JPH05269495A - Apparatus for digesting cake-like sludge - Google Patents

Abstract

PURPOSE:To provide the title apparatus capable of sufficiently stirring dehydrated cake-like sludge in a digestion tank and capable of efficiently digesting the cake-like sludge within a short time. CONSTITUTION:A digestion apparatus consists of a digestion tank 1, a supply tank 10, the circulating pipe 12 connected to the circulating pump 11 provided to the bottom part of the digestion tank 1 at one end thereof and connected to the supply port of the top wall of the digestion tank at the other end thereof in order to circulate the cake-like sludge digested in the digestion tank 1 and the supply pipe 16 connected to the pump 15 provided to the bottom part of the supply tank 10 at one end thereof and connected to the circulating pipe 12 on the sway thereof at the other end thereof. The cake-like sludge in the supply tank 10 is supplied to the digestion tank 1 through the supply pipe 16 and the circulating pipe 12 to be circulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for digesting cake-like sludge obtained by dehydrating organic sludge such as sewage.

[0002]

2. Description of the Related Art Sewage such as sewage is conventionally treated by the following method. That is, sewage is guided to a settling basin, and sludge such as sediment in the sewage is settled in the settling basin for primary separation. Then, the wastewater from which the sludge is primarily separated is guided to the aeration tank, and the wastewater is aerated in the aeration tank. In this way, the aeration-treated wastewater is guided to the final settling basin, and in the final settling basin, the sludge remaining in the wastewater is precipitated and separated. Next, the slurry-like sludge taken out from the final settling tank is concentrated in a concentration facility. Next, the concentrated slurry sludge is supplied to the digestion tank, and the digestion treatment is performed in the digestion tank. The sludge thus digested is discarded or incinerated.

FIG. 3 is a schematic vertical sectional view showing a conventional digester. As shown in FIG. 3, in the conventional digester, one end of the digester 1 and a supply port provided at the top wall of the digester 1 are connected to the concentrated slurry sludge in the digester 1. And a gas discharge pipe 3 for discharging the digested gas generated in the digestion tank 1, one end of which is connected to a gas discharge port provided on the top wall of the digestion tank 1. The gas blowing pipe 4 vertically inserted through the top wall of the digestion tank 1 and one end of the gas discharging pipe 3 are connected to the gas discharging pipe 3 and the other end of the gas blowing pipe 4 is connected to the gas discharging pipe 3. And a branch pipe 5 provided with a gas compressor 6.

The concentrated slurry-like sludge passes through the supply pipe 2 and is supplied from the supply port provided on the top wall of the digestion tank 1. The slurry sludge thus supplied is allowed to stay in the digestion tank 1 in an anaerobic state for a certain period of time to ferment methane, thereby decomposing organic matter in the sludge. The digestion gas generated by fermentation is discharged from the digestion tank 1 through the gas discharge pipe 3. The discharged digested gas is collected and used as fuel for a boiler or the like, while a part of the digested gas is passed through the gas blowing pipe 4 and the digestion tank 1 is used.
Blow in. The slurry-like sludge supplied into the digestion tank 1 is agitated by the digested gas blown into the digestion tank 1 to accelerate its digestion.

FIG. 4 is a schematic vertical sectional view showing another example of the conventional digester. In this example, the gas blowing tube 4 described above is not inserted into the digestion tank 1, but instead, the stirring shaft 8 having the draft tube 7 is vertically inserted into the digestion tank 1 through its top wall. ing. When the stirring shaft 8 is rotated by the motor 9, the slurry sludge supplied into the digestion tank 1 is mechanically stirred and its digestion is promoted.

[0006]

The above-mentioned conventional apparatus has the following problems. Recently, the slurry sludge taken out from the final settling tank was concentrated in a concentrating facility,
Next, the concentrated slurry sludge is dehydrated in a dehydration facility to form a cake, and the dehydrated cake sludge is supplied to a digestion tank and digested in the digestion tank. Since the water content of the dehydrated cake-like sludge is about 75 to 80%, the volume of the digestion tank 1 to which such dehydrated cake-like sludge is supplied can be made smaller than the conventional one. The digestion equipment cost can be reduced.

However, since the dehydrated cake-like sludge has a low water content of about 75 to 80% as described above, its fluidity is much worse than that of the non-dehydrated slurry-like sludge. As a result, the conventional digester shown in FIGS. 3 and 4 cannot stir the cake-like sludge supplied into the digestion tank, and as a result, it takes a lot of time to digest the cake-like sludge. Moreover, digestion becomes insufficient. Furthermore,
It is also difficult to discharge the digested cake-like sludge from the digestion tank 1 by gravity flow.

Therefore, an object of the present invention is to solve the above-mentioned problems and to allow the dehydrated cake-like sludge to be sufficiently agitated in the digestion tank, whereby the cake-like sludge can be efficiently provided in a short time. An object of the present invention is to provide a digester for cake-like sludge, which can digest the cake-like sludge and can easily discharge the digested cake-like sludge from the digestion tank.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems. As a result, a part of the cake-like sludge digested in the digestion tank is circulated by the circulation mechanism provided outside the digestion tank, and the dehydrated cake-like sludge to be digested is circulated. If it is supplied into the sludge, it is possible to sufficiently stir the dehydrated cake sludge to be digested together with the circulating sludge in the digestion tank, whereby the cake sludge can be efficiently produced in a short time. It was found that it can be digested.

The present invention has been made on the basis of the above findings, and the apparatus of the present invention supplies cake-like sludge to the digestion tank and the digestion tank provided in the vicinity of the digestion tank. Supply tank, a circulation mechanism for forcibly circulating a part of the cake-like sludge that has been supplied into the digestion tank and digested in the digestion tank, and the digested cake-like sludge in the digestion tank And a discharge mechanism for forcibly discharging the cake-like sludge in the supply tank together with a part of the digested cake-like sludge that circulates into the digester tank. It is characterized by the fact that

Next, the device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic vertical sectional view showing a first embodiment of the device of the present invention. As shown in FIG. 1, the apparatus according to the first embodiment of the present invention includes a digestion tank 1, a supply tank 10 provided near the digestion tank 1, and a circulation pump 11 provided at the bottom of the digestion tank 1. And a circulation pipe 12, one end of which is connected to the circulation pump 11 and the other end of which is connected to a supply port provided on the top wall 1a of the digestion tank 1, and a branch of the circulation pipe 12 close to the circulation pump 11 The discharge pipe 14 having the first switching valve 13 in the middle thereof, the supply pump 15 provided at the bottom of the supply tank 10, one end of which is connected to the pump 15, and the other end in the middle of the circulation pipe 12. Of the supply pipe 16 connected to the circulation pipe 12,
It is composed of a second switching valve 17 provided between a connection portion with the discharge pipe 14 and a connection portion with the supply pipe 16.

The cross-sectional shape of the digestion tank 1 is circular or square so that sludge digested in the digestion tank 1 can be efficiently supplied to the circulation pump 11 provided in the lower portion of the digestion tank 1. The lower part 1b of the digestion tank 1 has a hopper shape. A screw conveyor for scraping the digested cake-like sludge may be provided at the lower end discharge port of the digestion tank 1. Reference numeral 3 is a gas discharge pipe connected to the gas discharge port of the top wall 1a of the digestion tank 1.

[0013]

[Function] The second switching valve 17 is opened and the circulation pump 11 is driven to forcibly discharge the digested cake-like sludge in the lower portion 1b of the digestion tank 1 from the digestion tank 1 and pass through the circulation pipe 12 again. It is supplied into the upper part of the digestion tank 1 from the supply port of its top wall. In this way, the cake sludge is removed from the digestion tank 1 and the circulation pipe.
Cycle through 12. On the other hand, the cake-like sludge A, which has been concentrated in a not-illustrated concentrator and then dehydrated in the not-illustrated dehydrator, is supplied into the supply tank 10 from above.

The cake-like sludge A in the supply tank 10 is
By the supply pump 15 provided in the lower part of the, through the supply pipe 16, circulates in the circulation pipe 12, is supplied into the digested cake-like sludge as seed sludge, in the circulation pipe 12,
After being mixed with the digested cake-like sludge, it is supplied into the digestion tank 1. Therefore, the cake-like sludge A, which has poor fluidity,
It is mixed with seed sludge in the circulation pipe 12 and sufficiently stirred while circulating in the circulation pipe 12 and the digestion tank 1. In this way, the cake-like sludge A supplied into the digestion tank 1 is allowed to stay in the digestion tank 1 in an anaerobic state for a certain period of time to ferment methane. As a result, the cake-like sludge in the digestion tank 1 is decomposed and its organic components are digested.

The surplus digested cake-like sludge in the digestion tank 1 is forcibly discharged by the circulation pump 11 through the discharge pipe 14 by closing the second switching valve 17 and opening the first switching valve 13. .. The digestion gas generated in the digestion tank 1 is discharged from the digestion tank 1 through the gas discharge pipe 3, and is collected and used as fuel for a boiler or the like.

FIG. 2 is a schematic vertical sectional view showing a second embodiment of the device of the present invention. As shown in FIG. 2, in the device according to the second embodiment of the present invention, a circulation pipe is provided between the circulation pump 11 provided at the bottom of the digestion tank 1 and the upper portion of the supply tank 10.
18 is connected, and a supply pipe 19 is connected between the supply pump 15 provided at the bottom of the supply tank 10 and the supply port provided at the top wall 1a of the digestion tank 1. Second switching valve
The difference from the device of the first embodiment is that 17 is provided.

A part of the cake-like sludge digested in the digestion tank 1 passes through the circulation pipe 18 and is supplied into the supply tank 10 from above as seed sludge. The cake-like sludge A in the supply tank 10 is supplied into the digestion tank 1 through the supply pipe 19 together with the digested cake-like sludge supplied in the supply tank 10, and is digested in the digestion tank 1. A part of the excess digested cake-like sludge is discharged from the digestion tank 1 by the circulation pump 11, supplied again into the supply tank 10 through the circulation pipe 18 and into the digestion tank 1 through the supply pipe 19. Will be returned. In this way, the cake sludge is supplied to the circulation pipe 18, the supply tank 10, and the supply pipe 19.
And while circulating through digester 1, well mixed and agitated with seed sludge.

[0018]

As described above, according to the apparatus of the present invention, the dehydrated cake-like sludge can be sufficiently mixed with the digested cake-like sludge (seed sludge), and the mixture can be stirred. It is possible to efficiently digest the cake-like sludge in a short time, and the digested cake-like sludge can be easily discharged from the digestion tank. Since there is no need to install a device, maintenance is easy, and many industrially useful effects are brought about.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a first embodiment of the device of the present invention.

FIG. 2 is a schematic vertical sectional view showing a second embodiment of the device of the present invention.

FIG. 3 is a schematic vertical sectional view showing an example of a conventional device.

FIG. 4 is a schematic vertical sectional view showing another example of a conventional device.

[Explanation of symbols]

 1 digestion tank 2 supply pipe 3 discharge pipe 4 gas injection pipe 5 branch pipe 6 gas compressor 7 draft tube 8 stirring shaft 9 motor 10 supply tank 11 circulation pump 12 circulation pipe 13 first switching valve 14 discharge pipe 15 pump 16 supply pipe 17 Second switching valve 18 Circulation pipe 19 Supply pipe A Cake sludge

Claims (3)

[Claims] 1. A digestion tank, a supply tank provided adjacent to the digestion tank for supplying cake-like sludge into the digestion tank, and a supply tank supplied to the digestion tank and in the digestion tank. A circulation mechanism for forcibly circulating a part of the digested cake-like sludge, a discharge pipe for forcibly discharging the digested cake-like sludge from the digestion tank, and the inside of the supply tank And a supply mechanism for supplying a part of the digested cake-like sludge that circulates into the digestion tank, the digester for cake-like sludge. 2. The digestion device, wherein one end of the circulation mechanism is connected to a circulation pump provided at the bottom of the digestion tank and the other end is connected to a supply port provided at the top wall of the digestion tank. A supply pipe having a circulation pipe provided outside the tank, the supply mechanism having one end connected to a pump provided at the bottom of the supply tank and the other end connected in the middle of the circulation pipe. Characterized in that the cake-like sludge in the supply tank is supplied and circulated through the circulation pipe into the digestion tank together with a part of the digested cake-like sludge passing through the circulation pipe. The device according to claim 1, wherein 3. The circulation mechanism comprises a circulation pipe, one end of which is connected to a circulation pump provided at the bottom of the digestion tank, and the other end of which is located above the supply tank. , A cake in the supply tank, one end of which is connected to a pump provided at the bottom of the supply tank and the other end of which is a supply pipe connected to a supply port provided at the top wall of the digestion tank. The sludge is supplied and circulated through the supply pipe into the digestion tank together with a part of the digested cake-like sludge supplied through the circulation pipe into the supply tank. The device according to claim 1.