JP2003062600A - Method for thickening and dehydrating sludge and apparatus for thickening sludge used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for thickening and dehydrating sludge capable of dehydrating hardly-dehydratable sludge without adding much coagulant thereto, and an apparatus for thickening the sludge used therefor. SOLUTION: Coagulated sludge is thickened through a thickening apparatus 3 by separating from water without breaking floe and is dehydrated by force feeding to a pressure dehydrator. The thickening apparatus 3 has a structure wherein a screen 11 is provided in a pressure vessel 10, inside of the screen being a sludge channel 12 and outside being a filtrate chamber 13, and the sludge channel 12 is provided therein with a hollow scraper 18, slowly rotating along the inner surface of the screen 11, the hollow scraper 18 having through holes, through which the filtrate in the filtrate chamber 13 is sucked in via the screen 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge concentrating and dewatering method and a sludge concentrating apparatus used therefor.

[0002]

2. Description of the Related Art Conventionally, various dehydrating devices have been used for dehydrating sewage sludge and the like, but most of them have a complicated structure and are large in size, and also have a problem of odor leakage. Therefore, as a dehydrating device that solves such a problem, a press-fitting type dehydrator as shown in FIG. 4 has recently been proposed.

This press-fitting type dehydrator has a circular casing 5
A disk-shaped rotor 52 that rotates at a low speed is provided inside 1, and the gap between the casing 51 and the rotor 52 is a filter chamber 54 sandwiched by screens 53 on both sides. The sludge agglomerated by the aggregating device is press-fitted into the filter chamber 54, and while moving in the casing 51 as the rotor 52 and the screen 53 rotate, moisture is discharged through the screen 53 to the outer filtrate flow channel 55, and gradually. Dehydration progresses. Then, the dehydrated sludge is discharged to the outside while pushing and opening the gate valve 56 provided at the end of the filter chamber 54. Such a press-fitting type dehydrator has the advantages that the device structure is simple and compact, there is almost no noise, and the odor is unlikely to leak to the outside due to the closed structure.

However, when attempting to dehydrate difficult-to-dewater sludge such as digested sludge and excess sludge by the press-fitting type dehydrator, a large amount of coagulant must be added in advance in a flocculator (coagulating device). However, there is a problem that running cost becomes high. In addition, such a press-fitting type dewatering machine structurally has a short residence time of sludge, so if the treatment amount is increased when dewatering hard-to-dewater sludge, the free water in the sludge will not be exhausted, and it will remain as it is before entering the pressing process. There is a possibility that it will be discharged and it will become impossible to dehydrate.
Therefore, such a press-fitting type dehydrator is difficult to be used for dehydrating difficult-to-dewater sludge such as digested sludge and excess sludge.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and is capable of dewatering hard-to-dewater sludge such as digested sludge and excess sludge without adding a large amount of coagulant. The first is to provide a method of concentrating and dehydrating sludge that can be performed
Is the purpose of. The second object of the present invention is to
It is an object of the present invention to provide a sludge concentrating device capable of concentrating non-dewatering sludge without destroying agglomerated flocs and without causing clogging.

[0006]

In order to achieve the above-mentioned first object, the invention of claim 1 does not break flocs by passing the coagulated sludge through a sludge flow path surrounded by a screen. It is characterized in that water is separated and concentrated, and then it is driven into a press-fitting type dehydrator for dehydration.
Here, as the press-fitting type dehydrator, it is preferable to use a disc-shaped rotor that rotates at a low speed inside the casing, and a gap between the casing and the rotor is a filter chamber whose both sides are sandwiched by screens.

In order to achieve the above-mentioned second object, the invention of claim 3 provides a cylindrical screen inside the pressure vessel, the inside of which is a sludge flow path, and the outside is a filtrate chamber. In addition, a hollow scraper that gently rotates along the inner peripheral surface of the screen is provided in the sludge channel, and this scraper is provided with a through hole for sucking the filtrate in the filtrate chamber through the screen. It is what In addition, it is preferable to have a structure in which a filtrate discharge pump is connected to the rotary shaft of the scraper, and the filtrate discharge pump keeps a constant differential pressure between the sludge feed port to the sludge flow path and the filtrate chamber. It is preferable.

According to the method for concentrating and dehydrating sludge of the present invention, a large amount of coagulant is added to sludge that is difficult to dehydrate such as digested sludge and surplus sludge by separately performing concentration and dehydration of sludge. You can dehydrate without doing. Further, according to the sludge concentrating device of the present invention, the coagulated sludge is caused to flow in the sludge flow path formed inside the cylindrical screen, so that the hardly dehydratable sludge can be concentrated without destroying the coagulated flocs. You can Moreover, since the filtrate in the filtrate chamber is sucked through the screen from the through hole provided in the scraper, the screen will not be clogged even if the apparatus is not stopped and washed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention are shown below. FIG. 1 is an overall view for explaining the method for concentrating and dehydrating sludge of the present invention, in which 1 is a flocculator (coagulation device), 2
Is a sludge concentrating device of the present invention, and 3 is a press-fitting type dehydrator. The flocculator 1 is well-known, and a polymer flocculant is added to the sludge (generally, sludge having a solid content of about 2 to 4%) supplied by the sludge supply pump 4 by the coagulant pump 5.
It is an apparatus that forms agglomerated flocs by stirring in a tank equipped with a stirrer. The coagulated sludge is sent to the sludge concentrating device 2, concentrated as described below, and then dehydrated by the press-fitting type dehydrator 3.

As shown in FIGS. 2 and 3, the sludge concentrator 2 is provided with a cylindrical screen 11 inside a cylindrical pressure vessel 10, the inside of which is a sludge channel 12, and the outside is a filtrate chamber 13. It was done. The coagulated sludge is fed into the sludge flow passage 12 from the sludge inlet 14 at one end of the pressure vessel 10, and while traveling inside the sludge flow passage 12, free water escapes to the filtrate chamber 13 side through the surrounding screen 11. Is concentrated until the solid content becomes about 7 to 8%. The concentrated sludge is continuously taken out from the discharge port 15 at the other end.

A hollow shaft 16 is provided inside the sludge passage 12.
A scraper 18 is provided which is gently rotated by a motor 17 around the center. This scraper 18 is a hollow one that gently rotates along the inner peripheral surface of the screen 11. In this embodiment, three rod-shaped bodies parallel to the hollow shaft 16 are integrated by a hollow arm 19 at the end. Has become. The number of scrapers 18 can be appropriately increased or decreased. In order to prevent the flocculation of flocs, it is preferable that the scraper 18 be rotated at a low speed of 1 rpm or less.

A large number of through holes 20 are formed on the surface of the scraper 18 that contacts the screen 11. While the opening diameter of the screen 11 is 0.5 to 1 mm,
The diameter of the through hole 20 of the scraper 18 is set to be as large as about 5 mm. Each through hole 20 communicates with the inside of the hollow shaft 16 via the hollow arm 19 of the scraper 18. Further, since the filtrate discharge pump 21 is connected to the end of the hollow shaft 16, the through hole 20 of the scraper 18 is formed in the screen 1
The filtrate in the filtrate chamber 13 on the outer side can be sucked through 1 through 1. Therefore, the screen 11 is washed with the filtrate each time it comes into contact with the rotating scraper 18, and there is no risk of clogging. As the filtrate discharge pump 21, a uniaxial eccentric rotary pump known as a MONO pump (trade name) can be used.

As shown in FIG. 2, the sludge inlet 14 and the filtrate chamber 13 are provided with pressure sensors 22 and 23, respectively, so that the pressure of the filtrate chamber 13 is always more constant than the pressure of the sludge inlet 14. The filtrate discharge pump 21 is controlled so as to lower the value. As a result, the filtration differential pressure by the screen 11 is controlled so as not to become excessive and the aggregation flocs are prevented from being broken. In this way, the coagulated sludge is concentrated in the sludge concentrating device 2 without destroying the coagulated flocs.

The press-fitting type dehydrator 3 has a structure as shown in FIG. 4, and has a filter chamber 54 sandwiched between a disk-shaped rotor 52 rotating at a low speed and a screen 53 inside the casing 51 as described above. It is a thing. The sludge concentrated in the sludge concentrating device 2 until the water content becomes 7 to 8% is pressed into the filter chamber 54, dehydrated while moving in the casing 51, and discharged to the outside while opening the gate valve 56. . Since the free water is separated in the sludge concentrating device 2 before being driven into the press-fitting type dehydrator 3, the press-fitting type dehydrator 3
In this case, dehydration is surely performed, and even sludge that is difficult to dehydrate can be dehydrated until the solid content becomes 20 to 25%. The dehydrated sludge thus obtained is sent to a subsequent process such as drying, incineration, melting and the like for treatment.

[0015]

As described above, according to the method for concentrating and dewatering sludge of the present invention, the sludge concentrating device and the press-fitting type dehydrator are combined to perform the free water separating step and the squeezing step respectively. By carrying out the treatment, it is possible to dehydrate the sludge that is difficult to dehydrate without difficulty. Therefore, it is possible to reduce the running cost without requiring a large amount of a flocculant as in the conventional case.

Further, according to the sludge concentrating device of the present invention, it is possible to concentrate the hardly dehydratable sludge without destroying the flocs. Moreover, since the filtrate in the filter chamber can be sucked through the screen through the through holes provided in the scraper, it is possible to prevent clogging of the screen, so there is no need to stop the operation and perform cleaning. There is an advantage that water is unnecessary.

[Brief description of drawings]

FIG. 1 is an overall diagram illustrating a method for concentrating and dehydrating sludge according to the present invention.

FIG. 2 is an axial sectional view of the sludge concentrating device of the present invention.

FIG. 3 is a cross-sectional view of the sludge concentrator of the present invention in a direction perpendicular to the axis.

4A and 4B are explanatory views of a press-fitting type dehydrator, in which FIG. 4A is a cross-sectional view in the direction of the rotating shaft, and FIG. 4B is a cross-sectional view in the direction perpendicular to the rotating shaft.

[Explanation of symbols]

1 flocculator, 2 sludge concentrator, 3 press-fitting dehydrator, 4 sludge supply pump, 5 coagulant pump, 10
Pressure vessel, 11 screen, 12 sludge channel, 13
Filtrate chamber, 14 sludge inlet, 15 discharge port, 16 hollow shaft, 17 motor, 18 scraper, 19 hollow arm, 20 through hole, 21 filtrate discharge pump, 22
Pressure sensor, 23 pressure sensor, 51 casing, 52 rotor, 53 screen, 54 filter chamber, 5
5 filtrate flow path, 56 gate valve

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Claims (5)

[Claims] 1. A sludge characterized in that coagulated sludge is passed through a sludge channel surrounded by a screen to separate and concentrate water without breaking flocs, and is then driven into a press-fitting type dehydrator for dehydration. Concentration dehydration method. 2. The press-fitting type dehydrator, wherein a disk-shaped rotor that rotates at a low speed is provided inside a casing, and a gap between the casing and the rotor is a filter chamber whose both sides are sandwiched by screens. Condensation and dewatering method of sludge. 3. A cylindrical screen is provided inside the pressure vessel, the inside of which serves as a sludge channel and the outside thereof as a filtrate chamber, and the sludge channel gently rotates along the inner peripheral surface of the screen. A sludge concentrating device characterized in that a hollow scraper is provided, and a through hole for sucking the filtrate in the filtrate chamber through a screen is provided in this scraper. 4. The sludge concentrating device according to claim 3, wherein a filtrate discharge pump is connected to the rotary shaft of the scraper. 5. The filtrate discharge pump keeps a constant differential pressure between the sludge feed port to the sludge passage and the filtrate chamber.
The described sludge concentrator.