JP2018058083A - Operation method of screw press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of a screw press for reducing a discharge quantity of a dewatering cake, in the operation method of the screw press 1.SOLUTION: A sludge undiluted solution is pressed in a screw press 1, and when a filtration chamber 7 reaches predetermined filtration pressure, supply of the undiluted solution is stopped. Solid-liquid separation of the undiluted solution compacted in the filtration chamber 7 is promoted by gravity dewatering by standing of a constant time, or by rotating an outer cylinder 4 or a screw shaft 6 after stopping the supply of the undiluted solution. An operation state can be continued without stopping the screw press 1 even in a processing place less in a generation quantity of the sludge undiluted solution by reducing supply of the undiluted solution and discharge of a dewatering cake as much as possible.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a screw press operating method in which a sludge generation amount is retained in a filtration chamber for a long time by a control method in which a sludge supply amount and a dewatered cake discharge amount are reduced in a screw press operating in a treatment plant with a small amount of sludge generation.

Conventionally, screw presses that concentrate and dehydrate organic sludge such as sewage, human waste, and food production processing wastewater are generally known. Since the screw press is a device that continuously concentrates and dewaters sludge, the sludge is continuously supplied to the screw press and the dewatered cake is continuously discharged from the screw press.
Therefore, when the amount of sludge generated at the treatment plant decreases and the supply amount to the screw press becomes insufficient, the operation of the screw press is stopped because the operation becomes idle and the stability deteriorates. Thereafter, when the sludge storage amount increases to some extent, the operation is resumed.
The operation method is disclosed in Patent Document 1 as a technique for detecting the liquid level position of a hopper installed in the front stage of the screw press and stopping the rotation of the screw press when the liquid level position falls below the lower limit water level. .

Japanese Patent No. 3760083

According to Patent Document 1, when sludge supply is interrupted during operation, air is mixed into the dewatering device and a stable dewatered cake cannot be generated. Therefore, the operation / stop is based on the storage amount of the hopper that temporarily stores sludge. Judgment is made. However, once the operation of the screw press is stopped, the pressure in the filter chamber of the dehydrator (corresponding to a cylindrical strainer), the dehydration status such as clogging will change over time, and the dehydration discharged from the outlet during re-operation The moisture content of the cake is not stable.

Generally, since stable operation of a screw press requires about 1 to 3 hours from the start of operation, it is said to be unsuitable for a small-scale processing plant that frequently operates / stops a screw press. It was.

  In order to stabilize the dewaterability of the sludge discharged from the screw press in a screw press operating in a treatment plant with a small amount of sludge generated, this invention reduces the amount of dehydrated cake discharged by increasing the residence time in the filtration chamber. An operation method of a screw press that continues to maintain the continuous operation state of the screw press is provided.

In this invention, a screw shaft is arranged inside an outer cylinder in which a screen is stretched, and a solid content in the filtration chamber is conveyed by solid-liquid separation of the stock solution supplied to the filtration chamber by the screen, and a dehydrated cake is discharged from the discharge port. In the operation method of the screw press that discharges the stock solution, the stock solution is supplied with the rotation of the screw shaft and the outer cylinder stopped. When the filtration pressure is less than the reference filtration pressure, the supply of the stock solution is continued, and the filtration pressure is higher than the reference filtration pressure. In the case of dehydration, the stock solution is dehydrated in a stationary state where the supply of the stock solution is stopped for a predetermined time, and when the filtration pressure is lower than the reference filtration pressure after standing, the stock solution supply is started. When the pressure is higher than the pressure, the screw shaft is rotated by a predetermined amount, and the operation is performed to reduce the supply amount to the screw press and the discharge amount from the screw press as much as possible. There is no operation / stop of the screw press, stable dewatering operation can be continued.

If the filtration pressure is equal to or higher than the reference filtration pressure after standing, rotate the outer cylinder by a predetermined amount and let it stand again.If the filtration pressure is less than the reference filtration pressure after resting, supply the stock solution. When the filtration pressure is higher than the reference filtration pressure after resting, the screw shaft is rotated by a predetermined amount, and when rotating the screw shaft, the reverse rotation of the predetermined screw shaft or the rotation of the outer cylinder is combined. Therefore, the pressure density in the filtration chamber is improved, and a dehydrated cake having a low water content can be generated.

The outer cylinder is divided into an outer cylinder in the concentration zone in the first half and an outer cylinder in the filtration / dehydration zone in the second half, and each is rotated individually, and the rotation of the outer cylinder is a combination of predetermined forward rotation and reverse rotation. Therefore, forward rotation to improve the pressure density by transporting the stock solution compacted from one side in the filtration chamber to the supply side, and transporting the cake in the filtration chamber to the discharge side to the supply side of the stock solution Solid-liquid separation is further promoted by reversal that creates voids.

According to this invention, since the operation for reducing the supply amount to the screw press and the discharge amount from the screw press is performed as much as possible, the sludge supply to the screw press is not interrupted even in a treatment plant with a small amount of sludge generation. Therefore, there is no screw press operation / stop due to fluctuations in the sludge supply amount, and stable dehydration operation can be continued. In addition, since there is no labor at the time of starting up the screw press operation and no stable time for dehydration, maintenance management becomes easy. By retaining in the filtration chamber for a long time, the pressure density in the filtration chamber is improved, and a dehydrated cake having a low water content can be generated.

It is a partially vertical side view of the screw press according to the present invention. Similarly, it is an enlarged view of the discharge side of the screw press. It is an operation control system figure concerning the present invention. 3 is a flowchart of control according to the present invention. 3 is a flowchart according to the present invention.

FIG. 1 is a partially longitudinal side view of a screw press.
Reference numeral 1 denotes a screw press, in which a screw shaft 6 around which screw blades 5 are wound is arranged inside a cylindrical outer tube 4 in which screens supported by front and rear frames 2 and 3 are stretched around the periphery. Has been established. The screw shaft 6 is expanded from the sludge supply side toward the cake discharge side, and the filtration chamber 7 between the outer cylinder 4 and the screw shaft 6 is decreased from the supply side toward the dewatering side. In addition, a series of scrapers having elasticity such as rubber are disposed at the tip of the screw blade 5 wound around the screw shaft 6 from the start end of the concentration zone A to the end of the filtration / dehydration zone B. Also good.

FIG. 2 is an enlarged view of the supply side of the screw press.
A flange 8 is connected to the supply side of the outer cylinder 4, and the flange 8 is pivotally supported on a rotary plate bearing 9 provided on the frame 2. A sprocket 10 is fitted to the flange 8, and a chain 14 is hung on a sprocket 13 of an outer cylinder driving machine 12 that can be rotated forward and backward and is placed on a frame 11 of the frame 2. A sludge supply pipe 15 is connected to the start end of a screw shaft 6 provided in the outer cylinder 4, and a bearing 16 fitted to the supply pipe 15 is pivoted by a flange 8 connected to the outer cylinder 4. I support. A sludge supply path 17 is provided in the screw shaft 6 connected to the supply pipe 15, and a supply hole 17 a is opened in the filtration chamber 7 on the start end side of the concentration zone A. Since the sludge supply hole 17a is formed in the screw shaft 6, the sludge is supplied without being affected by the rotation of the screw blade 5, and the soft flocs aggregated by the flocculant are not destroyed, and the dehydrating property is eliminated. Will not be damaged.

FIG. 3 is an enlarged view of the discharge side of the screw press.
A rotating plate 18 connected to the outer cylinder 4 is pivotally supported on a rotating plate bearing 19 disposed on the frame 3. A screw drive shaft 20 is connected to a rear end portion of the screw shaft 6 provided in the outer cylinder 4. As shown in FIG. 1, the screw drive shaft 20 is pivotally supported by a bearing 22 provided on a frame 21 of the frame 3. A sprocket 23 is fitted on the screw drive shaft 20, and a chain 27 is hung on a sprocket 26 of a screw drive 25 mounted on a frame 24 of the frame 3. The screw shaft 6 provided in the outer cylinder 4 is rotated by a screw driver 25, and the sludge in the filtration chamber 7 is transferred from the supply side toward the cake discharge side by the screw blades 5 while the screen of the outer cylinder 4 is moved. Drain the filtrate.

A presser 29 for adjusting the back pressure is disposed at the discharge port 28 of the outer cylinder 4, and the presser 29 is movably supported on a presser moving shaft 30 disposed on the frame 3. The presser 29 is moved by a cylinder 31 disposed in the frame 3, and the back pressure is applied to the cake in the filtration chamber 7 while adjusting the opening amount of the discharge port 28 to make moisture uniform, and the outer cylinder of the filtration / dehydration zone B A back pressure is applied in 4b to promote solid-liquid separation and adjust moisture.

As shown in FIG. 1, the cylindrical outer cylinder 4 is divided into an outer cylinder 4a in the first half of the concentration zone A and an outer cylinder 4b in the second half of the filtration / dehydration zone B. An intermediate bearing 28 is interposed between the outer cylinder 4 b of the filtration / dehydration zone B. The outer cylinder 4a on the concentration zone A side linked to the outer cylinder driving machine 12 is configured to be able to rotate freely in contact with and away from the outer cylinder 4b on the filtration / dehydration zone B side.

FIG. 4 is a system diagram according to the present invention.
The sludge undiluted solution generated at the factory or treatment plant is temporarily stored in the undiluted solution storage tank 32. Thereafter, the undiluted solution supply pump 33 supplies the screw press 1 from the undiluted solution storage tank 32 through the undiluted solution supply pipe 34. The stock solution may be conditioned with a polymer flocculant by interposing a coagulation / mixing tank 35 as necessary. A pressure gauge 36 for measuring the press-fitting pressure (filtration pressure) to the screw press 1 is disposed in the stock solution supply pipe 34 at the front stage of the screw press 1. The measured value of the press-fitting pressure is transmitted to the control device 37, and the control device 37 gives an instruction to the stock solution supply pump 33, the outer cylinder driving device 12, and the screw driving device 25 according to the received measured value, and the screw press 1 Operation control is performed.

When the sludge stock solution is pressed into the screw press 1 and the filtration chamber 7 reaches a predetermined filtration pressure, the supply of the stock solution is stopped. After the supply of the stock solution is stopped, gravity dehydration by standing for a certain time and rotation of the outer cylinder 4 or the screw shaft 6 promotes solid-liquid separation of the consolidated stock solution in the filtration chamber 7.
By reducing the stock solution supply and dewatered cake discharge as much as possible, the operation state can be continued without stopping the screw press 1 even in a treatment plant where the amount of sludge stock solution generated is small.

FIG. 5 is a flowchart according to the present invention. The present invention is an embodiment of the screw press 1 in which the outer cylinder 4 is rotatable, and the screw press 1 to which the outer cylinder 4 is fixed has no flow relating to the rotation of the outer cylinder 4.
A. Initial setting The reference filtration pressure P0 of the screw press 1 is set according to the sludge properties and the model of the screw press 1. In this embodiment, the filtration pressure is measured in real time by a pressure gauge 36 disposed in the front stage of the screw press 1.
Moreover, the stationary time which filters by gravity during stationary, the rotational speed and rotational time of the outer cylinder 4, the reference rotational speed N0 of the screw shaft 6, the rotational speed N and rotational time of the screw shaft 6 are set.
Furthermore, the measurement time of the filtration pressure P and the rotation speed N of the screw shaft 6 is set.

B. The stock solution is supplied from the stock solution supply pump 33 to the screw press 1 while the rotation of the stock solution supply screw shaft 6 and the outer cylinder 4 is stopped. In this embodiment, the conditioned solution is supplied through the coagulation / mixing tank 35. The solid content of the supplied stock solution remains in the filtration chamber 7, and moisture permeates from the screen of the outer cylinder 4. When the stock solution supply is continued, the solid content is gradually consolidated in the filtration chamber 7 and the filtration pressure P increases. The filtration pressure P is measured by the pressure gauge 36, and the measured value is transmitted to the control device 37.

C. The filtration pressure P1 measured by the filtration pressure comparison control device 37 is compared with a predetermined reference filtration pressure P0. When the filtration pressure P1 is smaller than the reference filtration pressure P0 (P1 <P0) as a result of comparison by the control device 37, the process proceeds to B in the flowchart and the stock solution supply by the stock solution supply pump 33 is continued.
When the filtration pressure P1 reaches the reference filtration pressure P0 or more (P0 ≦ P1), the operation of the stock solution supply pump 33 is stopped and the process proceeds to D in the flowchart.

D. The supply of the stock solution to the stationary screw press 1 is stopped, and dehydration is performed by gravity filtration. It is allowed to stand for a predetermined time, the filtration pressure during that time is measured, and the measured value is transmitted to the control device 37.

E. The filtration pressure P2 in the filtration chamber 7 of the screw press 1 after the filtration pressure comparison and stationary is compared with a predetermined reference filtration pressure P0. When the filtration pressure P2 is smaller than the reference filtration pressure P0 (P2 <P0) as a result of comparison by the control device 37, the process proceeds to B in the flowchart, and the stock solution supply by the stock solution supply pump 33 is resumed.
When the filtration pressure P2 maintains the reference filtration pressure P0 or more (P0 ≦ P2), the process proceeds to F in the flowchart.

F. Outer cylinder rotation The outer cylinder 4 is rotated at a predetermined number of rotations to promote gravity filtration of the stock solution in the filtration chamber 7. At this time, the stock solution compressed from one side in the filtration chamber 7 is conveyed to the supply side to further promote solid-liquid separation to improve the pressure density, and the cake in the filtration chamber 7 is discharged. It is rotated in combination with a reverse rotation that creates a gap on the supply side of the filtration chamber 7 by being conveyed to the side. The outer cylinder 4 may rotate only the outer cylinder 4a of the concentration zone A.
The rotation speed, rotation time, etc. of each of the outer cylinders 4 and 4a are determined in advance according to the capability of the screw press 1 and the properties of the stock solution.
Note that this flow is omitted for the screw press 1 to which the outer cylinder 4 is fixed.

G. The filtration pressure P3 in the filtration chamber 7 of the screw press 1 after rotating the filtration pressure comparison outer cylinder 4 is compared with a predetermined reference filtration pressure P0. If the filtration pressure P3 is smaller than the reference filtration pressure P0 (P3 <P0) as a result of comparison by the control device 37, the process proceeds to B in the flowchart, and the stock solution supply by the stock solution supply pump 33 is resumed.
When the filtration pressure P3 maintains the reference filtration pressure P0 or more (P0 ≦ P3), the process proceeds to H in the flowchart.

H. Screw shaft rotation (forward rotation)
The screw shaft 6 is rotated at a predetermined rotation speed set in advance to convey the stock solution in the filtration chamber 7 to the discharge side and discharge the dewatered cake from the discharge port 28.
The rotation speed and rotation time of the screw shaft 6 are determined in advance according to the capability of the screw press 1 and the properties of the stock solution.
After the screw shaft 6 operates at a predetermined rotation, the process proceeds to I in the flowchart.

I. The filtration pressure P4 in the filtration chamber 7 of the screw press 1 after rotating the filtration pressure comparison screw shaft 6 is compared with a predetermined reference filtration pressure P0. As a result of comparison by the control device 37, when the filtration pressure P4 maintains the reference filtration pressure P0 or more (P0 ≦ P4), the process proceeds to H in the flowchart and the rotation of the screw shaft 6 is continued.
When the filtration pressure P4 is smaller than the reference filtration pressure P0 (P4 <P0), the process proceeds to J in the flowchart, and the rotation speed of the screw shaft 6 rotated in the flowchart H is compared.

J. et al. The rotation speed N of the screw shaft 6 rotated in the screw shaft rotation speed comparison flowchart H is compared with a predetermined reference rotation speed N0. When the rotation speed N of the screw shaft 6 is greater than the reference rotation speed N0 (N0 <N) as a result of comparison by the control device 37, the process proceeds to B in the flowchart.
When the rotation speed N of the screw shaft 6 is equal to or less than the reference rotation speed N0 (N ≦ N0), the process proceeds to K in the flowchart.

K. Since the stock solution in the outer cylinder rotation / screw shaft reverse rotation filtration chamber 7 is transported to the discharge side and the dehydrated cake is discharged, the compacted stock solution in the filtration chamber 7 may be destroyed. The pressure density is improved by performing forward rotation of the outer cylinder 4 in combination, and conveying the stock solution consolidated from one side in the filtration chamber 7 to the supply side. The outer cylinder 4 may rotate only the outer cylinder 4b of the filtration / dehydration zone B.
Further, the reverse rotation of the screw shaft 6, the start of rotation of the outer cylinder 4, the rotation speed, the rotation time, and the like are determined in advance according to the capability of the screw press 1 and the properties of the stock solution.
In addition, about the screw press 1 with which the outer cylinder 4 is being fixed, the flow regarding rotation of the outer cylinder 4 is abbreviate | omitted.
After the screw shaft 6 and the outer cylinders 4 and 4b are operated at a predetermined rotation, the process proceeds to B in the flowchart.

The operation method of the screw press according to the present invention is a useful operation method capable of maintaining stable dewatering performance even in a treatment plant with a small amount of inflowing sludge. In addition, since there is no labor and dehydration instability time when starting up the screw press operation, maintenance management becomes easy, and the manageability of the entire treatment plant including the front and rear stages of the dehydrator is improved.

1 Screw press 4, 4a, 4b Outer cylinder 6 Screw shaft 7 Filtration chamber 28 Outlet N Rotational speed N0 Standard rotational speed P Filtration pressure P0 Standard filtration pressure A Concentration zone B Filtration / dehydration zone

Claims (5)

The screw shaft (6) is arranged inside the outer cylinder (4) with the screen stretched, and the solid content in the filtration chamber (7) is separated from the stock solution supplied to the filtration chamber (7) by solid-liquid separation with the screen. In the operation method of the screw press that conveys and discharges the dehydrated cake from the discharge port (28),
The stock solution is supplied in a state where the rotation of the screw shaft (6) and the outer cylinder (4) is stopped,
When the filtration pressure (P) is less than the standard filtration pressure (P0), continue the stock solution supply,
When the filtration pressure (P) is equal to or higher than the reference filtration pressure (P0), dehydration is performed in a stationary state in which the stock solution supply is stopped for a predetermined time,
When the filtration pressure (P) is less than the reference filtration pressure (P0) after standing, the stock solution supply is started,
When the filtration pressure (P) is equal to or higher than the reference filtration pressure (P0) after standing, the screw shaft (6) is rotated by a predetermined amount until the filtration pressure (P) becomes less than the reference filtration pressure (P0). The operation method of the screw press characterized by continuing. When the filtration pressure (P) is equal to or higher than the reference filtration pressure (P0) after the standing, the outer cylinder (4) is rotated by a predetermined amount,
When the filtration pressure (P) is less than the reference filtration pressure (P0) after rotating the outer cylinder (4), the stock solution supply is started,
The screw according to claim 1, wherein when the filtration pressure (P) is equal to or higher than the reference filtration pressure (P0) after rotating the outer cylinder (4), the screw shaft (6) is rotated by a predetermined amount. How to operate the press. By rotating the screw shaft (6), the filtration pressure (P) becomes less than the reference filtration pressure (P0),
When the rotational speed (N) of the screw shaft (6) exceeds the reference rotational speed (N0), the stock solution supply is started,
When the rotation speed (N) of the screw shaft (6) is equal to or less than the reference rotation speed (N0), the reverse rotation of the screw shaft (6) or the rotation of the outer cylinder (4) is combined in a predetermined amount. The operation method of the screw press according to claim 1 or 2. The outer cylinder (4) is divided into an outer cylinder (4a) in the first half of the concentration zone (A) and an outer cylinder (4b) in the second half of the filtration / dehydration zone (B), and each is rotated individually. The operating method of the screw press according to claim 2 or 3, characterized in. The screw press operating method according to any one of claims 2 to 4, wherein the rotation of the outer cylinder (4, 4a, 4b) is a predetermined combination of forward rotation and reverse rotation.

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