JP6849848B1 - Cleaning and wastewater treatment equipment for marine exhaust gas - Google Patents

Abstract

[Purpose] To provide a cleaning wastewater treatment device for marine exhaust gas that can purify scrubber-contaminated water and reduce the SS concentration and oil concentration to the extent that it can be dumped into the ocean. [Structure] A scrubber that includes an exhaust gas recirculation unit 1 and a buffer tank 5 that stores scrubber wastewater, and circulates between the buffer tank 5 and the exhaust gas recirculation unit 1 at a pressure higher than atmospheric pressure via a circulation pump 3. A scrubber circulation system is formed between the drainage and the scrubber water, and a solid-liquid separator that introduces the scrubber drainage in the buffer tank 5 and separates the separation liquid and the solid content is provided, and the drainage supply pipe 14 and the return pipe 16 are provided. A solid-liquid separation circulation system is formed by the above, and a scrubber circulation system and a solid-liquid separation circulation system are independently formed in the buffer tank 5, and the exhaust gas recirculation unit 1 is formed from the buffer tank 5 in the scrubber circulation system. The scrubber water supplied to the vehicle includes scrubber water purified by the solid-liquid separation circulation system. [Selection diagram] Fig. 1

Description

The present invention relates to a cleaning wastewater treatment device for marine exhaust gas that transfers pollutants contained in marine exhaust gas to a liquid phase by scrubber cleaning and treats them. The present invention relates to a washing wastewater treatment device for marine exhaust gas whose concentration can be reduced.

Europe and the United States have already designated SECA (SOx Emission Control Area) for the sulfur content of ship fuel used in ship engines, generators, and boilers, and the sulfur content of fuel has been reduced within SECA since 2015. It regulates the use of fuel that does not exceed 0.1%.

On the other hand, MEPC70 (70th Marine Environmental Protection Committee) decided to increase the upper limit of sulfur concentration of fuel oils used in general sea areas to 0.5% from January 1, 2020, and for low sulfur fuels. It was decided that the use would be obligatory.

In addition, the 73rd Marine Environmental Protection Committee (MEPC 73) of the International Maritime Organization (IMO) adopted a ban on the retention of non-conforming fuel oils for the purpose of use, which will come into effect on March 1, 2020 ( MARPOL Annex VI, Rule 14).

However, ships equipped with an exhaust gas cleaning device (scrubber) will continue to be designed to remove sulfur oxides from the exhaust gas from their engines and boilers and reduce sulfur emissions to sub-acceptable levels. It is said that it can retain fuel oil with a sulfur content exceeding 0.5%.

Against this background, the existence of a wet scrubber for removing sulfur oxides from exhaust gas can retain fuel oil with a sulfur content exceeding 0.5%, so its significance has become more important than ever. It was.

Furthermore, the operation will start in January 2016, and it is necessary to perform Tier 3 operation in the designated sea area (ECA). And the compatible oil suitable as the fuel oil in the designated sea area (ECA) is the fuel oil having 0.1% sulfur content. If EGR is used in the meantime, drainage outside the designated sea area (ECA) is permitted if the oil concentration of the treated water of the exhaust gas meets the standard. Therefore, the wastewater monitoring item in this case is the oil concentration in the wastewater.

Japanese Patent No. 6177835

Environmental pollutants contained in marine exhaust gas include sulfur oxides (SOx), nitrogen oxides (NOx), soot and dust, and unreacted substances of lubricating oil.

In Patent Document 1, these environmental pollutants are scrubbed and the contaminated scrubber water is treated by a centrifuge. Wastewater containing soot and oil is treated by a centrifuge, but if it does not satisfy the disposal standard to the sea, it is stored in a sewage drainage tank (reference numeral 19) in Patent Document 1. In order to satisfy the disposal standard to the sea, Patent Document 1 states that the treatment is performed by a centrifuge using a coagulant.

However, it is difficult to reduce the SS concentration value to 200 to 300 ppm or less by the treatment with a centrifuge. In a centrifuge, the solid content can be separated by the difference in specific gravity, but the suspended component, which is not a solid content but is detected as the SS concentration, has the same specific gravity as water in the first place, and it is difficult to separate it by the centrifuge.

Therefore, it is an object of the present invention to provide a cleaning wastewater treatment device for marine exhaust gas capable of purifying scrubber-contaminated water and reducing the SS concentration and oil concentration to the extent that it can be dumped into the ocean.

In addition, other problems of the present invention will be clarified by the following description.

The above problems are solved by the following inventions.
(Claim 1)
An exhaust gas recirculation unit that includes a cleaning unit that cleans ship exhaust gas with scrubber water and recirculates part of the exhaust gas to the engine of the ship to reduce the amount of nitrogen oxides in the exhaust gas.
It is provided with a buffer tank for storing scrubber wastewater containing the environmental pollutant phase in the exhaust gas by cleaning in the cleaning unit of the exhaust gas recirculation unit.
A scrubber circulation system of scrubber drainage and scrubber water that circulates at a pressure higher than atmospheric pressure is formed between the buffer tank and the exhaust gas recirculation unit via a circulation pump.
A solid-liquid separator that introduces the scrubber drainage in the buffer tank and separates it into a separation liquid and a solid content is provided.
The buffer tank and the above are provided by a drainage supply pipe that supplies the scrubber drainage in the buffer tank to the solid-liquid separator and a return pipe that returns the separated liquid separated by the solid-liquid separator into the buffer tank. A solid-liquid separation circulatory system is formed between the solid-liquid separator and the solid-liquid separator.
A scrubber circulation system and a solid-liquid separation circulation system are independently formed in the buffer tank.
The scrubber water supplied from the buffer tank in the scrubber circulation system to the exhaust gas recirculation unit contains the scrubber water purified by the solid-liquid separation circulation system .
The solid-liquid separator comprises a centrifuge and a membrane device.
The membrane device has a structure using a hollow fiber membrane suspended from a single tube plate.
The membrane device opens the air bleeding control valve once before the membrane treatment, bleeds the air in the membrane device, and opens the air bleeding control valve for a certain period of time even during the membrane treatment at predetermined time intervals. A cleaning wastewater treatment device for marine exhaust gas, which is characterized by treating a membrane.
(Claim 2)
The cleaning wastewater treatment device for marine exhaust gas according to claim 1, wherein the buffer tank is provided with a scum removing device for floating and removing scum containing soot and oil.
(Claim 3)
The washing wastewater treatment device for marine exhaust gas according to claim 1 or 2 , wherein the membrane-treated treated water satisfies the drainage standard to the sea without adjusting the pH.
(Claim 4)
The scrubber circulation system according to claim 1, 2 or 3 , wherein a bypass flow path for supplying high-pressure scrubber wastewater is formed in the exhaust gas recirculation unit without going through the buffer tank. Cleaning and wastewater treatment equipment for marine exhaust gas.

According to the present invention, it is possible to provide a cleaning wastewater treatment device for ship exhaust gas capable of purifying scrubber-contaminated water and reducing the SS concentration and oil concentration to the extent that it can be dumped into the ocean.

A flow chart showing an example of a washing wastewater treatment device for ship exhaust gas according to the present invention. The figure which shows an example of the centrifuge which concerns on this invention A graph showing the separation efficiency and SS concentration of the treatment liquid according to the present invention. The figure which shows an example of the membrane apparatus which concerns on this invention. A treatment flow chart showing another example of the washing wastewater treatment apparatus for ship exhaust gas according to the present invention. A graph showing the results of air backwashing with the liquid with and without the addition of the flocculant performed in Experimental Example 3 and examining the relationship between the amount of filtration and the membrane flux.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a flow chart showing an example of a washing wastewater treatment device for ship exhaust gas according to the present invention.

First, the outline of ship exhaust gas will be described.
Sulfur (S) is contained in fossil fuels, _{and when combined with oxygen (O 2} ) during the combustion process, sulfur dioxide (SO ₂ ), sulfur trioxide (SO ₃ ), sulfurous acid (H ₂ SO ₃ ), etc. Generates sulfur oxides. Since these sulfur oxides are particularly susceptible to water, they react with oxygen in the atmosphere _{to generate sulfuric acid (H 2} SO ₄ ), which causes acid rain.

Europe and the United States have already designated SECA (SOx Mission Control Area) for the sulfur content of ship fuel used in ship engines, generators, and boilers, and since 2015, the sulfur content of fuel will be in SECA. It regulates the use of fuel that does not exceed 0.1%.

On the other hand, MEPC70 (70th Marine Environmental Protection Committee) decided to increase the upper limit of sulfur concentration of fuel oil used in general sea areas to 0.5% from January 1, 2020, and it is low. It was decided to oblige the use of sulfur fuel.

In addition, the 73rd Marine Environmental Protection Committee (MEPC73) of the International Maritime Organization (IMO) has adopted a ban on the retention of non-conforming fuel oils for the purpose of use, which will come into effect on March 1, 2020 (MARPOL). Convention Annex VI, Rule 14).

However, ships equipped with an exhaust gas cleaning device (scrubber) will continue to be designed to remove sulfur oxides from the exhaust gas from their engines and boilers and reduce sulfur emissions to sub-acceptable levels. It is said that it can retain fuel oil with a sulfur content exceeding 0.5%.

Against this background, the existence of a wet scrubber for removing sulfur oxides from exhaust gas can retain fuel oil with a sulfur content exceeding 0.5%, so its significance is more important than ever. It has become.

By the way, the exhaust gas also contains nitrogen oxides (NOx). In marine engines, exhaust gas recirculation (EGR: Exhaust Gas Recirculation) using this nitrogen oxide is carried out, and a part of the exhaust gas discharged from the combustion chamber of the engine is recirculated to the combustion chamber of the engine. .. The significance of this EGR is that the oxygen concentration of the supply air can be lowered by mixing a part of the exhaust gas with almost no oxygen concentration with the scavenging air (supply air) that has a high oxygen concentration supplied to the engine. The oxygen concentration of the gas is relatively reduced, the maximum combustion temperature is lowered, and the amount of NOx is reduced.

FIG. 1 shows a flow in which a scrubber circulation system SC1 including an exhaust gas recirculation unit (EGR unit) 1 having an exhaust gas recirculation function by a wet scrubber is formed.

The wet scrubber contains environmental pollutants such as sulfur oxide SOx, nitrogen oxide NOx, soot and dust, and unreacted substances (for example, oil) of lubricating oil contained in the marine exhaust gas in the exhaust gas by injecting scrubber water. The environmental pollutant phase shifts from the gas phase to the liquid phase, the exhaust gas is cleaned, and dirty scrubber wastewater containing the environmental pollutant phase is produced.

In the present embodiment, the EGR unit 1 includes an exhaust gas cleaning unit 100 to which a prespray liquid is supplied as a cleaning liquid to clean the exhaust gas, an EGR cooler 101 to cool the cleaned exhaust gas, and a mist catcher 102 to collect scrubber wastewater. There is.

The exhaust gas cleaning unit 100 injects the prespray liquid, brings the exhaust gas into contact with the prespray liquid, cleans the exhaust gas, transfers the pollutant phase contained in the exhaust gas to the prespray liquid, and causes the environmental pollutant phase. The transferred prespray solution is produced as scrubber effluent.

The EGR cooler 101 has a function of cooling the exhaust gas. As the cooling water for cooling the exhaust gas, a cleaning liquid sprayed with a prespray liquid can be used.

The mist catcher 102 has a function of collecting scrubber wastewater to which the pollutant phase has been transferred. The mist in the scrubber wastewater adheres to the treatment equipment, and the scale of soot accumulates, reducing the risk of malfunction of the treatment equipment, sensors, transmitters, etc. The mist catcher 102 can prevent the pollutant phase contained in the scrubber wastewater from being supplied to the purified exhaust gas side.

When the purified exhaust gas that has passed through the mist catcher 102 is mixed with the scavenging air supplied to the engine, the oxygen concentration of the scavenging air can be lowered. The scrubber wastewater that has passed through the mist catcher 102 flows to the receiving tank 2 and is recovered as condensed water containing an environmental pollutant phase such as soot and oil in the exhaust gas.

The opening degree of the valve 4 is adjusted so that the liquid level in the receiving tank 2 becomes constant, and the condensed water in the exhaust gas is stored in the buffer tank 5.

Fresh water can be supplied in the buffer tank 5. Shimizu is used when starting up the scrubber circulatory system. Also, various salts from the exhaust gas are dissolved in the salting out water during the scrubber process, so there is a risk of salting out sedimentation, but supplying fresh water reduces the risk of salting out sedimentation.

The liquid in the buffer tank 5 is supplied to the exhaust gas cleaning unit 100 by the scrubber pump 6 via the pipes 7 and 8. The cleaning liquid contains caustic soda supplied from the caustic soda tank 10 using the pump 11. When the cleaning liquid containing caustic soda comes into contact with the exhaust gas, sulfuric acid, which is an acidic component in the exhaust gas, is neutralized. Further, the scrubber pump 6 is supplied to the cleaning unit 100 as the prespray liquid which is the cleaning water and to the EGR cooler 101 as the cooling water via the pipe 7, the pipe 8 and the pipe 9.

The cleaning liquid containing caustic soda, that is, the scrubber water, passes through the exhaust gas cleaning unit 100, the EGR cooler 101, and the mist catcher 102 through the pipe 7, the pipe 8, and the pipe 9, and reaches the receiving tank 2, where the pH is adjusted by the pH adjuster 12. Is circulated by the circulation pump 3 to complete the neutralization of sulfuric acid by caustic soda while measuring.

That is, in the present invention, a scrubber circulation system SC1 is formed in which scrubber water is supplied from the buffer tank 5 via the scrubber pump 6 and circulated to the EGR unit 1 via the circulation pump 3.

Further, it is preferable that the scrubber circulation system SC1 is formed with a bypass flow path 31 for supplying high-pressure scrubber drainage to the EGR unit 1 without going through the buffer tank 5. Further, it is preferable that the bypass flow path 31 is provided with a bypass valve 30.

The scrubber circulation system SC1 can control the scrubber water by adjusting the opening degrees of the valve 4 and the bypass valve 30 based on the data of the liquid level of the receiving tank 2, the pH adjuster 12, and the like.

Then, when the high-pressure scrubber water is circulated, the pressure of the cleaning liquid can be supplied to the EGR unit 1 at a predetermined pressure by making the pressure of the circulation pump 3 and the pressure of the scrubber pump 6 about the same. At the same time, the pressure of the scrubber drainage from the bypass flow path 31 can be supplied at a predetermined pressure.
The pressure of the circulation pump 3 can be higher than the atmospheric pressure, and is preferably about 0.3 to 0.5 MPa, more preferably 0.4 MPa.

Further, FIG. 1 shows a circulation flow including the solid-liquid separation circulation system SC2.
A drainage supply pipe 14 for circulation and a return pipe 16 are connected between the buffer tank 5 and the centrifuge 15 which is an example of a solid-liquid separator. The wastewater supply pipe 14 is provided with a wastewater purification pump 13, and the return pipe 16 is provided with a control valve 17.

The wastewater purification pump 13 is driven to open the control valve 17, and the scrubber wastewater in the buffer tank 5 is subjected to a solid-liquid separation process by the centrifuge 15 until the liquid level reaches a certain level.

In the present invention, the drainage supply pipe 14 that supplies the scrubber drainage in the buffer tank 5 to the centrifuge 15 and the return pipe 16 that returns the separated liquid separated by the solid-liquid separator into the buffer tank 5 are provided. A solid-liquid separation circulation system SC2 is formed between the buffer tank 5 and the centrifuge 15 which is a solid-liquid separator.

Therefore, as shown in FIG. 1, the scrubber circulation system SC1 and the solid-liquid separation circulation system SC2 are independently formed in the buffer tank 5 in the present invention. Therefore, since the operation of the scrubber circulation system SC1 for collecting the scrubber wastewater and the operation of the solid-liquid separation circulation system SC2 for purifying the scrubber wastewater are performed independently, the operation can be performed without interfering with each other. As a result, stable operation becomes possible.

As the scrubber water supplied from the buffer tank 5 to the EGR unit 1 in the scrubber circulation system SC1, the scrubber water purified by the solid-liquid separation circulation system SC2 can be used, so that the exhaust gas cleaning by the scrubber can be surely performed. As a result, the SS concentration can be reduced to the extent that the scrubber wastewater can be purified and dumped in the ocean.

In the present embodiment, in the solid-liquid separation by the centrifuge 15, the separated liquid on the liquid side is returned to the buffer tank 5, and the sludge on the solid side is stored in the EGR contaminated water tank 21 via the pipe 20, and the contaminated water thereof. Is landed by the landing supply pump 29.

After the inside of the buffer tank 5 reaches a certain liquid level, the operation mode of the solid-liquid separation and circulation system SC2 is set, and a coagulant is added to the outlet of the wastewater purification pump 13. The coagulant is added from the coagulant tank 18 to the wastewater supply pipe 14 on the outlet side of the wastewater purification pump 13 via the coagulant pump 19.

By adding the coagulant, soot, oil and the like can be coagulated to enhance the solid-liquid separation effect of the centrifuge 15. Substances that could not be recovered by the centrifuge 15 are removed by a total filtration method with a membrane device 22, which is another example of the solid-liquid separator.

In FIG. 1, a line mixer (not shown) can be provided at a site where a coagulant is added in the wastewater supply pipe 14 between the wastewater purification pump 13 and the centrifuge 15. The reaction between the flocculant and the liquid can be accelerated by stirring with a line mixer.
Further, instead of the line mixer, an agglutination reaction tank (not shown) having a residence time of 30 seconds or more may be used, or the length of the drainage supply pipe 14 is set to the time from the position of the agglutinant pump 19 to the centrifuge 15. The pipe length may be set to about 30 seconds.

The amount of the coagulant added is set to a flow rate such that the addition concentration becomes a predetermined value with respect to the flow rate of the wastewater purification pump 13.
For example, in the formula of the coagulant addition flow rate (L / min) = wastewater purification pump flow rate (L / min) × coagulant addition concentration (%), the coagulant addition concentration is in the range of 0.01 to 0.1%. It is preferable to select a constant concentration in, and it is preferable not to change it for each engine load.

The treatment liquid of the centrifuge 15 is sent to the membrane device 22 via the pipe 23. Reference numeral 24 denotes a control valve provided in the pipe 23. The opening degree of the control valve 24 can be adjusted according to the processing capacity of the membrane device.
After passing through the membrane device 22, it is confirmed by the drainage monitoring monitor 25 that it is below the drainage standard value, and if there is no problem, it is discharged to the sea.

In the example shown in FIG. 1, an example of a configuration in which the wastewater monitoring monitor 25 monitors the entire amount of the membrane treatment liquid that has passed through the membrane device 22 is shown.

The membrane treatment liquid that has passed through the membrane device 22 is preferably partially monitored from the viewpoint of saving space in the device and limiting the specifications (for example, flow rate) of the device. Furthermore, regarding the wastewater monitoring regulation by the treaty, the monitoring by partial monitoring can be dealt with without any problem. In the partial monitoring, a part of the membrane treatment liquid that has passed through the membrane device 22 is branched into a branch flow path 40 described later, and the branched membrane treatment liquid is monitored by the wastewater monitoring monitor 25. Details will be described later.

When the treatment liquid of the centrifuge 15 is membrane-treated by the membrane device 22, it is unlikely that the wastewater standard value is exceeded, but the treatment liquid of the centrifuge 15 is sent to the sea without going through the membrane device 22. When the wastewater is discharged, it may exceed the drainage standard value. Therefore, depending on the value of the drainage monitoring monitor 25, switching between discharging to the sea and returning to the buffer tank 5 is performed by the three-way valve 26.

Wastewater monitoring standards for discharge to the sea are set by the International Maritime Organization (IMO) for the flush water of exhaust gas treatment equipment, and the turbidity, pH, and PAHs (polycyclic aroma) are set by the wastewater monitoring monitor 25. Monitor group hydrocarbon) concentrations.
In the designated sea area, when the fuel oil containing 0.1% sulfur of the compatible oil in the designated sea area is used, it is designated if the oil concentration of the cleaning water of the exhaust gas by EGR meets the specified wastewater standard. Since wastewater can be discharged outside the sea area, the oil concentration of the treated water generated by using the exhaust gas treatment equipment when using compatible oil in the designated sea area is monitored as the wastewater monitoring standard. For non-compliant oils, in addition to the above, add nitrates to the wastewater monitoring items for monitoring.

In a preferred embodiment of the present invention, the buffer tank 5 in which the membrane-treated water returned through the membrane device 22 and the condensed water in the exhaust gas are stored so as to flow to the EGR drain tank 27 by an overflow pipe (not shown). It is composed. With such a configuration, the stored liquid does not overflow from the inside of the buffer tank 5. Further, a flow path for returning from the EGR drain tank 27 to the buffer tank 5 may be formed.

In the present embodiment, it is preferable that the flow path from the scrubber circulation system SC1 to the buffer tank 5 is provided with a bubble generating portion for generating bubbles for floating the scum in which soot and oil are floated. As the bubble generating portion, for example, it is preferable that the valve 4 provided in the flow path from the scrubber circulation system SC1 to the buffer tank 5 is a pressure reducing mechanism such as a pressure reducing valve. In the present embodiment, the bubble generating portion is not limited to the depressurizing mechanism as long as it is provided with a mechanism for generating bubbles that scum the soot and oil in the buffer tank 5 as a result.
For example, here, the gas dissolved in the scrubber wastewater is the gas dissolved in the scrubber wastewater generated by the contact between the scrubber water having a pressure higher than the atmospheric pressure in the scrubber circulation system SC1 and the exhaust gas. The high-pressure scrubber drainage in which this gas is dissolved is reduced to atmospheric pressure by opening the valve 4 which is a pressure reducing valve, and the gas dissolved in the scrubber drainage is dissipated and generated as bubbles. By utilizing the generated bubbles, soot and oil in the buffer tank 5 can be floated as scum.

Further, for example, in the present embodiment, it is preferable that the valve 4 functions not as a pressure reducing valve but as an on-off valve, and a gas-liquid mixer is provided in the flow path from the scrubber circulation system SC1 to the buffer tank 5.
In the gas-liquid mixer, a pipe connecting the outside air and the flow path is provided in the flow path from the scrubber circulation system SC1 to the buffer tank 5, and the ejector action can be utilized from the pipe. As a result, since the scrubber drainage having a pressure higher than the atmospheric pressure is flowing, the air around the device can be mixed with the scrubber drainage having a higher pressure. As a result, bubbles that scum soot and oil can be generated in the buffer tank.

It is preferable that the buffer tank 5 is provided with a scum removing device that periodically collects scum.

In FIG. 1, the scum in the buffer tank 5 is sent to the EGR contaminated water tank 21 via the scum discharge pipe 28.

In this embodiment, since the buffer tank 5 has a tank structure in which an aggregate in which soot and oil are floated by bubbles is generated as a scum, the aggregate in which soot and oil are floated by bubbles can be removed in the buffer tank 5. Therefore, the solid content in the contaminated scrubber wastewater is removed. For this reason, the amount of solid content discharged per treatment time of the centrifuge 15 can be suppressed as compared with the case where scrubber wastewater is introduced and treated by the centrifuge 15 without removing the scum, and the treatment of the centrifuge 15 is performed. You can lengthen the time.

In some cases, the scum treatment and the membrane treatment by the membrane device 22 alone may satisfy the regulation value for discharging the treatment liquid to the sea. In this case, the centrifuge 15 can function as a pretreatment device for the membrane device 22.

Next, as an example of a solid-liquid separator that processes and recovers soot and agglomerates as solid content, the centrifuge 15 will be described with reference to FIG.

The rotor 150 of the centrifuge 15 is configured to rotate about the rotation axis X, and the scrubber drainage is solid-liquid separated in the separation chamber 151 to separate the separated liquid and the solid content.

The separation chamber 151 is configured by stacking a plurality of conical trapezoidal separation plates 152 in order to realize efficient separation of liquids.

The sewage to be treated is supplied from the upper inlet 154 via an inlet pipe 153 extending into the rotor 150.
The separated water is discharged to the separation liquid outlet 156 via the separation liquid discharge pipe 155.
At the lower part of the rotor 150, an outlet 157 for discharging a high-density component such as a solid-liquid separated precipitate is provided in the sludge space 158.

The contaminated liquid enters from the upper inlet 154 of the apparatus and is supplied into the separation plate 152, and the one having a heavy specific gravity is accumulated in the sludge space 158 by centrifugal force, and the one having a light specific gravity flows to the outlet 156.

What accumulates in the sludge space 158 needs to be discharged on a regular basis. If the accumulated material in the sludge space 158 is not properly discharged, the accumulated material may be rolled up and sludge may be mixed in the outlet side.

An experimental example in which this is verified is shown in FIG. Using the centrifuge 15 shown in FIG. 2, the supply amount of the undiluted solution was 12.7 (L / min), the SS concentration of the undiluted solution was 723.6 (mg / L), and the concentration of the coagulant added was 0.09%. Separation efficiency (%) = (SS concentration of undiluted solution-SS concentration of treatment solution) / (SS concentration of undiluted solution) was used to determine the separation efficiency, and the transition is shown in FIG.

From FIG. 3, it can be seen that the SS concentration of the treatment liquid increases with the passage of time. From this, it is inferred that sludge is mixed in on the outlet side.

The treatment by the membrane device 22 is the second stage treatment of solid-liquid separation, and the solid matter that could not be recovered by the centrifuge 15 is recovered. By including the membrane device 22, not only the solid matter that could not be recovered by the centrifuge 15 can be recovered, but also the treated water after the membrane treatment can be surely satisfied with the drainage standard to the sea without adjusting the pH. Can be increased to a degree.

Examples of the control method of the membrane device 22 include a method of confirming a decrease in flow rate with a constant differential pressure and a method of confirming an increase in differential pressure with a constant flow rate.
In the experimental example (Experimental Example 3) described later, the experiment was conducted by the method of confirming the decrease in the flow rate while keeping the differential pressure constant, but in the embodiment, any of them may be used.

As the membrane, a hollow fiber membrane is used. As the material of the hollow fiber membrane, for example, hydrophilized polyvinylidene fluoride (PVD) is preferably used.

The membrane filtration method includes a total amount filtration method and a cross flow filtration method, but in the present invention, the total amount filtration method is preferable. In either filtration method, it is preferable to perform cleaning regularly.

Further, if the impurities are sticky such as oil, the filtration performance may not be restored even by backwashing with air. Therefore, in the present invention, it is desirable to take measures against sticky impurities such as oil. In the present invention, if the oil content can be recovered together with the soot by the centrifuge 15 or, preferably, can be treated in the pre-stage of the centrifuge 15 by the scum treatment, the influence of the oil content in the membrane treatment is small.

An example of a membrane device that can be preferably used in the present invention will be described with reference to FIG.

In FIG. 4, 220 is a membrane device main body and is formed in a cylindrical shape.
A treatment liquid storage unit 221 is formed on the upper portion, and a treatment liquid pipe 222 is provided. A large number of hollow fiber membranes 223 are suspended below the treatment liquid storage unit 221.

The upper part of the hollow fiber membrane 223 is embedded in a pipe plate 225 that separates the stock solution supply section 224 and the treatment liquid storage section 221. The plurality of hollow fiber membranes (membrane modules) 223 are fixed to the tube plate 225 so that the tips thereof open in the treatment liquid storage unit 221.
In the present invention, a structure in which a plurality of hollow fiber membranes (membrane modules) 223 are suspended from one tube plate 225 is preferable.

The method of fixing the plurality of hollow fiber membranes 223 to the tube plate 225 is not particularly limited, but for example, the hollow fiber membranes 223 are fixed around the plurality of hollow fiber membranes 223 using a resin or an adhesive as a tube plate material. It may be. The tube plate 225 is formed by curing the resin and the adhesive.

The upper part of the hollow fiber membrane 223 penetrates the tube plate 225 and opens to the processing liquid storage unit 221. The lower part of the hollow fiber membrane 223 is suspended in the stock solution supply unit 224.

Pore is formed on the surface of the hollow fiber membrane 223, and the undiluted solution can be filtered into the inside of the hollow fiber by external pressure, or the hollow fiber membrane 223 can be sucked and filtered.

The lower tip of the hollow fiber membrane 223 does not open in the stock solution supply unit 224. This is to prevent contamination of the undiluted solution. FIG. 4 shows a mode in which adjacent membranes are connected to each other in a U shape, but the present invention is not limited to this, and is configured so as not to open in the stock solution supply unit 224 such as sealing the tip. I just need to be there.

It is the stock solution supply pipe 226 that supplies the stock solution to the stock solution supply unit 224. The stock solution supply pipe 226 is provided from the lower side to the upper side of the center of the membrane device main body 220. The stock solution supply pipe 226 is provided with a plurality of stock solution discharge units 227.

A water supply pump 228 (a wastewater purification pump 13 can also be used), a pressure gauge 229 (PI-1), a control valve AV1, and a supply pipe 230 are connected to the stock solution supply pipe 226.

An air supply source (not shown), a flow meter 231 (FI-3), a control valve AV8, and an air supply pipe 232 are connected to the stock solution supply pipe 226.

The treatment liquid pipe 222 is provided with a pressure gauge 233 (PI-2), a control valve AV2, and a flow meter 234 (FI-1).

Further, an air supply pipe 235 and a control valve AV5 are connected to the treatment liquid pipe 222.

The drain pipe 236 is formed in the lower part of the membrane device main body 220, and the drain pipe 237 is formed in the upper part of the membrane device main body 220.

A drain drain pipe 238 is connected to the drain pipe 236, and a control valve AV4 is provided. The drain pipe 237 is connected to the drain drain pipe 238 via the drain drain pipe 239. A control valve AV3 is connected to the drain pipe 237.

The air supply pipe 240 is provided with an air supply source (not shown), a flow meter 241 (FI-2), and a control valve AV6, and is connected to the lower part of the membrane device main body 220.

Further, a drain drain pipe 242 is provided from the treatment liquid pipe 222, and has a control valve AV7.

An example of the method of operating the above film device 22 will be described.

First, raw water is filled inside the membrane module to bleed air. The control valves shown in FIG. 4 were AV1 (open) and AV3 (open), and the other control valves AV2 and AV4 to AV8 were closed.

Next, the raw water is filtered through a hollow fiber membrane and separated into solid and liquid. The control valves were AV1 (open) and AV2 (open), and the other AV3 and AV4 to AV8 were closed.

Next, air is pressurized from the treatment liquid storage unit 221 side, and backwashed with the treatment water remaining in the hollow fiber membrane. The control valves were AV4 (open) and AV5 (open), and the other AV1, AV2, AV3, and AV6 to AV8 were closed.

Next, the hollow fiber membrane is shaken from the lower part by the air bubble supplied from the air supply pipe 240 to peel off the contaminants adhering to the film surface. The control valves were AV3 (open) and AV6 (open), and AV1, AV2, AV4, AV5, AV7, and AV8 were closed.

Next, the hollow fiber membrane is shaken from the upper part by the air bubble supplied from the undiluted solution discharge portion 227 of the undiluted solution supply pipe 226 from the air supply pipe 232 to peel off the contaminants adhering to the film surface. The control valves were AV8 (open) and AV3 (open), and AV1, AV2, AV4, AV5, AV6, and AV7 were closed.

Next, the water containing the exfoliated material is discharged under pressure. The control valves were AV8 (open) and AV4 (open), and AV1, AV2, AV3, AV5, AV6, and AV7 were closed.

Further, in the present invention, the hollow fiber membrane uses a total filtration method, and since air bubbles mixed in the separation liquid by the centrifuge 15 are not permeated, it is preferable to periodically remove air.

Specifically, before the membrane treatment, if the amount of air is large, the control valve (AV3) cannot be completely removed, and if the control valve (AV3) is left open, the amount of drainage increases, so the control valve (AV3) is opened for a predetermined time. , It is preferable to bleed air while filling raw water. As a result, bubbles mixed in the separation liquid can be removed before the membrane treatment, and a stable membrane treatment can be performed.
Further, since the air bleeding valve is not used during the treatment process, air bubbles mixed in the separation liquid are likely to accumulate. Therefore, after the membrane treatment, the backwash with air is performed, and then the air is bleeded before the membrane treatment. That is, the membrane treatment can be stably performed by periodically bleeding air before the membrane treatment. Further, even during the membrane treatment, more stable membrane treatment can be performed by opening the air bleeding control valve for a certain period of time to bleed the air at predetermined time intervals.

As a method of bleeding air, a method of providing a control valve for bleeding air or a method of intermittently opening air from a control valve (AV3) for bleeding drain can be performed. The air discharge destination is not limited to the EGR drain tank 27, but may be the buffer tank 5.

Next, the mode of performing the above-mentioned partial monitoring will be described with reference to FIG.
FIG. 5 is a treatment flow chart showing another example of the washing wastewater treatment device for ship exhaust gas. In FIG. 5, the parts having the same reference numerals as those in FIG. 1 have the same configuration, and thus the description thereof will be omitted.

As shown in FIG. 5, it is preferable that the washing wastewater treatment device is provided with a branch flow path 40 for extracting a part of the membrane treatment liquid that has passed through the membrane device 22. In the present embodiment, it is preferable to provide a wastewater monitoring monitor 25 in the branch flow path 40 to partially monitor the extracted membrane treatment liquid. The partially monitored membrane treatment liquid is returned to the buffer tank 5 again.

In the membrane treatment liquid that has passed through the membrane device 22, the dissolved gas may not be completely removed and may be dissipated to form bubbles. In this case, the drainage monitoring monitor 25 provided with the optical sensor may erroneously detect. In order to prevent erroneous detection of the drainage monitoring monitor 25, it is preferable to provide a defoaming device 41. By providing the defoaming device 61, stable measurement can be performed. The defoaming device 41 may be any device having a defoaming function, and examples thereof include a hollow fiber membrane device and a vacuum device.

Further, as the operation is continued, the membrane device 22 may be clogged and the inlet pressure of the membrane may increase. Therefore, a pressure difference occurs before and after the membrane device 22, and dissolved gas may increase in the membrane treatment liquid that has passed through the membrane device 22. Even in this case, stable measurement can be performed by installing the defoaming device 41. Further, according to the present embodiment, since the total amount is not monitored, the defoaming device 41 can be miniaturized.

As described above, according to the present embodiment, partial monitoring can contribute to space saving of the entire device such as a drainage monitoring monitor and a defoaming device, and further, there is a specification limitation on the flow rate of the entire device. However, the monitoring state of the processing liquid can be maintained by adjusting the flow rate of branching to the branch flow path with a valve or the like (not shown). Furthermore, the wastewater monitoring regulations under the treaty can be dealt with without problems by monitoring by partial monitoring.

Examples (experimental examples) will be described below.

Experimental Example 1
1. 1. The scrubber drainage at the inlet of the centrifuge, the separation liquid at the outlet of the centrifuge (inlet of the membrane device), and the membrane treatment liquid at the outlet of the membrane device were collected, and the components were analyzed and the pH was measured.

2. Results Table 1 shows the analysis results of the components of each liquid and the measured pH results.

3. 3. The pH of the membrane treatment solution collected at the outlet of the evaluation membrane device was 8, the pH of the scrubber drainage at the inlet of the centrifuge was 7.2, and the pH of the separation solution at the outlet of the centrifuge was 7.5. ..
Factors pH of membrane treatment solution becomes higher, mainly chloride ions in the solution, a sulfate ion (SO ₄ ^2-), nitrate ion (NO 3 ^_-) ions, it is estimated that because it was removed by film.

Experimental Example 2
1. 1. The following samples were used.
Sample 1: Scrubber drainage at the inlet of the centrifuge Sample 2: Separation liquid at the outlet of the centrifuge Sample 3: Membrane treatment liquid at the outlet of the membrane device

2. Coagulant A mixed liquid of basic aluminum chloride and a dimethylamine-epichlorohydrin copolymer (weight ratio 1: 1) was used.
The amount added was such that the addition concentration was 0.05%.

3. 3. Results The effect of adding the flocculant was measured by a portable turbidity meter, and the results are shown in Table 2.

From Table 2, it was found that the addition of the flocculant reduced the turbidity at the outlet of the centrifuge and the outlet of the membrane device.

Experimental Example 3
The liquid with and without the addition of the flocculant, which was carried out in Experimental Example 2, was ^{backwashed with air at every 50 L / m 2 of} the filtration amount, and the relationship between the filtration amount and the membrane flux was investigated.

Experiments were conducted with no coagulant added, 0.05% coagulant added, and 0.1% coagulant added.

The result is shown in FIG.

From this experimental result, when the coagulant was not added, the air backwash was applied, but the flux was not restored, but in the sample to which the coagulant was added at 0.05% and 0.1%, the air was reversed. It was found that the flux was restored by washing.

It is probable that the addition of the flocculant neutralized the soot and oil in the liquid in terms of electric charge, roughened them, and made it possible to remove them by backwashing.

1: EGR unit 2: Receiving tank 3: Circulation pump 4: Valve 5: Buffer tank 6: Scrubber pump 7, 8, 9: Piping 10: Caustic soda tank 11: Pump 12: pH adjuster 13: Wastewater purification pump 14: Wastewater supply Piping 15: Centrifugal separator (solid-liquid separator)
16: Return pipe 17: Control valve 18: Coagulant tank 19: Coagulant pump 20: Piping 21: EGR contaminated water tank 22: Membrane device (solid-liquid separator)
23: Piping 24: Control valve 25: Drainage monitoring monitor 26: Three-way valve 27: EGR drain tank 28: Scrub discharge piping 29: Landing supply pump 30: Bypass valve 31: Bypass flow path 40: Branch flow path 41: Desorption Foaming device SC1: Scrubber circulation system SC2: Solid-liquid separation circulation system

Claims (4)

An exhaust gas recirculation unit that includes a cleaning unit that cleans ship exhaust gas with scrubber water and recirculates part of the exhaust gas to the engine of the ship to reduce the amount of nitrogen oxides in the exhaust gas.
It is provided with a buffer tank for storing scrubber wastewater containing the environmental pollutant phase in the exhaust gas by cleaning in the cleaning unit of the exhaust gas recirculation unit.
A scrubber circulation system of scrubber drainage and scrubber water that circulates at a pressure higher than atmospheric pressure is formed between the buffer tank and the exhaust gas recirculation unit via a circulation pump.
A solid-liquid separator that introduces the scrubber drainage in the buffer tank and separates it into a separation liquid and a solid content is provided.
The buffer tank and the above are provided by a drainage supply pipe that supplies the scrubber drainage in the buffer tank to the solid-liquid separator and a return pipe that returns the separated liquid separated by the solid-liquid separator into the buffer tank. A solid-liquid separation circulatory system is formed between the solid-liquid separator and the solid-liquid separator.
A scrubber circulation system and a solid-liquid separation circulation system are independently formed in the buffer tank.
The scrubber water supplied from the buffer tank in the scrubber circulation system to the exhaust gas recirculation unit contains the scrubber water purified by the solid-liquid separation circulation system .
The solid-liquid separator comprises a centrifuge and a membrane device.
The membrane device has a structure using a hollow fiber membrane suspended from a single tube plate.
The membrane device opens the air bleeding control valve once before the membrane treatment, bleeds the air in the membrane device, and opens the air bleeding control valve for a certain period of time even during the membrane treatment at predetermined time intervals. A cleaning wastewater treatment device for marine exhaust gas, which is characterized by treating a membrane. The cleaning wastewater treatment device for marine exhaust gas according to claim 1, wherein the buffer tank is provided with a scum removing device for floating and removing scum containing soot and oil. The washing wastewater treatment device for marine exhaust gas according to claim 1 or 2 , wherein the membrane-treated treated water satisfies the drainage standard to the sea without adjusting the pH. The scrubber circulation system according to claim 1, 2 or 3 , wherein a bypass flow path for supplying high-pressure scrubber wastewater is formed in the exhaust gas recirculation unit without going through the buffer tank. Cleaning and wastewater treatment equipment for marine exhaust gas.

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