Treatment method of oxidation liquid in hydrogen peroxide extraction process

Abstract

The invention belongs to the technical field of hydrogen peroxide preparation, and particularly relates to a method for treating oxidation liquid in a hydrogen peroxide extraction process, which comprises the following steps: S1, feeding the oxidation liquid subjected to the extraction process into a pretreatment reactor filled with a reduction catalyst for pretreatment; s2, the pretreated oxidation liquid is fed into a vacuum dehydration tank for dehydration, an oil phase discharged by the vacuum dehydration tank is the oxidation liquid and is fed into a recovery tank for cyclic utilization, and mixed gas discharged by the vacuum dehydration tank is fed into a tail gas treatment device; and S3, separating oxidation liquid and vaporous water in the mixed gas by virtue of a tail gas treatment device, directly discharging the vaporous water obtained by separation, and feeding the oxidation liquid into a recovery tank for cyclic utilization. Through a serial process of pretreatment, vacuum dehydration and tail gas separation, free water in the oxidation liquid is removed to meet the circulation requirement, and the oxidation liquid carried in the tail gas of the vacuum dehydration tank can be recycled.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen peroxide preparation, and particularly relates to a treatment method for oxidation liquid in a hydrogen peroxide extraction process. BACKGROUND

[0002] The anthraquinone method is a mainstream method for preparing hydrogen peroxide in the industry at present, and has advantages such as mature process, high product purity and suitability for large-scale production. In the anthraquinone method for preparing hydrogen peroxide, the oxidation liquid after extraction is an important circulating material, and the anthraquinone solutes and solvents contained in the oxidation liquid can be recycled into the reaction cycle through recovery treatment.

[0003] At present, a vacuum dewatering tank is generally used in the industry to perform dewatering treatment on the oxidation liquid after extraction, so as to remove free water in the oxidation liquid, avoid catalyst deactivation and meet the requirement of recycling. However, in the operation process of the vacuum dewatering tank, a small amount of oxidation liquid is entrained in the mixed gas discharged from the vacuum dewatering tank. Since the oxidation liquid is dispersed in the mixed gas in the form of tiny droplets, if the entrained oxidation liquid is directly discharged with the tail gas, not only the raw materials such as anthraquinone solutes and solvents will be wasted, but also the atmosphere will be polluted, which does not meet the environmental protection requirement. SUMMARY

[0004] In order to solve the problems existing in the prior art, the application provides a treatment method for oxidation liquid in a hydrogen peroxide extraction process, which is a series process of pretreatment, vacuum dewatering and tail gas separation, and can not only remove free water in the oxidation liquid to meet the recycling requirement, but also recycle the oxidation liquid entrained in the tail gas of the vacuum dewatering tank.

[0005] The specific technical scheme adopted by the application is as follows: A treatment method for oxidation liquid in a hydrogen peroxide extraction process, comprising the following steps: S1, sending the oxidation liquid after the extraction process into a pretreatment reactor filled with a reduced catalyst for pretreatment; S2, sending the oxidation liquid after the pretreatment into a vacuum dewatering tank for dewatering, sending the oil phase of the oxidation liquid discharged from the vacuum dewatering tank to a recovery tank for recycling, and sending the mixed gas discharged from the vacuum dewatering tank to a tail gas treatment device; S3, separating the oxidation liquid and gaseous water in the mixed gas by means of the tail gas treatment device, directly discharging the gaseous water obtained by the separation, and sending the oxidation liquid to the recovery tank for recycling.

[0006] The reduced catalyst comprises a palladium-carbon catalyst or a platinum-carbon catalyst, the temperature for the pretreatment is 30-50 DEG C, and the reaction time is 10-20 min.

[0007] The tail gas treatment device comprises a shell, an air inlet pipe and an air outlet pipe arranged on the shell, a flow equalizing assembly and a flow guiding assembly arranged in the shell, a partition plate arranged between the flow equalizing assembly and the flow guiding assembly, a flow equalizing chamber and a separation chamber formed by the partition plate in the shell, and the mixed gas enters the flow equalizing chamber through the air inlet pipe and is flow-equalized, and the flow-equalized mixed gas enters the separation chamber and separates the oxidizing liquid from the gaseous water.

[0008] An oil discharge pipe is further arranged below the shell, the oxidizing liquid obtained by separating the mixed gas slides to the bottom of the shell along the side wall of the shell and is sent to a recovery tank through the oil discharge pipe.

[0009] An oil collecting ring is further arranged in the separation chamber along the circumference of the shell, the oil collecting ring is symmetrically arranged on both sides of the flow guiding assembly, the oil discharge pipe is arranged between the oil collecting rings on both sides, and the oil collecting ring blocks the escape of the oxidizing liquid and collects the oxidizing liquid to be discharged into the oil discharge pipe.

[0010] The circumferential side of the flow guiding assembly is rotationally connected to the inner wall of the shell through a bearing, the flow guiding assembly has the freedom of rotation around the axis of the shell, a plurality of groups of flow guiding assemblies are arranged along the axis of the shell, the mixed gas is subjected to centrifugal motion through the rotation of the flow guiding assembly and is separated into the oxidizing liquid and the gaseous water.

[0011] The flow guiding assembly comprises a rotating shaft and a flow guiding plate, the rotating shaft is suspended along the axis of the shell through a support frame fixedly connected to the inner wall of the shell, the rotating shaft is rotationally connected to the support frame, a plurality of groups of the flow guiding plates are radially and spacedly arranged around the rotating shaft, the flow guiding plate has a crimped structure, and the rotating shaft rotates through the thrust of the mixed gas acting on the surface of the flow guiding plate.

[0012] The temperature of the flow guiding plate is 105-120 DEG C.

[0013] The flow equalizing assembly comprises a flow equalizing pipe, a plurality of groups of the flow equalizing pipe are arranged in a honeycomb shape on the surface of the partition plate, the flow equalizing pipe is arranged along the axis of the shell, the air inlet pipe is arranged on the outer wall of the flow equalizing chamber close to the partition plate, the input end of the flow equalizing pipe is located on the side of the flow equalizing chamber away from the partition plate, and the output end of the flow equalizing pipe penetrates through the partition plate and communicates with the separation chamber.

[0014] The flow equalizing assembly further comprises a pressurizing pipe, the pressurizing pipe is connected to the port of the flow equalizing pipe and forms the output end of the flow equalizing pipe, the diameter of the pressurizing pipe is smaller than that of the flow equalizing pipe, and a sealing ring is arranged at the joint of the pressurizing pipe and the flow equalizing pipe.

[0015] The flow equalizing assembly further comprises an overflow hole and an overflow weir, the overflow hole is located at the bottom of the partition plate, and the overflow weir is arranged in the separation chamber and close to the overflow hole.

[0016] The beneficial effects of the present application are: 1、The present application is a series process of pretreatment, vacuum dewatering and tail gas separation, which not only removes free water in the oxidation liquid to meet the recycling requirement, but also recovers the oxidation liquid entrained in the tail gas of the vacuum dewatering tank.

[0017] Firstly, the residual hydrogen peroxide in the oxidation liquid is removed by reduction reaction with the catalyst through pretreatment, and then the free water and other aqueous phase substances in the oxidation liquid are removed by dewatering treatment to avoid the deactivation of the catalytic material in the oxidation liquid. Since a small amount of oxidation liquid is entrained in the mixed gas discharged from the exhaust end of the vacuum dewatering tank, the mixed gas is sent to the tail gas treatment device for gas-liquid separation, which not only recovers the oxidation liquid entrained in the mixed gas, but also only discharges gaseous water after separation without oxidation liquid pollution, avoiding the pollution of anthraquinone substances to the atmosphere and meeting the industrial waste gas emission standard.

[0018] 2、The present application separates the oxidation liquid from the gaseous water by means of the flow guide assembly. After the mixed gas contacts the flow guide assembly, the gaseous water will not condense after contacting the flow guide plate because the temperature of the flow guide plate is higher than the condensation temperature of water, and will still advance in the gaseous state and enter the exhaust pipe, while the oxidation liquid will be blocked after contacting the flow guide plate. At the same time, the flow guide plate will rotate under the push of the gaseous water, and the oxidation liquid adhered to the surface of the flow guide plate will be thrown to the inner wall of the shell under the action of centrifugal force and slide to the bottom of the shell along the oil discharge pipe for recovery. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structural schematic view of the tail gas treatment device; Figure 2 It is a sectional view of the tail gas treatment device; Figure 3 It is a front structural schematic view of the flow guide assembly; Figure 4 It is a structural schematic view of the flow guide plate; Figure 5 It is a structural schematic view of the flow equalizing assembly; In the drawings, 1 is a shell, 2 is an air inlet pipe, 3 is an exhaust pipe, 4 is an oil discharge pipe, 5 is a partition plate, 6 is a flow equalizing assembly, 601 is a flow equalizing pipe, 602 is a pressurizing pipe, 603 is a sealing ring, 604 is an overflow hole, 605 is an overflow weir, 7 is a flow guide assembly, 701 is a rotating shaft, 702 is a flow guide plate, 703 is a support frame, 704 is a bearing, and 8 is an oil collecting ring. DETAILED DESCRIPTION

[0020] The present application will be further described below in combination with the drawings and specific embodiments: The present application provides a treatment method for oxidation liquid in hydrogen peroxide extraction process, which comprises the following steps: S1, the oxidizing solution after the extraction process is sent to a pretreatment reactor filled with a reduced catalyst for pretreatment; S2, the pretreated oxidizing solution is sent to a vacuum dehydration tank for dehydration, the oil phase discharged from the vacuum dehydration tank is oxidizing solution and is sent to a recovery tank for recycling, and the mixed gas discharged from the vacuum dehydration tank is sent to a tail gas treatment device; S3, the mixed gas is separated into oxidizing solution and gaseous water by the tail gas treatment device, the gaseous water obtained by separation is directly discharged, and the oxidizing solution is sent to the recovery tank for recycling.

[0021] At present, a vacuum dehydration tank is generally used in the industry to dehydrate the oxidizing solution after extraction to remove free water in the oxidizing solution, avoid catalyst deactivation, and meet the recycling requirements. However, a small amount of oxidizing solution is entrained in the mixed gas discharged from the vacuum dehydration tank during operation. Since the part of the oxidizing solution is dispersed in the mixed gas in the form of tiny droplets, if the entrained oxidizing solution is directly discharged with the tail gas, not only the anthraquinone solute, solvent and other raw materials will be wasted, but also the atmosphere will be polluted, which does not meet the environmental protection requirements.

[0022] Therefore, the series process of pretreatment, vacuum dehydration and tail gas separation can not only remove free water in the oxidizing solution to meet the recycling requirements, but also recover the entrained oxidizing solution in the tail gas of the vacuum dehydration tank.

[0023] Firstly, the residual hydrogen peroxide in the oxidizing solution is removed by reduction reaction with the catalyst through pretreatment, and then the free water and other aqueous substances in the oxidizing solution are removed by dehydration treatment to avoid deactivation of the catalytic substances in the oxidizing solution. Since a small amount of oxidizing solution is entrained in the mixed gas discharged from the exhaust end of the vacuum dehydration tank, the mixed gas is sent to the tail gas treatment device for gas-liquid separation, which not only recovers the entrained oxidizing solution in the mixed gas, but also only discharges gaseous water after separation of the mixed gas, without oxidizing liquid pollutants, avoiding pollution of the atmosphere by anthraquinone substances, and meeting the industrial waste gas emission standard.

[0024] The reduced catalyst includes palladium-carbon catalyst or platinum-carbon catalyst, the pretreatment temperature is 30-50℃, and the reaction time is 10-20min.

[0025] The palladium-carbon catalyst or platinum-carbon catalyst can improve the decomposition efficiency of residual hydrogen peroxide in the oxidizing solution, and no by-product is generated in the reaction process. In addition, the reaction conditions of 30-50℃ will not damage the structure of anthraquinone solute in the oxidizing solution, ensuring the reaction activity of the recovered oxidizing solution.

[0026] For example, Figures 1-2As shown, the tail gas treatment device comprises a shell 1, an air inlet pipe 2 and an exhaust pipe 3 arranged on the shell 1, a flow equalizing assembly 6 and a flow guiding assembly 7 arranged in the shell 1, and a partition plate 5 arranged between the flow equalizing assembly 6 and the flow guiding assembly 7 in the shell 1. The chamber in the shell 1 is divided into a flow equalizing chamber and a separation chamber by the partition plate 5. The mixed gas enters the flow equalizing chamber through the air inlet pipe 2 and is flow-equalized. The flow-equalized mixed gas enters the separation chamber to separate the oxidizing liquid and the gaseous water in the mixed gas.

[0027] The mixed gas first enters the flow equalizing assembly 6 to be flow-equalized, so that the mixed gas enters the separation chamber at a stable flow rate and state. The partition plate 5 completely separates the flow equalizing chamber and the separation chamber, preventing the separated gaseous water and oxidizing liquid from mixing again and ensuring the separation effect. When the mixed gas contacts the flow guiding assembly 7, the gaseous water does not condense after contacting the flow guiding plate 702 because the temperature of the flow guiding plate 702 is higher than the condensation temperature of water, and the gaseous water still advances in a gaseous state and enters the exhaust pipe 3. The oxidizing liquid is blocked after contacting the flow guiding plate 702. At the same time, the flow guiding plate 702 rotates under the push of the gaseous water, and the oxidizing liquid adhered to the surface of the flow guiding plate 702 is thrown to the inner wall of the shell 1 under the action of centrifugal force and slides to the bottom of the shell 1 to be discharged through the oil discharge pipe 4 for recycling.

[0028] As shown in Figures 1-2 The shell 1 is further provided with an oil discharge pipe 4 below. The oxidizing liquid obtained by separating the mixed gas slides along the side wall of the shell 1 to the bottom of the shell 1 and is sent to a recycling tank through the oil discharge pipe 4.

[0029] The separated oxidizing liquid droplets slide to the bottom of the shell 1 along the side wall of the shell 1 under the action of gravity. The oil discharge pipe 4 is directly connected to the bottom of the shell 1, so that the settled oxidizing liquid can be discharged in time.

[0030] As shown in Figure 2 The separation chamber is further provided with an oil collecting ring 8 along the circumference of the shell 1. The oil collecting ring 8 is symmetrically arranged on both sides of the flow guiding assembly 7, and the oil discharge pipe 4 is located between the oil collecting rings 8 on both sides. The oil collecting ring 8 blocks the escape of the oxidizing liquid and collects the oxidizing liquid to be discharged into the oil discharge pipe 4.

[0031] The oil collecting ring 8 can concentrate the thrown oxidizing liquid in a local range, so that the oxidizing liquid at the bottom of the shell 1 can flow accurately into the oil discharge pipe 4, avoiding the scattering of the oxidizing liquid and the failure to converge into the oil discharge pipe 4.

[0032] As shown in Figures 2-3 The circumference of the flow guiding assembly 7 is rotatably connected to the inner wall of the shell 1 by bearings. The flow guiding assembly 7 has the freedom to rotate around the axis of the shell 1. The flow guiding assembly 7 is arranged in multiple groups along the axis of the shell 1. The mixed gas forms a centrifugal motion by the rotation of the flow guiding assembly 7 and separates the oxidizing liquid and the gaseous water.

[0033] The present application drives the guide plate 702 to rotate by the thrust of the mixed gas itself, without the need of a motor, thereby reducing the energy consumption and complexity of the equipment, and avoiding the problem that the oily working liquid easily corrodes the motor.

[0034] While the mixed gas drives the guide plate 702 to rotate, the rotation of the guide plate 702 acts on the mixed gas in the opposite direction, and the mixed gas moves centrifugally with the guide plate 702. The density of the oxidizing liquid droplets is much greater than that of the gaseous water, and under the action of centrifugal force, the oxidizing liquid moves to the inner wall of the shell 1, while the gaseous water moves to the center, thereby realizing gas-liquid separation.

[0035] As shown in Figures 2-4 , the guide assembly 7 includes a rotating shaft 701 and a guide plate 702. The rotating shaft 701 is suspended along the axis of the shell 1 by means of a support frame 703 fixedly connected to the inner wall of the shell 1. The rotating shaft 701 is rotationally connected to the support frame 703. The guide plate 702 is arranged in a radial manner with multiple groups centered on the rotating shaft 701. The guide plate 702 has a twisted structure. The rotating shaft 701 forms rotation by means of the thrust of the mixed gas acting on the surface of the guide plate 702.

[0036] The twisted structure of the guide plate 702 not only changes the flow direction of the mixed gas, enabling the guide assembly 7 to form self-rotation under the action of the mixed gas, but also increases the collision probability of the oxidizing liquid droplets with the guide plate 702, thereby promoting the gas-liquid separation effect.

[0037] The temperature of the guide plate 702 is 105-120℃.

[0038] The temperature of the guide plate 702 is maintained at 105-120℃, which can ensure that the water in the mixed gas always exists in a gaseous state, avoiding condensation into liquid water mixed with the oxidizing liquid. At the same time, controlling the temperature below 120℃ can avoid thermal decomposition of anthraquinone substances in the oxidizing liquid, thereby ensuring the quality of the recovered oxidizing liquid.

[0039] As shown in Figure 2 and Figure 5 , the flow equalizing assembly 6 includes a flow equalizing pipe 601. The flow equalizing pipe 601 is arranged in a honeycomb shape along the surface of the partition plate 5 with multiple groups. The flow equalizing pipe 601 is arranged along the axis direction of the shell 1. The gas inlet pipe 2 is arranged on the outer wall of the flow equalizing chamber close to one side of the partition plate 5. The input end of the flow equalizing pipe 601 is located in the flow equalizing chamber away from the partition plate 5. The output end of the flow equalizing pipe 601 penetrates through the partition plate 5 and communicates with the separation chamber.

[0040] The flow equalizing pipes 601 are evenly distributed in a honeycomb shape along the surface of the partition plate 5, and can uniformly distribute the mixed gas to each area of the separation chamber, so that the mixed gas enters the separation chamber at a stable flow rate and state. Meanwhile, the mixed gas can enter the separation chamber in parallel to the axial direction of the shell 1 through the guiding effect of the flow equalizing pipes 601, so that the mixed gas can hit the flow guide plates 702 and drive the flow guide plates 702 to rotate.

[0041] As shown in Figure 5 The flow equalizing assembly 6 further comprises a pressurizing pipe 602 connected with the ports of the flow equalizing pipes 601 and forming the output ends of the flow equalizing pipes 601. The diameter of the pressurizing pipe 602 is smaller than that of the flow equalizing pipes 601. A sealing ring 603 is arranged at the interface between the pressurizing pipe 602 and the flow equalizing pipes 601.

[0042] Through the design of the reduced diameter of the pressurizing pipe 602, the initial speed of the mixed gas entering the separation chamber can be improved, so that the flow guide plates 702 can obtain sufficient rotating power and better drive the flow guide plates 702 to rotate.

[0043] The flow equalizing assembly 6 further comprises an overflow hole 604 and an overflow weir 605. The overflow hole 604 is arranged at the bottom of the partition plate 5, and the overflow weir 605 is arranged in the separation chamber and close to the overflow hole 604.

[0044] Since a small amount of oxidizing liquid can remain in the flow equalizing chamber when the mixed gas enters the flow equalizing chamber, the overflow hole 604 is arranged to allow the oxidizing liquid in the flow equalizing chamber to enter the separation chamber and be discharged along the oil discharge pipe 4. Meanwhile, the overflow weir 605 is arranged, and through the blockage of the overflow weir 605, part of the oxidizing liquid can be gathered at the overflow hole 604 and form a liquid seal, so as to prevent the gas from escaping to the separation chamber along the overflow hole 604. In the initial stage of the exhaust gas treatment, a small amount of oxidizing liquid can be artificially added at the overflow weir 605 to form a liquid seal.

Claims

1. A method for treating the oxidation liquid in a hydrogen peroxide extraction process, characterized in that, Includes the following steps: S1. The oxidized liquid after the extraction process is sent to a pretreatment reactor filled with a reducing catalyst for pretreatment. S2. The pretreated oxidized liquid is sent to a vacuum dehydration tank for dehydration. The oil phase discharged from the vacuum dehydration tank is oxidized liquid and is sent to a recovery tank for recycling. The mixed gas discharged from the vacuum dehydration tank is sent to the tail gas treatment device. S3. The mixed gas is separated into oxidizing liquid and gaseous water by the tail gas treatment device. The separated gaseous water is discharged directly, while the oxidizing liquid is sent to the recovery tank for recycling.

2. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 1, characterized in that, The reducing catalyst includes a palladium-on-carbon catalyst or a platinum-on-carbon catalyst, and the pretreatment temperature is 30-50℃, and the reaction time is 10-20 min.

3. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 1, characterized in that, The exhaust gas treatment device includes a housing (1) and an intake pipe (2) and an exhaust pipe (3) disposed on the housing (1). A flow equalization component (6) and a flow guiding component (7) are disposed inside the housing (1). A partition plate (5) is disposed between the flow equalization component (6) and the flow guiding component (7) inside the housing (1). The chambers inside the housing (1) are separated by the partition plate (5) to form a flow equalization chamber and a separation chamber. The mixed gas enters the flow equalization chamber along the intake pipe (2) for flow equalization. The mixed gas after flow equalization enters the separation chamber to separate the oxidized liquid and gaseous water in the mixed gas. The gaseous water is discharged along the exhaust pipe (3).

4. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 3, characterized in that, An oil drain pipe (4) is also provided below the shell (1). The oxidized liquid obtained by the separation of mixed gas slides down the side wall of the shell (1) to the bottom of the shell (1) and is sent to the recovery tank along the oil drain pipe (4).

5. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 4, characterized in that, An oil collecting ring (8) is also provided in the separation chamber along the circumference of the shell (1). The oil collecting ring (8) is symmetrically arranged on both sides of the flow guiding component (7). The oil drain pipe (4) is located between the oil collecting rings (8) on both sides. The oil collecting ring (8) prevents the oxidizing liquid from escaping and collects the oxidizing liquid and sends it into the oil drain pipe (4) for discharge.

6. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 3, characterized in that, The peripheral side of the flow guide assembly (7) is rotatably connected to the inner wall of the shell (1) by means of the bearing (704). The flow guide assembly (7) has a degree of freedom to rotate around the axis of the shell (1). Multiple sets of flow guide assemblies (7) are arranged along the axis of the shell (1). The mixed gas forms centrifugal motion by means of the rotation of the flow guide assembly (7) and separates the oxidizing liquid and gaseous water.

7. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 6, characterized in that, The flow guiding assembly (7) includes a rotating shaft (701) and a flow guiding plate (702). The rotating shaft (701) is suspended along the axis of the housing (1) by means of a support frame (703) fixedly connected to the inner wall of the housing (1). The rotating shaft (701) is rotatably connected to the support frame (703). Multiple sets of flow guiding plates (702) are arranged radially with the rotating shaft (701) as the center. The flow guiding plate (702) has a twisted structure. The rotating shaft (701) rotates by means of the thrust of the mixed gas acting on the surface of the flow guiding plate (702).

8. The method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 3, characterized in that, The flow equalization assembly (6) includes a flow equalization tube (601). Multiple sets of the flow equalization tube (601) are arranged in a honeycomb pattern along the surface of the partition plate (5). The flow equalization tube (601) is arranged along the axial direction of the housing (1). The air inlet pipe (2) is arranged on the outer wall of the flow equalization chamber near the partition plate (5). The input end of the flow equalization tube (601) is located in the flow equalization chamber on the side away from the partition plate (5). The output end of the flow equalization tube (601) passes through the partition plate (5) and communicates with the separation chamber.

9. A method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 8, characterized in that, The flow equalization assembly (6) further includes a pressurizing pipe (602), which is connected to the port of the flow equalization pipe (601) and forms the output end of the flow equalization pipe (601). The diameter of the pressurizing pipe (602) is smaller than the diameter of the flow equalization pipe (601), and a sealing ring (603) is provided at the interface between the pressurizing pipe (602) and the flow equalization pipe (601).

10. A method for treating the oxidation liquid in a hydrogen peroxide extraction process according to claim 3, characterized in that, The flow equalization assembly (6) also includes an overflow hole (604) and an overflow weir (605). The overflow hole (604) is located at the bottom of the partition plate (5), and the overflow weir (605) is located in the separation chamber and is set near the overflow hole (604).

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