JP6653237B2 - Wastewater treatment device and wastewater treatment method - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method for treating a liquid used for cleaning exhaust gas, and more particularly, to improving the recovery efficiency of solid components contained in the liquid used for cleaning exhaust gas. The present invention relates to a wastewater treatment apparatus and a wastewater treatment method that can efficiently treat oil in a liquid used for cleaning exhaust gas.

  Various exhaust gas treatment devices (hereinafter, sometimes referred to as scrubbers) that bring seawater into contact with exhaust gas generated from the main engine of a ship and collect solid components such as dust and sulfide in the exhaust gas into seawater are proposed. (For example, see Patent Document 1).

  Patent Document 1 discloses an exhaust system in which waste water from a scrubber (hereinafter, sometimes referred to as scrubber waste water) is separated into a solid component and a liquid by a centrifugal separator, the solid component is stored in a sludge tank, and the liquid is discharged outboard. A gas processing device is proposed.

  During the supply of the scrubber wastewater to the centrifuge, the oil contained in the scrubber wastewater may be vigorously mixed with seawater and emulsified. Emulsions generated by emulsification of oil (hereinafter sometimes referred to as scum) may include solid components such as dust in scrubber drainage. This scum is a creamy fluid having a high viscosity and has a lower specific gravity than a scrubber drainage mainly composed of seawater.

  Since the scum has a lower specific gravity than the scrubber wastewater, when treated with a centrifuge, the scum was discharged together with the scrubber wastewater. In other words, solid components such as dust contained in the scum could not be separated and recovered from the scrubber drainage. Therefore, it has conventionally been difficult to improve the efficiency of collecting solid components such as dust contained in the scrubber wastewater.

  In addition, solid components such as dust may adhere to the oil that has not been emulsified. The solid component adhering to the oil component apparently has a specific gravity smaller than that of a liquid such as seawater, so that it was difficult to separate the solid component from the liquid by a centrifuge. Therefore, it has been difficult to improve the collection efficiency of solid components such as dust contained in the scrubber wastewater.

  On the other hand, since the scrubber wastewater cannot be discharged outboard when it contains oil, it is necessary to install equipment for removing oil from the scrubber wastewater. Since the number of devices that constitute the wastewater treatment device increases, a problem occurs in that the manufacturing cost of the wastewater treatment device increases. Also, it was necessary to secure a space for installing equipment for removing oil. When this equipment is installed on a ship, there is a problem that the space for storing cargo and the like must be reduced.

JP-A-2004-08933

  The present invention has been made in view of the above problems, and its object is to improve the recovery efficiency of solid components contained in a liquid used for cleaning exhaust gas, and to improve the efficiency of liquid used for cleaning exhaust gas. It is an object of the present invention to provide a wastewater treatment device and a wastewater treatment method that can efficiently treat oil.

The wastewater treatment apparatus of the present invention that achieves the above object is a buffer tank that stores a liquid containing a solid component in exhaust gas used for cleaning exhaust gas, and the liquid stored in the buffer tank and the liquid. In a wastewater treatment device including a solid-liquid separator for separating a solid component and a sludge tank for storing the solid component, a stirring mechanism for stirring the liquid stored in the buffer tank, and the buffer tank A collecting mechanism for collecting scum floating on the liquid surface of the liquid stored in the first area where the stirring mechanism is arranged and a second area where the collecting mechanism is arranged. A weir for dividing the buffer tank, wherein the weir is formed at an upper end located at a position lower than the liquid level, and is formed near a lower end, and the weir is formed from the first area to the second area. And a circulation port for moving and said Rukoto.

The wastewater treatment method of the present invention is used for washing exhaust gas, after storing a liquid containing a solid component in the exhaust gas in a buffer tank, the liquid and the solid component are separated by a solid-liquid separator, in waste water treatment method for storing the solid components in the sludge tank, the place the stirring mechanism in the buffer tank, and agitating the liquid stored in the buffer tank in this stirring mechanism, the liquid level of the liquid A collection mechanism is arranged in the vicinity, and the scum floating on the liquid surface is collected by the collection mechanism, and the buffer tank is divided into a first area where the stirring mechanism is arranged and a second area where the collection mechanism is arranged. A weir is provided to divide the liquid and the scum from the upper end of the weir from the first area to the second area, and a flow port is formed near the lower end of the weir. To characterized in that moving the liquid and the solid components from the first zone from the flow port to said second section.

  According to the present invention, since a solid component such as dust contained in the scum can be recovered by the recovery mechanism, it is advantageous to improve the recovery efficiency of the solid component contained in the liquid used for cleaning the exhaust gas. It is. Since the solid component adhering to the oil can be collected as scum, it is advantageous to improve the collection efficiency of the solid component.

  The contact and agitation of dust, oil, seawater and the like can be actively promoted by the stirring mechanism, so that the oil is emulsified and scum is easily generated. The generation of scum makes it easier to recover oil from the liquid used for cleaning the exhaust gas, and is therefore advantageous for efficiently recovering oil without increasing the manufacturing cost of the wastewater treatment device.

  It is possible to adopt a configuration including a pressure reducing mechanism that is disposed on the upstream side of the buffer tank and that reduces the pressure of the liquid used for cleaning the exhaust gas.

  By reducing the pressure of the liquid used for cleaning the exhaust gas by the pressure reducing mechanism, bubbles are generated in the liquid and scum is easily generated. By actively collecting the generated scum, the amount of oil in the liquid can be reduced.

  A configuration including a foaming agent supply mechanism that supplies the foaming agent to the buffer tank can be employed. The supply of the foaming agent easily causes scum in the buffer tank. Most of the oil in the liquid used for cleaning the exhaust gas can be used as scum, which is advantageous for efficiently recovering the oil.

  A configuration may be provided that includes a neutralizing agent supply mechanism that supplies a neutralizing agent to the buffer tank. By adjusting the pH in the buffer tank to a predetermined range by supplying the neutralizing agent, scum is easily generated in the buffer tank.

  It has a weir that divides the buffer tank into a first area where the stirring mechanism is arranged and a second area where the recovery mechanism is arranged, where the weir is located at a lower position than the liquid level and near the lower end. And a flow port for moving the liquid from the first section to the second section.

According to this configuration, the liquid in the second area is less likely to be affected by the agitation by the agitation mechanism and the flow of the liquid supplied from the supply pipe to the first area by the provision of the weir. The scum collected near the collection mechanism in the second area is difficult to disperse due to the flow of the liquid, so that the scum can be easily collected.

  When the wastewater treatment device is installed on a ship, a configuration in which the buffer tank is arranged near the bottom of the ship can be adopted. Since the buffer tank is less affected by the sway of the ship, scum can be efficiently collected.

It is explanatory drawing which illustrates the waste water treatment apparatus of this invention. It is explanatory drawing which illustrates the weir of FIG. It is explanatory drawing which illustrates the modification of the weir of FIG. It is explanatory drawing which illustrates another embodiment of a waste water treatment apparatus. 5 is a graph illustrating the relationship between the separation efficiency and the concentration of a foaming agent added. 5 is a graph illustrating a relationship between separation efficiency and pH in a buffer tank. FIG. 4 is an explanatory diagram illustrating a modification of FIG. 1. It is a graph which illustrates the relationship between a water content and a collection interval.

  Hereinafter, a wastewater treatment apparatus and a wastewater treatment method of the present invention will be described based on an embodiment shown in the drawings.

  As exemplified in FIG. 1, the wastewater treatment apparatus 1 of the present invention is capable of removing solid components such as dust and sulfide in exhaust gas by bringing a liquid such as seawater or fresh water into contact with exhaust gas discharged from a ship or the like. It is provided in the exhaust gas processing device 2 that collects in the liquid.

  The wastewater treatment apparatus 1 includes a buffer tank 3 that is used for cleaning exhaust gas and stores a liquid containing a solid component in the exhaust gas, and a solid tank that separates the liquid stored in the buffer tank 3 from the solid component. The apparatus includes a liquid separator 4 and a sludge tank 5 for storing a solid component. In this embodiment, the solid-liquid separator 4 is formed of a hollow fiber membrane.

  In addition, a pump P is installed in a pipe communicating with the scrubber 2 and the buffer tank 3. The pump P can be appropriately installed at a necessary place.

  The buffer tank 3 has a supply pipe 6 for supplying scrubber wastewater discharged from the scrubber 2 to the buffer tank 3, a stirring mechanism 7 for stirring the scrubber wastewater supplied to the buffer tank 3, and a liquid in the buffer tank 3. A collection mechanism 8 for collecting suspended matter floating on the surface is provided.

  In this embodiment, the stirring mechanism 7 is configured as a rotary stirring mechanism that stirs the scrubber drainage by rotating the blades arranged in the scrubber drainage by the power of the motor M. The configuration of the stirring mechanism 7 is not limited to the above, and it is sufficient that the scrubber drainage in the buffer tank 3 can be stirred. The stirring mechanism 7 may be constituted by a bubble stirring mechanism for stirring the scrubber drainage by supplying bubbles into the buffer tank 3, for example, or by a stirring mechanism combining a plurality of methods such as a rotary type and a bubble type. You may. That is, the stirring mechanism 7 may be configured as a stirring mechanism that rotates the blades disposed in the buffer tank 3 and generates air bubbles from the blades.

The inner diameter of the supply pipe 6 is set to such a size that the inside of the supply pipe 6 is always filled with scrubber drainage discharged from the scrubber 2. In addition, a weir 9 that divides the inside of the buffer tank 3 is disposed in a first section F1 in which the stirring mechanism 7 is disposed and in a second section F2 in which the recovery mechanism 8 is disposed.

  The scrubber wastewater supplied from the scrubber 2 to the buffer tank 3 through the supply pipe 6 is mainly composed of a liquid such as seawater. However, solid components such as dust and sulfide collected by washing exhaust gas, It contains oil such as unburned fuel and cylinder oil.

  In the process of supplying the scrubber wastewater from the scrubber 2 to the buffer tank 3, scum S is generated due to the emulsification of the oil. The scum S is generated when the oil and seawater are vigorously stirred in the supply pipe 6 and the buffer tank 3. The scum S is creamy and has a property of floating in a liquid such as seawater, and contains a solid component such as dust.

  As illustrated in FIG. 1, the lower end 6 a of the supply pipe 6 is set lower than the liquid level 10 of the liquid stored in the buffer tank 3. Since the scrubber drainage is supplied into the buffer tank 3 while filling the supply pipe 6, the scrubber drainage is supplied into the liquid without colliding with the liquid level 10 in the buffer tank 3. Therefore, it is possible to prevent the scum S in the scrubber drainage from colliding with the liquid surface 10 and being broken and separated into small pieces. Since the scum S is supplied to the buffer tank 3 in a relatively large lump state, the scum S having a relatively small specific gravity floats on the liquid surface 10 and is easily collected.

  Further, since the scrubber wastewater in the first section F1 is stirred by the stirring mechanism 7, scum S is also generated in the first section F1 from the stirred oil and dust. That is, the oil in the scrubber drainage is positively changed to scum S by the stirring mechanism 7. The scum S generated in the first section F1 floats on the liquid surface 10.

  Since the upper end 9b of the weir 9 is set below the liquid level 10, the scum S floating on the liquid level 10 gradually moves toward the second section F2. Since the weir 9 is provided in the buffer tank 3, the movement of the liquid in the second section F2 is limited, and the liquid surface 10 hardly swings in the second section F2. That is, the liquid in the second section F2 is hardly affected by the flow of the liquid generated by the stirring mechanism 7.

  Since the liquid level 10 hardly swings in the second section F2, the scum S can be easily collected around the collecting mechanism 8. The scum S collected around the collection mechanism 8 is collected by the collection mechanism 8 and sent to the sludge tank 5.

  The recovery mechanism 8 according to the present embodiment includes an arm portion that collects the scum S floating on the liquid surface 10 of the liquid in the buffer tank 3 and a recovery portion that collects the scum S collected by the arm portion. It can be composed of a collecting device. The configuration of the recovery mechanism 8 is not limited to the above, and another configuration may be adopted as long as it has a function of recovering the scum S floating on the liquid surface 10 and sending it to the sludge tank 5. The recovery mechanism 8 may be constituted by, for example, a scum skimmer or an overflow pipe for setting an opening at a predetermined height and collecting the scum S flowing into the opening.

  The collecting mechanism 8 may be configured to continuously collect the scum S, but is preferably configured to intermittently collect the scum S every predetermined time, for example, 20 minutes. When the scum S is intermittently collected by the collection mechanism 8, the ratio of the scum S to the whole collected matter increases, and the amount of excess liquid sent to the sludge tank 5 together with the scum S can be suppressed. This is advantageous for reducing the volume of the installed sludge tank 5.

The scrubber drainage supplied to the buffer tank 3 moves from the first section F1 to the second section F2 mainly through the lower end 9a of the weir 9. Scum S of solid components contained in scrubber wastewater
The solid components that have not been taken into the tank are settled in the buffer tank 3 and move to the second section F2 together with the scrubber drainage.

  Most of the scrubber drainage in the buffer tank 3 is extracted from the middle layer of the second section F2, sent to the scrubber 2, and circulated through the scrubber 2 and the buffer tank 3. A portion of the scrubber drainage is extracted from the bottom surface 3a of the buffer tank 3 and sent to a solid-liquid separator 4 such as a hollow fiber membrane. The solid-liquid separator 4 separates and collects solid components from the scrubber wastewater. The scrubber drainage from which solid components have been removed by the solid-liquid separator 4 is returned to the second section F2 of the buffer tank 3 via the three-way valve 11. The scrubber wastewater returned from the solid-liquid separator 4 to the buffer tank 3 may be returned to the first section F1.

  The amount of liquid in the buffer tank 3 may increase due to water or the like contained in exhaust gas generated by combustion of fuel. In such a case, the three-way valve 11 disposed on the downstream side of the solid-liquid separator 4 is switched to discharge the liquid not to the buffer tank 3 but to the outside of the boat.

  With the configuration in which the collection mechanism 8 is installed in the buffer tank 3, the solid components included in the scum S can be collected and sent to the sludge tank 5. Since the solid components that were previously included in the scum S and could not be recovered by the centrifuge can be recovered, the recovery efficiency of the solid components can be improved.

  With the configuration in which the stirring mechanism 7 is provided, the oil component to which the solid component adheres can be positively changed to the scum S. Since the solid component that has adhered to the oil and could not be recovered conventionally can be recovered as scum S, the recovery efficiency of the solid component can be improved.

  With the configuration in which the solid components are collected in a state where the solid components are included in the scum S, the scrubber can be simply formed by a hollow fiber membrane or the like without installing a solid-liquid separator 4 requiring a large power such as a large centrifuge. Solid components can be collected relatively efficiently from wastewater. The hollow fiber membrane may be replaced with a new one after the hollow fiber membrane has been used for a predetermined period, or may be configured so as to perform backwashing by passing a liquid through the hollow fiber membrane in a direction opposite to the normal direction. The solid-liquid separator 4 is not limited to the hollow fiber membrane, and may be constituted by a small centrifuge having relatively low power consumption or a metal filter.

  Since the oil is collected by the collection mechanism 8 after the oil is positively changed to the scum S which is relatively easy to collect, there is no need for a complicated and large installation space for separating the oil from the scrubber drainage. This is advantageous for efficiently recovering the oil in the scrubber wastewater.

  Since the very small amount of oil that has been difficult to recover efficiently is recovered as scum S, the amount of oil in the scrubber drainage can be reduced. When discharging the scrubber wastewater outboard, it is advantageous to suppress the amount of oil contained in the liquid.

  As illustrated in FIG. 2, the upper end 9 b of the weir 9 is set at a position lower than the liquid level 10. At the lower end 9a of the weir 9, a distribution port 12 for moving scrubber drainage from the first section F1 to the second section F2 is formed. The solid component precipitated in the first section F1 moves to the second section F2 through the circulation port 12 together with the scrubber drainage, and is then sent to the solid-liquid separator 4.

  In this embodiment, a flow port 12 is formed over the entire lower end 9 a of the weir 9, so that the entire lower end 9 a of the weir 9 does not contact the buffer tank 3. That is, the entire gap formed between the lower end 9a of the weir 9 and the bottom surface 3a of the buffer tank 3 becomes the circulation port 12.

The circulation port 12 is not limited to this configuration, and it is sufficient that the scrubber drainage can move from the first section F1 to the second section F2. For example, the distribution port 12 may be formed in a part of the lower end 9 a of the weir 9. That is, the lower end 9a of the weir 9 may be configured such that the distribution port 12 is formed in a state where the lower end 9a is not in contact with the bottom surface 3a of the buffer tank 3, and the other end of the lower end 9a is fixed in contact with the bottom surface 3a.

  Further, as illustrated in FIG. 3, the distribution port 12 may be formed at a position above the lower end 9a. In this case, the entire lower end 9a of the weir 9 comes into contact with the bottom surface 3a of the buffer tank 3, and the solid component precipitated in the first section F1 is difficult to move to the second section F2. It is necessary to remove precipitated solid components. For example, a configuration may be adopted in which a pipe communicating between the bottom surface 3a of the first section F1 and the solid-liquid separator 4 is provided, and the solid component precipitated in the first section F1 is sent to the solid-liquid separator 4.

  By setting the weir 9, even if the liquid in the first section F1 is stirred by the stirring mechanism 7, the liquid in the second section F2 is less affected by this. That is, since the liquid in the second section F2 is close to a state where the liquid is settled, the scum S floats on the liquid surface 10 and the solid component is easily precipitated. The scum S collected near the collection mechanism 8 in the second section F2 is hardly dispersed by the flow of the scrubber drainage, so that the collection mechanism 8 can efficiently collect the scum S.

  Although the side end of the weir 9 illustrated in FIG. 2 is configured to be in contact with the inner wall surface of the buffer tank 3, a gap is formed between the side end of the weir 9 and the inner wall surface of the buffer tank 3, This gap may be used as the distribution port 12. The scrubber drainage can move from the first section F1 to the second section F2 via the gap.

  In the present invention, the weir 9 is not an essential requirement. Therefore, even with a configuration in which the weir 9 is not installed, the effect of the present invention can be obtained to a certain extent. On the other hand, depending on the rotation speed of the stirring mechanism 7 and the size of the buffer tank 3, the stirred scrubber drainage may not generate a large flow in the buffer tank 3. In such a case, the effect of the present invention can be sufficiently obtained even without the weir 9.

  When the scrubber 2 is configured to supply cleaning water such as seawater to a flow path through which exhaust gas circulates at a high pressure such as 0.4 MPa, the scrubber drainage is discharged from the scrubber 2 at a high pressure such as 0.4 MPa. . In such a case, the pressure reducing mechanism 13 may be installed on the upstream side of the supply pipe 6 as shown by a broken line in FIG. The pressure of the scrubber wastewater of 0.4 MPa is reduced to, for example, 0.1 MPa by the pressure reducing mechanism 13 and then supplied to the buffer tank 3. The position at which the pressure reducing mechanism 13 is installed is not limited to the above, and may be any position upstream of the buffer tank 3. For example, the pressure reducing mechanism 13 may be incorporated in the supply pipe 6.

  When the high-pressure scrubber drainage is depressurized by the decompression mechanism 13, bubbles are generated in the liquid, and scum S is easily generated. That is, the scum S can be more positively generated.

  When the scrubber 2 is configured to supply cleaning water to a flow path in which exhaust gas at atmospheric pressure circulates, for example, the scrubber drainage discharged from the scrubber 2 also has atmospheric pressure. In such a case, there is no need to install the pressure reducing mechanism 13.

  As illustrated in FIG. 4, the stirring mechanism 7 is configured by a bubble-type stirring mechanism that stirs scrubber drainage by supplying bubbles into the buffer tank 3. Since the scrubber drainage in the buffer tank 3 is stirred by bubbles generated from the bubble stirrer, scum S is easily generated in the buffer tank 3.

A third section F3 may be formed in the buffer tank 3. In this embodiment, the second weir 14 is disposed between the second section F2 and the third section F3. The upper end of the second weir 14 is fixed to the inner surface of the buffer tank 3. Since the upper end of the second weir 14 is in a closed state, the scum does not move from the second section F2 to the third section F3. The second weir 14 has a flow port 12 formed near the lower end. A pipe for supplying the liquid from the buffer tank 3 to the scrubber 2 is connected to the bottom of the third section F3.

  Most of the scum S floats on the liquid surface 10 in the first section F1 and the second section F2, and is collected in the sludge tank 5 via the collection mechanism 8 and the solid-liquid separator 4. Most of the solid components are taken into the scum S and collected by the collection mechanism 8, and the remaining solid components not taken into the scum S precipitate in the first section F1 and the second section F2 and go to the third section F3. After moving, it moves to the scrubber 2.

  Due to the configuration in which the second weir 14 is provided, the third section F3 is hardly affected by the stirring by the stirring mechanism 7 and the flow by the scrubber drainage supplied from the supply pipe 6. That is, since the liquid is in a relatively quiet state, it is advantageous to cause the scum S slightly remaining in the liquid to float on the liquid surface 10 to precipitate the solid components.

  The scum S and solid components are hardly contained in the liquid in the third section F3. That is, since a relatively clean liquid can be supplied to the scrubber 2 from the bottom surface of the third section F3, the scrubber 2 can be efficiently cleaned of exhaust gas.

  With the configuration in which the liquid to be supplied to the scrubber 2 is taken out from the bottom surface of the third section F3, it is possible to suppress the accumulation of solid components that have moved to the third section F3. Even if the solid component moves to the third section F3, its amount is small, so that even if the solid component is contained in the liquid sent to the scrubber 2, there is no effect. This solid component is eventually taken in and recovered by the scum S in the process of circulating from the scrubber 2 to the buffer tank 3.

  There is a possibility that the scum S moves to the third area F3, though slightly. In order to remove the scum S from the third section F3, a recovery pipe 15 for returning the liquid near the liquid level 10 of the third section F3 to the first section F1 may be provided.

  Since the liquid discharged from the solid-liquid separator 4 has a relatively clean state from which solid components have been removed, it is desirable to return the liquid to the third section F3 via the three-way valve 11. The structure in which the liquid returned from the solid-liquid separator 4 to the buffer tank 3 is returned to the third section F3 prevents the liquid surface 10 in the first section F1 or the second section F2 from swinging and the scum S from being shredded. it can.

  A configuration in which a foaming agent supply mechanism 16 that supplies the foaming agent to the buffer tank 3 can be provided. The foaming agent supply mechanism 16 has a function of adjusting the supply amount of the foaming agent according to the flow rate of the scrubber drainage supplied to the buffer tank 3. For example, methyl isobutyl carbinol (MIBC) or the like can be used as the foaming agent. In this case, the amount of the foaming agent added is about 10 to 120 ppm based on the mass of the scrubber wastewater.

An experiment was conducted to determine the relationship between the concentration of the foaming agent (%) and the separation efficiency (%) of the scrubber wastewater. As illustrated in FIG. 5, as the amount of the foaming agent added increases, the separation efficiency can be improved. In the present specification, the separation efficiency refers to a ratio defined by the following formula 1.
Separation efficiency (%) = (SS concentration of scrubber wastewater−SS concentration of treated water) / (SS concentration of scrubber wastewater) × 100 Formula 1

  Here, the SS concentration of the scrubber wastewater indicates the weight concentration (mg / L) of the suspended substance (solid component) in the scrubber wastewater supplied to the buffer tank 3, and the SS concentration of the treated water is stirred by the stirring mechanism 7 and recovered by the collection mechanism. 8 shows the weight concentration (mg / L) of the suspended substance (solid component) in the liquid after the scum S was removed.

  A configuration in which a neutralizing agent supply mechanism 17 that supplies a neutralizing agent to the buffer tank 3 can be provided. The neutralizer supply mechanism 17 has a function of adjusting the supply amount of the neutralizer in accordance with the pH of the scrubber wastewater in the buffer tank 3. As the neutralizing agent, for example, an alkaline substance such as caustic soda can be used.

  An experiment was performed to determine the relationship between the pH value in the buffer tank 3 and the separation efficiency (%) of the scrubber wastewater. As illustrated in FIG. 6, the separation efficiency can be improved as the pH value increases (as the pH becomes more alkaline). This is because the scum S is less likely to be generated as the pH value of the scrubber drainage decreases (increases in acidity).

  The pH value in the buffer tank 3 is monitored by a pH meter or the like, and when the pH becomes lower than a predetermined value, an alkaline substance such as caustic soda is supplied into the buffer tank 3 as a neutralizing agent. Specifically, the pH value in the buffer tank 3 is controlled to be 6.5 or more by the neutralizing agent supply mechanism 17. Desirably, the pH value in the buffer tank 3 is maintained at 9.0 or more. It is advantageous to positively generate scum S in the buffer tank 3 to improve the separation efficiency.

  In this embodiment, the solid-liquid separator 4 is constituted by a filter press, and dewaters the scum S collected by the collection mechanism 8. Since the liquid collected by the collection mechanism 8 can be removed together with the scum S, the volume of the scum S collected by the sludge tank 5 can be reduced. Since the sludge tank 5 can be made smaller, it is advantageous to reduce the size of the entire wastewater treatment apparatus 1.

  In the present invention, since most of the solid components contained in the scrubber wastewater can be included in the scum S, there is almost no need to treat the liquid in the buffer tank 3 with the solid-liquid separator 4. Since there is no need to remove solid components from a large amount of liquid, a filter press can be used as the solid-liquid separator 4. Filter presses cannot process as much as centrifuges, but dewatering efficiency is far greater than centrifuges. This is advantageous for suppressing the volume of sludge sent to the sludge tank 5.

  As illustrated in FIG. 7, a three-way valve 18 is arranged in the middle of a flow path for sending the liquid from the buffer tank 3 to the scrubber 2, and the liquid is supplied from the three-way valve 18 to the solid-liquid separator 4. it can. A three-way valve 11 for discharging liquid outboard is disposed downstream of the solid-liquid separator 4. One end of the three-way valve 11 communicates with the outside of the ship, and the other end is connected to the sludge tank 5.

  When the amount of liquid in the buffer tank 3 increases, the flow rate of the pump P disposed between the buffer tank 3 and the three-way valve 18 is temporarily increased and supplied to the scrubber 2 through the three-way valve 18. A part of the liquid to be sent is sent to the solid-liquid separator 4. The liquid that has passed through the solid-liquid separator 4 and meets the criteria for discharging outboard is discharged outboard through the three-way valve 11, and the liquid that does not meet the criteria is discharged through the three-way valve 11 in the sludge tank 5. Sent to

  It is desirable to install a sensor 19 and the like for measuring the amount of solid components in the liquid discharged from the solid-liquid separator 4 on the downstream side of the solid-liquid separator 4. A control mechanism 20 for switching the three-way valve 11 based on the value of the sensor 19 may be provided in the three-way valve 11.

Using a pump P for sending a liquid from the buffer tank 3 to the scrubber 2, the buffer tank 3
1 can be sent to the solid-liquid separator 4, so that the number of pumps P required can be reduced as compared with the embodiment illustrated in FIG. This is advantageous for suppressing the manufacturing cost of the wastewater treatment device 1.

  As illustrated in FIG. 7, a configuration in which the surface reformer 21 is installed in the flow path between the scrubber 2 and the supply pipe 6 can be adopted. The surface reformer 21 is arranged in parallel with the flow path between the pressure reducing mechanism 13 and the supply pipe 6, and a part of the scrubber wastewater supplied to the supply pipe 6 is supplied to the surface reformer 21. It is desirable to have a configuration. Since part, but not all, of the liquid supplied to the supply pipe 6 can be sent to the surface reformer 21, there is almost no possibility that the surface reformer 21 will adversely affect the overall circulation of the scrubber wastewater.

  The surface reformer 21 can be configured by, for example, a stirrer that stirs the supplied liquid in a state where a high shearing effect is generated. The configuration of the surface reformer 21 is not limited to the above, and any structure may be used as long as it can exert an effect of positively attaching solid components such as dust to oil. Since the solid component can be made to adhere to the oil component by the surface reformer 21 and then positively taken into the scum S, it is advantageous to improve the efficiency of separating the solid component.

  When an experiment was conducted to measure the separation efficiency by changing the condition of only the use or non-use of the surface reformer 21, the separation efficiency when the surface reformer 21 was not used was 59.4%. The efficiency became 74.5%. Although the absolute value of the separation efficiency differs depending on the configuration of the wastewater treatment device 1, it was found from experiments that the separation efficiency could be improved by using the surface reformer 21.

  The sensor 19 for measuring the amount of the solid component in the liquid discharged from the solid-liquid separator 4 and the surface reformer 21 can be used in combination. With this sensor 19, it is possible to detect a state where the liquid discharged from the solid-liquid separator 4 does not satisfy the criterion for discharging outboard. In such a case, based on the signal from the sensor 19, control for operating the surface reformer 21 or increasing the flow rate of the scrubber wastewater sent to the surface reformer 21 can be performed.

  The configurations of the three-way valve 18 and the surface reformer 21 illustrated in FIG. 7 can be appropriately combined with the embodiment illustrated in FIG.

An experiment of wastewater treatment was performed using the wastewater treatment device 1 illustrated in FIG. In the experiment, the capacity of the buffer tank 3 was 2.3 m ³ , the flow rate of the scrubber drainage supplied from the scrubber 2 to the buffer tank 3 was 10 m ³ / hr, and the residence time of the scrubber drainage in the first section F1 and the second section F2 was respectively set. For 6 min, the inner diameter of the supply pipe 6 was set to 65 mm.

  The scum S generated in the buffer tank 3 was collected by the collection mechanism 8 while changing the collection time interval. As illustrated by the squares in FIG. 8, the water content of the scum collected by the collection mechanism 8 was about 95% regardless of the collection interval. Here, the water content is the ratio of the mass of water to the total mass of the scum S collected by the collection mechanism 8. The collection interval is a time interval (min) at which the scum S is sent to the sludge tank 5 by operating the collection mechanism 8.

  For the above experiment, as a comparative example, the scrubber wastewater in the buffer tank 3 was supplied to a centrifugal separator, and the moisture content of the solid recovered was measured. As illustrated by a circle in FIG. 8, when the collection interval is 30 min, the water content is 98.5%, and even when the collection interval is 60 min, the water content is 97.8%. That is, the amount of water accompanying the solid component is larger when the solid component is collected by the centrifugal separator than when the solid component is collected as the scum S.

Note that the collection interval by the centrifuge is a time interval (min) for discharging the solid separated by the centrifuge from the centrifuge. In a centrifuge, the separation between liquid and solid proceeds as the collection interval increases, but the total amount of scrubber wastewater that can be treated by the centrifuge decreases as the collection interval increases, resulting in poor efficiency.

  As illustrated in FIG. 8, the efficiency of collecting solid components is significantly improved when the solid components are included in the scum S and collected as scum S, as compared with the comparative example in which the solid components are separated by a centrifuge. It is advantageous to actively generate the scum S and collect the solid component as the scum S in order to improve the collection efficiency of the solid component.

  When the flow of the scrubber drainage in the supply pipe 6 becomes turbulent, agitation proceeds and scum S is more likely to be generated. Therefore, the specific size varies depending on the flow rate of the scrubber drainage drained from the scrubber 2, but the inner diameter of the supply pipe 6 is preferably relatively large. Further, it is desirable that the flow rate of the scrubber drainage passing through the supply pipe 6 is relatively high.

  The wastewater treatment device 1 of the present invention can be used not only in a case where the wastewater treatment device 1 is installed and used in a ship or the like but also in a factory or the like. When the wastewater treatment device 1 is installed on a ship, it is desirable that at least the buffer tank 3 be arranged near the bottom of the ship. With the configuration in which the buffer tank 3 is disposed on the bottom of the ship with less shaking with respect to waves and the like, the shaking of the buffer tank 3 is less likely to occur, so that the liquid in the buffer tank 3 can be made relatively quiet. It is advantageous to suppress the liquid in the buffer tank 3 from swaying and the scum from diffusing into the liquid.

  In this specification, the vicinity of the bottom of the ship refers to a position that is within 20% of the height from the bottom of the ship to the deck. More specifically, the upper end of the buffer tank 3 is located at a position within 20% of the bottom of the ship. Desirably, the upper end of the buffer tank 3 is arranged at a position where the height is within 10% from the ship bottom. The buffer tank 3 can be arranged, for example, between the main engine of the ship and the bottom of the ship. The buffer tank 3 can be arranged, for example, at a position between the bottom surface of the main engine and the upper surface of the main engine.

Reference Signs List 1 wastewater treatment device 2 scrubber 3 buffer tank 3a (buffer tank) bottom surface 4 solid-liquid separator 5 sludge tank 6 supply pipe 6a (supply pipe) lower end 7 stirring mechanism 8 collection mechanism 9 weir 9a (weir) lower end 9b ( Upper end of weir 10 Liquid level 11 Three-way valve 12 Distribution port 13 Decompression mechanism 14 Second weir 15 Recovery pipe 16 Foaming agent supply mechanism 17 Neutralizer supply mechanism 18 Three-way valve 19 Sensor 20 Control mechanism 21 Surface reformer P pump S scum F1 first area F2 second area F3 third area

Claims (9)

A buffer tank that stores a liquid containing a solid component in the exhaust gas used for cleaning the exhaust gas, a solid-liquid separator that separates the liquid and the solid component stored in the buffer tank, In a wastewater treatment device comprising a sludge tank for storing components,
A stirring mechanism for stirring the liquid stored in the buffer tank, and a recovery mechanism for recovering scum floating on the liquid surface of the liquid stored in the buffer tank ,
A weir that divides the buffer tank into a first area where the stirring mechanism is arranged and a second area where the collection mechanism is arranged,
Said weir, wastewater, wherein Rukoto includes an upper end disposed at a position lower than the liquid surface, and a through port in formed near the lower end moving the liquid to the second zone from the first zone Processing equipment.   2. The wastewater treatment apparatus according to claim 1, further comprising a pressure reducing mechanism that is disposed upstream of the buffer tank and that reduces a pressure of the liquid used for cleaning the exhaust gas. 3.   The wastewater treatment apparatus according to claim 1, further comprising a foaming agent supply mechanism that supplies a foaming agent to the buffer tank.   The wastewater treatment apparatus according to claim 1, further comprising a neutralizing agent supply mechanism that supplies a neutralizing agent to the buffer tank. The wastewater treatment device according to any one of claims 1 to 4 , wherein the buffer tank is arranged near a bottom of the ship. After storing a liquid containing a solid component in the exhaust gas used for cleaning the exhaust gas in a buffer tank, the liquid and the solid component are separated by a solid-liquid separator, and the solid component is stored in a sludge tank. Wastewater treatment method,
Said buffer tank to place the stirring mechanism, the liquid stored in the buffer tank in this stirring mechanism and agitated,
A collecting mechanism is disposed near the liquid surface of the liquid, and the scum floating on the liquid surface is collected by the collecting mechanism .
A weir that divides the buffer tank into a first area where the agitation mechanism is arranged and a second area where the recovery mechanism is arranged is installed, and the liquid and the scum are transferred from the upper end of the weir to the first area. Moving from the area to the second area, forming a flow port near the lower end of the weir, and moving the liquid and the solid component from the first area to the second area from the flow port. Wastewater treatment method. The wastewater treatment method according to claim 6 , wherein the pressure of the liquid is reduced before the liquid is supplied to the buffer tank. The wastewater treatment method according to claim 6 or 7 , wherein a foaming agent is supplied to the buffer tank when the liquid stored in the buffer tank is stirred. Wherein by measuring the pH value of the liquid stored in the buffer tank, when the value of pH of the liquid becomes smaller than the predetermined value, it claims supplying neutralizing agent to the buffer tank 6 The wastewater treatment method according to any one of claims 1 to 8 .

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