JP6280328B2 - EGR unit and engine system - Google Patents

Description

  The present invention relates to an EGR unit that recirculates exhaust gas in an engine.

  An EGR (Exhaust Gas Recirculation) unit is a unit mounted in an engine system and recirculates exhaust gas discharged from the engine to the engine. By recirculating the exhaust gas to the engine by the EGR unit, combustion is performed in a state where the oxygen concentration is low in the engine, and as a result, the combustion temperature is lowered and the generation of NOx can be suppressed.

  Further, marine diesel engines that use residual oil as fuel contain a large amount of particulate matter (PM) and sulfur oxide (SOx) in the exhaust gas. Therefore, an EGR unit mounted on a marine engine system or the like needs to include a device that removes PM and SOx from exhaust gas. As an apparatus for removing PM and SOx, a wet gas cleaning apparatus (scrubber) using a cleaning liquid is often employed.

  Further, if the exhaust gas recirculated to the engine is at a high temperature, the ratio of the scavenging gas (fresh air) to the gas supplied to the engine decreases, and the engine output may decrease. Therefore, when the exhaust gas flowing into the EGR unit is at a high temperature, it is common to provide a gas cooler in the EGR unit to lower the exhaust gas to the scavenging gas temperature.

  In patent document 1, the EGR unit (exhaust gas recirculation system) provided with the scrubber (wet scrubber 15) and gas cooler (cooler 16) mentioned above is disclosed (the name in the patent document 1 is in parentheses). In the EGR unit of Patent Document 1, the scrubber is arranged on the upstream side of the gas cooler.

JP 2011-157959 A

  Usually, the cleaning liquid used in the scrubber contains a neutralizing agent, and the SOx of the exhaust gas is removed (desulfurized) by dissolving in the cleaning liquid. However, if the temperature of the exhaust gas in the scrubber is high, SOx is difficult to dissolve in the cleaning liquid, and the desulfurization performance decreases. In the case of the EGR unit described in Patent Document 1, since the exhaust gas flows into the scrubber before passing through the gas cooler, the exhaust gas flowing in the scrubber is at a high temperature, and it is difficult to ensure high desulfurization performance. Although the exhaust gas is also cooled by the cleaning liquid, the pressure in the scrubber is high in the configuration as in Patent Document 1, and the saturation temperature that is the limit that can be cooled by the cleaning liquid also increases. Therefore, it is difficult to cool the exhaust gas to a temperature sufficient for desulfurization with only the cleaning liquid.

Moreover, the amount of the neutralizing agent contained in the cleaning liquid can be increased to increase the pH value, thereby improving the desulfurization performance. However, in this case, not only the running cost of the engine system increases, but also CO ₂ dissolves in the cleaning liquid and a solid content is precipitated, which may cause a failure of the scrubber.

  It is also conceivable to arrange a gas cooler upstream of the scrubber. When arranged in this way, the exhaust gas whose temperature has decreased flows into the scrubber, so that high desulfurization performance can be ensured. However, in this case, uncleaned exhaust gas, that is, exhaust gas containing a large amount of PM, flows into the gas cooler, which may cause clogging of the gas cooler. Although it is conceivable to install scrubbers on both the upstream and downstream sides of the gas cooler, the structure becomes complicated.

  Furthermore, when the scrubber is arranged on the upstream side of the gas cooler as in Patent Document 1, the condensed gas is generated in the gas cooler by cooling the exhaust gas saturated in the scrubber with the gas cooler. . On the other hand, SOx remains to some extent even in the exhaust gas that has passed through the scrubber. Therefore, the remaining SOx dissolves in the condensed water, so that the condensed water becomes a strong acid and may corrode the gas cooler.

  In view of the above circumstances, an object of the present invention is to provide an EGR unit that includes a scrubber and a gas cooler and that is unlikely to fail while ensuring high desulfurization performance.

  An EGR unit according to an embodiment of the present invention is an EGR unit that recirculates exhaust gas in an engine, and scrubbers that clean the exhaust gas using a first cleaning liquid, and the exhaust gas that has been cleaned by the scrubber. A gas cooler for cooling, and an injection section for injecting a second cleaning liquid to the exhaust gas passing through the gas cooler, wherein the first cleaning liquid and the second cleaning liquid contain a desulfurization neutralizing agent. .

According to this configuration, after desulfurization is performed by the scrubber, desulfurization is further performed on the exhaust gas cooled by the gas cooler. That is, since the exhaust gas is desulfurized in two stages including low-temperature desulfurization, high desulfurization efficiency can be ensured. Furthermore, according to the above configuration, since it is not necessary to increase the amount of the neutralizing agent, the solid content due to the dissolution of CO ₂ is hardly precipitated, and the SOx in the gas cooler is removed by the second cleaning liquid. The condensed water generated in the inside does not become a strong acid. Therefore, a failure that may occur in the gas cooler can be prevented.

  In the EGR unit described above, the second cleaning liquid ejected from the ejection unit may be a water cleaning liquid containing the used first cleaning liquid that has been purified and reused. According to such a configuration, the second cleaning liquid reuses the stored water cleaning liquid containing the first cleaning liquid. However, since the purification process is performed, the gas cooler is clogged even if the second cleaning liquid is injected in the gas cooler. Is unlikely to occur.

  In the above EGR unit, the first cleaning liquid may be a reuse of the stored cleaning liquid containing the used first cleaning liquid without purifying it. According to such a configuration, the purification processing apparatus that cleans the stored water cleaning liquid does not need to purify the first cleaning liquid, and thus can prevent the purification processing apparatus from becoming large.

  The EGR unit further includes a purification processing device that purifies the stored water cleaning liquid when the stored water cleaning liquid is drained, and the second cleaning liquid is a part of the stored water cleaning liquid purified by the purification processing device. It may be reused. For example, a marine engine system includes a purification processing device for purifying the used cleaning liquid when the used cleaning liquid is discharged to the outside of the ship. If it is an engine system provided with such a purification processing apparatus, the washing | cleaning liquid apparatus for carrying out the purification process of a 2nd washing | cleaning liquid does not need to be newly provided.

  The EGR unit may be configured to be able to switch between the injection and stop of the second cleaning liquid by the injection unit in accordance with the operating state of the engine. For example, when the engine is under a low load, if the pressure in the scrubber is low and the exhaust gas can be sufficiently cooled with the first cleaning liquid, sufficient desulfurization performance may be ensured with only the scrubber. According to the above configuration, in such a case, the injection of the second cleaning liquid can be stopped, and waste of energy used for the injection of the second cleaning liquid can be suppressed.

  In the EGR unit, the scrubber has an injection nozzle that injects the first cleaning liquid into the exhaust gas, and a relative injection speed of the second cleaning liquid injected from the injection unit with respect to the exhaust gas is an injection nozzle of the scrubber. The first cleaning liquid injected from the first cleaning liquid may be lower than the relative injection speed with respect to the exhaust gas. For removing PM, it is effective to make gas-liquid contact at high speed, and for removing SOx, it is effective to make gas-liquid contact for a long time. Therefore, according to the above configuration, the scrubber can efficiently remove PM by making gas-liquid contact at high speed. Further, in a gas cooler in which low temperature desulfurization is performed, SOx can be more efficiently removed by ensuring a sufficient time for gas-liquid contact while suppressing the relative injection speed.

  Furthermore, the engine system which concerns on a certain form of this invention is equipped with the EGR unit in any one of the above.

  According to said EGR unit, generation | occurrence | production of a failure can be suppressed, ensuring high desulfurization performance.

FIG. 1 is a block diagram of an engine system according to the first embodiment. FIG. 2 is a schematic diagram of the EGR unit according to the first embodiment. FIG. 3 is a schematic diagram of an EGR unit according to the second embodiment.

  Hereinafter, embodiments 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.

(First embodiment)
First, the first embodiment will be described with reference to FIGS. 1 and 2.

<Engine system>
First, the engine system 100 according to the present embodiment will be described. FIG. 1 is a block diagram of the engine system 100. As shown in FIG. 1, the engine system 100 includes an engine 10, a supercharger 20, and an EGR unit 30.

  The engine 10 in the present embodiment is a main propulsion device for a ship and is a two-stroke diesel engine. The engine 10 is supplied with scavenging gas (“charged gas” in the case of a four-stroke engine) from the supercharger 20 through the scavenging passage 11. Further, the exhaust gas discharged from the engine 10 is supplied to the supercharger 20 through the exhaust passage 12. The engine 10 may be a 4-stroke engine, a gas engine, or a gasoline engine. Further, the engine 10 is not limited to that used for ships, but may be used for power generation equipment.

  The supercharger 20 is a device that boosts air and supplies it to the engine 10. The supercharger 20 has a turbine part 21 and a compressor part 22. Exhaust gas discharged from the engine 10 is supplied to the turbine unit 21, and the turbine unit 21 is rotated by the energy of the exhaust gas. The turbine part 21 and the compressor part 22 are connected by a connecting shaft 23, and the compressor part 22 also rotates as the turbine part 21 rotates. When the compressor unit 22 rotates, air (atmosphere) taken from the outside is compressed, and the compressed air is supplied to the engine 10 as scavenging gas.

  The EGR unit 30 is a unit that returns (recirculates) exhaust gas discharged from the engine 10 to the engine 10. The EGR unit 30 of this embodiment is a so-called high pressure EGR type that extracts exhaust gas upstream of the supercharger 20 in the exhaust passage 12. Since the exhaust gas extracted on the upstream side of the supercharger 20 is high-temperature and high-pressure, the exhaust gas is washed by the scrubber 31, and then the exhaust gas is cooled by the gas cooler 32 located on the downstream side of the scrubber 31. An EGR blower (not shown) is provided downstream of the gas cooler 32, and exhaust gas in the EGR unit 30 is discharged to the scavenging passage 11 by this EGR blower.

<EGR unit>
Next, details of the EGR unit 30 will be described. FIG. 2 is a schematic diagram of the EGR unit 30 according to the present embodiment. Note that the black arrows in FIG. 2 indicate the flow of exhaust gas, and the broken lines indicate the flow of liquid such as cleaning liquid (the same applies to FIG. 3). As shown in FIG. 2, the EGR unit 30 includes a scrubber 31, a gas cooler 32, and an injection unit 33. In addition, the EGR unit 30 of this embodiment is an integrated type in which the scrubber 31 and the gas cooler 32 are integrally formed.

  The scrubber 31 is a part that cleans the exhaust gas. The scrubber 31 of this embodiment is a composite type that combines a spray type and a stored water type. The scrubber 31 has an introduction passage 34 that guides exhaust gas to the inside, and an injection nozzle 35 is provided at the inlet of the introduction passage 34. A first cleaning liquid 38 containing a neutralizing agent for desulfurization is injected from the injection nozzle 35. This first cleaning liquid 38 is obtained by pumping a stored water cleaning liquid 36, which will be described later, with a first circulation pump 37. By injecting the first cleaning liquid 38 into the exhaust gas, SOx contained in the exhaust gas is dissolved (desulfurized) in the first cleaning liquid 38, and PM is captured (dedusted) in the first cleaning liquid 38. The scrubber 31 and the gas cooler 32 are connected to each other at the bottom and have a common shared water reservoir 39. The water storage cleaning liquid 36 is stored in the shared water storage unit 39.

  The shared water storage unit 39 is provided with a level meter 40, and the pipe 41 connecting the shared water storage unit 39 and the injection nozzle 35 is provided with a pH meter 42. The common water storage unit 39 is supplied with a neutralizing agent from a neutralizing agent supply device 43 and supplied with fresh water from a fresh water supply device 44. In the EGR unit 30 according to the present embodiment, based on the measurement results of the level meter 40 and the pH meter 42, the neutralizer is used so that the pH value and the water level of the water storage cleaning liquid 36 in the common water storage unit 39 are within a predetermined range. The amount of neutralizer supplied from the charging device 43, the amount of fresh water supplied from the fresh water supply device 44, and the like are controlled. In addition, although sodium hydroxide, magnesium hydroxide, etc. can be used as a neutralizing agent, you may use seawater (or the component of seawater).

  The exhaust gas that has passed through the introduction passage 34 of the scrubber 31 is released into the stored water cleaning liquid 36 stored in the shared water storage unit 39. As a result, the exhaust gas is further cleaned by the stored water cleaning liquid 36. The first cleaning liquid 38 ejected from the ejection nozzle 35 is carried to the common water storage unit 39 by the exhaust gas, and taken into the stored water cleaning liquid 36 as it is. For this reason, the stored water cleaning liquid 36 includes the used first cleaning liquid 38 and naturally includes a large amount of PM. Further, the scrubber 31 and the gas cooler 32 are connected to each other through the communication port 45, and the exhaust gas discharged from the stored cleaning liquid 36 flows into the gas cooler 32 through the communication port 45. The exhaust gas that has passed through the scrubber 31 has dropped to the saturation temperature.

  The gas cooler 32 is located on the downstream side of the scrubber 31 and is a portion that cools the exhaust gas cleaned by the scrubber 31. The gas cooler 32 has a heat exchanger 46 and a mist catcher 47. The heat exchanger 46 has a cooling medium flowing therein, and heat exchange is performed between the cooling medium and the exhaust gas. As a result, the exhaust gas is cooled. The mist catcher 47 is located on the downstream side of the heat exchanger 46, and is generated by the first cleaning liquid 38 carried by the exhaust gas, the second cleaning liquid 48 injected from the injection unit 33 described later, and the heat exchanger 46. Captures the condensed water. When the liquid captured by the mist catcher 47 gathers and reaches a certain size, it falls by its own weight and is collected by the shared water storage unit 39. The exhaust gas passes through the gas cooler 32 and is then mixed with the scavenging gas and supplied to the engine 10 (see FIG. 1).

  The injection part 33 is a part for injecting the second cleaning liquid 48 containing a neutralizing agent for desulfurization into the exhaust gas passing through the gas cooler 32. The second cleaning liquid 48 ejected by the ejection unit 33 is obtained by purifying the stored water cleaning liquid 36 stored in the shared water storage unit 39 by the purification processing device 49 and reusing it. The purification treatment device 49 is mainly configured by a centrifuge, for example, and can remove PM from the stored water cleaning liquid 36. However, the neutralizing agent contained in the stored water cleaning liquid 36 is not removed. That is, the second cleaning liquid 48 contains the desulfurization neutralizing agent contained in the stored water cleaning liquid 36 as it is. The relative injection speed of the second cleaning liquid 48 injected from the injection unit 33 with respect to the exhaust gas is smaller than the relative injection speed of the first cleaning liquid 38 injected from the injection nozzle 35 of the scrubber 31 with respect to the exhaust gas. The relative injection speed can be adjusted by changing the flow rate and flow direction of the exhaust gas, and can also be adjusted by changing the injection speed and the injection direction of the cleaning liquids 38 and 48.

  Part of the stored water washing liquid 36 that has passed through the purification treatment device 49 is supplied to the injection unit 33 by the second circulation pump 50 provided on the outlet side of the purification treatment device 49, and the rest is drained out of the ship. An injection adjustment valve 52 is provided in the pipe 51 connecting the injection unit 33 and the purification treatment device 49, and a waste water adjustment valve 54 is provided in the pipe 53 connecting the outboard and the purification treatment device 49. In the present embodiment, when the load of the engine 10 is equal to or less than a predetermined value, the injection adjustment valve 52 is closed and the injection of the second cleaning liquid 48 from the injection unit 33 is stopped. When the load on the engine 10 exceeds a predetermined value, the injection adjustment valve 52 is opened to inject the second cleaning liquid 48 from the injection unit 33. Further, the opening of the injection adjusting valve 52, the opening of the waste water adjusting valve 54, and the output of the second circulation pump 50 are adjusted, and the second cleaning liquid 48 injected from the injection unit 33 as the load on the engine 10 increases. The injection amount is controlled to be large.

<Effects of this embodiment>
As described above, in this embodiment, after desulfurization and dedusting are performed in the scrubber 31, desulfurization is performed in the gas cooler 32 in a state where the temperature of the exhaust gas is low. That is, in this embodiment, since desulfurization is performed in two stages including low-temperature desulfurization in the subsequent stage, high desulfurization performance can be ensured.

  In this embodiment, the relative injection speed of the second cleaning liquid 48 injected from the injection unit 33 with respect to the exhaust gas is higher than the relative injection speed of the first cleaning liquid 38 injected from the injection nozzle 35 of the scrubber 31 with respect to the exhaust gas. small. For removing PM, it is effective to make gas-liquid contact at high speed, and for removing SOx, it is effective to make gas-liquid contact for a long time. Therefore, according to the present embodiment, the scrubber 31 efficiently removes PM by jetting the first cleaning liquid 38 at a high speed, and in the gas cooler 32, sufficient time for gas-liquid contact in low-temperature desulfurization is ensured. , SOx can be removed more efficiently.

Moreover, in this embodiment, since high desulfurization performance can be ensured, it is not necessary to increase the amount of neutralizing agent put into the cleaning liquid. Therefore, it is difficult for CO ₂ to dissolve in the cleaning liquid, and it is possible to suppress the occurrence of failure of each device due to precipitation of solid content. Furthermore, since the SOx in the gas cooler 32 is removed by the second cleaning liquid 48, the condensed water generated in the gas cooler does not become a strong acid. Therefore, corrosion that may occur in the gas cooler 32 can be prevented. In addition, since the second cleaning liquid 48 injected in the gas cooler 32 has been purified, clogging is unlikely to occur in the gas cooler 32. Furthermore, in this embodiment, since desulfurization is performed in two stages, the amount of the second cleaning liquid 48 injected in the gas cooler 32 is small, and a water film is not easily generated in the gas cooler 32. Thus, according to this embodiment, the cause of failure of the EGR unit 30 can be eliminated.

  Moreover, in this embodiment, since the 1st washing | cleaning liquid 38 used with the scrubber 31 is not purified, the purification processing apparatus 49 can be prevented from becoming too large, and the EGR unit 30 can be made compact. Further, the marine engine system as in the present embodiment includes a purification treatment device for purifying the cleaning liquid that is drained out of the ship (sea). Therefore, in this embodiment, it is not necessary to newly provide a purification processing apparatus for cleaning the second cleaning liquid 48.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram of the EGR unit 230 according to the present embodiment. The engine system 200 according to the present embodiment is different from the engine system 100 according to the first embodiment in that the EGR unit 230 is a separate type in which the scrubber 31 and the gas cooler 32 are separated.

  The EGR unit 230 according to the present embodiment includes a scrubber 31, a gas cooler 32, and an injection unit 33, and further includes a surge tank 60.

  As in the case of the first embodiment, the scrubber 31 is a composite type that combines a spray type and a stored water type. The first cleaning liquid 38 injected toward the exhaust gas at the inlet of the scrubber 31 is carried by the exhaust gas and stored in the scrubber water storage unit 61 corresponding to the bottom portion of the scrubber 31. Further, the exhaust gas that has passed through the introduction passage 34 is discharged into the first cleaning liquid 38 stored in the scrubber water reservoir 61. The first cleaning liquid 38 sprayed by the scrubber 31 is obtained by reusing the stored water cleaning liquid 36 stored in the surge tank 60. The scrubber 31 is provided with a drain port 62 at a predetermined height position. When the water surface of the first cleaning liquid 38 reaches the height position of the drain port 62, the first cleaning liquid 38 is discharged from the drain port 62 to the surge tank 60 through the drain trap 63 that does not allow air to pass through.

  The gas cooler 32 has a heat exchanger 46 and a mist catcher 47 as in the case of the first embodiment. The heat exchanger 46 cools the exhaust gas, and the mist catcher 47 captures the first cleaning liquid 38 carried by the exhaust gas, the second cleaning liquid 48 injected from the injection unit 33, and the condensed water generated in the heat exchanger 46. To do. The liquid captured by the mist catcher 47 falls due to its own weight, and is discharged from the drain port 64 formed on the bottom surface of the gas cooler 32 to the surge tank 60 via the drain trap 65.

  The injection unit 33 injects the second cleaning liquid 48 into the exhaust gas that passes through the gas cooler 32. The second cleaning liquid 48 is obtained by purifying the stored water cleaning liquid 36 with a purification treatment device 49. As will be described later, the stored water cleaning liquid 36 contains the neutralizing agent supplied by the neutralizing agent charging device 43, and the purification treatment device 49 does not remove the neutralizing agent from the stored water cleaning liquid 36. Contains a neutralizing agent for desulfurization.

  The surge tank 60 is a tank for storing the first cleaning liquid 38 discharged from the scrubber 31 and the liquid discharged from the gas cooler 32. In other words, the water storage cleaning liquid 36 containing the first cleaning liquid 38 is stored in the surge tank 60. In addition, a pH meter 42 is attached to the surge tank 60, and the neutralizing agent is charged from the neutralizing agent charging device 43 so that the stored water cleaning liquid 36 has a predetermined pH value, and the fresh water supply device 44. Supply of fresh water.

  As described above, also in the EGR unit 230 according to this embodiment, after desulfurization and dedusting are performed in the scrubber 31, low-temperature desulfurization is further performed in the gas cooler 32. That is, in this embodiment, since desulfurization is performed in two stages including low temperature desulfurization in the latter stage, exhaust gas can be efficiently desulfurized.

  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, in the above description, the case where the used first cleaning liquid 38 and the used second cleaning liquid 48 are mixed to form the stored water cleaning liquid 36 and the stored water cleaning liquid 36 is reused as the first cleaning liquid 38 or the second cleaning liquid 48 will be described. However, the first cleaning liquid 38 and the second cleaning liquid 48 may be circulated separately. In that case, if a predetermined amount of neutralizing agent is added not only to the first cleaning liquid 38 but also to the second cleaning liquid 48, low-temperature desulfurization is performed in the gas cooler 32, and thus high desulfurization performance can be ensured. .

  Moreover, although the case where the scrubber 31 is a combined type combining the spray type and the stored water type has been described above, the scrubber 31 may adopt only one of the spray type and the stored water type. Other methods may be employed.

  According to the EGR unit according to the present invention, it is possible to suppress the occurrence of failure while ensuring high desulfurization performance. Therefore, it is useful in the technical field of the EGR unit.

DESCRIPTION OF SYMBOLS 10 Engine 30, 230 EGR unit 31 Scrubber 32 Gas cooler 33 Injection part 35 Injection nozzle 36 Reservoir cleaning liquid 38 First cleaning liquid 48 Second cleaning liquid 49 Purification processing apparatus 100, 200 Engine system

Claims (7)

An EGR unit for recirculating exhaust gas to the engine,
A scrubber for cleaning the exhaust gas using a first cleaning liquid;
A gas cooler for cooling the exhaust gas cleaned by the scrubber;
An injection unit that injects a second cleaning liquid into the exhaust gas in the gas cooler ,
An EGR unit in which the first cleaning liquid and the second cleaning liquid contain a desulfurization neutralizing agent.   2. The EGR unit according to claim 1, wherein the second cleaning liquid ejected from the ejecting unit is a water storage cleaning liquid containing the used first cleaning liquid, which is purified and reused.   2. The EGR unit according to claim 1, wherein the first cleaning liquid is obtained by reusing a stored water cleaning liquid containing the used first cleaning liquid without purifying the first cleaning liquid.   The apparatus further comprises a purification processing device for purifying the stored water cleaning liquid when the stored water cleaning liquid is drained, wherein the second cleaning liquid is a part of the stored water cleaning liquid purified by the purification processing device. Item 3. The EGR unit according to Item 2.   The EGR unit according to any one of claims 1 to 4, wherein the EGR unit is configured to be able to switch between injection and stop of the second cleaning liquid by the injection unit in accordance with an operation state of the engine. The scrubber has an injection nozzle that injects a first cleaning liquid into the exhaust gas;
The relative injection speed with respect to the exhaust gas of the second cleaning liquid injected from the injection unit is smaller than the relative injection speed with respect to the exhaust gas of the first cleaning liquid injected from the injection nozzle of the scrubber. The EGR unit according to any one item.   The engine system provided with the EGR unit as described in any one of Claims 1 thru | or 6.

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