JP2021193189A - Mesh body washing device and mesh body washing method - Google Patents

Abstract

To enable a sludge content contained in ammonia water discharged through an ammonia water discharge port to be reduced while a separation tank is not necessarily increased in size.SOLUTION: There is provided a tar decanter device 1 in which a liquid substance including tar from a coke oven and ammonia water is supplied to a separation tank 2 from an upstream side thereof, the supplied liquid substance is gravity-separated into a tar layer ARA1 and an ammonia water layer ARA2, and the ammonia water in the ammonia water layer ARA2 is discharged through an ammonia water discharge port 4 provided on a downstream side of the separation tank. The tar decanter device is provided with a mesh body 10 disposed before the ammonia water discharge port 4 so as to prevent a sludge content 7 included in the ammonia water layer ARA2 from moving to the ammonia water discharge port 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for a tar decanter device for recovering cheap water by separating coal tar and cheap water from a liquid substance containing tar and cheap water generated from a coke oven, and a mesh body cleaning device.

When refining the coke oven gas (hereinafter, also referred to as COG) generated in the coke oven, the gas generated from the coke oven is cooled and washed. In this cooling and cleaning treatment, for example, after spraying and cooling the gas with dry men, the liquefied tar, the liquid substance containing the cheap water and the COG are separated, and the COG is sent to the purification step. Further, the liquid substance separated from the COG is discharged to the separation tank of the tar decanter device.
As described in Patent Document 1, the liquid substance supplied to the tar decanter device is separated into the upper safe water layer and the lower tar layer by specific gravity in the separation tank. The solid state or muddy sludge (tar slag) settled on the bottom side of the separation tank in the tar layer is conveyed by the scraper and discharged to the outside of the separation tank. The tar (oil content) in the tar layer is discharged from the tar discharge port provided on the downstream side of the separation tank. Since the tar in the separation tank contains sludge, for example, the sludge is separated by a centrifuge.
On the other hand, the cheap water (moisture) constituting the safe water layer is discharged from the cheap water discharge port provided on the downstream side of the separation tank and stored in the cheap water tank. The cheap water stored in the cheap water tank is reused for the above-mentioned cooling treatment of COG.

Japanese Unexamined Patent Publication No. 2013-231123

The ammonia recovered by the tar decanter device is reused and sprayed to cool the coke oven gas. If tar or sludge (hereinafter, also referred to as slag) is mixed in the recovered cheap water, it may cause the spray nozzle that ejects the cheap water to be blocked. Therefore, it is preferable that the amount of slag mixed in the safe water recovered by the tar decanter device is small.
Here, since the difference in specific gravity between ammonia and tar is small, if the slag content in the aqueous layer is to be reduced below a predetermined value, for example, separation is performed in order to secure a sufficient residence time for specific gravity separation (static separation). It is necessary to take measures such as increasing the length of the tank and using multiple separation tanks.
The present invention focuses on the above points, and an object of the present invention is to suppress the slag contained in the cheap water discharged from the cheap water discharge port without necessarily increasing the size of the separation tank.

In order to solve the problem, in one aspect of the present invention, a liquid substance containing tar and safe water generated from a coke furnace is supplied to the upstream side of the separation tank, and the supplied liquid substance is supplied to the tar layer and the safe water layer. It is a tar decanter device that is separated by specific gravity and discharges the cheap water in the safe water layer from the low water discharge port provided on the downstream side. The gist is to provide a mesh body that suppresses the movement of the contained slag to the above-mentioned safe water discharge port.
Further, in the safe water separation method according to another aspect of the present invention, liquid substance waste containing tar and cheap water generated by cooling and cleaning the coke oven gas is supplied to the upstream of the separation tank, and the supplied liquid substance is used. In the separation tank, the tar layer and the cheap water layer are separated by specific gravity, and the cheap water constituting the safe water layer after the specific gravity separation is discharged from the cheap water discharge port provided on the downstream side via the mesh body. Is the gist.
Further, the mesh body cleaning device according to another aspect of the present invention is a mesh body cleaning device that is arranged in a liquid layer containing slag and cleans a mesh body through which the liquid constituting the liquid layer passes. The gist is to provide a plurality of nozzles capable of injecting a fluid having a temperature higher than that of the liquid layer toward the mesh body from the downstream side in the moving direction of the liquid on the surface of the mesh body.

According to the aspect of the present invention, the slag contained in the slag is captured by the mesh body when the slag in the sewage layer passes through the mesh body and then is discharged from the sewage outlet. As a result, the amount of slag in the cheap water collected from the safe water discharge port is reduced.
In addition, since the slag is captured in the eyes of the mesh body, the flow resistance in the mesh body increases with the use over time. On the other hand, by injecting a fluid (for example, water vapor) having a temperature higher than that of the safe water layer (liquid layer) from the downstream side onto the surface of the mesh body, the eyes of the mesh body are washed and the flow resistance of the mesh body is reduced. It becomes possible to do.

It is a side view explaining the tar decanter apparatus which concerns on embodiment based on this invention. It is a front view seen from the mesh body side which explains the mesh body cleaning apparatus. It is a side view explaining the mesh body cleaning apparatus.

Next, an embodiment of the present invention will be described with reference to the drawings.
(composition)
As described above, the tar decanter device is a device for separating ammonia and tar from the liquid substance generated by cooling and cleaning the gas generated from the coke oven.
As shown in FIG. 1, the tar decanter device 1 of the present embodiment includes a separation tank 2, a scraper 3, and a liquid substance supply pipe 6.
The separation tank 2 constitutes the main body of the tar decanter device 1. Although the separation tank 2 of the present embodiment is a ship bottom type separation tank, the present invention can be applied to a separation tank having another structure.

A safe water discharge port 4 and a tar discharge port 5 are provided on the wall portion 2C on the downstream side of the separation tank 2 (the wall portion on the right side in FIG. 1). The safe water discharge port 4 is formed within a certain height range of the safe water layer ARA 2 separated by specific gravity in the separation tank 2. The tar discharge port 5 is formed within the height range of the tar layer ARA 1 separated by specific gravity in the separation tank 2.
A ceiling portion 2A is provided above the separation tank 2.
The scraper 3 is arranged along the bottom surface 2B of the separation tank 2, transports sludge accumulated on the upward surface to the upstream side of the separation tank 2, and sludge formed on the upstream end side of the separation tank 2. Discharge from the discharge port 2E.
The liquid substance supply pipe 6 constitutes a pipeline for introducing a liquid substance containing coal tar and cheap water upstream of the separation tank 2.

The liquid substance is introduced into the separation tank 2 through the liquid substance supply pipe 6. The liquid substance introduced into the separation tank 2 is separated by specific gravity (static separation) into the lower tar layer ARA1 and the upper safe water layer ARA2 in the separation tank 2. The specific gravity-separated aqueous solution constituting the aqueous solution layer ARA 2 and the tar constituting the tar layer ARA 1 are individually discharged from the aqueous water discharge port 4 and the tar discharge port 5, respectively. Due to this discharge, the ammonia constituting the aqueous layer ARA2 and the tar constituting the tar layer ARA1 are sequentially separated by specific gravity, and the inside of the separation tank 2 is moved from the upstream side to the downstream side (from the left side to the right side in FIG. 1). Move to.

Here, the height of the interface of the tar layer ARA1 is measured by a level meter (not shown). Based on the measured value of the level meter, the amount of tar discharged from the tar discharge port 5 is adjusted so that the interface height of the tar layer ARA 1 becomes a predetermined height. As a result, the safe water discharge port 4 and the tar discharge port 5 are at height positions facing the cheap water layer ARA 2 and the tar layer ARA 1, respectively.
The tar decanter device 1 of the present embodiment includes a mesh body 10 and a mesh body cleaning device 20.

The mesh body 10 is made of, for example, a wire mesh. The mesh body 10 is not limited to the wire mesh, and is not limited as long as it has a mesh-like shape and can capture the slag 7 in the Aquatic layer ARA2.
The size of the mesh of the mesh body 10 is set to a size that does not allow the slag 7 such as tar and sludge exceeding a predetermined value to pass through. The mesh body 10 of the present embodiment is composed of one piece, but may be composed of two or more pieces.
The size of the mesh of the mesh body 10 is, for example, an opening through which safe water passes is 0.1 mm or more and 10 mm or less. Since the slag in the cheap water is mixed with the heavy component in the tar to form a viscous substance, even a slag smaller than the opening can be captured to some extent.

The mesh body 10 is arranged in front of the safe water discharge port 4 (downstream position of the separation tank 2). The mesh body 10 has a function of suppressing the movement of the slag 7 contained in the safe water layer ARA 2 to the low water discharge port 4 side. The safe water layer ARA 2 is divided into an upstream side low water layer and a downstream side low water layer with the mesh body 10 as a boundary.
The mesh body 10 is arranged so that its surface faces a direction intersecting the moving direction of the water layer ARA 2 (for example, a direction orthogonal to each other) and covers the entire width cross section of the water layer ARA 2. As a result, the cheap water constituting the low water layer ARA 2 is configured to always move to the low water discharge port 4 side via the mesh body 10.

Even if the lower end of the mesh body 10 is set at a position slightly lower than the reference interface height of the tar layer ARA1 and the interface height of the tar layer ARA1 fluctuates, the safe water layer ARA2 is formed. The tarnish is always passed through the mesh body 10 before moving to the tartar outlet 4.
In the present embodiment, the upper end portion of the mesh body 10 is supported by the ceiling portion 2A.
Further, as shown in FIGS. 2 and 3, the mesh body cleaning device 20 includes a main pillar pipe 21, a nozzle body 22, and an elevating mechanism.

The main pillar pipe 21 is composed of a hollow pipe body extending vertically.
The nozzle body 22 includes a plurality of nozzle headers 23 extending in the left-right direction, and a support tube 24 connecting the central portions of the plurality of nozzle headers 23. The plurality of nozzle headers 23 are arranged vertically, and the hollow portions of the plurality of nozzle headers 23 are communicated with each other by a support tube 24 extending vertically. Each nozzle header 23 has a length such that both left and right ends are located in the vicinity of the left and right side walls 2D of the separation tank 2. The lower nozzle header 23 is formed so that both left and right ends are obliquely upward and outward.
A plurality of nozzles 25 are formed in each nozzle header 23 along the extending direction of the nozzle header 23, and fluid can be injected from each nozzle 25 toward the front (mesh body 10 side). The left and right pitches of the nozzles 25 are set so that the injection ranges from the nozzles 25 adjacent to each other on the left and right overlap each other.

As shown in FIG. 3, the central portion of the column pipe 24 has a connecting portion 24A extending rearward.
Further, the fluid pipe line 26 extends coaxially downward from the upper opening of the main pillar pipe 21 in the main pillar pipe 21, and the fluid pipe line 26 is mainly at the lower end portion of the main pillar pipe 21. It penetrates the pillar pipe 21 toward the front. The connecting portion 24A of the nozzle body 22 is connected to the lower end portion 26A of the fluid pipeline 26 extending forward thereof. With the above pipe configuration, when the fluid is pumped from the upper end of the fluid pipeline 26, the fluid is pumped to the nozzle body 22 through the fluid pipeline 26, and the fluid is pumped forward from each nozzle 25 of the nozzle header 23. Is jetted.
A pump 27 for fluid pressure feeding is connected to the upper end of the fluid pipeline 26, and by driving the fluid pump 27, fluid is pumped toward the nozzle body 22 and from each nozzle 25 to the mesh body 10. The fluid can be injected toward it.

Here, the distance between the nozzle body 22 and the mesh body 10 is set to a distance at which the pressure due to the fluid jetted from each nozzle 25 can act on the surface of the mesh body 10.
If the distance between the nozzle body 22 and the mesh body 10 is too narrow, the mesh body 10 may come into contact with the nozzle body 22, but for example, the nozzle 25 is formed by a hole formed in the front surface of the nozzle header 23. If this is the case, the nozzle body 22 is prevented from being caught by the mesh body 10 when the nozzle body 22 is moved up and down. However, a state in which the nozzle body 22 is in contact with the mesh body 10 at a pressure equal to or higher than a predetermined value causes a deterioration in the distribution of the mesh body 10 when the mesh body 10 is not washed. It is preferable that there is little contact.

The distance between the nozzle body 22 and the mesh body 10 is, for example, 5 mm or more and 100 mm or less.
Further, the fluid to be injected from the nozzle 25 is a fluid (liquid or gas) having a temperature higher than that of the Aquatic layer ARA2. Since the cheap water layer ARA2 is usually about 70 ° C., the temperature of the fluid to be injected is preferably 80 ° C. or higher. The fluid may be a liquid such as high-temperature water, but a gas is preferable because it is lighter and has less influence on cheap water. In this embodiment, water vapor is used as a gas having a temperature of 80 ° C. or higher.

By using a fluid having a temperature higher than that of the cheap water layer ARA2, the tar (oil) adhering to the mesh body 10 is melted and the slag 7 is easily peeled off from the mesh body 10.
The injection pressure of the fluid from the nozzle 25 is preferably 0.11 MPa or more and 1.00 MPa or less at the surface position of the mesh body 10.
It is preferable that the cleaning operation of the mesh body 10 is carried out in a state where the discharge of the cheap water from the cheap water discharge port 4 is stopped, and the discharge of the cheap water is restarted after a predetermined time has elapsed after the cleaning. However, the tar of the tarsal layer ARA2 is configured to always pass through the mesh body 10, and the elevating of the nozzle body 22 is slowed down by adopting the elevating mechanism described later. Disturbance to the lower tar layer ARA1 can be suppressed to a small extent. Therefore, the cheap water may be discharged while cleaning the mesh body 10.

The elevating mechanism is a mechanism for elevating and lowering the nozzle body 22 constituting the plurality of nozzles 25.
The elevating mechanism of the present embodiment includes a counterweight 33 for the nozzle body 22, an air box 31 connected to the nozzle body 22, and an air pressure feeding device 35 such as an air compressor capable of pumping air to the air box 31. ..
The upper part of the main pillar pipe 21 is supported by a guide portion 30 provided on the ceiling portion 2A so as to be slidable in the vertical direction. The guide portion 30 is preferably configured to guide the upper portion of the main pillar pipe 21 only in the vertical direction. For example, a key portion extending up and down is provided on the outer surface of the upper part of the main pillar pipe 21, and the key portion restrains the rotation of the main pillar pipe 21.

The counterweight 33 and the connecting portion of the nozzle body 22 are connected by a chain 32. The chain 32 has one end 32a fixed to the connection portion and extends upward, extends downward via a pulley 34 rotatably provided on the ceiling portion 2A, and the other end portion 32b is fixed to the counterweight 33. There is. By balancing the mass of the counterweight 33 with the mass of the main body of the mesh body cleaning device 20 mainly composed of the nozzle body 22 and the strut tube 24, the nozzle body 22 and the strut tube 24 can easily move up and down.
The mass of the counterweight 33 may be set slightly lighter than the mass of the main body of the mesh body cleaning device 20. As a result, the nozzle body 22 and the support tube 24 are positioned at the lower standby positions when not in use. FIG. 2 shows the state of the standby position.

Here, when the nozzle body 22 descends due to its own weight, as shown in FIG. 2, both sides of the lower nozzle header 23 abut on the side wall 2D of the separation tank 2 and the lower end position of the main body of the mesh body cleaning device 20 ( The lower limit position of the lower end of the device) is regulated. It is preferable that the lower limit position of the lower end of the device is adjusted so as to be located in the vicinity of the lower limit values of the water layer ARA2 and the tar layer ARA1, preferably in the water layer ARA2. A stopper may be provided at the upper end of the main pillar pipe 21 to regulate the lower limit position of the lower end of the device, but both sides of the lower nozzle header 23 are brought into contact with the side wall 2D of the separation tank 2 and downward. It is a simpler configuration to regulate the movement of.
The air box 31 is fixed to the lower end of the main pillar pipe 21. The upper part of the air box 31 communicates with the inside of the main pillar pipe 21. The air box 31 of the present embodiment has a shape in which the bottom is open.

The inside of the main pillar pipe 21 (the space between the inner wall of the main pillar pipe 21 and the outer wall of the fluid pipeline 26) forms a passage through which air can be pumped to the air box 31, and the upper side wall portion of the main pillar pipe 21 is formed. Is formed with a joint portion connected to the pneumatic feeding device 35. Then, by intermittently driving the pneumatic feeding device 35, for example, periodically, the strut pipe 24 and the nozzle body 22 connected to the strut pipe 24 can repeatedly move up and down. That is, when the air pressure feeding device 35 is driven to pump air, air is introduced into the air box 31, and the buoyancy of the air is introduced into the air box 31. When the air in the box 31 leaks and the fluid enters from the lower side of the air box 31, the buoyancy by the air box 31 becomes small, and the support tube 24 and the nozzle body 22 descend. By intermittently driving and controlling the pneumatic feeding device 35 in this way, the column tube 24 and the nozzle body 22 move up and down. An air vent valve for exhausting the air in the air box 31 may be provided in the line for pumping air from the air pressure feeding device 35.
Here, the elevating mechanism does not have to be a mechanism that utilizes the above-mentioned counterweight 33 and buoyancy. As the elevating mechanism, a known mechanism such as a hydraulic cylinder device may be used to elevate the strut pipe 24.

(Operation and others)
A liquid substance containing coal tar and safe water is introduced into the separation tank 2 and separated by specific gravity (static separation) into the upper safe water layer ARA 2 and the lower tar layer ARA 1. There is a possibility that slag 7 such as tar (oil) and sludge is mixed in the cheap water constituting the low water layer ARA2 separated by specific gravity, but the low water constituting the low water layer ARA2 forms the mesh body 10. By passing through, the slag 7 having a size larger than a predetermined value is captured by the mesh body 10. As a result, the slag 7 having a size equal to or larger than a predetermined value is removed from the Aquatic layer ARA2 located downstream from the installation position of the mesh body 10. The cheap water constituting the cheap water layer ARA2 in such a state is discharged from the cheap water discharge port 4 and reused.

By providing the mesh body 10 in this way, the slag 7 such as tar and sludge mixed in the recycled cheap water is significantly filtered, and the particle size of the remaining slag 7 is also small. This makes it possible to suppress the clogging of the spray nozzle for cooling even if the recovered aqueous water is used for cooling the coke oven gas.
Further, when the mesh body 10 is used for a long time, tar (oil content), sludge, and the like adhere to the mesh body 10 more and more. If the mesh body 10 is clogged due to use over time, the cheap water may not flow and the cheap water may be caught in the tar layer ARA1.

In order to prevent this, the mesh body cleaning device 20 is periodically operated to blow high-temperature fluid from the plurality of nozzles 25 onto the mesh body 10 while raising and lowering the nozzle body 22. As a result, the slag 7 adhering to the mesh body 10 is melted by a high-temperature fluid to facilitate peeling, and is peeled off toward the upstream side of the separation tank 2 by injection pressure. As a result, the mesh body 10 is washed.
Here, when the worker manually cleans the mesh body 10 in the separation tank 2 without using the mesh body cleaning device 20, for example, the worker forms the ceiling portion 2A. A special jig is inserted in the opening, and steam is injected toward the mesh body 10 to remove the clogging.

However, it is not preferable in terms of safety and health because the worker sucks in the odor leaking from the opening of the ceiling portion 2A during the cleaning of the mesh body 10. Here, tar is a second type of specified chemical substance. In addition, the opening must be large enough to accommodate one person, and if it falls, there is a risk of a serious disaster, so a lifeline is essential. Further, if an object is dropped from the opening, there is a risk that the tar sludge accumulated at the bottom of the separation tank will be caught in the scraper 3 and the operation of the tar decanter device will be stopped. In addition, since the operator has to move the heavy jig up, down, left, and right in the separation tank, it takes a long time to work, which is one of the difficult tasks.

On the other hand, in the present embodiment, by adopting the above-mentioned mesh body cleaning device 20, it is possible to more safely and efficiently remove the clogging of the mesh body 10 in the tar decanter device.
Here, the cleaning of the mesh body 10 had to be performed every day while using the tar decanter device. It took about 20 to 30 minutes to clean the mesh body 10 when it was performed manually as described above, but it was confirmed that cleaning can be performed in about 5 minutes when the above mesh body cleaning device 20 is used. did.

(others)
In the above description, a configuration for separating and removing the slag 7 from the safe water layer ARA 2 in the separation tank 2 will be described as an example. The above-mentioned mesh body cleaning device 20 may be adopted for a tank configuration in which the liquid layer is arranged in the liquid layer containing the slag 7 and the liquid constituting the liquid layer is passed through the mesh body 10 to be filtered.
Further, the present embodiment may have a configuration in which the mesh body cleaning device 20 is not provided in the separation tank 2.

(Effects, etc.)
(1) In the tar decanter device 1, the present embodiment is a mesh body that is arranged in front of the cheap water discharge port 4 and suppresses the movement of the slag 7 contained in the cheap water layer ARA 2 to the cheap water discharge port 4. 10 is provided.
According to this configuration, the cheap water in the cheap water layer ARA 2 passes through the mesh body 10 to filter the slag portion 7, and then is discharged from the cheap water discharge port 4. That is, the slag 7 contained in the safe water is captured by the mesh body 10 in the eyes of the mesh body 10. As a result, the slag 7 in the safe water collected from the safe water discharge port 4 is reduced. Further, the size of the recovered slag 7 in the safe water can be suppressed to less than the size of the mesh of the mesh body 10.

(2) A mesh body cleaning device provided with a plurality of nozzles 25 arranged to face the surface of the mesh body 10 on the side of the safe water discharge port 4 and capable of injecting a fluid having a temperature higher than that of the cheap water layer ARA 2 toward the mesh body 10. 20 is provided.
By capturing the slag 7 in the eyes of the mesh body 10, the flow resistance in the mesh body 10 increases with time.
On the other hand, according to this configuration, the oil content adhering to the mesh body 10 is removed by injecting a fluid (for example, steam) having a temperature higher than that of the safe water layer ARA2 (liquid layer) onto the surface of the mesh body 10 from the downstream side. Further, the slag 7 is peeled off from the mesh body 10 toward the upstream side by the injection pressure, and the mesh body 10 is washed. As a result, the flow resistance of the mesh body 10 is reduced.

(3) The fluid to be injected from the nozzle 25 is preferably steam.
According to this configuration, by using steam which is a gas, it is possible to reduce the weight of the fluid and to easily use a high temperature fluid.

(4) The mesh body cleaning device 20 includes an elevating mechanism for raising and lowering a plurality of nozzles 25 up and down.
According to this configuration, the entire mesh body 10 can be washed.
It should be noted that, for example, if the nozzle 25 is to be arranged for each stitch of the mesh body 10, the nozzle body 22 may hinder the movement of the safe water layer ARA2, which is not preferable. On the other hand, by raising and lowering, the pitch between the upper and lower nozzles 25 can be set large, and the weight of the nozzle body 22 can be reduced.

(5) The elevating mechanism includes a counterweight 33 for a nozzle body 22 having a plurality of nozzles 25, an air box 31 connected to the plurality of nozzles 25, and an air pressure feeding device 35 capable of pumping air to the air box 31. To prepare for.
According to this configuration, the nozzle body 22 constituting the plurality of nozzles 25 can be easily moved up and down with a simple configuration.

1 Tar decanter device 2 Separation tank 2A Ceiling part 3 Scraper 4 Safe water discharge port 5 Tar discharge port 6 Liquid substance supply pipe 10 Mesh body 20 Mesh body cleaning device 21 Main pillar pipe 22 Nozzle body 23 Nozzle header 24 Strut pipe 25 Nozzle 26 Fluid pipeline 31 Air box 33 Counter weight ARA1 Tar layer ARA2 Low water layer

Claims (9)

The liquid substance containing tar and cheap water generated from the coke oven is supplied to the upstream side of the separation tank, and the supplied liquid substance is separated into the tar layer and the cheap water layer by specific gravity, and the cheap water in the above low water layer is separated. It is a tar decanter device that discharges from the cheap water discharge port provided on the downstream side.
A tar decanter device provided in front of the safe water discharge port and provided with a mesh body that suppresses the movement of slag contained in the safe water layer to the safe water discharge port. It is provided with a mesh body cleaning device which is arranged to face the surface of the mesh body on the side of the safe water discharge port and has a plurality of nozzles capable of injecting a fluid having a temperature higher than that of the cheap water layer toward the mesh body. The tar decanter device according to claim 1. The tar decanter device according to claim 2, wherein the fluid is steam. The tar decanter device according to claim 2 or 3, wherein the mesh body cleaning device includes an elevating mechanism for raising and lowering the plurality of nozzles up and down. The elevating mechanism includes a counterweight for a nozzle body provided with the plurality of nozzles, an air box connected to the nozzle body provided with the plurality of nozzles, and an air pressure feeding device capable of pumping air to the air box. The tar decanter device according to claim 4, wherein the tar decanter device is provided. A liquid substance containing tar and cheap water generated by cooling and cleaning the coke oven gas is supplied upstream of the separation tank, and the supplied liquid substance is separated into the tar layer and the cheap water layer by specific gravity in the separation tank. A safe water separation method characterized in that the cheap water constituting the safe water layer after separation is discharged from a cheap water discharge port provided on the downstream side via a mesh body. The sixth aspect of claim 6 is characterized in that clogging of the mesh body is reduced by injecting a fluid having a temperature higher than the temperature of the cheap water layer onto the surface of the mesh body from the safe water discharge port side. Ansui separation method. A mesh body cleaning device that is placed in a liquid layer containing slag and cleans a mesh body through which the liquid constituting the liquid layer passes, and the liquid is applied to the surface of the mesh body from the downstream side in the moving direction of the liquid. A mesh body cleaning device comprising a plurality of nozzles capable of injecting a fluid having a temperature higher than that of a layer toward the mesh body. The mesh body cleaning device according to claim 8, further comprising an elevating mechanism for raising and lowering the plurality of nozzles up and down.

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