JPH0498123A - Method and device for detecting boundary of sludge - Google Patents

Abstract

PURPOSE:To detect the boundary of sludge without no affection by an electric resistance characteristic, density, permeability and the like of slurry by using a difference between the back pressures of two air purge pipes so as to detect the boundary of sludge. CONSTITUTION:A winch 36 is rotated for pay-off by means of a control circuit 56 in response to a signal which indicates that a rake 3 passes through a predetermined position so that first and second air purge pipes 21, 22 are lowered into slurry. When the opening 21a is inserted into sludge, the difference P2 between the back pressures is given by P2=(rho2-rho1)a+rho1h, where rho1 is the specific gravity of clean water and rho2 is the specific gravity of the sludge, a is the distance from the boundary of the sludge to the opening 21a of the air purge pipe 21, and h is a vertical difference between the first and second air purge pipes 21, 22. Accordingly, by previously setting the value (a) and then by inserting the air purge pipes 21, 22 into the sludge 10a until the pressure difference becomes P2, the boundary 10c of the sludge 10a can be known.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method and apparatus for detecting a sludge interface in a settling tank in which a slurry containing sludge is sedimented and separated.

<Conventional technology> By precipitating and separating slurry containing sludge,
FIG. 8 shows an outline of a settling tank for obtaining clarified liquid (supernatant liquid) and sludge.

1 is a sedimentation tank having a discharge port 2 at the center of the bottom, and a rake 3 is provided in the sedimentation tank. This rake 3 is rotated at low speed by a drive system 4. A discharge pipe 5 is connected to the discharge port 2, and a pump 6 is provided on the discharge pipe 5. On the other hand, a gutter-shaped overflow passage 8 is provided around the upper part of the settling tank 1 via an overflow weir 7, and a discharge passage 8a is also connected to this overflow passage 8. 9 is a slurry supply path, and slurry containing sludge is supplied from above to the settling tank 1 through this slurry supply path 9.

The portion containing solids in the slurry 10 supplied into the settling tank 1 is precipitated to become sludge 10a, and on the upper side there is 1Il.
A clear N liquid 10b is separated.

The sludge 10a is scraped up by the rotating rake 3,
It is discharged from the discharge port 2 in the center of the bottom. On the other hand, clear liquid 10
b crosses the overflow weir 7, enters the overflow channel 8, and enters the discharge channel 8a.
It is collected after

By the way, in such a settling tank, if the interface 10c between the sludge 10a and the clarified liquid 10b (the top surface of the sludge 10a) is high, that is, if a large amount of the sludge 10a is accumulated, the residence time of the incoming slurry 10 will be shortened. If the slurry 10 becomes too short, solid-liquid separation may not be carried out sufficiently, and the components of the slurry 10 may become too hard to be discharged due to the compaction effect.

On the other hand, if the slurry interface 10c is too low, the consolidation effect cannot be obtained and the sludge 10a cannot be thickened.

Therefore, attempts have been made to maintain the sludge interface 10c properly, and various methods have been used to control the sludge interface 10c.
c has been detected or measured.

Conventionally, methods and devices for detecting the sludge interface 10c include:
JP-A-59-26015, JP-A-51-1451
69, Japanese Unexamined Patent Publication No. 1105121, etc. are provided.

The method described in JP-A-59-26015 detects the sludge interface based on the difference in electrical resistance between clear water and sludge.

The method described in JP-A-51-145169 detects the sludge interface based on the concentration difference between supernatant water and sludge.

The method described in JP-A-1.105121 detects the sludge interface based on the difference in light transmittance between supernatant water and sludge.

In addition to these methods, a method has also been implemented in which a pipe is inserted into the settling tank and the sludge interface is detected from the position of the sludge adhering to the pipe.

<Problems to be Solved by the Invention> However, in the method using the difference in electrical resistance described in JP-A-59-26' (115), some slurries have a tendency to conduct electricity (for example, a large amount of metal ions). When applied to such materials, there is a problem that there is no noticeable difference in electrical resistance and it is difficult to distinguish the sludge interface.

In the method using the concentration difference described in JP-A-51-145169, depending on the slurry, a considerable amount of solid particles may be dispersed even in the clarified liquid. The problem is that it is difficult to distinguish between

Furthermore, the method described in JP-A-1-105121, which utilizes the difference in light transmittance, has a problem in that it cannot be applied to slurries in which clear water contains colored particles.

In the last method using a pipe, it is difficult to obtain accurate readings due to individual differences, and when the pipe is pulled up, the sludge adhering to the pipe is washed away by the supernatant liquid. This poses problems such as causing reading errors.

As described above, all of the conventional methods for detecting the sludge interface have problems such as limitations in application depending on the components and properties of the slurry.

<Means for Solving the Problems> The structure of the method according to the present invention for solving the above problems is such that a pair of air purge pipes whose open ends are vertically shifted are lowered into a sedimentation tank, and a pair of air purge pipes lζ The apparatus according to the present invention is characterized in that the interface of the sludge is detected by the change in the back pressure difference between the air purge and the air purge. a vertical movement means for moving the tubes and the pair of air purge tubes up and down in the sedimentation tank to which slurry is supplied; a position detection means for detecting the positions of the pair of air purge tubes; and supplying air to the pair of air purge tubes. A special feature is that it includes an air supply means and a back pressure difference measuring means for measuring the back pressure difference generated between the pair of air purge pipes.

<Embodiment> Fig. 1 shows an embodiment of the sludge interface detection device according to the present invention together with a circuit system, and Fig. 2 shows the front of a sedimentation tank equipped with the detection device. , Figure 3 shows the first part.
The arrow shows the view. In addition, the details of part ■ in Figure 3 are shown in Figure 4.
This is shown in Figure 6.

First, there is a settling tank, in which a rake 3 which is driven and rotated at a low speed is supported. There are 11 pillars on the floor of the sedimentation tank 1.
A cross beam 12 that crosses over the surface of the sedimentation tank is passed between the support columns 11. A sludge interface detection device 13 is supported on the first and second cross beams 12.

A support frame 14 extends from the crossbeam 12, and a pedestal 15 is supported by the support frame 14. The pedestal 15 extends in the vertical direction, and has vertical and horizontal frames l, ], 5 n
, 15b, 15c.

It is formed into a frame shape by 15d. A pair of brackets 16 and 17 are provided projecting from the upper and lower parts of the frame 15, and the upper and lower parts of two parallel rod-shaped slide guides 18 are attached to these brackets 16 and 17, respectively.

A slider 19 is attached to the slide guide 18 so as to be movable up and down using the slide guide 18 as a guide. The slider 19 has slide pipes 19a on the left and right,
By fitting these pipes 19a into the slide guide 18, the slider 19 can move up and down. At the top of this slider 19 is a fixed side bracket 20.
is installed protrudingly.

On the other hand, the two air purges '121.22 in which the positions of the lower end openings 21a and 22a, which are open ends, are vertically shifted are -
Being a companion. Near the top of the air purge pipes 21 and 22, as shown in FIG.
is connected to the fixed side bracket 20 on the upper part of the slider 19 by a pin 26.

Therefore, the air purge tubes 21, 22 can freely rotate around the pin 26. The lower portions of the air purge pipes 21 and 22 are passed through a guide 27 attached to the lower frame 15b of the pedestal 15. The guide 27 restrains the air purge pipe 21.22 only in a direction perpendicular to the rotation direction of the rake 3, and does not restrain the air purge pipe 21.22 in the same direction as the rotation direction of the rake 3.

A reinforcing frame 2 is installed slightly above the vertical middle of the pedestal 15.
This reinforcing frame 28 is provided with an L-shaped bracket 28a, and an air purge pipe 28 is provided at the tip of the bracket 28a.
A collar 29 is attached to keep the parts 1 and 22 in a vertical position. Further, the bracket 28a is provided with an adjustment screw 30, and this screw 30 and the air purge pipe 21,
A spring (tension spring) 33 is tensioned between the metal fitting 32 attached to 22 with a U bolt 31. This spring 33 elastically presses the air purge pipes 21 and 221f against the stopper 29.

In other words, the air purge pipes 21 and 22 are kept vertical under normal conditions, and when the rake 3 rotates and hits the air purge pipes 21 and 22, they rotate in the direction of rotation of the rake 3 to avoid damage. There is.

One end of a wire rope 34 is connected to the upper surface of the slider 19. The wire rope 34 passes through a guide pulley 35 provided on the upper frame 15a of the pedestal 15, and then passes through a winding device 36 as a vertical movement means installed on the crossbeam 12.
It is designed to be wound up or rewound. Accordingly, the pair of air purge pipes 21 and 22 are moved up and down together with the slider 19 by driving the winding device 36, and are lowered into the slurry in the sedimentation tank 1 or pulled up. The winding device 36 is equipped with a level meter (depth sounder) of the →knowing type, which detects the positions of the apurge pipes 21 and 22 from the winding amount of the wire rope 34, and the detected value is controlled. The data is input to the memory 60 of the system 47.

Next, details of the two air purge pipes 21 and 22 and their circuit system will be explained.

The two air-pierced tubes 2], 22 have their tips (
The positions of the openings 21n and 22a at the lower end are shifted by h in the vertical direction.

An air supply section 37 is provided at the upper end of the air purge pipes 21 and 22.
．． 38 are provided, and air pipes 39 and 40 connected to an air supply source 61 are connected to these air supply sections 37 and 38. In the figure, numerals 41 and 42 are check valves and pressure reducing valves provided in the air pipes 39 and 40. Further on the 1 m side of the air purge pipe 21.22, there is a back pressure extraction part 43.
44, and pipes 45.44 connected thereto, respectively.
46 is connected to a differential pressure transmitter 48 for measuring the differential pressure within the air purge pipes 21, 22 and transmitting the differential pressure to the control system 47. The differential pressure signal from the differential pressure transmitter 48 is sent to the control system 47.
The signal is input to the drive system of the winding device 36 via an alarm setting device 49.

The air purge pipes 21 and 22 are provided with water injection nozzles 50° 51, and these water injection nozzles 50° 51 are connected to a water supply source 62.
Water injection pipes 52 and 53 are connected. With the air purge pipes 21° 22 raised, the insides of the air purge pipes 21° 22 are cleaned by injecting water into the air purge pipes 21° 22, and the air purge pipes 21 are cleaned by slurry, etc.
．． 22 is prevented from clogging.

In the figure, numeral 54 is a solenoid valve provided in water injection pipes 52 and 53, and is controlled to open and close by commands from a control system 47.

In the device B, the slurry interface is detected by the air purge pipe 21.22 after the rake 3 passes below the air purge pipe 21.22 in order to avoid collision with the rake 3.

Therefore, rake 3 passes the predetermined position and reaches 1. Proximity switch 55a for detecting.

55b is provided for the rotation system of the rake 3, and its detection signal is input to the control circuit 56 of the control system 47.

In addition, the air purge pipes 2], 22 are connected as described above.
Even if it collides with the key 3, it will rotate and its destruction will be avoided, but in that case, the air purge pipe 21 is forcibly raised by the winding device 36.
A proximity switch 57 for detecting rotation of the angle 22 is provided on the guide 27 at the bottom of the pedestal 15. The signal from the proximity switch 57 is also input to the control circuit 56, and the L1 control circuit 56 outputs a regular winding command for the winding device 36.

Next, the operation of detecting the sludge interface by the sludge interface detection device having the above configuration, that is, the method according to the embodiment of the present invention will be explained. Note that for convenience of explanation, the opening 21. a is the air purge located below [21 is the first air purge pipe 21
This is called an air par, pipe 2, in which the opening 22a is shifted upward.
2 is called a second air purge pipe 22.

Proximity switch 5 indicates that rake 3 has passed a predetermined position.
When detected by 5a and 55b, the drive system of the winding device 36 is actuated via the control circuit 56 by the detection signal,
As the winding device 36 is rewound, the slider 19
Along with the first. The second air purge pipes 21, 22 descend into the slurry.

1st. Sludge interface 10 by second air purge pipe 21, 22
The detection principle of c will be explained based on FIG. 7 (al(b)).

1st. Air is supplied from the air supply source to the second air purge pipe 21.22 through the air pipe 39.40. 1st. Second
Openings 21a, 22. of air purge pipes 21°22. Bubbles are continuously generated from a, and back pressure is generated in the pipes 45 and 46. The specific gravity of the clear liquid 10b in the upper part of the settling tank 1 is ρ,
Then, 1st. Opening 2 of second air purge pipe 21.22
When 1a and 22a are in the clear liquid 10b, l, the back pressure difference Pl, becomes Pl-ρ1h.

As shown in FIG. 7 (bl), when the opening 21a of the first air purge pipe 21 is inserted into the sludge 10a, the sludge 10a
Assuming that the specific gravity is ρ, the back pressure difference P is as follows: P2=(p2-p,) a+p,h. Here, a is the distance from the sludge interface 10c to the opening 21a of the first air purge pipe 21.

Therefore, by setting a in advance, the upper clarified liquid 10
．． By actually measuring the specific gravity ρ1 of b and the specific gravity ρ2 of sludge 10a, the value of P2 is known, so until the differential pressure reaches P2,
If the air purge pipes 21 and 22 are inserted into the sludge 10a,
The interface 10c of the sludge 10a can be known. In other words, since the distance to the tip of the first air purge pipe 21 is measured by the sounding type level meter provided in the winding device 36, the position obtained by subtracting a from that distance becomes the slurry interface 10c. .

After detecting the slurry interface 10C, the winding bag M36 is rolled up to form the first. The second air purge pipe 2], 22 is pulled up to a predetermined position (M to the extent that it does not interfere with the rake 3),
Waiting for the next measurement. If this pull-up is not done and rake 3, which came with 1 revolution, becomes the 1st. Second air purge pipe 2
1.22, the 1st and second air purge pipes 21 and 22 can freely rotate in the moving direction of the rake 3 as described above, so even if the 1st. Breaking of the second air purge pipes 21 and 22 is prevented. Also, 1st. When the second air purge pipe 21, 2.2 is rotated, it is detected by the proximity switch 57, and through the control circuit 56, the winding device 36 together with the slider 19 detects the rotation of the second air purge pipe 21, 2.2. The second air purge pipes 21 and 22 are forcibly pulled up.

The first one waiting above. In order to prevent clogging of the pipes with slurry, water is injected into the second air purge pipes 21 and 22 through pipes 52 and 53 17 to clean the insides of the pipes.

Note that although the above series of operations are performed under automatic control, they can also be performed manually if necessary.

<Effects of the Invention> According to the sludge interface detection method and device according to the present invention, the sludge interface is detected using the back pressure difference between two air purge pipes, and the electrical resistance characteristics, concentration, and permeability of the slurry are detected. It becomes possible to accurately detect the sludge interface without being affected by such factors.

Furthermore, since the measurement method is simple, the number of measurements can be increased, and the accuracy of monitoring the sludge interface is improved.

Furthermore, since it can be automated, it can be simplified,
Test content will also be stabilized.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram showing an embodiment of the sludge interface detection device according to the present invention together with a circuit system, Fig. 2 is a front view of a settling tank equipped with the detection device, and Fig. 3 is an I-I arrow thereof. View, 4th
The figure is an enlarged view of part ■ in Fig. 3, Fig. 5 is a side view, Fig. 6 is an enlarged view of the upper part of the air purge pipe, Fig. 7 is a principle diagram of sludge interface detection, and Fig. 8 is a diagram of the settling tank. It is a schematic diagram of an example. In the drawings, 1 is a settling tank, 3 is a rake, 7 is a hot flow weir, 10 is a slurry 10a, 10b is a clarified liquid, 10c is a sludge interface, 13 is a sludge interface detection device, 15 is a frame, 19 is a slider, 21.22 is an air purge pipe, 26 is a pin, 27 is a guide, 291 is a stopper, 30 is a spring adjustment screw, 33 is a spring, 34 is a wire rope, 36 is a winding device, 39.40 is an air piping, 45.46 is piping, 47 is a control system, 48 is a differential pressure transmitter, 50.51 is a water injection nozzle, 55 a, 55 b, 57 is a nearby switch, 56
1 is a control circuit, 61 is an air supply source, and 62 is a water supply source. Patent use by Hikoshima Seiyari

Claims (2)

[Claims] (1) A pair of air purge pipes whose open ends are shifted up and down are lowered into the settling tank, and the sludge interface is detected by the change in back pressure difference caused by supplying air to the pair of air purge pipes. A sludge interface detection method characterized by: (2) A pair of air purge tubes whose open ends are shifted up and down, a vertical movement means for moving the pair of air purge tubes up and down in a sedimentation tank supplied with slurry, and a position for detecting the position of the pair of air purge tubes. A sludge interface detection device comprising a detection means, an air supply means for supplying air to a pair of air purge pipes, and a back pressure difference measuring means for measuring a back pressure difference generated between the pair of air purge pipes.