WO2011118283A1

WO2011118283A1 - Solid-liquid separation method

Info

Publication number: WO2011118283A1
Application number: PCT/JP2011/052933
Authority: WO
Inventors: 正國谷
Original assignee: メタウォーター株式会社
Priority date: 2010-03-26
Filing date: 2011-02-10
Publication date: 2011-09-29
Also published as: CN102741174A; KR20130018279A; JPWO2011118283A1; JP5636040B2; HK1173717A1; CN102741174B; KR101435308B1

Abstract

The disclosed solid-liquid separation method comprises: a suction filtration step, wherein, whilst decompressing a secondary-side space (5) which is the space on one surface side of a filter cloth (1), sludge (16) is supplied to a primary-side space (4) which is the space on the other surface side of the filter cloth (1), the sludge (16) is filtered by the filter cloth (1), and concentrated sludge (initial concentrated sludge) is attached to a primary-side surface (6) which is the other surface, as described above, of the filter cloth (1); a pressure filtration step, wherein the secondary-side space (5) is decompressed, both sludge is supplied to the primary-side space (4) and said space is pressurised, the sludge (16) is filtered by the filter cloth (1), and additional concentrated sludge (17) (second layer concentrated sludge) is attached on top of the concentrated sludge (16) (initial concentrated sludge) which is attached to the primary-side surface (6) of the filter cloth (1); a compression step wherein the concentrated sludge (17) attached to the primary-side surface (6) of the filter cloth (1) is compressed, and compressed sludge is obtained; and an extraction step wherein the compressed sludge is peeled off the filter cloth. The disclosed solid-liquid separation method uses a single solid-liquid separation device, and enables sludge which is 1% by mass solid content to be concentrated to sludge which is at least 40% by mass solid content.

Description

Solid-liquid separation method

The present invention relates to a solid-liquid separation method, and more specifically, it is possible to concentrate sludge having a solid content of about 1% by mass to obtain a sludge having a solid content of 40% by mass or more using a single solid-liquid separator. The present invention relates to a simple solid-liquid separation method.

In water purification plants, water for drinking is produced by removing solids from the raw water taken using a method such as coagulation sedimentation. At this time, the solid content in the raw water is discharged as sludge having a solid content concentration of about 0.1 to 1.0% by mass.

Conventionally, the sludge having a solid content concentration of about 0.1% by mass is concentrated to about 1 to 2% by mass by natural sedimentation and the like, and then the solid content concentration is about 50% by mass using a filtration device and a dehydrator. The high-concentration sludge obtained was discarded or reused. More specifically, the sludge concentrated to a solid content concentration of about 1 to 2% by mass is concentrated to a solid content concentration of about 3 to 5% by mass using a siphon type filtration concentration device or the like (see, for example, Patent Document 1). The obtained concentrated sludge was concentrated to a solid content concentration of 40% by mass or more by a pressure dehydrator or the like (for example, see Patent Document 2).

Japanese Examined Patent Publication No. 61-57043 Japanese Patent Laid-Open No. 7-124212

In general, the pressure dehydration apparatus and the like deteriorates as the raw water concentration decreases. For example, when the raw water concentration is 2%, the filtration rate (the amount of dry solids per unit time) is when the raw water concentration is 5%. Is about one third of the filtration rate. Furthermore, when the raw water concentration is 1% or less, the performance becomes extremely low, making the treatment difficult. Further, in the case of a drying method such as incineration, as the raw water concentration decreases, the energy required for combustion increases, leading to an increase in cost and an increase in the amount of exhaust gas. Therefore, it is common to perform dehydration and drying after adjusting to an appropriate concentration using a filtration concentrator or the like. That is, conventionally, it was not realistic to treat 1% or less of sludge with a pressure dehydrator.

For this reason, in the conventional sludge treatment method, in order to concentrate the sludge having a solid content concentration of about 1% by mass to a solid content concentration of 40% by mass or more, two devices of a filtration device and a dehydration device are required. . In other words, sludge having a solid content concentration of about 1% by mass could not be concentrated to a solid content concentration of 40% by mass or more with one apparatus.

More specifically, in the conventional sludge treatment method using two devices, a filtration device and a dewatering device, the filter cloth used in the filtration device has a large opening formed by a monofilament, The filter cloth used in the dehydrator had a small opening diameter formed by multifilaments. In particular, in the filtration device, from the viewpoint of prevention of clogging, improvement of peelability, etc., a high pressure is applied when dewatering sludge with a dehydrator using a filter cloth formed of monofilament made of nylon or the like. In order to perform dehydration, a filter cloth formed from a multifilament made of polyester or the like has been used from the viewpoints of improvement in solid content capture efficiency, improvement in strength, improvement in durability, and the like. Note that when sludge is filtered using a filtration device, the concentration of the concentrated sludge adhering to the filter cloth is low, and the peelability of the adhering concentrated sludge tends to decrease. By using the filter cloth, the peelability of the concentrated sludge can be improved. Here, the filtration device is a device that performs solid-liquid separation at a pressure of 1.0 MPa or less using a filter cloth, and the dehydration device is a device that performs solid-liquid separation at a pressure exceeding 1.0 MPa using a filter cloth. It is.

Thus, the types of filter cloth that can be used differ between the filtration device and the dehydration device. If the filter cloth used in the filtration device is used in the dehydration device, the filter cloth is formed of monofilament. Therefore, in the dehydration device that performs dehydration at a high pressure, the solid content is removed when the dehydration is performed. The problem of passing through arises. Also, if the filter cloth used in the dehydrator is used in the filter apparatus, the filter cloth is formed of multifilaments, so the filter cloth is likely to be clogged during filtration, and further adheres to the filter cloth. There arises a problem that the concentrated sludge is difficult to peel off.

As described above, since it is necessary to use different filter cloths for the filtration device and the dehydration device, it is common to use two devices, a filtration device and a dehydration device, when concentrating sludge. It was. For this reason, not only a space for installing the two devices is required, but also a sludge transfer operation between the two devices is required. Moreover, since the dehydration speed is different between the two apparatuses, continuous work is difficult. That is, since the dehydration time by the dehydrator is shorter than the filtration time by the filter device, the entire time of the dehydration and filtration process is limited by the filtration time by the filter device. Furthermore, in order to adjust the time between the two devices, a temporary sludge storage place is required.

The present invention has been made in view of the above-described problems, and uses a single solid-liquid separator to concentrate sludge having a solid content of about 1% by mass to obtain a sludge having a solid content of 40% by mass or more. An object of the present invention is to provide a solid-liquid separation method capable of achieving the above.

In order to solve the above-described problems, the present invention provides the following solid-liquid separation method.

[1] While reducing the pressure on the secondary side space on one side of the filter cloth, the sludge is supplied to the primary side space on the other side of the filter cloth, Filtration of sludge, suction filtration step of attaching the concentrated sludge to the primary surface, which is the other surface of the filter cloth, and decompressing the secondary space, and supplying the sludge to the primary space And pressurizing and filtering the sludge with the filter cloth, and further applying the concentrated sludge on the concentrated sludge attached to the primary side surface of the filter cloth, and the filter cloth A solid-liquid separation method comprising: a pressing step for compressing concentrated sludge adhering to a primary side surface to obtain compressed sludge; and a discharging step for peeling the pressed sludge from a filter cloth.

[2] In the suction filtration step, when the solid content concentration of the filtrate flowing out to the secondary space reaches 0.02 to 0.04 mass%, the pressure filtration step is started. The solid-liquid separation method described.

[3] The solid-liquid separation method according to [1] or [2], wherein in the suction filtration step, the pressure in the secondary side space reduced in pressure is set to −0.08 to −0.02 MPa (gauge pressure).

[4] In the pressure filtration step, the pressure for pressurizing sludge is intermittently increased from 0.2 to 0.4 MPa (gauge pressure) to 0.6 to 1.5 MPa (gauge pressure) [ [1] The solid-liquid separation method according to any one of [3].

[5] The solid-liquid separation method according to any one of [1] to [4], wherein the pressure when the concentrated sludge is squeezed is 0.2 to 1.8 MPa (gauge pressure) in the pressing step.

[6] The solid content concentration of the sludge supplied to the primary side space is 0.7 to 2.0% by mass, and the solid content concentration of the compressed sludge obtained in the pressing step is 40 to 45% by mass. The solid-liquid separation method according to any one of [1] to [5].

According to the solid-liquid separation method of the present invention, in the suction filtration step, the concentrated sludge is attached to the primary side surface of the filter cloth, and in the pressure filtration step, the above-mentioned “attached to the primary side surface of the filter cloth”. Concentrated sludge is further deposited on top of the `` concentrated sludge '', and pressure is applied in stages to form a new adhesion layer, while forming an old adhesion layer (adhesion layer generated in the suction filtration process or the previous pressurization). In order to obtain the compressed sludge by compressing the concentrated sludge (whole) adhering to the primary side surface of the filter cloth in the pressing step, finally, one solid-liquid separator It is possible to concentrate sludge having a solid content of about 1% by mass to obtain a sludge having a solid content of 40% by mass or more.

It is a schematic diagram which shows the solid-liquid separation apparatus used for one Embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the cross section of the filter used for one Embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the state which the sludge has adhered to the surface of the primary side of a filter cloth in the suction filtration process while showing the cross section of the filter used for one Embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the state which the sludge has adhered to the primary side surface of the filter cloth in the pressure filtration process while showing the cross section of the filter used for one Embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the state by which concentrated sludge is squeezed in a pressing process while showing the cross section and sludge pressing mechanism of a filter used for one embodiment of the solid-liquid separation method of this invention. While showing the cross section of the filter used for one embodiment of the solid-liquid separation method of the present invention, it is a mimetic diagram showing signs that compressed sludge is discharged in a discharge process. It is a schematic diagram which shows the solid-liquid separation apparatus used for other embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the cross section of the filter used for other embodiment of the solid-liquid separation method of this invention. It is a side view which shows typically the filter used for other embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the state which the sludge has adhered to the primary side surface of the filter cloth in the suction filtration process while showing the cross section of the filter used for other embodiment of the solid-liquid separation method of this invention. The section which shows the section of the filter used for other embodiments of the solid-liquid separation method of the present invention, and in the pressure filtration process, the state where the sludge adheres to the primary side surface of the filter cloth while forming a plurality of layers It is a schematic diagram which shows. While showing the cross section of the filter used for other embodiment of the solid-liquid separation method of this invention, it is a schematic diagram which shows the state by which concentrated sludge is squeezed in a pressing process. It is a schematic diagram which shows a mode that discharged | squeezed sludge is discharged | emitted in a discharge process while showing the cross section of the filter used for other embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the cross section of the filter used for other embodiment of the solid-liquid separation method of this invention. It is a schematic diagram which shows the cross section of the filter and pressure-reducing means used for other embodiment of the solid-liquid separation method of this invention. It is a graph which shows the relationship between the filtration time and the amount of filtrates in the solid-liquid separation method of Examples 3 and 4. 1 is a schematic diagram showing a cross section of a filter used in Example 1. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. It should be understood that design changes, improvements, and the like can be made as appropriate based on ordinary knowledge.

According to the solid-liquid separation method of the present invention, “sludge is supplied to the primary side space that is the space on the other side of the filter cloth while the secondary side space that is the space on the one side of the filter cloth is decompressed. Then, the sludge is filtered by the filter cloth, and the concentrated sludge (initial concentrated sludge) is attached to the primary side surface which is the “other surface” of the filter cloth. Concentrated sludge (initial concentrated sludge) adhered to the primary side surface of the filter cloth by reducing the pressure of the side space, supplying sludge to the primary side space and applying pressure, filtering the sludge with the filter cloth ) Pressure filtration step to further attach concentrated sludge (second layer concentrated sludge) from above, and “pressing concentrated sludge adhering to the primary side surface of the filter cloth to obtain compressed sludge” And a discharge step of “peeling the compressed sludge from the filter cloth”. “Supplying sludge to the primary side space and pressurizing” means “suppressing sludge while pressurizing” or “pressurizing sludge after supplying sludge” to the primary side space. Means. Moreover, in the case of “supplying sludge while pressurizing” and “pressing sludge after supplying sludge”, the pressure in the primary side is pressurized, and the filtrate passes through the filter cloth by the pressure. It will be pushed out to the secondary space.

As described above, in the solid-liquid separation method of the present invention, the concentrated sludge is attached to the primary side surface of the filter cloth in the suction filtration step, and the sludge is supplied to the primary side space in the pressure filtration step. And pressurize together to compress (densify) the sludge previously attached to the filter cloth surface while further attaching the concentrated sludge from above the “concentrated sludge attached to the primary surface of the filter cloth”. In order to obtain the compressed sludge by squeezing the concentrated sludge adhering to the primary side surface of the filter cloth in the squeezing process, and finally using a single solid-liquid separator, It is possible to concentrate sludge having a content of about 1% by mass to obtain a sludge having a solid content of 40% by mass or more.

(1) One embodiment of the solid-liquid separation method of the present invention:
The solid-liquid separation apparatus for carrying out one embodiment of the solid-liquid separation method of the present invention is not particularly limited. For example, a solid-liquid separation apparatus 100 as shown in FIG. 1 can be used. The solid-liquid separator 100 includes a filter cloth 1 and a filter body 2 that is partitioned by the filter cloth 1. The solid-liquid separator 100 is a space on one side of the filter cloth 1 and a space where the filtrate is discharged. The secondary side space 5 is depressurized with the filter 3 in which the secondary side space 5 and the primary side space 4 which is the space on the other surface side of the filter cloth 1 and the sludge are supplied are formed. Pressure reducing means 11 capable of supplying sludge to the primary side space 4, and sludge pressurizing means 13 capable of pressurizing the sludge supplied to the primary side space 4. Is. As shown in FIG. 5, the solid-liquid separator 100 is a surface on the primary side space side of the filter cloth 1 when the sludge supplied to the primary side space is filtered by the filter cloth 1. The sludge pressing mechanism 15 which can squeeze the concentrated sludge adhering to the surface 6 of the next side is provided. The concentrated sludge that has been pressed becomes compressed sludge 18. The sludge supply means 12 used in the solid-liquid separation method of the present embodiment is a sludge storage tank 12a arranged vertically above the filter 3. This is to supply the sludge 16 from the sludge storage tank 12a to the filter 3 by gravity by disposing the sludge storage tank 12a above the filter 3 in the vertical direction.

Here, FIG. 1 is a schematic diagram (flow diagram) showing a solid-liquid separation apparatus used in one embodiment of the solid-liquid separation method of the present invention. FIG. 5 shows the cross section of the filter 3 and the sludge pressing mechanism used in one embodiment of the solid-liquid separation method of the present invention, and the concentrated sludge is compressed (pressed sludge 18 is formed) in the pressing step. It is a schematic diagram which shows a state. In addition, in FIG. 1, the sludge storage tank 12a is expressed so that the sludge 16 stored inside can be seen through. Moreover, the filter 3 is expressed so that the filter cloth 1 and the filtrate permeation | transmission member 27 arrange | positioned inside, and the concentrated sludge adhering to the filter cloth can be seen through. Moreover, the filtrate storage tank 14 is expressed so that the filtrate 19 stored inside can be seen through.

Further, as shown in FIG. 2, the filter 3 includes a “bottomed cylindrical main body 23 having a bottom 24 at one end 21 and an opening 25 at the other end 22” and “main body 23, the filter body 2 having a lid 26 "detachably disposed in the opening 25 of the 23, the filter body 2 in the space on the lid 26 side (primary side space 4) and the space on the bottom 24 side ( And a filter cloth 1 disposed in the filter body 2 so as to be partitioned into a secondary space 5). An inflow port 26 a is formed in the lid portion 26, and a discharge port 24 a is formed in the bottom portion 24. An inflow nozzle 26 b is disposed at the inflow port 26 a of the lid portion 26, and a discharge nozzle 24 b is disposed at the discharge port 24 a of the bottom portion 24. The filter cloth 1 is preferably a filter cloth formed of monofilament. Moreover, although the filter main body 2 of this embodiment is cylindrical, it is not limited to this shape. The bottom surface may be a polygonal cylinder such as a square, or the bottom surface may be an elliptical cylinder. Here, FIG. 2 is a schematic view showing a cross section of the filter 3 used in one embodiment of the solid-liquid separation method of the present invention.

Further, a filtrate transmitting member 27 is disposed in the secondary side space 5 of the filter 3 so as to support the filter cloth 1. The filtrate transmitting member 27 is a structure through which the filtrate passes. The filtrate permeable member 27 is capable of allowing the filtrate to pass through easily while having a rigidity that does not cause a large deformation with respect to pressure. Specifically, the filtrate permeating member 27 is formed of a wire mesh formed of a metal wire such as stainless steel, “ceramic, synthetic resin, etc.”, and “a plurality of through holes are formed in the thickness direction”. A board etc. can be used. The sludge that is subjected to solid-liquid separation by the solid-liquid separation method of the present invention is sludge that is discharged when preparing clean water (tap water) at a water purification plant, and has a solid content concentration of 0.7 to 2.0. It is preferable that it is mass%.

One embodiment of the solid-liquid separation method of the present invention will be described step by step.

(1-1) suction filtration step;
As shown in FIGS. 1 to 3, the suction filtration step in the solid-liquid separation method of the present embodiment is described as follows: “A secondary side space 5 that is a space on one side (secondary side surface 7) side of the filter cloth 1 is removed. While reducing the pressure, the sludge 16 is supplied to the primary side space 4 that is the space on the other side of the filter cloth 1, and the sludge 16 is filtered by the filter cloth 1. This is a step of “adhering the concentrated sludge 17 (initial concentrated sludge 17a) to a certain primary surface 6”. In the suction filtration step, as shown in FIG. 1, the sludge 16 is supplied to the sludge supply means 12, and the sludge 16 is supplied from the sludge supply means 12 to the primary space 4 of the filter 3. After the supply, the secondary space 5 of the filter 3 is depressurized by the depressurization means 11 through the filtrate storage tank 14. Thereby, the solid content in the sludge 16 is collected as the concentrated sludge 17 by the filter cloth 1, and the filtrate 19 that has passed through the filter cloth 1 passes through the secondary side space 5 and is sent to the filtrate storage tank 14. Stored. In the solid-liquid separator 100, the sludge pressurizing means 13 and the sludge storage tank 12a are connected by a pipe, the sludge storage tank 12a and the filter 3 are connected by a pipe, and the filter 3 and the filtrate storage tank 14 are connected. Are connected by piping, and the filtrate storage tank 14 and the decompression means 11 are connected by piping. Each pipe and device is preferably equipped with valves and instruments as necessary. Here, FIG. 3 shows a cross section of the filter 3 used in one embodiment of the solid-liquid separation method of the present invention, and sludge (initial concentrated sludge) on the primary side surface 6 of the filter cloth 1 in the suction filtration step. It is a schematic diagram which shows the state which 17a) has adhered.

As described above, in the solid-liquid separation method of the present embodiment, first, in the suction filtration step, the initial concentrated sludge 17a is attached to the primary side surface 6 of the filter cloth 1, so that the filtration is performed in the next pressure filtration step. Even if sludge is supplied to the primary side space 4 of the vessel 3 and pressurized, it is possible to suppress the solid content in the sludge from passing through the filter cloth 1 and leaking into the secondary side space 5. This is because the initial concentrated sludge 17a attached to the filter cloth 1 has a function of collecting solids in the sludge together with the filter cloth 1. Thus, even when a device (filter 3) provided with “a filter cloth formed of a monofilament made of nylon and having a large opening diameter”, which is normally used in the suction filtration step, is used. The pressure filtration in the pressure filtration step can be performed using the apparatus (filter 3) used in the step. That is, suction filtration and pressure filtration can be performed by one filter 3 (solid-liquid separation device 100).

In the suction filtration step, it is preferable to start the pressure filtration step when the solid content concentration of the filtrate flowing out to the secondary space 5 reaches 0.02 to 0.04 mass%. If it is lower than 0.02% by mass, the initial concentrated sludge 17a is not sufficiently formed, and the initial concentrated sludge 17a itself passes through the filter cloth 1 and leaks into the secondary space 5 due to the applied pressure in the pressure filtration process. May be issued. If it is higher than 0.04% by mass, the time for the suction filtration process becomes longer, and therefore the total time for solid-liquid separation of sludge may become longer.

If the filtration time in the suction filtration process is too short, the initial concentrated sludge 17a does not sufficiently adhere to the filter cloth 1, and the initial concentrated sludge 17a itself passes through the filter cloth 1 due to the applied pressure in the pressure filtration process, and the secondary side. May flow into space 5. When the time for filtering the sludge with the filter cloth 1 is long, the entire filtration time is extended.

In the suction filtration step, the pressure when the secondary side space 5 is depressurized (the pressure of the depressurized secondary side space 5) is −0.08 to −0.02 MPa when the sludge of the water purification plant is used as a raw material. Gauge pressure) is preferable. If it is lower than −0.08 MPa, the solid content may pass through the secondary side space 5 without staying on the filter cloth surface, and the initial concentrated sludge 17a may not adhere to the primary side surface 6 of the filter cloth 1. is there. If it is higher than −0.02 MPa, the suction filtration process may take a long time. The “gauge pressure” is a pressure displayed on a pressure gauge with the atmospheric pressure set to “0 MPa”.

In the suction filtration step, a vacuum pump or the like can be used as the decompression means 11 that decompresses the secondary space 5 of the filter 3. Further, as the decompression means 11, a means for decompressing the secondary side space 5 of the filter 3 according to the principle of siphon is also a preferable aspect. In addition, when a vacuum pump is used as the decompression means 11 for decompressing the secondary side space 5 of the filter 3 (see FIG. 1), the secondary side space of the filter 3 is also used in the pressure filtration process and the squeezing process. As the decompression means for decompressing 5, it is preferable to use the decompression means 11 used in the suction filtration step. Further, when a pressure reducing means based on the principle of siphon is used as the pressure reducing means 11 for reducing the pressure on the secondary space 5 of the filter 3, a vacuum pump can be used in the pressure filtration step even if the pressure reducing means based on the principle of siphon is used. May be used, and a vacuum pump may be used in the pressing step.

The magnitude | size of the filter 3 which comprises the solid-liquid separation apparatus used with the solid-liquid separation method of this embodiment shown by FIG. 2 is not specifically limited, In industrial use, in a water purification plant or a sewage treatment plant It is preferable that the size corresponds to the processing amount. Moreover, the material of the main-body part 23 and the cover part 26 is not specifically limited, Stainless steel etc. can be used suitably.

The filter cloth 1 is preferably a filter cloth formed of monofilaments, and more preferably a filter cloth formed of polyamide resin monofilaments. The air permeability of the filter cloth is preferably 20 to 90 (cm ³ / (cm ² · sec)). The air permeability of the filter cloth is a value obtained by measuring the amount of air per unit area / unit time passing through the filter cloth from the primary side toward the secondary side. The sludge supply means may be a sludge storage tank 12a arranged vertically above the filter 3 as shown in FIG. 1, but the “sludge storage tank 12a” and the sludge storage tank 12a You may comprise from the "pump etc." for sending sludge to the filter 3. FIG. In the case where the sludge supply means is the sludge storage tank 12a disposed vertically above the filter 3, the sludge is supplied from the sludge storage tank 12a to the primary space of the filter 3 by gravity. Further, when the sludge supply means is constituted by “sludge storage tank 12 a” and “a“ pump or the like ”for feeding the sludge in the sludge storage tank 12 a to the filter 3”, the sludge storage tank 12 a Sludge can be supplied to the filter 3 using a pump or the like.

The size of the sludge storage tank 12a is not particularly limited, and can be appropriately determined depending on the amount of sludge to be processed. Moreover, although the material of the sludge storage tank 12a is not specifically limited, Steel (steel), polyvinyl chloride, etc. can be used conveniently, and stainless steel can be used suitably as steel (steel). Moreover, in order to receive sludge in the sludge storage tank 12a, it is preferable that a sludge inlet 12b is formed on the upper side in the vertical direction when the sludge storage tank 12a is installed. Moreover, in order to discharge the sludge, it is preferable that a sludge discharge port 12c is formed in the sludge storage tank 12a on the lower side in the vertical direction when the sludge storage tank 12a is installed. Moreover, even if the sludge discharge port 12c is formed in the wall surface (wall surface of the sludge storage tank 12a) which faces a "lateral direction (for example, horizontal direction)" with respect to the vertical direction when the sludge storage tank 12a is installed. Good. For example, in the case of the pit method (made of concrete), it is preferable that the sludge discharge port 12c is formed on the wall surface facing the “lateral direction”. It is preferable that piping is arrange | positioned at the sludge inlet 12b and the sludge outlet 12c, respectively. When the sludge supply means is the sludge storage tank 12a arranged vertically above the filter 3, the pipe connected to the sludge discharge port 12c is directly connected to the filter 3. Further, when the sludge supply means is constituted by “sludge storage tank 12a” and “a pump or the like for feeding the sludge in the sludge storage tank 12a to the filter 3”, it is connected to the sludge discharge port 12c. The pipe is connected to the filter 3 via a “pump or the like”.

(1-2) pressure filtration step;
As shown in FIGS. 1 and 4, the pressure filtration step in the solid-liquid separation method of the present embodiment decompresses the secondary side space 5 and “pressurizes” the sludge 16 in the primary side space 4. In this step, the sludge 16 is further filtered by the filter cloth 1. In the suction filtration step preceding this step, concentrated sludge adheres on the filter cloth, so that the turbidity of the filtrate is reduced, but the flow rate of the filtrate is reduced. Therefore, it is a process for ensuring the processing flow rate of the filtrate by pressurization. In addition to this, in this step, the concentrated sludge 17 (second-layer concentrated sludge 17b) is further adhered on the concentrated sludge 17 (initial concentrated sludge 17a) adhering to the primary side surface 6 of the filter cloth 1, It is also a step of compressing the initial concentrated sludge 17a to increase its density (densify) and enhance the filtration function with the filter cloth and the concentrated sludge adhering thereto. The filtrate 19 that has passed through the filter cloth 1 is discharged from the discharge port 24 a, sent to the filtrate storage tank 14 through the discharge nozzle 24 b and the piping, and stored in the filtrate storage tank 14. When supplying the sludge to the primary side space 4 while “pressurizing”, it is preferable to pressurize the entire “primary side surface 6” of the filter cloth 1 with the sludge 16. FIG. 4 shows a cross section of the filter 3 used in one embodiment of the solid-liquid separation method of the present invention, and sludge (concentrated sludge 17 (initial stage) on the primary side surface 6 of the filter cloth 1 in the pressure filtration step. It is a schematic diagram which shows the state which the concentrated sludge 17a and the 2nd layer concentrated sludge 17b) have adhered.

Thus, in the pressure filtration step, the filter cloth 1 is pressurized with sludge and the initial concentrated sludge 17a is compressed in order to filter the sludge under pressure with the initial concentrated sludge 17a attached to the filter cloth 1. Thus, it performs a filtering function according to the degree of densification of the initial concentrated sludge 17a. Thereby, even if the filter cloth 1 is a monofilament, pressure filtration can be performed while preventing leakage of solid contents. Further, concentrated sludge having a solid content concentration of 9 to 16% by mass can be obtained by the pressure filtration step.

When the sludge is supplied under pressure with the initial concentrated sludge 17a attached to the filter cloth 1 and the pressure of the supplied sludge changes (rises) rapidly, the concentrated sludge formed on the filter cloth surface is filtered. It may flow out into the secondary space through the cloth. In that case, the solid content is not sufficiently recovered, and solid-liquid separation by concentrated sludge cannot be performed sufficiently. Therefore, when the sludge is filtered under pressure with the initial concentrated sludge 17a attached to the filter cloth 1, it is preferable to reduce the pressure change in one pressurization and increase the pressure several times stepwise. Thereby, the concentrated sludge adhering to the filter cloth 1 can be densified while preventing the solid content from leaking into the secondary side space, and finally it is possible to perform filtration at a high pressure. And since it is possible to densify concentrated sludge, the solid content density | concentration of the concentrated sludge finally obtained (discharged) can be made high.

In the pressure filtration step, the pressure for pressurizing the sludge is from 0.2 to 0.4 MPa (gauge pressure) (minimum filtration pressure) to 0.6 to 1.5 MPa (gauge pressure) (maximum filtration pressure). It is preferable to raise it intermittently. Thereby, it can prevent more effectively that solid content in sludge permeate | transmits a filter cloth, and flows out into the filtrate side. Here, the “minimum filtration pressure” is the first (first stage) pressure and the lowest pressure when the sludge is pressurized in the pressure filtration step. The “maximum filtration pressure” is the last (last stage) pressure and the highest pressure when the sludge is pressurized. If the minimum filtration pressure is lower than 0.2 MPa, the time required for solid-liquid separation may become longer. When the minimum filtration pressure is higher than 0.4 MPa, solid content may easily pass through the filter cloth when performing pressure filtration. Moreover, when the maximum filtration pressure is lower than 0.6 MPa, the time required for solid-liquid separation may become longer. When the maximum filtration pressure is higher than 1.5 MPa, the solid content may easily pass through the filter cloth. “To increase the pressure to pressurize the sludge intermittently” means to increase the pressure to pressurize the sludge in a stepped manner, and to “Pressure constant (maintain constant pressure)” and “Pressure increase” It is to increase the “pressure to pressurize sludge” while repeating “state (pressure increase operation)” alternately. Moreover, in the pressure filtration process, since the filter cloth is pressurized with sludge, the sludge pressure fills the primary space 4 of the filter 3 and the sludge pressure in the primary space (pressure in the primary space). Is preferably set to the predetermined pressure. Therefore, it is preferable to supply the sludge to the primary space 4 of the filter 3 at the predetermined pressure.

Further, in the pressure filtration step, when the pressure in the primary side space (pressure for pressurizing sludge) is intermittently increased from the minimum filtration pressure to the maximum filtration pressure, the pressure is increased by a single pressure increase (pressure increase operation). The pressure is preferably 0.2 to 0.7 MPa (rising range), and more preferably 0.2 to 0.4 MPa. Thereby, the concentrated sludge adhering to the filter cloth can be densified more effectively, and solid content leakage from the filter cloth can be suppressed. If the pressure raised by one pressurization is less than 0.2 MPa, the time required for solid-liquid separation may be increased. If the pressure raised by one pressurization is greater than 0.7 MPa, the solid content may easily leak from the filter cloth. Further, the pressure to be raised by one boosting may be a constant value or may be different depending on the boosting stage. Further, the pressure increase rate (MPa / min) in the pressure increase operation is not particularly limited, but it is preferable to set the rate so that the solid content is not mixed into the filtrate. If the pressure increase rate is too high, solids may be mixed in the filtrate, and the concentrated sludge layer adhering to the filter cloth may be broken, which is not preferable. As the pressure increase rate, for example, 0.5 to 2 minutes is preferable. Within the range of the pressure increase rate, it is preferable to adjust the pressure increase rate appropriately so that “the solid content is not mixed in the filtrate or the layer of concentrated sludge adhering to the filter cloth does not collapse”. .

In the pressure filtration step, when the pressure in the primary space (pressure for pressurizing sludge) is intermittently increased from the minimum filtration pressure to the maximum filtration pressure, the pressure is increased from the “constant pressure state”. Switching to “state” is performed after confirming the state of the filtrate.

Specifically, immediately after pressurization, the turbidity of the filtrate increases. This turbidity decreases with time. This decrease in turbidity is caused by densification of the initial concentrated sludge 17a and formation of a new layer of concentrated sludge (second layer concentrated sludge 17b) on the initial concentrated sludge 17a. And the second-layer concentrated sludge 17b "has achieved a filtration function together with the filter cloth 1, and is in a state suitable for sludge filtration so that the sludge can be satisfactorily filtered even at a new (high) pressure. Show. Therefore, it can be determined that the initial concentrated sludge 17a is densified and a new concentrated sludge layer is formed on the initial concentrated sludge 17a due to the decrease in turbidity.

The time for densification of the initial concentrated sludge 17a after pressurization and the formation of a new concentrated sludge layer, that is, the time until the turbidity is lowered to a predetermined value depends on the composition and concentration of the sludge to be treated. Different. Accordingly, whether the initial concentrated sludge 17a is densified or whether a new concentrated sludge layer is sufficiently formed is determined by measuring the turbidity and concentration of the filtrate. Alternatively, the turbidity may be measured with a turbidimeter, and the above determination may be made when the turbidity is below a certain value.

In addition, the flow rate of the filtrate immediately after pressurization changes with the densification of the initial concentrated sludge 17a and the formation of a new concentrated sludge layer. It is also possible to determine that a sludge layer has been formed. For these determinations, the filtrate may be temporarily taken out of the filtrate storage tank 14. Moreover, since the time when a filtrate with high turbidity is generated is very small when viewed from the whole filtrate, it may be allowed to flow into the filtrate storage tank 14 as it is.

Also, in normal suction filtration, as the filtration proceeds, the sludge adheres to the filter cloth surface, the filtration flow rate decreases, and the amount of sludge treatment decreases. However, the step-by-step pressure increase of the pressure filtration process of the present invention allows the sludge treatment amount to be secured while functioning the adhering concentrated sludge as a part of the filter cloth. A predetermined amount of sludge can be concentrated in a shorter time.

Further, in the pressure filtration step in the present invention, filtration is performed while the sludge is pressurized, so that the new sludge is attached to the filter cloth surface first while maintaining the state where the sludge is supplied to the filter cloth. Filtration is performed while the “sludge adhering first” is compressed, while adhering onto the “sludge”. In particular, maintaining the state in which the sludge is supplied to the filter cloth means that the concentrated sludge adhering to the filter cloth is mechanically pressurized (pressed by pressing the structure) without the sludge being supplied to the filter cloth. Thus, it is different from the “squeezing process” in which the moisture in the concentrated sludge is squeezed.

In the pressure filtration step, the primary space 4 is pressurized with the filtrate (the filter cloth 1 is pressurized with the filtrate) and the secondary space 5 is depressurized, but the pressure when the secondary space 5 is depressurized. The (pressure in the reduced secondary space 5) is preferably −0.08 to −0.02 MPa (gauge pressure). If it is higher than -0.02 MPa, the concentration of the finally obtained compressed sludge may be less than 40% by mass, and it takes a long time to increase the concentration of the compressed sludge to 40% by mass or more. There is.

In the pressure filtration step, as shown in FIG. 1, the sludge 16 supplied to the primary space 4 of the filter 3 is pressurized by the sludge pressurizing means 13, and the filter cloth 1 (1 The inside of the secondary space 4) is pressurized. As the sludge pressurizing means 13, a method using air, a cylinder such as “inert gas such as nitrogen”, an air compression device (compressor) or the like, or a mechanical pressurization method in which sludge is compressed directly with a piston by hydraulic pressure or the like. Can be adopted. When the sludge 16 is pressurized by the sludge pressurizing means 13, as shown in FIG. 1, the sludge in the “sludge storage tank 12 a storing sludge” is pressurized and pressurized by the sludge pressurizing means 13. It is preferable to send the sludge in the sludge storage tank 12a to the primary space 4 of the filter 3 and pressurize the primary space 4 (filter cloth). In this case, the pressurized “pressurizing medium such as air and nitrogen” is sent from the sludge pressurizing means 13 to the sludge storage tank 12a, whereby the inside of the sludge storage tank 12a is pressurized.

In the pressure filtration step, as shown in FIG. 1, when the sludge 16 supplied to the primary space 4 of the filter 3 is pressurized by the sludge pressurizing means 13, the pressure of the sludge is adjusted by the pressure adjusting means 13 a. Is preferably adjusted. An example of the pressure adjusting means 13a is a pressure adjusting valve. It is preferable that the pressure adjustment means 13a is provided in piping which connects the sludge pressurization means 13 and the sludge storage tank 12a.

(1-3) pressing process;
As shown in FIG. 5, the pressing step in the solid-liquid separation method of the present embodiment is a step of obtaining the pressing sludge 18 by pressing the concentrated sludge adhering to the primary side surface 6 of the filter cloth 1. After the pressure filtration operation (pressure filtration step) is completed, the sludge remaining in the filter is removed, and then the concentrated sludge is squeezed (squeezing step). Also, if the sludge does not remain in the filter by the pressure filtration operation (pressure filtration step), after the pressure filtration step is completed, an operation to remove the remaining sludge is performed. Without squeezing, the pressing process can be started. When the sludge remaining in the filter is removed, the sludge taken out from the filter is preferably returned to the sludge storage tank and subjected to solid-liquid separation.

In the pressing process, “squeezing the concentrated sludge” means that the concentrated sludge adhering to the filter cloth is mechanically pressurized (pressed by pressing the structure, or the structure without supplying the sludge to the filter cloth). It means that the moisture in the concentrated sludge is squeezed out.

In the pressing step, the pressure when pressing the concentrated sludge is preferably 0.2 to 1.8 MPa (gauge pressure). Furthermore, in the said pressure range, it is preferable to squeeze concentrated sludge, raising the pressure when squeezing concentrated sludge intermittently. When the pressure is intermittently increased, it is preferable to start the pressure increase from a pressure higher than the “maximum filtration pressure” in the pressure filtration step. When the pressure at the time of pressing concentrated sludge is lower than 0.2 MPa, the solid content concentration of the compressed sludge may not increase, and the pressing process may take a long time. When the pressure at the time of pressing concentrated sludge is higher than 1.8 MPa, a part of concentrated sludge (or compressed sludge) may permeate | transmit a filter cloth. Here, “intermittently increasing the pressure when squeezing the concentrated sludge” means increasing the pressure for squeezing the concentrated sludge in a stepped manner, and “constant pressure state (maintenance of constant pressure)” It is to increase the “pressure for squeezing the concentrated sludge” while alternately repeating “the state of increasing pressure (pressure increasing operation)”.

In addition, when the pressure applied to the concentrated sludge is intermittently increased as described above in the pressing process, from a pressure (minimum pressing pressure) that is 0.2 to 0.4 MPa higher than the “maximum filtering pressure” in the pressure filtering process. The pressure is preferably intermittently increased to a pressure (maximum pressing pressure) higher by 0.7 to 1.0 MPa than the “maximum filtration pressure” in the pressure filtration step. Thereby, it becomes possible to perform dehydration by causing them to function as a filtration membrane without breaking the layer of concentrated sludge adhering to the filter cloth 1. That is, it is possible to more effectively prevent the solid content in the concentrated sludge from passing through the filter cloth and flowing out to the filtrate side. Here, the “minimum pressing pressure” is the first (first stage) pressure and the lowest pressure when the concentrated sludge is pressurized in the pressing step. The “maximum squeezing pressure” is the last (last stage) pressure and the highest pressure when the concentrated sludge is pressurized. When the minimum squeezing pressure is higher than “a pressure higher by 0.4 MPa than the maximum filtration pressure in the pressure filtration step”, the solid content may easily pass through the filter cloth when the concentrated sludge is pressurized. Moreover, in the solid-liquid separation method of this embodiment, in order to pressurize the filter 3 to the above high pressure in a pressing process, it is preferable that the filter 3 is a pressure | voltage resistant structure. In the pressing step, it is preferable that the pressure finally applied to the concentrated sludge is 1.5 to 1.8 MPa.

In the pressing process, when the pressure applied to the concentrated sludge is intermittently increased from the minimum pressing pressure to the maximum pressing pressure, the pressure to be increased in one pressurization (pressure increasing operation) is 0.2 to 0.4 MPa (increase) Width). Thereby, pressing sludge with high solid content concentration can be obtained, suppressing the leakage of solid content from a filter cloth more effectively. If the pressure raised by one pressurization is less than 0.2 MPa, the time required for solid-liquid separation may be increased. If the pressure raised by one pressurization is larger than 0.4 MPa, the solid content may easily leak from the filter cloth. Further, the pressure to be raised by one boosting may be a constant value or may be different depending on the boosting stage. Further, the pressure increase rate (MPa / min) in the pressure increase operation is not particularly limited, but it is preferable to set the rate so that the solid content is not mixed into the filtrate. If the pressure increase rate is too high, solids may be mixed in the filtrate, and the concentrated sludge layer adhering to the filter cloth may be broken, which is not preferable. As the pressure increase rate, for example, 0.5 to 2 minutes is preferable. Within the range of the pressure increase rate, it is preferable to adjust the pressure increase rate appropriately so that “the solid content is not mixed in the filtrate or the layer of concentrated sludge adhering to the filter cloth does not collapse”. .

In the pressing process, when the pressure applied to the concentrated sludge is intermittently increased from the minimum pressing pressure to the maximum pressing pressure, switching from the “constant pressure state” to the “pressurizing state” requires that the flow rate of the filtrate be It is preferably performed when the flow rate is 15 to 25% of the initial flow rate in the “constant pressure state”.

In the pressing step, it is preferable to pressurize the concentrated sludge and depressurize the secondary space 5. Since the filtrate 19 near the surface of the compressed sludge (particularly the surface in contact with the filter cloth) is quickly discharged by pressurizing the concentrated sludge and depressurizing the secondary space 5, the surface is more dry. Thus, when the compressed sludge is peeled off from the filter cloth, it can be peeled off more easily. The pressure when the secondary side space 5 is decompressed (the pressure of the decompressed secondary side space 5) is preferably −0.08 to −0.02 MPa (gauge pressure). If it is higher than −0.02 MPa, the surface of the pressed sludge may be difficult to dry.

The solid concentration of the compressed sludge obtained in the pressing step is preferably 40 to 45% by mass. When the solid content concentration of the compressed sludge is lower than 40% by mass, the load on the combustion furnace may be increased when the compressed sludge is burned and discarded. The higher the solid content concentration of the compressed sludge, the better. However, in the solid-liquid separation method of the present embodiment, the upper limit is about 45% by mass.

The sludge squeezing mechanism 15 used in the squeezing process shown in FIG. 5 includes a cylinder part 15b, a “piston part 15e capable of reciprocating in the cylinder part 15b”, and a “piston part 15e disposed at the tip of the piston part 15e. A pressurizing part 15a having a pressurizing plate 15f having a pressurizing surface 15g perpendicular to the moving direction of the part 15e, and a pressurizing means 15c that pressurizes the inside of the cylinder part 15b and moves the pressurizing part 15a. is there. In order to adjust the pressure when the inside of the cylinder portion 15b is pressurized by the pressurizing means 15c, it is preferable that the pressure adjusting means 15d is attached to a pipe connecting the pressurizing means 15c and the cylinder portion 15b. Drawing 5 is a mimetic diagram showing the state where concentrated sludge is squeezed while showing the section of filter 3 and sludge pressing mechanism 15 used for one embodiment of the solid-liquid separation method of the present invention. Note that the lid 26 (see FIG. 2) is not shown in FIG.

In the pressing step, when the sludge pressing mechanism 15 is used, it is preferable to remove the lid 26 (see FIG. 2) from the filter 3. Moreover, it is also a preferable aspect that the lid part or a part of the lid part has a structure that can be used as the pressurizing part 15a.

In the sludge squeezing mechanism 15, the structure and material of the cylinder portion 15b and the pressurizing portion 15a are not particularly limited as long as they can press the entire surface of the concentrated sludge evenly with a predetermined pressure. The pressurizing means 15c is not particularly limited, but an air compression device (compressor) or the like can be used. Further, the pressure adjusting means 15d is not particularly limited, but may include a pressure adjusting valve.

(1-4) Discharging process;
As shown in FIG. 6, the discharge step in the solid-liquid separation method of the present embodiment is a step of peeling the compressed sludge 18 from the filter cloth 1, and the pressed sludge 18 peeled from the filter cloth 1 is removed from the filter 3. Discharged. FIG. 6 is a schematic view showing a state of discharging the compressed sludge in the discharging step while showing a cross section of the filter 3 used in one embodiment of the solid-liquid separation method of the present invention. In addition, the sludge pressing mechanism 15 is not illustrated in FIG.

In the discharging step, it is preferable to flow compressed air from the secondary side space toward the primary side space (so as to pass through the filter cloth 1) and to peel the compressed sludge 18 from the filter cloth 1 by the compressed air. It is also possible to mechanically peel the comb-shaped member by moving it along the filtration membrane. In addition, if the filter is small and can be easily handled by human hands, the method of scraping out the compressed sludge with human hands, the method of discharging the compressed sludge by tilting the filter, and after removing the compressed sludge with the filter cloth It is also possible to peel the pressed sludge from the filter cloth by a method such as peeling from the filter cloth.

(2) Another embodiment of the solid-liquid separation method of the present invention:
Next, another embodiment of the solid-liquid separation method of the present invention will be described. A solid-liquid separation device 200 (see FIG. 7) for carrying out another embodiment of the solid-liquid separation method of the present invention includes a filter 3 (see FIG. 1) in the solid-liquid separation device 100 shown in FIG. The filter 53 is replaced with a filter 53 as shown in FIGS. 8A and 8B. Therefore, the solid-liquid separation method of the present embodiment is the same as that of the above-described embodiment of the solid-liquid separation method of the present invention except that the filter 53 shown in FIGS. 8A and 8B is used as the filter. FIG. 7 is a schematic diagram (flow diagram) showing a solid-liquid separation device 200 used in another embodiment of the solid-liquid separation method of the present invention. FIG. 8A is a schematic view showing a cross section of a filter 53 used in another embodiment of the solid-liquid separation method of the present invention. FIG. 8B is a side view schematically showing a filter 53 used in another embodiment of the solid-liquid separation method of the present invention. In addition, in FIG. 7, the sludge storage tank 12a is expressed so that the sludge 16 stored inside can be seen through. The filter 53 is expressed so as to show a cross section. Moreover, the filtrate storage tank 14 is expressed so that the filtrate 19 stored inside can be seen through.

The filter 53 used in the solid-liquid separation method of the present embodiment shown in FIGS. 8A and 8B has two filtrates in which the filter body 52 is “disposed at an interval and the inside becomes the secondary space 55”. A

drain tank

61, 61, and a concentration tank 62, which is arranged so as to be sandwiched between the two

filtrate discharge tanks

61, 61 and becomes the primary side space 54, and has two filtrate discharge tanks 61, One filter cloth 51 is provided at the boundary between each of 61 and the concentration tank 62, and

filtrate permeating members

63 and 63 are provided in the two

filtrate discharge tanks

61 and 61 so as to support the filter cloth 51. . Then, the sludge squeezing mechanism moves so that the two

filtrate discharge tanks

61 and 61 approach each other by narrowing the primary side space 54, and the primary side surfaces 56 and 56 of the two

filter cloths

51 and 51, respectively. This is a mechanism for sandwiching and squeezing the concentrated sludge adhering to the two

filtrate discharge tanks

61, 61.

The two

filtrate discharge tanks

61 and 61 are square columnar tanks in which openings 65a and 65a are formed in opposite walls 65 and 65 and the inside is formed in a hollow shape, and close the openings 65a and 65a. Thus, the

filter cloths

51 and 51 are provided. The concentrating tank 62 includes walls 65 and 65 and

filter cloths

51 and 51 facing each other of the two

filtrate discharge tanks

61 and 61, and a “space between the two filtrate discharge tanks 61 and 61 (primary space 54. ) Is formed by a body portion 64 "disposed along the outer edge of the mutually opposing walls 65, 65 of the two

filtrate discharge tanks

61, 61". Therefore, the opposing walls 65 and 65 and the

filter cloths

51 and 51 of the two

filtrate discharge tanks

61 and 61 are also part of the concentration tank 62. The concentration tank 62 is formed with an inlet 71 for allowing the sludge 16 to flow inside, and the filtrate discharge tank 61 is formed with an outlet 72 for allowing the filtrate 19 to flow outside. .

Further, the body part 64 forming the outer periphery of the concentration tank 62 is formed in a cylindrical shape, and one end part is joined to the “opposing wall 65” of one filtrate discharge tank 61, and the other end part is The primary side space 54 is formed inside by joining to the “opposing wall 65” of the other filtrate discharge tank 61. Further, the body portion 64 is formed to be extendable so that the two

filtrate discharge tanks

61 and 61 can be moved closer to each other and the two

filtrate discharge tanks

61 and 61 can be moved away from each other. ing. Further, as shown in FIGS. 8A and 8B, when the filter 53 is arranged so that the central axis of the cylindrical body part 64 faces the horizontal direction, on the lower side in the vertical direction of the body part 64, An opening / closing part 73 is formed. The opening / closing part 73 is in a closed state in the suction filtration process, the pressure filtration process and the compression process, but in the discharge process, the two

filtrate discharge tanks

61 and 61 are moved away from each other to extend the body part 64. It is the part that opens when In the discharging step, the compressed sludge is discharged from the “opening / closing portion 73”.

In the solid-liquid separation method of this embodiment, the sludge 16 flows into the concentration tank 62 (primary space 54) from the inlet 71, the sludge 16 is filtered by the filter cloth 51, and the filtrate 19 is the filtrate discharge tank. 61 (secondary side space 55), the solid (concentrated sludge) adheres to the primary surface 56 of the filter cloth 51 and flows into the filtrate discharge tank 61 (secondary side space 55). The filtrate 19 flows out from the outlet 72.

Hereinafter, another embodiment of the solid-liquid separation method of the present invention will be described for each step.

(2-1) Suction filtration step;
In the suction filtration step in the solid-liquid separation method of the present embodiment, the sludge 16 is first supplied to the primary space 54 as shown in FIGS. Then, while reducing the pressure on the secondary side space 55 that is the space on the one side (secondary side surface 57) side of the filter cloth 51, the primary side space 54 that is the space on the other side of the filter cloth 51 The sludge 16 is further supplied, the sludge 16 is filtered by the filter cloth 51, and the concentrated sludge 17 (initial concentrated sludge 17a) is attached to the primary side surface 56 which is the other surface of the filter cloth 51. . The secondary side space 55 of the filter 53 is decompressed by the decompression means 11 via the filtrate storage tank 14. As a result, the solid content in the sludge 16 is collected by the filter cloth 51 as the concentrated sludge 17 (initial concentrated sludge 17a), and the filtrate 19 that has passed through the filter cloth 51 passes through the secondary side space 55 to pass through the filtrate. It is sent to the storage tank 14 and stored. In addition, the sludge storage tank 12a and the concentration tank 62 of the filter 53 are connected by piping, and the filtrate discharge tank 61 and the filtrate storage tank 14 of the filter 53 are connected by piping. Each pipe and device is preferably equipped with valves and instruments as necessary. Here, FIG. 9 shows a cross section of the filter 53 used in another embodiment of the solid-liquid separation method of the present invention, and sludge (initial concentrated sludge) on the primary side surface 56 of the filter cloth 51 in the suction filtration step. It is a schematic diagram which shows the state which 17a) has adhered.

Thus, in the solid-liquid separation method of the present embodiment, first, in the suction filtration step, the initial concentrated sludge 17a is attached to the primary side surface 56 of the filter cloth 51. Even if the sludge 16 is supplied to the primary side space 54 of the filter 53 and pressurized, the solid content in the sludge 16 is prevented from passing through the filter cloth 51 and leaking into the secondary side space 55. can do. This is because the initial concentrated sludge 17a attached to the filter cloth 51 has a function of collecting solids in the sludge together with the filter cloth 51. Thus, even when a device (filter 53) provided with a “filter cloth formed of a monofilament made of nylon and having a large opening diameter”, which is normally used in the suction filtration step, is used. The pressure filtration in the pressure filtration process can be performed using the apparatus (filter 53) used in the process. That is, suction filtration and pressure filtration can be performed by one filter 53 (solid-liquid separation device 200).

In the suction filtration step, “time for filtering sludge with filter cloth” and “pressure when decompressing the secondary space (pressure of the decompressed secondary space)” are the solid-liquid separation method of the present invention. It is preferable that the conditions are preferable in one embodiment.

In the suction filtration step, a vacuum pump or the like can be used as the decompression means 11 for decompressing the secondary side space 55 of the filter 53. Further, as shown in FIG. 14, a siphon tube 74 may be used as the decompression unit 11. The filter 53a shown in FIG. 14 uses a siphon tube 74 as the pressure reducing means 11, and depressurizes the secondary space 55 of the filter 53a according to the principle of siphon. When the pressure is reduced by the principle of siphon, there is an advantage that the initial concentrated sludge 17a adhering to the filter cloth 51 is hardly broken. In addition, when a vacuum pump is used as the decompression means 11 for decompressing the secondary space 55 of the filter 53 (see FIG. 7), the secondary space of the filter 53 is also used in the pressure filtration process and the squeezing process. As the depressurizing means for depressurizing 55, it is preferable to use the depressurizing means 11 used in the suction filtration step. Further, when the siphon tube 74 is used as the decompression means 11 for decompressing the secondary space 55 of the filter 53a (see FIG. 14), the vacuum pump can be used even in the pressurization filtration process even if the siphon tube 74 is used. You may use, and it is preferable to use a vacuum pump in a pressing process. Therefore, as shown in FIG. 14, even when a siphon tube is provided as a pressure reducing means in the filter, it is preferable to further include another pressure reducing means 11 such as a vacuum pump as shown in FIG. FIG. 14 is a schematic diagram showing a cross section of the filter 53a and the decompression means 11 (siphon tube 74) used in still another embodiment of the solid-liquid separation method of the present invention.

Further, the filter cloth 51 and the sludge supply means are preferably the conditions of the filter cloth 1 (see FIG. 2) and the sludge supply means, which are preferable in the embodiment of the solid-liquid separation method of the present invention.

(2-2) pressure filtration step;
In the pressure filtration step in the solid-liquid separation method of the present embodiment, as shown in FIGS. 7 and 10, the secondary side space 55 is decompressed and the sludge 16 is supplied to the primary side space 54 while being pressurized, The sludge 16 is filtered by the filter cloth 51, and the concentrated sludge 17 (second-layer concentrated sludge 17b) is further adhered on the concentrated sludge 17 (initial concentrated sludge 17a) adhering to the primary-side surface 56 of the filter cloth 51. At the same time, the initial concentrated sludge 17a is compressed to increase its density to enhance the filtration function. Furthermore, in the suction filtration step, it is also a step for recovering (increasing) the flow rate of the filtrate that has decreased due to the concentrated sludge adhering to the filter cloth. The filtrate 19 that has passed through the filter cloth 51 is discharged from the outlet 72, sent to the filtrate storage tank 14 through the piping, and stored in the filtrate storage tank 14. When the sludge 16 is supplied to the primary side space 54 while “pressurizing the filter cloth 51”, the entire surface of the filter cloth 51 is preferably pressurized by the sludge 16. FIG. 10 shows a cross section of a filter 53 used in another embodiment of the solid-liquid separation method of the present invention, and sludge (concentrated sludge 17 (initial stage) on the primary side surface 56 of the filter cloth 51 in the pressure filtration step. It is a schematic diagram which shows the state which the concentrated sludge 17a and the 2nd layer concentrated sludge 17b)) have adhered, forming a some layer. The concentrated sludge 17 (second layer concentrated sludge 17b) is attached on the initial concentrated sludge 17a.

Thus, in the pressure filtration step, the sludge is filtered with the initial concentrated sludge 17a attached to the filter cloth 51. Therefore, the initial concentrated sludge 17a also serves to filter the sludge together with the filter cloth 51. Even if it is a monofilament, pressure filtration can be performed while preventing leakage of solid content.

In the pressure filtration process, “pressure to pressurize the filter cloth with sludge (pressure increase, pressure range)”, “pressure increase rate when increasing pressure from minimum filtration pressure to maximum filtration pressure (MPa / min)”, “ "Speed at which the filtrate is discharged from the filter", "Pressure to be increased by one pressurization when intermittently increasing pressure from the minimum filtration pressure to the maximum filtration pressure", "Intermittently from the minimum filtration pressure to the maximum filtration pressure" In the case of boosting, the interval between boosting (the time from the end of one boosting to the start of the next boosting) and the pressure for decompressing the secondary space (pressure in the decompressed secondary space) ")" Is preferably the respective conditions that are preferable in one embodiment of the solid-liquid separation method of the present invention.

In the pressure filtration process, as shown in FIG. 7, the sludge 16 supplied to the primary space 54 of the filter 53 is pressurized by the sludge pressurizing means 13, and the filter cloth (primary It is preferable to pressurize the side space. The condition of the sludge pressurizing means is preferably a condition that is preferable in one embodiment of the solid-liquid separation method of the present invention.

In the pressure filtration process, as shown in FIG. 7, when the sludge 16 supplied to the primary space 54 of the filter 53 is pressurized by the sludge pressurizing means 13, the pressure of the sludge is adjusted by the pressure adjusting means 13 a. Is preferably adjusted. An example of the pressure adjusting means 13a is a pressure adjusting valve. It is preferable that the pressure adjustment means 13a is provided in piping which connects the sludge pressurization means 13 and the sludge storage tank 12a.

(2-3) pressing process;
As shown in FIG. 11, the pressing step in the solid-liquid separation method of the present embodiment compresses concentrated sludge (initial concentrated sludge and second-layer concentrated sludge) adhering to the primary side surface 56 of the filter cloth 51. This is a step of obtaining the compressed sludge 18. The filter 53 used in the solid-liquid separation method of the present embodiment has a sludge that remains in the filter after the pressure filtration operation (pressure filtration step) is completed. Therefore, the concentrated sludge is removed after the remaining sludge is removed. Squeeze. When the sludge remaining in the filter is removed, the sludge taken out from the filter is preferably returned to the sludge storage tank and subjected to solid-liquid separation. When discharging the sludge remaining in the primary side space 54, the two

filtrate discharge tanks

61, 61 are moved away from each other, and the opening / closing part 73 of the body part 64 of the concentration tank 62 is opened, It is preferable to discharge from the opened opening / closing part 73. FIG. 11 is a schematic view showing a section of the filter 53 used in another embodiment of the solid-liquid separation method of the present invention and a part of the pressing process.

In the pressing step, “pressure when squeezing concentrated sludge”, “how to increase pressure when squeezing concentrated sludge (pressure applied to concentrated sludge), etc.” are one implementation of the solid-liquid separation method of the present invention. It is preferable that each of the conditions is preferable in the form.

In the pressing step, it is preferable to pressurize the concentrated sludge and depressurize the secondary side space 55. When the concentrated sludge is pressurized and the secondary side space 55 is depressurized, the surface of the compressed sludge (particularly the surface in contact with the filter cloth) becomes a more dry state, and when the compressed sludge is peeled off from the filter cloth, It can be more easily peeled off. The pressure when depressurizing the secondary side space (the pressure of the depressurized secondary side space) is preferably a condition that is preferable in one embodiment of the solid-liquid separation method of the present invention.

In the solid-liquid separation method of the present embodiment, as shown in FIG. 11, the sludge squeezing mechanism used in the squeezing process is such that the two

filtrate discharge tanks

61 and 61 narrow the primary side space 54 and approach each other. It is a mechanism that moves and squeezes the concentrated sludge adhering to the primary-

side surfaces

56 and 56 of the two

filter cloths

51 and 51 between the two

filtrate discharge tanks

61 and 61. The concentrated sludge is squeezed between two “filter cloths 51 whose secondary surface 57 side is supported by the filtrate permeable member 63”. The filtrate discharged by pressing the concentrated sludge passes through the filter cloth 51 and flows into the primary space 54 and is discharged from the outlet 72. The concentrated sludge from which moisture (filtrate) has been squeezed between the two

filter cloths

51, 51 becomes the compressed sludge 18. In addition, it is preferable that the conditions of the filtrate permeation | transmission member 63 used in the solid-liquid separation method of this embodiment are the conditions made preferable in one embodiment of the said solid-liquid separation method of this invention.

The method for moving the filtrate discharge tank 61 is not particularly limited. For example, as shown in FIG. 13, a support portion 77 disposed in each filtrate discharge tank 61 and the tip of the support portion 77 are movably attached. A method using a moving mechanism 75 including a guide portion 76 is preferable. The number and the mounting position of the moving mechanism 75 are not particularly limited, but it is preferable that the number and the position can stably support each filtrate discharge tank 61. As shown in FIG. 13, it is also a preferable aspect that two support portions 77 are attached to each of the filtrate discharge tanks 61 on the opposing walls. Moreover, it is preferable that the “facing walls” to which the support portion 77 is attached are a wall on the upper side in the vertical direction and a wall on the lower side in the vertical direction. Moreover, it is preferable that the guide part 76 is arrange | positioned so that all the directions to which the attached "front-end | tip of the support part 77" moves may become parallel. Since the filtrate discharging layer 61 is provided with the moving mechanism 75 as described above, the filtrate discharging layer 61 to which the supporting portion 77 is attached is moved by moving the tip of the supporting portion 77 along the guide portion 76. Can move with the support 77. FIG. 13 is a schematic view showing a cross section of a filter 53 used in another embodiment of the solid-liquid separation method of the present invention.

The shape of the support portion 77 is not particularly limited, and examples thereof include a member in which a wheel is disposed at the tip of a rod-like or plate-like member. Although the material of the support part 77 is not specifically limited, Stainless steel etc. can be mentioned. Although the shape of the guide part 76 is not specifically limited, When the wheel is arrange | positioned at the front-end | tip of the support part 77, it is preferable that it is a shape which has a rail which the support part 77 can move with the said wheel.

(2-4) Discharging process;
As shown in FIG. 12, the discharging step in the solid-liquid separation method of the present embodiment is a step of peeling the compressed sludge 18 from the filter cloth 51, and the compressed sludge 18 peeled from the filter cloth 51 is removed from the filter 53. Discharged. FIG. 12 is a schematic diagram showing a cross section of a filter used in another embodiment of the solid-liquid separation method of the present invention and showing how the compressed sludge is discharged in the discharge step.

In the discharge step in the solid-liquid separation method of the present embodiment, the two

filtrate discharge tanks

61 and 61 are moved away from each other to extend the trunk part 64 and are formed on the lower side in the vertical direction of the trunk part 64 of the concentration tank 62. The opened opening / closing part 73 is opened, and the compressed sludge is discharged from the “opened opening / closing part 73”. The opening / closing part 73 is preferably a “cut” formed in the body part 64.

In the discharging step, it is preferable to flow compressed air from the secondary side space toward the primary side space (so as to pass through the filter cloth 51), and the compressed sludge 18 is peeled off from the filter cloth 51 by the compressed air.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
In the solid-liquid separation apparatus 100 shown in FIG. 1, “a filter 83 as shown in FIG. 16 was used as a filter” to produce a solid-liquid separation apparatus. The filter 83 has a first frame 82a (a shape in which a recess is formed in a rectangular parallelepiped) having a recess 88a and a second frame 82b (a shape in which a recess is formed in a rectangular parallelepiped) having a recess 88b. A bag-like filter cloth 81 sandwiched between the filter body 82, "the surface of the first frame 82a on which the recess 88a is formed" and "the surface of the second frame 82b on which the recess 88b is formed". Are provided. The outer periphery (outer edge) of the bag-shaped filter cloth 81 has a “surface of the first frame 82a on which the recess 88a is formed (outer edge)” and a “surface of the second frame 82b on which the recess 88b is formed ( A closed space is formed in the central portion by being sandwiched by “outer edge” ”(in addition, movement of gas and liquid passing through the filter cloth is possible). Moreover, the shape of the opening part of the recessed part 88a of the 1st frame 82a and the shape of the opening part of the recessed part 88b of the 2nd frame 82b were made into the same size circle. Then, the first frame 82a and the second frame are formed such that the circular shape of the opening of the recess 88a of the first frame 82a and the circular shape of the opening of the recess 88b of the second frame 82b overlap without being displaced. The body 82b is arranged. The diameter of the opening of the recess 88a of the first frame 82a was 180 mm, and the diameter of the opening of the recess 88b of the second frame 82b was 180 mm. Moreover, the depth (depth of the deepest position) of the recessed part 88a of the 1st frame 82a shall be 50 mm, and the depth (depth to the rubber film 86 for pressing) of the recessed part 88b of the 2nd frame 82b, 50 mm. FIG. 16 is a schematic diagram illustrating a cross section of the filter 83 used in the first embodiment.

And the sludge supply pipe | tube 12 (refer FIG. 1) which the sludge introduction pipe | tube 87 is arrange | positioned by the 1st frame 82a, and has the sludge pressurization means 13 (refer FIG. 1) and the pressure adjustment means 13a (refer FIG. 1). The sludge supplied from the inlet C flows into the sludge introduction pipe 87 from the inlet C, and is supplied to the bag-like filter cloth 1 through the sludge introduction pipe 87. By increasing the supply pressure and pressurizing sludge, sludge pressurization in the pressure filtration process is performed.

In addition, a rubber film 86 for squeezing is disposed in the recess 88b of the second frame 82b, and the rubber film 86 for squeezing allows a space by the recess 88b to be separated into a space 88ba on the bottom side of the recess 88b and a recess 88b. Is divided into a space 88bb on the opening side (surface side on which the recess 88b is formed).

The filter 83 is a space formed by the filter cloth 81 and the recess 88a of the first frame 82a and a space 88bb on the opening side of the filter cloth 81 and the recess 88b of the second frame 82b. Is the secondary space 85. Further, the space in the bag of the bag-shaped filter cloth 81 becomes the primary space 84.

Further, the filter 83 was used by being arranged so that the joint surface between the first frame body 82a and the second frame body 82b was orthogonal to the horizontal plane. When the filter 83 is arranged in this way, in order to depressurize the “space formed by the filter cloth 81 and the concave portion 88a of the first frame 82a (primary side space 85)” and discharge the filtrate, An “outlet A” is formed on the lower side in the vertical direction of the first frame 82a to allow the primary space 85 and the outside to pass through. Furthermore, in order to depressurize “the space 88bb (primary space 85) on the opening side of the recess 88b of the filter cloth 81 and the second frame 82b” and discharge the filtrate, the second frame 82b is vertically below. On the side, an “outlet B” is formed through the primary space 85 and the outside. The outlet A and the outlet B are connected to the filtrate storage tank 14 (see FIG. 1).

Further, in order to squeeze the sludge in the filter cloth 81 in the squeezing step, the “pressurizing port D” for introducing the pressurized gas into the space 88ba on the bottom side of the recess 88b of the second frame 82b is the second. It is formed above the frame body 82b in the vertical direction. In the pressing step, a pressurized gas is introduced into the space 88ba on the bottom side of the recess 88b from the pressure port D of the second frame 82b, and the inside of the space 88ba on the bottom side of the recess 88b is pressurized to compress the rubber film 86 for pressing. The filter cloth 81 containing sludge is pressed by the rubber film 86 for squeezing and the sludge is squeezed. The pressurizing port D is connected to the sludge pressurizing means 13 (see FIG. 1).

As the sludge pressurizing means 13 (see FIG. 1), a nitrogen cylinder was used. A pressure reducing valve was used as the pressure adjusting means 13a (see FIG. 1). As the sludge storage tank 12a (see FIG. 1), a 25 liter tank formed of iron was used. The filtrate discharge tank 61 was made of iron. As the filter cloth 51, a filter cloth formed by satin weaving nylon monofilament was used. As the filtrate storage tank 14, a tank made of transparent vinyl chloride was used. A vacuum pump was used as the decompression means 11 (see FIG. 7) for decompressing the filtrate storage tank 14.

Using the obtained solid-liquid separator, solid-liquid separation was performed using sludge having a solid content of 0.74% by mass discharged at the water purification plant.

In the suction filtration step, sludge was supplied to the primary space for 60 minutes while reducing the secondary space at “−0.033 MPa (gauge pressure)” (suction filtration was performed for 60 minutes).

In the pressure filtration step, sludge was pressurized at 0.4 MPa (gauge pressure) while the secondary side space was depressurized at “−0.033 MPa (gauge pressure)”, and supplied to the primary side space for 10 minutes. This step-up operation was performed once.

In the squeezing step, sludge pressurizing means is applied from the pressurizing port D of the second frame 82b to the space 88ba on the bottom side of the recess 88b while reducing the secondary side space at “−0.033 MPa (gauge pressure)”. Pressurized gas from 13 (see FIG. 1) was introduced. Then, the inside of the space 88ba on the bottom side of the concave portion 88b of the second frame 82b is pressurized with the introduced pressurized gas to swell the rubber film 86 for squeezing outward, and the sludge is sludged by the rubber film 86 for squeezing. The filter cloth 81 containing was pressed and sludge was squeezed. The pressing pressure was 1.5 MPa (gauge pressure), and the pressing time was 10 minutes.

In the discharging step, the first frame 82a and the second frame 82b are separated, the filter cloth 81 having the compressed sludge in the filter body 82 is taken out, and the compressed sludge is peeled off from the filter cloth and taken out. .

The solid content concentration of the obtained compressed sludge was measured by the following method. The results are shown in Table 1. In Table 1, the “pressure” column of the “suction filtration step” indicates the pressure of the secondary space being depressurized, and the “time” column indicates the time of vacuum filtration. In the “pressure filtration step”, the “pressure” column indicates the pressure in the primary space being pressurized, and the “time” column indicates the pressure filtration time. Further, the “pressure” column of the “squeezing step” indicates the pressure applied to the concentrated sludge when the concentrated sludge is compressed, and the “time” column indicates the time of pressing. The column “solid content concentration” indicates the solid content concentration of the compressed sludge. The column “Solid Concentration” in Comparative Example 1 indicates the solid concentration of the concentrated sludge obtained by the suction filtration process.

(Solid content concentration)
Measure the mass (mass before drying) of the measurement object (pressed sludge or concentrated sludge) before drying, measure the mass (mass after drying) of the measurement object after drying with a dryer, A value obtained by dividing the value obtained by subtracting the mass after drying by the mass before drying is 100 times the solid content concentration (% by mass). The measurement object was dried at 110 ° C. for 8 hours.

(Example 2)
Sludge was separated into solid and liquid in the same manner as in Example 1 except that the “pressure (gauge pressure)” and “time” in the pressure filtration step and the pressing step were changed as shown in Table 1. In the same manner as in Example 1, the “solid content concentration” of the compressed sludge was measured by the above method. The results are shown in Table 1. In Table 1, “0.2-0.8” in the “Pressure” column of “Pressure filtration step” is a pressure increase from −0.033 MPa to 0.2 MPa in 1 minute, and is held at 0.2 MPa for 9 minutes. Then, the pressure was increased from 0.2 MPa to 0.4 MPa in 1 minute, held at 0.4 MPa for 9 minutes, then increased from 0.4 MPa to 0.6 MPa in 1 minute, then at 0.6 MPa for 4 minutes, and then 0 It shows that the primary space was continuously pressurized in a pressure increasing pattern in which the pressure was increased from 6 MPa to 0.8 MPa in 1 minute and held at 0.8 MPa for 4 minutes. Then, “30” in the “time” column of the “pressure filtration step” indicates that the time for pressurizing the primary space (time for performing pressure filtration) is 30 minutes in total. “1.5-1.8” in the “Pressure” column of the “Pressing step” is a pressure increase from 0.8 MPa to 1.5 MPa in 1 minute, and is held at 1.5 MPa for 4 minutes. It shows that the concentrated sludge was continuously squeezed (pressurized) in a pressure increasing pattern in which the pressure was increased from 5 MPa to 1.8 MPa in 1 minute and held at 1.8 MPa for 5 minutes. And "10" of the column of "time" of a "squeezing process" shows that the time which squeezes the said concentrated sludge is 10 minutes in total.

(Comparative Example 1)
Sludge was subjected to solid-liquid separation in the same manner as in Example 1 except that the pressure filtration step and the pressing step were not performed. In the same manner as in Example 1, the “solid content concentration” of the compressed sludge was measured by the above method. The results are shown in Table 1.

According to the solid-liquid separation method of Example 1, from Table 1, using one solid-liquid separation device, the solid content concentration of 0.74% by mass (about 1% by mass) from the sludge with a solid content concentration of 45% by mass is obtained. It turns out that sludge was obtained. In addition, by the solid-liquid separation method of Example 2, the suction filtration time in the suction filtration process was shortened to 10 minutes, and each “pressure” was increased step by step in the pressure filtration process and the compression process. It can be seen that the total time for liquid separation was significantly reduced. Moreover, it turns out that the solid content density | concentration of concentrated sludge does not rise so much only by the suction filtration process by the solid-liquid separation method of the comparative example 1.

(Example 3)
The solid content concentration of the sludge used for the solid-liquid separation is 1.2% by mass, except that the conditions of the suction filtration process, the pressure filtration process and the compression process are changed as follows, as in Example 1, Solid-liquid separation of sludge was performed. In the suction filtration step, the pressure in the secondary space was set to “−0.025 MPa (gauge pressure)” and the filtration time was set to 10 minutes (conditions of the suction filtration step). In the pressure filtration step, the pressure in the secondary space is maintained at “−0.025 MPa (gauge pressure)” and the primary space is pressurized at “0.20 MPa (gauge pressure)” for 30 minutes. Pressurization was carried out for 20 minutes at “0.39 MPa (gauge pressure)” (conditions for pressure filtration step). In the pressing step, the pressure in the secondary space is maintained at “−0.025 MPa (gauge pressure)” and the primary space is pressurized at “1.5 MPa (gauge pressure)” for 10 minutes (pressing step) Conditions). FIG. 15 shows the relationship between the filtration time and the amount of filtrate discharged into the secondary space. FIG. 15 is a graph showing the relationship between the filtration time and the filtrate amount in the solid-liquid separation methods of Examples 3 and 4.

Example 4
The solid content concentration of the sludge used for the solid-liquid separation is 1.2% by mass, except that the conditions of the suction filtration process, the pressure filtration process and the compression process are changed as follows, as in Example 1, Solid-liquid separation of sludge was performed. In the suction filtration step, the pressure in the secondary space was set to “−0.025 MPa (gauge pressure)”, and the filtration time was set to 90 minutes (conditions of the suction filtration step). In the pressure filtration step, the pressure in the secondary space is maintained at “−0.025 MPa (gauge pressure)” and the primary space is pressurized at “0.39 MPa (gauge pressure)” for 10 minutes ( Pressure filtration process conditions). In the pressing step, the pressure in the secondary side space is maintained at “−0.025 MPa (gauge pressure)” and the primary side space is pressurized at “1.5 MPa (gauge pressure)” for 16 minutes (pressing step) Conditions). FIG. 15 shows the relationship between the filtration time and the amount of filtrate discharged into the secondary space.

From FIG. 15, in the solid-liquid separation method of Example 3, 3.5 kg of filtrate was discharged in about 70 minutes, whereas in the solid-liquid separation method of Example 4, 3.5 kg was discharged in about 110 minutes. It can be seen that the filtrate is discharged. From this, in the solid-liquid separation method of this invention, it turns out that solid-liquid separation of sludge can be performed in a short time by shortening a suction filtration process to about 10 minutes and switching to a pressure filtration process. The difference between Example 3 and Example 4 is that in Example 3, when the pressure filtration for 40 minutes was performed after the suction filtration for 10 minutes (total of 50 minutes), the amount of filtrate reached 3 kg. On the other hand, in Example 4, the amount of the filtrate reached 3 kg after suction filtration for 90 minutes. That is, rather than continuing the suction filtration process for a long time, the filtration time can be significantly shortened by ending the suction filtration process in a short time and switching to the pressure filtration process.

The solid-liquid separation method of the present invention can be suitably used for treating sludge having a solid content concentration of about 1% by mass discharged from a water purification plant.

1: filter cloth, 2: filter body, 3: filter, 4: primary space, 5: secondary space, 6: primary surface, 7: secondary surface, 11: pressure reducing means , 12: sludge supply means, 12a: sludge storage tank, 13: sludge pressurization means, 13a: pressure adjustment means, 14: filtrate storage tank, 15: sludge pressing mechanism, 15a: pressurization part, 15b: cylinder part, 15c : Pressurizing means, 15d: Pressure adjusting means, 15e: Piston part, 15f: Pressurizing plate, 15g: Pressurizing surface, 16: Sludge, 17: Concentrated sludge, 17a: Initial concentrated sludge, 17b: Second layer concentrated sludge, 18 : Pressed sludge, 19: filtrate, 21: one end, 22: the other end, 23: main body, 24: bottom, 24a: discharge port, 24b: discharge nozzle, 25: opening, 26: lid 26a: inlet, 26b: inflow nozzle, 27: filtrate permeation member, 51: filter cloth, 52 Filter body, 53: Filter, 54: Primary side space, 55: Secondary side space, 56: Primary side surface, 57: Secondary side surface, 61: Filtrate discharge tank, 62: Concentration tank, 63: Filtrate permeable member, 64: Body part, 65: Opposing wall, 65a: Opening part, 71: Inlet, 72: Outlet, 73: Opening / closing part, 74: Siphon tube, 75: Moving mechanism, 76: Guide Part, 77: support part, 81: filter cloth, 82: filter body, 82a: first frame, 82b: second frame, 83: filter, 84: primary side space, 85: secondary side space 86: Rubber film for pressing, 87: Sludge introduction pipe, 88a: Recessed portion (of the first frame), 88b: Recessed portion (of the second frame), 88ba: Space on the bottom side, 88bb: Space on the opening side A, B: Outlet, C: Inlet, D: Pressurization port, 100, 200: Solid-liquid separator.

Claims

While depressurizing the secondary side space that is the space on one side of the filter cloth, the sludge is supplied to the primary side space that is the space on the other side of the filter cloth, and the sludge is filtered by the filter cloth. And a suction filtration step of attaching concentrated sludge to the primary side surface, which is the other surface of the filter cloth,
The secondary side space is depressurized, the sludge is supplied to the primary side space and pressurized, the sludge is filtered by the filter cloth, and the concentrated sludge adhering to the primary side surface of the filter cloth A pressure filtration process for further attaching concentrated sludge from above;
A squeezing step of squeezing the concentrated sludge adhering to the primary side surface of the filter cloth to obtain a compressed sludge;
A solid-liquid separation method including a discharging step of peeling the compressed sludge from the filter cloth.
2. The solid filtration according to claim 1, wherein, in the suction filtration step, the pressure filtration step is started when a solid content concentration of the filtrate flowing out into the secondary space reaches 0.02 to 0.04 mass%. Liquid separation method.
The solid-liquid separation method according to claim 1 or 2, wherein, in the suction filtration step, the pressure in the secondary side space reduced in pressure is -0.08 to -0.02 MPa.
The solid pressure according to any one of claims 1 to 3, wherein in the pressure filtration step, the pressure for pressurizing the sludge is intermittently increased from 0.2 to 0.4 MPa to 0.6 to 1.5 MPa. Liquid separation method.
The solid-liquid separation method according to any one of claims 1 to 4, wherein a pressure when the concentrated sludge is squeezed is 0.2 to 1.8 MPa in the pressing step.
The solid content concentration of sludge supplied to the primary side space is 0.7 to 2.0% by mass, and the solid content concentration of the compressed sludge obtained in the pressing step is 40 to 45% by mass. Item 6. The solid-liquid separation method according to any one of Items 1 to 5.