JP5843701B2 - Waste water treatment device, exhaust gas recirculation unit, engine system, and ship - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus for removing dust from scrubber wastewater containing dust. The present invention also relates to an exhaust gas recirculation unit, an engine system, and a ship provided with this wastewater treatment apparatus.

  As a technique for reducing the amount of nitrogen oxide (NOx) contained in the exhaust gas discharged from the engine for large ships, there is an exhaust gas recirculation (EGR) technique for returning the exhaust gas to the engine. In the exhaust gas recirculation of engines for large ships that use heavy oil as fuel, it is necessary to remove suspended particulate matter (SPM) such as carbon floating in the exhaust gas when returning the exhaust gas to the engine. As an apparatus for removing suspended particulate matter from exhaust gas, there is a cleaning dust collecting apparatus (scrubber) using cleaning water.

  The pre-purified water used as waste water (hereinafter referred to as “scrubber waste water”) in this cleaning dust collector contains a lot of dust (solid particles such as soot), so its turbidity is very high. It is expensive and cannot be discharged out of the ship. For example, according to the guidelines of IMO (International Maritime Organization), the turbidity emission regulation value is defined as 25 NTU (Nephelometric Turbidity Units). Therefore, in order to discharge the scrubber wastewater to the outside of the ship, it is necessary to remove the dust contained therein by some method.

  In this regard, Patent Document 1 proposes a wastewater treatment apparatus including a centrifugal separator that separates dust from water used for exhaust cleaning (that is, scrubber wastewater). That is, in the invention described in Patent Document 1, dust is removed from scrubber wastewater using a centrifuge.

JP 2004-81933 A

  Here, according to the experiments by the inventors, when a general industrial centrifuge is used, the turbidity of the scrubber wastewater is less than the specified discharge value unless the centrifuge process is performed 2 to 3 times. It turned out not to be. Therefore, when trying to reduce the turbidity of the scrubber wastewater below the specified discharge value with only the centrifuge, either two to three centrifuges are arranged in series, or two to three times the processing capacity. The treated scrubber wastewater must be repeatedly treated using a centrifuge with In any case, the wastewater treatment apparatus becomes larger as a whole, and a large amount of energy (electric power) is required for the treatment of scrubber wastewater.

  In an industrial centrifuge, a large number of umbrella-shaped (conical) members that create centrifugal force are arranged in the axial direction. And the space | interval of the adjacent umbrella-shaped member is as very narrow as about 0.5 mm. However, the scrubber wastewater contains not only small particles having a small particle size but also large particles having a particle size exceeding 0.5 mm. Therefore, when scrubber wastewater is treated only with a centrifuge, the centrifuge is likely to be clogged with dust, and frequent maintenance is required. As described above, the centrifugal separator is suitable for a process of removing small particles with a small particle size from the scrubber waste water because it uses centrifugal force, but is not suitable for a process of removing particles with a large particle size.

  A method of increasing the interval between the umbrella-shaped members provided in the centrifuge and making the centrifuge less likely to be clogged with dust is also possible, but such a configuration is not preferable because the efficiency of the separation process is reduced. Although a method of installing a filter upstream of the centrifuge is also conceivable, the filter is clogged immediately due to a large particle size soot, and frequent maintenance is still necessary.

  The present invention has been made in view of the above circumstances, can be operated with small energy, can be easily maintained, can reduce the installation space, and can accurately remove dust from scrubber waste water, An object is to provide a wastewater treatment apparatus.

  A wastewater treatment apparatus according to an embodiment of the present invention is a wastewater treatment apparatus that removes dust from scrubber wastewater containing dust, and has an inclined surface that forms a predetermined inclination angle with respect to the horizontal direction. A precipitation separation unit for precipitating the dust and separating the dust from the scrubber waste water; and a centrifugal separation unit disposed downstream of the precipitation separation unit and separating the dust from the scrubber waste water by a centrifugal separation process. .

  In the sedimentation separation unit located upstream of the wastewater treatment apparatus, soot and dust are separated by sedimentation, so that a large amount of energy is not required for operation, and soot and dust with a large particle size are not easily clogged. Moreover, since the centrifuge part located downstream of a wastewater treatment apparatus isolate | separates soot and dust by a centrifugation process, soot with a small particle diameter can also be removed accurately. Therefore, according to this wastewater treatment apparatus, the separation parts that complement each other are combined in an optimal arrangement, so that the whole can be operated with small energy, easy to maintain, the installation space can be reduced, and from the scrubber wastewater. Soot and dust can be removed with high accuracy.

  An exhaust gas recirculation unit according to an embodiment of the present invention is an exhaust gas recirculation unit that returns exhaust gas from a diesel engine to the diesel engine, and is a cleaning dust collector that cleans the exhaust gas and discharges scrubber waste water. And the above-mentioned waste water treatment device for removing dust from the scrubber waste water discharged from the cleaning dust collecting device.

  Moreover, the engine system which concerns on a certain form of this invention is equipped with the diesel engine and said exhaust gas recirculation unit. Moreover, the ship which concerns on a certain form of this invention is equipped with said engine system.

  According to the wastewater treatment apparatus described above, it can be operated with small energy, maintenance is easy, installation space can be reduced, and dust can be accurately removed from scrubber wastewater.

FIG. 1 is a block diagram of an engine system according to an embodiment of the present invention. FIG. 2 is a block diagram of the wastewater treatment apparatus shown in FIG. FIG. 3 is a schematic diagram of the precipitation separation unit shown in FIG. FIG. 4 is a schematic diagram of the centrifuge shown in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

<Engine system>
First, the engine system 101 according to the present embodiment will be described. FIG. 1 is a block diagram of the engine system 101. The thick solid line in FIG. 1 shows the flow of scavenging (“scavenging” in a 2-cycle engine and “supplying air” in a 4-cycle engine, but both are collectively referred to as “scavenging” below) The thick broken line indicates the flow of exhaust. The engine system 101 according to the present embodiment is a marine engine system 101 mounted on the marine vessel 100. As shown in FIG. 1, the engine system 101 includes a diesel engine 10, a supercharger 20, and an exhaust gas recirculation unit 30.

  The diesel engine 10 is a central component of the engine system 101. The diesel engine 10 is connected to a propeller for propulsion (not shown) and rotates the propeller. The diesel engine 10 of the present embodiment is for a large ship and uses so-called heavy oil as fuel, so that its exhaust includes not only SOx but a large amount of soot.

  The supercharger 20 is a device for supplying compressed air to the diesel engine 10. The supercharger 20 has a turbine part 21 and a compressor part 22. Exhaust gas is supplied from the diesel engine 10 to the turbine unit 21, and the turbine unit 21 is rotated by the speed energy of the exhaust gas. The turbine part 21 and the compressor part 22 are connected by a shaft part 23, and the compressor part 22 also rotates as the turbine part 21 rotates. When the compressor unit 22 rotates, the air taken in from the outside is compressed, and the compressed air is supplied to the diesel engine 10 as scavenging air.

  The exhaust gas recirculation unit 30 is a unit that returns exhaust gas to the diesel engine 10. Exhaust gas discharged from the diesel engine 10 is supplied not only to the supercharger 20 but also to the exhaust gas recirculation unit 30. As will be described in detail later, the exhaust gas supplied to the exhaust gas recirculation unit 30 is returned to the diesel engine 10 after removing suspended particulate matter. Since the exhaust gas discharged from the diesel engine 10 has a low oxygen concentration, the combustion temperature is lowered by returning it to the diesel engine 10. As a result, the amount of NOx discharged from the diesel engine 10 can be reduced.

<Exhaust recirculation unit>
Next, the exhaust gas recirculation unit 30 according to the present embodiment will be described. As described above, the exhaust gas recirculation unit 30 is a unit that returns exhaust gas to the diesel engine 10. As shown in FIG. 1, the exhaust gas recirculation unit 30 includes a cleaning dust collection device (scrubber) 31, a wastewater treatment device 32, and an EGR blower 33.

  The cleaning dust collection device 31 is a device that removes suspended particulate matter from the exhaust of the diesel engine 10. As described above, since exhaust gas from a diesel engine for a large vessel contains a large amount of suspended particulate matter, a cleaning dust collection device is required for the exhaust gas recirculation unit used in the large vessel. The cleaning dust collector 31 uses cleaning water to remove suspended particulate matter from the exhaust. There are methods to remove suspended particulate matter from the exhaust, such as a method of passing the exhaust through the cleaning water, a method of injecting the cleaning water into the exhaust, and a method of passing the exhaust between the members soaked with the cleaning water. The method may be adopted. The cleaning water used in the cleaning dust collecting device 31 is discharged to the waste water treatment device 32 as scrubber waste water.

  The wastewater treatment device 32 is a device for treating scrubber wastewater discharged from the cleaning dust collection device 31. Scrubber wastewater contains a large amount of particulate matter with suspended particulate matter and cannot be drained out of the ship. If the scrubber wastewater is drained out of the ship, the turbidity of the scrubber wastewater needs to be lowered to a predetermined value or less by the wastewater treatment device 32. Note that the scrubber wastewater discharged from the cleaning and dust collecting device 31 includes various particle sizes of dust from small to large particles. In addition, the detail of the waste water treatment apparatus 32 is mentioned later.

  The EGR blower 33 is a device that boosts the exhaust gas that has passed through the cleaning dust collector 31 and returns the boosted exhaust gas to the diesel engine 10 as scavenging air. The EGR blower 33 has a blower 34 and an electric motor 35. The blower 34 is driven by an electric motor 35. The exhaust gas from which the suspended particulate matter has been removed by the cleaning dust collector 31 is pressurized by the driven blower 34. The exhaust gas whose pressure has been increased by the EGR blower 33 (blower 34) is mixed with the atmosphere compressed by the supercharger 20 and supplied to the diesel engine 10.

<Waste water treatment equipment>
Next, the wastewater treatment apparatus 32 according to this embodiment will be described. The wastewater treatment device 32 is a device that removes dust from the scrubber wastewater. Here, FIG. 2 is a block diagram of the wastewater treatment apparatus 32. As shown in FIG. 2, the wastewater treatment device 32 includes a sedimentation separation unit 40 and a centrifugal separation unit 60 located downstream of the sedimentation separation unit 40. Hereinafter, each of these components will be described in order.

  The precipitation separation unit 40 is a part that removes the dust from the scrubber waste water by precipitating the dust. Here, FIG. 3 is a schematic diagram of the precipitation separation unit 40 according to the present embodiment. For convenience, the upper, lower, left, and right sides of FIG. 3 are simply referred to as “upper”, “lower”, “left”, and “right”. Note that the vertical direction in FIG. 3 corresponds to the vertical direction (the direction in which gravity is applied). As shown in FIG. 3, the precipitation separation unit 40 is mainly configured by a water tank 41, a partition plate 42, and an inclined tube group 43.

  The inside of the water tank 41 is filled with scrubber waste water. A partition plate 42 is disposed near the center in the left-right direction of the water tank 41 and above the bottom surface 44 of the water tank 41. An inclined tube group 43 is disposed between the partition plate 42 and the right side wall of the water tank 41. The lower end portion of the inclined tube group 43 is located above the bottom surface 44 of the water tank 41. Hereinafter, a region 45 in the water tank 41 that is a combination of the region on the left side of the inclined tube group 43 and the region below the inclined tube group 43 is referred to as a “first region”. 43 and the area 46 surrounded by the right side wall of the water tank 41 (the upper right area of the water tank 41) 46 are referred to as “second area”.

  Then, it can be said that the inclined tube group 43 is located at the boundary between the first region 45 and the second region 46. The inclined tube group 43 is formed by integrating a large number of inclined tubes 47 whose horizontal cross section is rectangular. 3 shows a plurality of inclined tubes 47 arranged in the left-right direction, but a large number of inclined tubes 47 are arranged not only in the left-right direction but also in the depth direction of the page of FIG. Each inclined tube 47 has a lower portion opening in the first region 45 and an upper portion opening in the second region 46. That is, the first region 45 communicates with the second region 46 through each inclined tube 47. Each inclined tube 47 is inclined by a predetermined inclination angle (for example, 60 degrees) with respect to the horizontal direction. Therefore, each inclined pipe 47 has an inclined surface 48, and this inclined surface 48 is inclined (upward) obliquely upward (upper left) by being inclined by a predetermined inclination angle with respect to the horizontal direction.

  An inflow port 49 that opens to the first region 45 is formed on the left side wall of the water tank 41. An outflow port 50 that opens to the second region 46 is formed on the right side wall of the water tank 41. As shown in FIG. 2, scrubber wastewater flows from the cleaning dust collector 31 into the sediment separator 40, and this scrubber wastewater flows into the water tank 41 through the inflow port 49. When the scrubber wastewater flowing into the water tank 41 enters the first region 45 of the water tank 41 as shown by the arrows in FIG. It flows from the bottom to the top and flows into the second region 46 and is finally discharged from the outflow port 50.

  As described above, the scrubber wastewater that has entered the water tank 41 always passes through one of the inclined pipes 47. Then, when the scrubber wastewater passes through the inclined pipe 47, the dust in the scrubber wastewater settles on the inclined surface 48 of each inclined pipe 47. If the dust settles on the bottom surface 44 of the water tank 41, the dust must settle on a relatively long distance in order to settle on the bottom surface 44 and complete the precipitation. On the other hand, in this embodiment, since the dust settles on the inclined surface 48 of the inclined pipe 47, the precipitation is completed by sedimentation of a short distance. Further, in the present embodiment, since a large number of inclined pipes 47, that is, a large number of inclined surfaces 48 are arranged side by side, the area of the surface on which the dust settles is very large. Thereby, in this embodiment, precipitation of a large amount of dust can be completed in a short time. Note that the dust deposited on the inclined surface 48 of each inclined tube 47 falls to the bottom surface 44 of the water tank 41 by its own weight when accumulated to some extent. The scrubber waste water is discharged from the outflow port 50 to the centrifugal separator 60 after the dust is separated (removed) in this manner.

  As described above, the sedimentation separator 40 separates the dust from the scrubber wastewater using gravity. Therefore, large power is not necessary for operation. Furthermore, since the scrubber wastewater does not pass through a narrow gap, even if the scrubber wastewater contains a large amount of soot with a large particle size, it is difficult to clog. Therefore, the sedimentation separation unit 40 of the present embodiment can be operated with small energy, and maintenance is very easy. In addition, when processing the same amount of scrubber wastewater, the precipitation separation part 40 can be comprised smaller as a whole than the centrifugation part 60 mentioned later.

  Subsequently, the centrifugal separator 60 of the present embodiment will be described. The centrifugal separator 60 is a part that removes dust from the scrubber wastewater by centrifugal separation. Here, FIG. 4 is a schematic diagram of the centrifuge 60 according to the present embodiment. As shown in FIG. 4, the centrifugal separator 60 includes a storage container 61, a shaft tube 62, and a large number of rotating plates 63.

  The storage container 61 is a container that stores the shaft tube 62 and the rotating plate 63. The storage container 61 has a cylindrical portion 64 formed in a cylindrical shape and an upper surface portion 65 disposed above the cylindrical portion 64. An outflow pipe 66 penetrating the upper surface portion 65 is disposed at the center of the upper surface portion 65, and an inflow pipe 67 penetrating the outflow tube 66 is disposed inside the outflow tube 66.

  The shaft tube 62 is a tubular member accommodated in the storage container 61. The shaft tube 62 communicates with the inflow tube 67 and extends along the central axis of the container 61 (main body portion 64). Furthermore, the shaft tube 62 rotates at a high speed (for example, 10,000 rpm) using an electric motor (not shown) as a drive source. As shown in FIG. 2, the scrubber wastewater discharged from the sedimentation separator 40 flows into the centrifugal separator 60. Specifically, the scrubber wastewater flows into the shaft pipe 62 through the inflow pipe 67. Furthermore, the scrubber wastewater that has flowed into the shaft tube 62 flows into the storage container 61 through an outflow hole 68 formed at the lower end.

  The rotating plate 63 is a member that rotates together with the shaft tube 62. The rotating plates 63 are arranged along the axial direction of the shaft tube 62 and are directly fixed to the shaft tube 62 during operation. The rotating plate 63 has an umbrella-like (conical) shape, and is formed with circulation holes 69 arranged at equal intervals in the circumferential direction. Further, although the interval between the rotating plates 63 is illustrated widely in FIG. 4, it is actually very narrow, and the interval is, for example, 0.5 mm. In order to maintain this distance, a spacer (not shown) having a thickness of 0.5 mm, for example, is inserted between the rotating plates 63 in this embodiment.

  The scrubber wastewater that has flowed into the storage container 61 through the shaft pipe 62 passes through the flow holes 69 of the respective rotating plates 63 and is discharged from the discharge pipe 66 to the outside of the ship. When the scrubber wastewater passes through the rotating plate 63, centrifugal force is applied to the scrubber wastewater, and soot and dust having a large specific gravity is separated from the scrubber wastewater. The separated dust is deposited on the inner wall of the cylindrical portion 64. Thus, the scrubber wastewater that has flowed into the centrifugal separator 60 is discharged from the centrifugal separator 60 (the container 61) after the dust particles are forcibly separated.

  In addition, since each rotation plate 63 constituting the centrifugal separator 60 has a very small interval, if the scrubber wastewater that flows in contains a large amount of dust with a large particle size, the dust is immediately converted into the rotation plate 63. It will get stuck in between. On the other hand, since the centrifugal separation unit 60 forcibly separates dust using centrifugal force, it is possible to accurately separate dust with a small particle size. That is, the centrifugal separator 60 is not good at removing soot and dust having a large particle size, but is very effective for removing dust having a small particle size.

  As described above, in the wastewater treatment apparatus 32 according to the present embodiment, the precipitation separation unit 40 effective for removing dust with a large particle size is disposed on the upstream side. And the sedimentation separation part 40 can be operated with small energy, is easy to maintain, and can be configured smaller than the centrifugal separation part 60. In addition, a centrifugal separator 60 that is effective for removing dust with small particles is disposed on the downstream side. In addition, since the sedimentation separation unit 40 is disposed upstream of the centrifugal separation unit 60, soot with a large particle diameter hardly flows into the centrifugal separation unit 60. As described above, the wastewater treatment apparatus 32 according to the present embodiment has the separation units 40 and 60 that complement each other combined in an optimal arrangement, can be operated with a small amount of energy as a whole, is easy to maintain, and has a small installation space. It can be made small, and dust can be accurately removed from the scrubber wastewater.

  In addition, it was confirmed by the inventors' experiment that the turbidity is reduced to 110 NTU when the scrubber wastewater having a turbidity of 5000 NTU passes through the precipitation separation unit 40. Furthermore, it was confirmed that the scrubber wastewater having a turbidity of 110 NTU decreases to 5 NTU when passing through the centrifugal separator 60. Therefore, if the turbidity is scrubber wastewater of about 5000 NTU, the turbidity is reduced to 25 NTU or less of the emission regulation value defined in the IMO guidelines by passing the wastewater treatment device 32 according to this embodiment only once. As a result, the water can be drained out of the ship.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to these embodiments, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the scrubber wastewater treatment device 32 for treating the scrubber wastewater used for washing the exhaust of the diesel engine 10 has been described above. However, the scrubber wastewater used by the wastewater treatment device for washing the exhaust of the boiler and the exhaust of the incinerator. Even those that process are included in the present invention.

  The wastewater treatment apparatus according to the present invention can be operated with small energy, can be easily maintained, can reduce the installation space, and can accurately remove dust from the scrubber wastewater. Therefore, it is useful in the technical field of wastewater treatment equipment.

DESCRIPTION OF SYMBOLS 10 Diesel engine 30 Exhaust gas recirculation unit 31 Washing dust collection apparatus 32 Waste water treatment apparatus 40 Precipitation separation part 48 Inclined surface 60 Centrifugation part 100 Ship 101 Engine system

Claims (4)

A wastewater treatment device for removing dust from scrubber wastewater used to clean diesel engine exhaust ,
A plurality of inclined pipes having inclined surfaces that form a predetermined angle with respect to the horizontal direction , and when the scrubber wastewater passes through the multiple inclined pipes from the bottom to the top, dust is deposited on the inclined surfaces of the inclined pipes. precipitation separation unit for separating the dust from the scrubber effluent Te,
It has a large number of rotating plates arranged downstream of the sedimentation separation unit and arranged in the direction of the rotation axis. When passing through the large number of rotating plates, centrifugal force is applied to the scrubber wastewater, and the scrubber wastewater is separated from the scrubber wastewater by centrifugation. A wastewater treatment apparatus comprising: a centrifuge for separating dust. An exhaust gas recirculation unit that returns exhaust gas from a diesel engine to the diesel engine,
A cleaning dust collector for cleaning the exhaust and draining scrubber waste water;
An exhaust gas recirculation unit comprising: the wastewater treatment device according to claim 1, wherein dust is removed from scrubber wastewater discharged from the cleaning dust collection device.   An engine system comprising a diesel engine and the exhaust gas recirculation unit according to claim 2.   A ship provided with the engine system according to claim 3.

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