by the compressed air supplied to the sludge mixing tank (6) is mixed and stirred with the dewatering aid.