JPH08281147A - Cleaning of pressured centrifugal concentrator - Google Patents

Abstract

PURPOSE: To enhance the cleaning effects on a pressured centrifugal concentrator and, at the same time, make the supply of cleaning water unnecessary during a cleaning operation by reducing the liquid quantity of a bowl to a lower level than a full fill state, and allowing the bowl to do a cleaning work at a lower rotating speed than the critical number of rotation in a consequent state that a void is created, after the completion of treating sludge. CONSTITUTION: A pressured centrifugal concentrator with a screw conveyor 2 insetted in a freely rotatable manner, in a bowl 1, is subjected to a cleaning work after treating sludge-therewith in its steady-state loaded operation. In this case, first, a separation liquid adjusting valve 5 is closed, and a concentrate adjusting valve 6 is opened. Thus, a cleaning water is supplied to the bowl 1 for about 10 minutes until the bowl 1 stops to discharge a concentrate from the concentrator. After that, the liquid is drained in such a state that the separation liquid adjusting valve 5 is opened and the concentrate adjusting valve 6 is closed. Further, both adjusting valves 5, 6 are closed after the residue in the bowl 1 is reduced to about 1/2. In addition, the bowl is operated at a lower rotating speed than the critical number of rotation, at which the bowl 1 is exposed to 1G or less in such a state that a void is present in the bowl 1. Thus, the concentrator is cleaned and rinsed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurizing type centrifugal concentrator for concentrating sludge generated in a sewage treatment plant, a night soil treatment plant, etc., more specifically, as shown in FIG. Of bowl 1, and within bowl 1, coaxial with the bowl,
And a screw conveyor 2 having a rotation difference and rotating in the same direction, and a centrifugal force is applied to the sludge supplied into the bowl through the hollow support shaft 3 to separate and settle the concentrated liquid on the inner wall side of the bowl. After being accumulated on one side in the bowl by a screw conveyor, a pressure-type centrifugal concentrator for discharging the separated liquid from which the solid content has been separated and the concentrated liquid from the inside and outside of the discharge pipe 4 having a double pipe structure, or A double pipe structure supply / discharge pipe is installed at the shaft center on one side, and the concentrated liquid that has separated and settled on the inner wall side of the bowl is discharged from the other side of the bowl by the screw conveyor, while the separated liquid from which the solid content has been separated is supplied and discharged together with the sludge. The present invention relates to a method for cleaning a pressure-type centrifugal concentrator, which discharges and supplies from inside and outside of a pipe.

[0002]

2. Description of the Related Art In a centrifugal concentrator of this type, during operation, the concentrated liquid separated and settled on the inner wall of the bowl is transferred to the outlet side by a screw conveyor as described above, but when the operation is stopped, the inner wall of the bowl and the screw conveyor are stopped. Collect between
The solid content that is not scraped off by the screw conveyor gradually hangs down due to its own weight and tends to accumulate in the lower layer portion, and when the operation is restarted in this state, vibration may occur due to imbalance. In Japanese Patent Laid-Open No. 4-108548, in order to prevent the solidification of the residual solids after the operation is stopped, after the sludge treatment is completed, the rotation speed is reduced and the solid matter is washed while being rotated at a low speed. A method has been proposed.

[0003]

When cleaning is performed by the above method, water must be continuously supplied during cleaning.
The present inventors repeated various experiments on the cleaning method of the above-mentioned pressure type centrifugal concentrator, when the liquid amount in the bowl was in a semi-water state, and the cleaning was performed by rotating at low speed in the state where there was a void in the bowl, It has been found that the cleaning effect is improved and the cleaning can be performed without supplying cleaning water during cleaning.

The present invention has been made on the basis of this finding, and an object thereof is to provide a method in which the cleaning effect of a pressurized centrifugal concentrator is improved, and further, the cleaning can be performed during the cleaning without supplying cleaning water. Is what you are trying to do.

[0005]

Therefore, the present invention has a bowl that rotates in one direction and a screw conveyor that is coaxial with the bowl within the bowl and that rotates in the same direction with a rotation difference. Centrifugal force is applied to the sludge supplied into the bowl from the side axis to separate and settle the concentrated liquid on the inner wall side of the bowl, which is then accumulated on the other side in the bowl by the screw conveyor, and then the solid content is separated. In a pressurized centrifugal concentrator that discharges the separated liquid and the concentrated liquid from the inside and outside of the discharge pipe of the double pipe structure provided on the shaft center of the other side, after the sludge treatment is completed, the liquid amount in the bowl is full With a smaller number of voids, the bowl is rotated at a low speed below the critical rotation speed of 1 G or below to perform cleaning. In another method, instead of the above-mentioned pressurizing type centrifugal concentrator, a double pipe structure supply / discharge pipe is provided on one side, and the concentrated liquid is discharged from the other side of the bowl, while the separated liquid in which the solid content is separated is A centrifugal concentrator of a type adapted to discharge and supply from the inside and outside of a supply / discharge pipe together with sludge is used.

In each of the above methods, by rotating the bowl at a critical rotational speed of 1 G or less, the liquid in the bowl follows the bowl and then returns to its original state by its own weight, and the rinsing operation is repeated. Cleaning is performed. In another invention, after the sludge treatment is finished, the bowl is washed by alternately repeating rotations of 1 G or more and below the critical rotation speed in a state in which the amount of liquid in the bowl is smaller than that in a full state and has a gap. It is a thing.

When the rotation speed of the bowl becomes higher than the critical rotation speed, the liquid in the bowl sticks to the entire circumference of the bowl due to centrifugal force, and when the rotation speed becomes lower than the critical rotation speed, the liquid sticking to the upper part of the bowl by its own weight. Falls. Therefore, by repeating the rotation of the bowl alternately above and below the critical number of revolutions, the liquid in the bowl clings to the entire circumference and then falls, which causes repeated turbulence and impact of the liquid. The solid content adhering to the inner circumference of the bowl is peeled off and washed.

In still another aspect of the invention, the cleaning is performed by alternately repeating the rotation of the critical speed or more and stopping. In each of the above inventions, the washing can be performed only with the residual liquid remaining in the bowl after the sludge treatment is completed, but preferably after the sludge treatment is completed,
It is desirable that the cleaning water is once passed through the bowl and then the cleaning is performed in a state where a certain amount of cleaning water is accumulated in the bowl. Even when cleaning water is used, the cleaning water is not supplied during cleaning, so the amount of cleaning water used is reduced.

[0009]

【Example】

Example 1 Using the centrifugal concentrator shown in FIG. 1 having a bowl diameter of 700 mmφ and a bowl length of 2100 mm, sludge was treated at a constant load operation of 30 m ³ / hr as shown in FIG. After that, the operation was stopped and
The separated liquid adjusting valve 5 was closed and the concentrated liquid adjusting valve 6 was opened to supply washing water at 30 m ³ / hr for 10 minutes until the bowl stopped, and the concentrated liquid inside the machine was discharged. After that, the separation liquid adjusting valve 5
Was opened, and the concentrated liquid adjusting valve 6 was left open to drain the liquid. After 3 minutes when the residual liquid in the bowl became about 1/2, both adjusting valves 5 and 6 were closed.

Next, the bowl was rotated at a low speed to 0.8 G, and after 21 minutes, the separation liquid adjusting valve 5 and the concentrated liquid adjusting valve 6 were opened to supply 30 m ³ / hr of washing water for 3 minutes, and the flow was continued. After watering, the rotation of the bowl was stopped and the liquid was drained. After stopping, the apparatus was disassembled and the inside of the bowl was inspected, and the thickness of the adhered solid matter was 0. The washing water used at this time was 6.5 m ³ .

Example 2 Sludge treatment was performed using the same centrifugal concentrator as in Example 1, the operation was stopped, and as in Example 1, wash water was supplied for 10 minutes until the bowl stopped, then It was drained to reduce the residual liquid in the bowl to about 1/2. Next, as shown in FIG.
Repeat the operation of rotating the bowl and stopping when it reaches 1 to 4 G (time from drive to stop is 3 minutes).
After the lapse of time, as in Example 1, the cleaning water was supplied to fill the inside of the bowl with water, and then the rotation of the bowl was stopped and the liquid was drained. After stopping, the apparatus was disassembled and the inside of the bowl was inspected, and the thickness of the adhered solid matter was 0. The washing water used was 6.5 m ³ as in Example 1.

Comparative Example Sludge treatment was performed using the same centrifugal concentrator as in Example 1, and then the speed was reduced and the bowl was rotated at a low speed of 3 G for 12 minutes, 15 minutes, 18 minutes.
Experiments were carried out by driving for 30 minutes, 24 minutes, 27 minutes, or 30 minutes, and in each experiment, washing water was supplied at a rate of 30 m ³ / hr for the same period of time as the deceleration was started, and washing was performed in a full state. Then, after draining once at each time of each experiment, the device was disassembled, and the solid adhesion state in the bowl was inspected. As a result, as shown in FIG. 4, there is almost no change in the case of washing for 12 minutes, about 3 mm, 2.5 mm in 18 minutes, 2.0 mm in 24 minutes, 1 mm in 27 minutes, and 0 in 30 minutes. there were. The washing water required for washing for 30 minutes was 20 m ³ . FIG. 5 shows a time chart at that time.

[0013]

The present invention is configured as described above and has the following effects. According to the cleaning method of the first and second aspects, the cleaning is performed by rinsing, the cleaning effect is improved, and since the cleaning water is not used during the cleaning, the amount of cleaning water used is reduced. According to the cleaning method of claim 3 or 4, since the liquid in the bowl once rises and then repeats falling, the turbulence of the liquid becomes severe and the liquid drops adhere to the inner wall of the bowl due to the impact when falling. The solid content is peeled off, and as a result, the cleaning effect is improved and the cleaning time is shortened.
In addition, since washing water is not used during washing, the amount of washing water used can be small.

If cleaning water is used for cleaning as in the cleaning method according to the fifth aspect, the cleaning can be performed more effectively.

[Brief description of drawings]

FIG. 1 is a schematic view of a pressure-type centrifugal concentrator used in the present invention.

FIG. 2 is a time chart of the first embodiment.

FIG. 3 is a time chart of the second embodiment.

FIG. 4 is a diagram showing a relationship between a cleaning time and a solid content deposition amount in a comparative example.

FIG. 5 is a time chart of a comparative example.

[Explanation of symbols]

1 ・ ・ Bowl 2 ・ ・ Screw conveyor 3 ・ ・ Hollow shaft 4 ・ ・ Drain pipe 5 ・ ・ Separated liquid adjusting valve 6 ・ ・ Concentrated liquid adjusting valve

Claims (5)

[Claims] 1. A bowl that rotates in one direction, and a screw conveyor that is coaxial with the bowl in the bowl and that rotates in the same direction with a rotation difference, are provided inside the bowl from an axial center of one side. Centrifugal force is applied to the supplied sludge to separate and settle the concentrated liquid on the side of the inner wall of the bowl, which is then accumulated on the other side of the bowl by a screw conveyor, and then the separated liquid from which the solid content has been separated and the concentrated liquid. In a pressurizing type centrifugal concentrator that discharges from the inside and outside of the discharge pipe of the double pipe structure provided on the shaft center on the other side, after the sludge treatment is completed, reduce the liquid volume in the bowl to less than the full state and create a gap. 1 bowl while standing
A cleaning method for a pressure-type centrifugal concentrator, characterized in that the cleaning is performed by rotating at a low speed at a critical rotation speed of G or less. 2. A bowl that rotates in one direction and a screw conveyor that is coaxial with the bowl in the bowl and that rotates in the same direction with a rotation difference, are provided in the bowl from an axial center of one side. Centrifugal force is applied to the supplied sludge to separate and settle the concentrated liquid on the side of the inner wall of the bowl, which is then accumulated on the other side of the bowl by a screw conveyor, and then the separated liquid from which the solid content has been separated and the concentrated liquid. In a pressurizing type centrifugal concentrator that discharges from the inside and outside of the discharge pipe of the double pipe structure provided on the shaft center on the other side, after the sludge treatment is completed, reduce the liquid volume in the bowl to less than the full state and create a gap. 1 bowl while standing
A cleaning method for a pressure-type centrifugal concentrator, characterized in that the cleaning is performed by alternately repeating the rotations not less than the critical rotation speed of G and below. 3. A pressurizing type centrifugal concentrator, wherein instead of the centrifugal concentrator that discharges the concentrated liquid and the separated liquid from the inside and outside of the discharge pipe of the double pipe structure, a double pipe structure is provided on one side axis. A centrifugal concentrator of the type in which the concentrated liquid is discharged from the shaft center on the other side and the separated liquid and solid sludge are discharged and supplied from the inside and outside of the supply and discharge pipe, respectively, is provided. The method for cleaning a pressurized centrifugal concentrator according to claim 1 or 2. 4. The cleaning method for a pressurized centrifugal concentrator according to claim 2, wherein, instead of alternately repeating the rotation speed equal to or higher than the critical rotation speed and the rotation speed equal to or lower than the critical rotation speed, the rotation and the stop at the critical rotation speed or higher are alternately repeated. 5. The method according to any one of claims 1 to 4, wherein after the sludge treatment is finished, the washing water is once passed through the bowl and washed, and then the bowl is washed with a certain amount of washing water. Cleaning method of the pressure type centrifugal concentrator.