JP2010119957A - Apparatus and method for concentrating slurry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for concentrating slurry which can be operated continuously since a moving medium can be actuated under low pressure and which is suitable for obtaining low-concentration slurry and to provide a method for concentrating slurry. <P>SOLUTION: The apparatus for concentrating slurry in which one or more filtration cylinders 2 each consisting of a filter medium are arranged and the slurry is fed forcibly to the inside of the filtration cylinder 2 to perform filtration/concentration, includes: a guide rod 11 fixed/arranged along the axial center of the filtration cylinder 2; a piston 12 which is inserted into the filtration cylinders to be slid on the guide rod 11, has the outer peripheral surface of the diameter smaller than the inside diameter of the filtration cylinder 2 and is reciprocated from one end of the filtration cylinder 2 to the other end thereof; and a slurry supply unit for forcibly feeding the slurry to the inside of the filtration cylinder 2. Both ends of the filtration cylinder 2 are connected respectively to side pipes 3a, 3b for performing introduction and discharge of the slurry and each of the side pipes 3a, 3b is connected to the slurry supply unit while interposing a changeover valve between them. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a slurry concentration process for wastewater treatment facilities such as a water purification plant and a sewage treatment plant, and more particularly to a slurry concentration apparatus and a concentration method optimal for a low concentration slurry concentration process in a water purification plant that is becoming a problem in recent years. .

A method of continuously performing filtration and concentration while moving the moving body that reciprocates inside the filter cylinder by the press-fitting pressure of the slurry and scraping the cake layer on the surface of the filter medium is disclosed in JP-A-57-65309. This is proposed in Japanese Unexamined Patent Publication No. 60-31806 and Japanese Unexamined Patent Publication No. 8-290018.
In these systems, in order to update the entire cake layer on the filtration surface, the cake layer was scraped while contacting the filter medium surface with a moving body or a ring attached to the moving body.
When the slurry is press-fitted into the filter medium and concentrated by filtration, a cake layer is formed on the surface of the filter medium and grows along with the filtration time. The cake layer has the effect of clarifying the filtrate, but as the cake layer thickness increases, the filtrate discharge resistance increases remarkably, so the filtration rate decreases with the filtration time. Thus, although the high filtration rate can be maintained by removing the cake layer with a moving medium, the method of scraping the cake layer while contacting the filtration surface has the following problems.

(1) Since the cake layer on the surface of the filter medium is scraped by contacting the filter medium with a moving body such as a piston having an outer diameter equal to or larger than the inner diameter of the filter medium, the surface of the filter medium or the moving body is worn. Can not move the piston frequently.
(2) If all cake layers on the surface of the filter medium are scraped off, the filtrate at the beginning of filtration loses its clarity due to leakage from the filter medium, so that the piston cannot be moved frequently. Further, if the filter medium is made finer in order to maintain the clarity of the filtrate, the filter medium will be clogged early.
(3) When the filter medium and the moving body are in close contact with each other, a large moving thrust is required to move the moving body. Moreover, there is a possibility that the filter medium and the moving body may stick during operation stop.
(4) If the roundness of the filtration cylinder is poor, the moving body will not move smoothly. If high roundness is required, it is difficult to manufacture and expensive.
(5) Since the moving thrust of the moving body is a pressure difference generated between the driving side and the discharging side where the slurry flows in from the moving body, the pressure in the filter medium and the side pipe becomes equal. The filtration surface cannot be renewed by the moving body during the filtration process without any.

(6) If the slurry concentration inside the filter medium becomes high and the filter medium is filled with high-concentration concentrated sludge, the moving resistance of the moving body increases, making it difficult to discharge. It had to be discharged or operated at high pressure.
(7) If the length of the filter medium is increased, the amount of concentrated sludge pushed out by the moving body will increase, the moving resistance of the moving body will increase, and it will become difficult to discharge. It was necessary to discharge at low concentrations or to operate at high pressure.
(8) When filtration is performed at high pressure, the energy required for operation increases. Moreover, since a strong cake layer with high density is formed on the surface of the filter medium, the movement resistance of the moving body is increased.
JP 57-65309 A JP-A-60-31806 JP-A-8-290018

    The present invention eliminates the above-mentioned problems of the prior art, does not require high pressure for the operation of the moving body, can move the moving body at a low pressure and can be continuously moved, and is suitable for low-concentration slurry. It is an object to provide a concentrating device and method.

  In order to solve the above-mentioned problems, in the present invention, in a slurry concentrating apparatus in which one or more filter cylinders made of a filter medium are provided and the slurry is concentrated by press-fitting the slurry inside the filter cylinder, the shaft core of the filter cylinder A guide rod that is fixedly installed along the guide rod, and a piston that is slidably inserted into the guide rod, has an outer peripheral surface that is smaller in diameter than the inner diameter of the filtration cylinder, and reciprocates from one end to the other end of the filtration cylinder; A slurry concentrating device comprising a slurry supply device for press-fitting slurry inside the filtration cylinder.

In the slurry concentrating device, the filter cylinder can be one in which a reinforcing material is installed on the outer periphery of the filter medium, and both ends of the filter cylinder are connected to a side pipe for inflow and discharge of slurry, and the side pipe Is connected to the slurry supply device via a switching valve, and the slurry supply device can be a slurry pump capable of press-fitting slurry or a slurry storage tank into which compressed air is injected.
Further, in the slurry concentrator, the filtration cylinder is connected to a side pipe for both inflow and discharge of the slurry at both ends, and the side pipes at both ends are connected to a slurry circulation pipe via a valve. Can be connected to a slurry circulation device for alternately introducing slurry from the side pipes at both ends into the inside of the filtration cylinder to form a circulation flow, and the slurry circulation apparatus is connected to the filtration pipe at the side pipes at both ends. From the above, a slurry circulation pump capable of alternately introducing and circulating the slurry or a slurry storage tank capable of injecting and discharging compressed air can be provided.

Further, in the present invention, in the slurry concentration method for performing filtration concentration by press-fitting slurry into one or more filter cylinders made of a filter medium, the diameter of the filter cylinder is smaller than the inner diameter of the filter cylinder, and the filter cylinder in the filtration concentration process A piston that reciprocates from one end of the filtration cylinder to scrape the cake layer formed inside the tube is inserted into a guide rod that is guided when the piston reciprocates, and the piston is moved along the guide rod. The slurry concentrating method is characterized in that filtration is concentrated by reciprocating, leaving a thin cake film on the filtration surface of the filtration cylinder, and pressing the slurry into the inside of the filtration cylinder.
In the slurry concentration method, the concentrated sludge discharged by filtration concentration can be further circulated inside the filter cylinder and concentrated by filtration to perform high-magnification concentration.

According to the present invention, the following effects can be achieved.
(1) By installing the guide rod and making the outer diameter of the piston smaller than the inner diameter of the filter medium, the filter medium and the piston are brought into non-contact, thereby preventing the surface of the filter medium and the moving medium from being worn. “Non-contact” refers to a state in which the inner peripheral surface of the filter medium and the outer peripheral surface of the piston are non-contact in dimension, and the same applies hereinafter. In addition, it is possible to prevent damage to the seam (perforation in the case of a filter cloth, welded portion in the case of a metal filter medium) when the filter medium is formed into a cylindrical shape. Therefore, it becomes possible to move a piston with the frequency as needed, and a high filtration rate can be maintained.
(2) Since the piston and the filter medium are not in contact with each other, not only the cake layer on the surface of the filter medium is scraped directly with the piston, but also the slurry ejected from the gap between the filter medium and the piston due to the slurry driving pressure when the piston moves. By blowing off the soft and relatively high moisture content cake layer on the filter medium surface and renewing the filtration surface, the filtration rate is prevented from decreasing, but the thin low moisture content cake film on the filter medium surface remains without peeling. Therefore, a filtrate can be obtained while maintaining clarity.

(3) Since the piston and the filter medium are not in contact with each other, the thrust required for the movement of the piston is low, and it is possible to move even with a water flow in the filter medium, so that it can be operated with a low slurry supply pressure. By making the filtration pressure low, the cake layer on the surface of the filter medium has a low density and is easy to remove. Moreover, the leakage from the filter medium at the beginning of filtration can be prevented. In addition, when the supply pressure of the slurry is low, by installing the slurry supply device at a position higher than the concentration device, it is possible to perform the filtration and concentration operation at the water head pressure, and there is also an energy saving effect.
(4) Since the piston and the filter medium are not in contact with each other, the required accuracy of the roundness of the filter cylinder is low and the manufacture is easy, so that the equipment is inexpensive.
(5) Since the piston and the filter medium are not in contact with each other and a thin cake film is held on the surface of the filtration surface, a clear filtrate can be secured even at the initial stage of slurry injection or immediately after the movement of the piston. Therefore, it becomes possible to move the piston frequently. Further, as described above, since the slurry supply pressure is low and the slurry is prevented from being leaked by cake filtration using a cake film, the opening of the filter medium can be increased, so that the filter medium can be prevented from being clogged.

(6) By installing the guide rod at the center of the filter medium, the volume of the filter medium can be reduced with respect to the filtration area, so the filtration time is shortened.
(7) By having a power source that generates a circulating flow inside the filter medium, it can be circulated and concentrated, and the filtration surface can be renewed by the piston during the filtration process. It becomes possible to maintain the high filtration rate at the beginning of filtration and to concentrate at a high magnification.
(8) By making the inner side of the filter medium negative by the suction pressure of the circulation pump, air is sucked in from the outer side of the filter medium, so there is a backwashing effect.
As described above, it is possible to operate at low pressure, and by circulating and concentrating, highly concentrated sludge can be discharged at a high filtration rate, and maintenance work for replacing consumable parts due to clogging or wear of pistons or filter media is small. Concentrator.

Hereinafter, detailed configuration requirements for carrying out the present invention will be described in detail.
The filter medium used in the filter cylinder for performing filtration and concentration of the slurry used in the present invention is appropriately selected according to the slurry, such as a metal perforated plate or a resin filter cloth, but when using a filter cloth, It is better to install a reinforcing material on the outer periphery of the filter cloth. The shape of the filter medium correlates with the guide rod. When the guide rod has a small diameter or is long, the guide rod bends by its own weight, which hinders the smooth movement of the piston. When the guide rod has a large diameter, the apparatus becomes larger with respect to the filtration area. When the filter medium is short, the number of filter mediums increases and the manufacturing cost increases. Therefore, the diameter of the filter medium is 6 to 15 cm, while the diameter of the guide rod is preferably about 2 to 10 cm smaller than the filter medium, and the length of the filter medium is preferably about 100 to 200 cm. Moreover, the cross-sectional shape of the filtration cylinder is not limited to a circle, but may be an ellipse or a square.

If the gap between the piston and the filter medium that reciprocates inside the filter cylinder is small, the piston and filter medium come into strong contact with each other, preventing reciprocation. If the gap is large, there is no such contact, Since the cake layer remaining on the surface of the material becomes thick, the filtration speed is significantly reduced. Therefore, the gap between the piston and the filter material is about 0.5 to 2 mm, the length of the piston is preferably 6 to 15 cm, and the material is A lightweight material such as resin is preferable.
Side pipes for inflow and discharge of slurry are installed at both ends of the filter cylinder. When there are a plurality of the filtration cylinders, the side pipe is a header pipe connecting a plurality of filtration media.
The side pipe shape may be not only a cylindrical pipe but also a square shape or a semicircular shape.

Further, in the present invention, in order to hold the piston, a solid rod or a hollow pipe guide rod that extends parallel to the filtration cylinder and is arranged at the axial center of the filtration cylinder is provided to hold the guide rod. A retainer is provided in the side pipe.
Thereby, the central part of the piston is penetrated by the guide rod, and the piston reciprocates along the guide rod. However, since the piston outer diameter is smaller than the filter medium inner diameter, the piston and the filter cylinder do not contact in dimension. . A plurality of the guide rods can be installed in one filtration cylinder, and in that case, the guide rods are arranged symmetrically with respect to the central axis of the filtration cylinder. The guide rod retainer also serves as a stopper serving as the end of movement of the piston.
The side pipe has a slurry inflow valve that supplies and stops slurry from the slurry supply device, and a sludge discharge valve that discharges the concentrated sludge to the concentrated sludge tank.
The slurry supply device includes a slurry pump or a method of storing slurry in a storage tank and pumping the slurry by injecting compressed air into the storage tank.

  Next, the operation of the concentration device of the present invention will be described. When the slurry supply device is operated, the sludge discharge valve of the side pipe on one side is closed, and the slurry inflow valve is opened, the slurry is supplied into the filter medium. The piston inside the filter medium is pushed by the slurry supply pressure. In this state, the sludge discharge valve and the slurry inflow valve of the other side pipe are closed, and filtration concentration is performed. When the filtration concentration is completed, the slurry inflow valve of the side pipe on the slurry supply side is closed and the sludge discharge valve is opened. At the same time or after discharging a predetermined amount of concentrated sludge, when the slurry inflow valve of the other side pipe is opened and the slurry is pressed in from the opposite direction, the piston is pushed to the pressure of the slurry. By moving the piston, the concentrated sludge inside the filter medium is discharged leaving a thin cake membrane on the filter surface of the filter medium. By repeating the same operation, the side pipe is operated while switching between the slurry supply side and the discharge side.

In addition, when the sludge is discharged | emitted and the slurry in a filter medium is discharged | emitted, in the case of a flexible filter cloth, a filter cloth may bend partially. Even if the gap between the piston and the filter cloth is not in contact before the filtration and concentration apparatus is operated, the bent part of the filter cloth may come into contact with the piston. However, this contact is partial, the pressure at the time of contact is low, and there is a gap in which the filter cloth can be easily deformed. Therefore, the resistance when moving the piston is low, and the cake film on the inner surface of the filter cloth is not greatly damaged.
In the present invention, the concentration of slurry that can be treated is 0.5 to 3%, and the concentration ratio can be arbitrarily set at about 1.5 to 6 times, but as a useful condition, the pressure of the slurry to be pressed into the filter medium May be about 0.02 to 0.1 Mpa, and the concentration factor is preferably 1.5 to 3 times.

Next, the high magnification concentration in the present invention will be described. In the high-magnification concentration, apart from the slurry supply and concentrated sludge discharge, the side pipe is provided with a slurry circulation pipe that allows both ends of the filter medium to communicate with each other.
The slurry circulation pipe is preferably connected to the upper side of the side pipe so as to feed the diluted slurry into the filter medium.
In addition, the slurry circulation pipe may have a slurry circulation valve and a slurry circulation pump for generating a circulation flow, or a slurry storage tank capable of injecting and discharging compressed air.

When the slurry circulation pump is connected to the slurry circulation pipe, the slurry circulation valve on the slurry supply side is placed on the suction side of the slurry circulation pump and the slurry circulation valve on the other side pipe is placed on the slurry circulation pump during the filtration and concentration process. By switching each so that it is connected to the discharge side of the slurry, the supply side and the discharge side of the previous slurry are switched, and when the slurry circulation pump is operated, the piston is moved by the circulating flow of the slurry and the concentrated sludge is moved forward. The filter medium is discharged to the side pipe, and the inside of the filter medium is filled with the unconcentrated slurry that has remained in the side pipe.
At this time, if a single screw pump capable of forward / reverse operation is used for the slurry circulation pump, the supply side and the discharge side are switched by the forward / reverse operation of the slurry circulation pump, so that the valve switching operation described in the previous section becomes unnecessary.

By repeating this process, the cake layer formed on the filtration surface is scraped off while leaving a thin cake film, so that the slurry concentration in the system is maintained while maintaining the clarification of the filtrate and the filtration rate. Becomes higher, and high-magnification concentration becomes more efficient.
Next, the case where a slurry storage tank (pressure tank) capable of injecting and discharging compressed air is connected will be described. A pressure tank equal to or greater than the filter medium capacity is installed in the side pipe, and the slurry is placed in one pressure tank on one side. When filling and injecting compressed air into the pressure tank, the slurry in the pressure tank moves to the pressure tank installed in the other side pipe. By moving the piston by the flow at the time of the movement, the above-described efficient high magnification concentration can be performed without using a circulation pump.

In the present invention, the filter medium and the piston are not in contact with each other by the guide rod and the small diameter piston, and wear of the filter medium and the piston surface is prevented. In general, as the filtration proceeds, the moisture content of the cake decreases from the portion of the cake close to the surface of the filter medium, and the thickness of the cake with the low moisture content gradually increases to form a hard cake layer. However, in the present invention, the cake layer having a low water content remaining after being scraped by the movement of the piston does not become thick any more, and the water content newly formed in a short time from the scraping surface after scraping with the piston. A high soft cake is periodically scraped by the piston. Therefore, if the scraping cycle is made constant or gradually shortened, the movement resistance of the piston will not increase. Further, the cake layer can be blown off by slurry ejected from the gap between the filter medium and the piston by the slurry driving pressure when the piston moves.
In addition, since the piston and the filter medium are not in contact, the thrust required to move the piston is low, and it is possible to move with the water flow in the filter medium. As a result, the filtration speed can be improved and the required accuracy of the roundness of the filtration cylinder has been lowered, making the production easier.

Furthermore, since the thin cake film | membrane is hold | maintained on the filtration surface surface layer by making the piston and the filter medium non-contact, a clear filtrate can be ensured from the beginning of slurry injection. In addition, since the slurry is prevented from being leaked by cake filtration using a cake film, the opening of the filter medium can be increased, and therefore the filter medium can be prevented from being clogged.
As described above, by moving the piston during the filtration process, concentrated sludge can be discharged before it is excessively concentrated inside the filter medium, so there is no need for high pressure to move the piston, and the amount of concentrated sludge inside the filter medium. Since the piston can be moved in a state where there is little, the length of the filter medium can be increased, and these can be arbitrarily performed during the filtration process, so it is possible to perform filtration until the required concentration concentration is reached become.

Next, the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of the slurry concentrating device of the present invention, FIG. 2 is a partial configuration diagram of a slurry concentrating unit in FIG. 1, and FIG. 3 is an enlarged configuration diagram of an installation portion of a filter cylinder.
1-3, 1 is a slurry concentrating part of the slurry concentrating device, 2 is a filtration cylinder, 3a and 3b are side pipes, 4a and 4b are slurry supply valves, 5a and 5b are slurry discharge valves, 6 is a slurry supply tank, 7 is an air tank, 8 is a concentrated slurry extraction pump, 9 is a slurry circulation pipe, 10 is a slurry circulation pump, 11 is a guide rod, 12 is a piston, 13 is a reinforcing pipe, 14 is a guide rod holder, 15 is a filtrate receiver, 16 is slurry, 17 is compressed air, 18 is filtrate, 19 is concentrated sludge, 20 is a partition plate, and 21a and 21b are slurry circulation valves.

The slurry concentration process of the present invention will be described with reference to FIGS.
1 to 3, the slurry 16 is introduced into the slurry supply tank 6, and the compressed air 17 is introduced into the slurry supply tank 6 through the air tank 7. When only the slurry supply valve 4a of the slurry concentrating part 1 is opened, the slurry is introduced from the slurry supply tank into the filter cylinder 2 through the slurry supply valve 4a and the side pipe 3a by the pressure of the compressed air. The piston 12 moves to the side pipe 3b side, and the slurry is concentrated. The filtrate 18 is discharged through the filtrate receiver 15 and the concentrated sludge forms a cake layer on the filter medium.

  After performing the concentration treatment for a predetermined time, when the slurry supply valve 4a is closed, the slurry discharge valve 5a is opened, and the slurry supply valve 4b is opened, the slurry is supplied from the side pipe 3b side by the pressure of the compressed air. It is introduced into the filter medium 2 while moving the piston 12 to the 3a side, and the cake layer in the filter medium 2 is peeled off leaving a thin cake film by the movement of the piston, and as the concentrated sludge 19 through the side pipe 3a. It is discharged from the slurry discharge valve 5a. In the case where the concentration treatment is performed for a predetermined time, the time until the filtrate corresponding to the predetermined concentration ratio is discharged or the time until the predetermined amount of slurry is supplied can be set as a target. After the piston 12 has moved to the side pipe 3a side or after a predetermined amount of concentrated sludge has been discharged, the slurry discharge valve 5a is closed to perform the slurry concentration process. As described above, the slurry concentration process can be continuously performed by repeatedly opening and closing the slurry supply valves 4a and 4b and the slurry discharge valves 5a and 5b.

Next, the high-magnification concentration treatment of the slurry will be described with reference to FIG.
In the high-magnification concentration process, only the slurry supply valve 4a is closed, or 4a and 4b are closed, the slurry circulation valves 21a and 21b of the slurry circulation pipe 9 are opened, and the slurry circulation pump 10 is operated. . When the pipe of the slurry circulation valve 21a is connected to the suction side of the slurry circulation pump 10 and the pipe of the slurry circulation valve 21b is connected to the discharge side of the slurry circulation pump 10, the piston moves from the side pipe 3b side to the 3a side by the circulation flow of the slurry. Then, the concentrated sludge is moved to the side pipe 3a side, and the inside of the filter medium 2 is filled with unconcentrated slurry staying in the side pipe 3b and concentrated by filtration. By repeating this process while switching the forward / reverse operation of the slurry circulation pump 10, the slurry concentration in the system becomes higher, and higher-concentration concentration becomes possible.

In addition, since the filtration rate becomes slow as the slurry concentration in the apparatus increases, it is possible to perform an operation of shortening the time of the repeated filtration process as the concentration proceeds. For example, the first filtration step is performed for 20 minutes, the piston is moved to the opposite end, the second filtration step is performed for 15 minutes, the piston is moved to the original end, and the third filtration is performed for 10 minutes. By moving to the opposite end, a high filtration rate can be maintained.
The above describes the operation of increasing the concentration factor. On the other hand, if the concentration ratio is lowered by the same processing method, high-speed processing can be performed in which a large amount of slurry is processed in a short time.

Below, an example of the operation result by the experimental plant which actually incorporated this invention is demonstrated in detail. In addition, this invention is not restrict | limited at all by this Example.
In the present example, the two types of sludge, sludge a generated at the A water purification plant and sludge b generated at the B water purification plant, were concentrated using the slurry concentrating device of the present invention.
The apparatus configuration of this apparatus is the same as that shown in FIG. 1, and the filter cylinder 2 is arranged on the inner surface of the filter pipe 13 having a diameter of 100 mm and a length of 500 mm, and is guided by the guide lot 11 in the filter pipe 13. There is an arbitrarily movable piston 12. As the filter cylinder 2, a relatively thin filter having a thickness of 0.6 mm was employed. In the slurry concentrating device, two filter pipes 13 are installed in parallel, and an effective filtration area is 0.3 m ² . The outer diameter of the piston 12 was such that the clearance with the filter cylinder 2 was 1.5 mm.

In Example 1, the sludge a was used as the target sludge, and in Example 2, the sludge b was used as the target sludge. In Example 3, a high-speed processing method is adopted in which the sludge b is the target sludge, and the circulation pump 10 is used under a predetermined pressure using the circulation pipe 9 to move the piston 12 left and right at intervals of 5 minutes. did.
In parallel with the sludge concentration operation by this experimental plant, the concentration operation by the conventional method was also performed. As a conventional concentrator, the guide lot 11 does not exist inside the filter medium of the slurry concentrator of the present invention, and the free piston outer diameter is the same in design as the filter inner diameter inside the filter medium. The sludge concentrator having the same configuration as that of the slurry concentrating device of the present invention was used except that it was installed as described above.

As a method for evaluating the sludge concentration performance by the conventional method and the four types of methods of Examples 1, 2, and 3, the sludge concentration rate is set to 2 times, and the sludge driving pressure is set to 30, 50, Concentration treatment was performed by changing the process in five stages of 70, 100, and 200 kPa, and as a result, the concentration operation and the piston start-up pressure were low, the filtration speed was high, and the SS operation was possible. The method of judging that the concentration performance is excellent was adopted.
In addition, the supplementary explanation of the relationship between sludge "injection pressure" and "piston start-up pressure" means "injection pressure" means "filtration pressure" during the concentration operation, and the sludge supplied by the sludge supply pump In this embodiment, the pressure generated in the filter pipe is a pressure set in advance in the range of 30 to 200 kPa. “Piston start-up pressure” is the pressure required when the piston starts to move as it moves from one end in the filter pipe to the other end.

  In the slurry concentrating device of the present invention used in this example, the clearance between the piston outer diameter and the filter inner surface is 1.5 mm in terms of manufacturing dimensions, so there is no friction of the device itself. However, if the cake layer is generated on the inner surface of the filter as the filtration progresses and the thickness exceeds the clearance, the cake layer moves while peeling off a part of the cake layer when the piston moves. The pressure required to exceed the static frictional resistance received from the cake layer at the time of piston activation at this time was defined as “piston activation pressure”. When “injection pressure”> “piston activation pressure”, the piston is activated every time the slurry supply valves 4a and 4b are switched at the set “injection pressure” and moved from one end to the other end. However, if the static frictional resistance received from the cake layer is large and "impulse pressure" <"piston activation pressure", the pressure is temporarily increased above the preset "impulse pressure" to activate the piston. It is necessary to let The necessity of such a treatment is disadvantageous because it is necessary to increase the sludge supply pump power to a level at which a pressure equal to or higher than the “driving pressure” can be exerted.

In order to set the concentration rate to 2 times, the concentrated sludge discharge amount per piston movement (one batch) is set to 5 L by sludge discharge valve control in advance, and the filtrate discharge amount per batch is set to 5 L. 1 batch is completed at the time of reaching (that is, “sludge supply amount ≒ filtrate discharge amount + concentrated sludge discharge amount”, so when the sludge supply amount per batch reaches 10L), then the sludge supply valve is switched. Then, by supplying the sludge from the opposite side of the piston, the piston was moved to the opposite side and moved to the next batch. For each batch, the amount of sludge supplied from one side of the piston is always set to 10L, the filtrate is 5L, and the discharge concentrated sludge is 5L, so the concentration factor can be doubled, but due to the difference in concentration performance Since a difference occurs in the time until 10 L of sludge is concentrated twice (that is, “filtration rate” per unit filtration area), in the case of this test, it is determined from this “filtration rate” and the amount of SS contained in the filtrate. The concentration performance can be evaluated based on the SS recovery amount, the driving pressure, and the piston starting pressure.
The moisture content of the cake in the vicinity of the filtration surface was measured by scraping the cake remaining on the filtration surface after allowing the unconcentrated slurry inside the apparatus to flow out after moving the piston.

The experiment was conducted for about 50 hours for each operating condition. The test results are shown in Table 1.

In addition, FIG. 4 shows the relationship between the driving pressure and the filtration speed in each method, FIG. 5 shows the relationship between the driving pressure and the required pressure at the start of the piston, and FIG. 6 shows the relationship between the driving pressure and the moisture content of the cake near the filtration surface. The relationship between the pressure and the SS recovery rate is shown in FIG.
A test result is demonstrated based on the said Table 1 and FIGS. In the conventional method using sludge a having a relatively low sludge concentration of 9 g / l and the test of Example 1, as the driving pressure was increased from 30 kPa to 200 kPa, both the conventional method and Example 1 were filtered. Increased, the moisture content of the cake near the filtration surface decreased, and they showed almost the same value. However, the starting pressure for moving the piston to the opposite side by switching the driving valve needs to be higher in the conventional method, and once it is raised to about 100 kPa, the driving is performed immediately after the movement of the piston is completed. The piston could not be moved without taking a method of reducing the pressure to a predetermined pressure.

Further, the pressure at the time of starting the piston according to the conventional method has to be increased as the driving pressure becomes higher. As a cause of this, it was considered that there was a part that was in strong contact with the piston due to the roundness of the inner diameter of the filter medium, preventing the movement. In addition, the cake near the filtration surface becomes harder as the driving pressure increases, and the conventional method has no clearance between the piston and the filter cylinder, so the piston moves while peeling the hardened cake from the filter cylinder. Therefore, it was considered that the piston movement resistance was relatively high.
On the other hand, in Example 1, since there is always a clearance of 1.5 mm, when moving the piston, only a cake layer having a high moisture content is scraped off while leaving a part of the cake layer in the vicinity of the filtration surface. The starting pressure was always 50 kPa or less.
Moreover, in the conventional system, the SS recovery rate was relatively poor at 86 to 92% at a sludge driving pressure of 100 kPa or more. This is because the cake filtration action is reduced because the cake layer in the vicinity of the filter body is scraped almost every time the piston moves, and it is considered that SS leaked under a relatively high pressure of 100 kPa or more. From this result, it was proved that the system of Example 1 has the advantage that the low power operation by the low power equipment is possible and the SS recovery rate is high as compared with the conventional system.

Next, in Examples 2 and 3 using 23 g / l of sludge b, both the Examples 2 and 3 were filtered as the driving pressure was increased from 30 kPa to 200 kPa, as in the previous test using sludge a. The speed increased, the water content of the cake near the filtration surface decreased, and the filtration performance of Example 3 was about 20% larger than that of Example 2 and the concentration performance was improved. Moreover, there was no big difference in the cake moisture content, the piston starting pressure, and the SS recovery rate. The reason why the concentration performance of Example 3 was high is that Example 3 employs a circulation system, so the cake layer that began to harden in the vicinity of the filter cylinder was scraped at a rate of once every 5 minutes, It is considered that the filtration resistance of the cake layer can be maintained without being too high.
From the above results, in the concentration test using the sludge b, it can be determined that Example 3 adopting the circulation method has higher concentration performance and the effect of the circulation method than Example 2 adopting the standard method.

The whole block diagram which shows an example of the concentration apparatus of this invention. The partial block diagram of the slurry concentration part of FIG. The expanded block diagram of the installation part of the cylindrical filter material of this invention. The graph which shows the relationship between the driving pressure of each system, and the filtration rate. The graph which shows the relationship between the driving pressure of each system, and the required pressure at the time of piston starting. The graph which shows the relationship between the implantation pressure of each system, and the moisture content of the cake near a filtration surface. The graph which shows the relationship between the implantation pressure of each system, and SS recovery rate.

Explanation of symbols

  1: Slurry concentration section, 2: Filtration cylinder, 3a, 3b: Side pipe, 4a, 4b: Slurry supply valve, 5a, 5b: Slurry discharge valve, 6: Slurry supply tank, 7: Air tank, 8: Extraction of concentrated slurry Pump: 9: Slurry circulation pipe, 10: Slurry circulation pump, 11: Guide rod, 12: Piston, 13: Reinforcement pipe, 14: Guide rod holder, 15: Filtrate receiver, 16: Slurry, 17: Compressed air, 18: Filtrate, 19: Concentrated sludge, 20: Partition plate, 21a, 21b: Slurry circulation valve

Claims (8)

  In a slurry concentrating device that is provided with one or more filter cylinders made of a filter medium and performs filtration concentration by press-fitting slurry inside the filter cylinder, a guide rod fixedly installed along the axis of the filter cylinder, A slurry that is slidably inserted into the guide rod, has an outer peripheral surface smaller in diameter than the inner diameter of the filter cylinder, and reciprocates from one end to the other end of the filter cylinder, and a slurry that press-fits slurry into the inner side of the filter cylinder A slurry concentrating device comprising a supply device.   The slurry concentrating apparatus according to claim 1, wherein the filter cylinder is provided with a reinforcing material on an outer periphery of the filter medium.   3. The filter cylinder according to claim 1, wherein both ends of the filtration cylinder are connected to a side pipe that performs inflow and discharge of slurry, and the side pipe is connected to the slurry supply device via a switching valve. Slurry concentrator.   4. The slurry concentrating device according to claim 1, wherein the slurry supplying device is a slurry pump capable of press-fitting slurry or a slurry storage tank into which compressed air is injected.   Both ends of the filtration cylinder are connected to side pipes that allow the inflow and discharge of slurry, and the side pipes at both ends are connected to a slurry circulation pipe via a valve, and the slurry circulation pipe includes an inner side of the filtration cylinder. The slurry concentrating device according to claim 1 or 2, wherein a slurry circulating device for alternately introducing slurry from side pipes at both ends to form a circulating flow is connected to the slurry concentrating device.   6. The slurry circulation device is a slurry circulation pump capable of alternately introducing and circulating slurry from side pipes at both ends inside the filtration cylinder, or a slurry storage tank capable of injecting and discharging compressed air. The slurry concentrator described.   In a slurry concentration method in which filtration is concentrated by press-fitting slurry into one or more filter cylinders made of a filter medium, the diameter is smaller than the inner diameter of the filter cylinder, and is formed inside the filter cylinder in the filtration concentration process. A piston that reciprocates from one end to the other end of the filter cylinder for scraping the cake layer is inserted into a guide rod that is guided when the piston reciprocates, the piston is reciprocated along the guide rod, and the filtration A slurry concentration method comprising performing filtration and concentration by leaving a thin cake film on a filtration surface of a cylinder and press-fitting the slurry into the inside of the filtration cylinder.   8. The slurry concentration method according to claim 7, wherein the concentrated sludge discharged by filtration and concentration is further circulated inside the filter cylinder to be concentrated by filtration and concentrated at a high magnification.

Images