JP5044601B2 - Large two-cycle diesel engine with exhaust gas scrubber - Google Patents

Description

The present invention relates to a large heavy oil diesel engine such as a main engine of an open-sea ship to which an exhaust gas scrubber for reducing the SO ₂ content of exhaust gas is attached.

Background of the Invention

  Public awareness of environmental issues is growing rapidly. The International Maritime Organization (IMO) continues to discuss emissions control in the form of air pollution at sea. Authorities in various parts of the world are taking similar measures. An example is the United States Environmental Protection Agency (EPA) bill under discussion.

However, for cost reasons, large two-cycle diesel engines are generally operated with heavy oil, which is a fuel with a relatively high sulfur content. As a result, the exhaust gas has a high SO ₂ content. Known methods for reducing the SO ₂ level in the exhaust gas to produce a vapor of salt water, there is an exhaust gas include the application of an exhaust gas scrubber to pass. The SO ₂ molecules in the exhaust gas are combined with alkali ions in the salt water droplets. The effectiveness of the scrubber depends on the amount of water pumped through the scrubber and the salinity (strictly alkalinity) of the water. In ocean vessels, seawater is the most obvious choice as a saltwater source. However, for optimum results, approximately 4 kilograms of seawater per kilogram of exhaust gas must be pumped through the exhaust gas scrubber. Large two-cycle diesel engines produce up to 500.000 tonnes of exhaust gas per hour, which requires that 2.000.000 tonnes of seawater be pumped through an exhaust gas scrubber It means that there is. The amount of energy required to pump such amounts of seawater to the exhaust gas scrubber on the upper side of the ship (where the exhaust pipe is located) is enormous and is notable for specific fuel oil consumption Adversely affect.

From such a background, an object of the present invention is to reduce energy used by a system for removing SO ₂ from exhaust gas in a large two-cycle diesel engine.

The object is a large two-cycle diesel engine fueled with heavy oil, a turbocharger having an exhaust gas driven turbine for supplying scavenging gas to an engine cylinder, and a compressor driven by the turbine, and the compressor A seawater-operated scavenging and humidifying unit having a seawater intake and a return water discharge disposed downstream of the turbine, and a saltwater-operated exhaust gas purification scrubber having a salt water intake disposed downstream of the turbine, An exhaust gas purification scrubber that generates salt water vapor to allow the exhaust gas to pass therethrough to reduce the SO ₂ content of the exhaust gas, and a pipe that leads the return water from the scavenging humidification unit to the intake of the exhaust gas purification scrubber. This is achieved by providing an engine comprising:

Including a higher salinity than seawater, by using the return water from the scavenging humidifying unit, also reduces the amount of water required to obtain a SO ₂ level of a predetermined decrease in the exhaust gas. The water from the scavenging humidification unit typically has twice the salinity of seawater. As a result, the amount of water required to pump into the exhaust gas purification scrubber can be substantially halved.

  The exhaust gas purification scrubber may include a salt water recirculation system.

  The return water from the scavenging and humidifying unit has a salinity substantially higher than the salinity of the seawater introduced into the scavenging and humidifying unit (12). Preferably, the return water from the scavenging humidification unit has a salinity of at least twice the salinity of the seawater introduced into the scavenging humidification unit.

Further, the object is a large two-cycle diesel engine using heavy oil as fuel, an exhaust gas driven turbine for supplying scavenging gas to an engine cylinder, and a turbocharger having a compressor driven by the turbine, A fresh water generator driven by engine waste heat, wherein the fresh water generator has a sea water intake, a fresh water supply port and a high salinity waste water discharge port, and is disposed downstream of the turbine, and is a salt water intake A salt water operation type exhaust gas purification scrubber comprising: an exhaust gas purification scrubber for generating salt water vapor for passing the exhaust gas to reduce the SO ₂ content of the exhaust gas; and from the fresh water generator This is accomplished by providing an engine comprising a pipe for leading waste water to the intake of the exhaust gas purification scrubber.

  The exhaust gas purification scrubber may include a salt water recirculation system.

  The waste water from the fresh water generator has a salinity substantially higher than the salinity of seawater introduced into the air fresh water generator. Preferably, the waste water from the fresh water generator has a salinity of at least twice the salinity of the seawater introduced to the air fresh water generator.

  The above object is also a method for operating an exhaust gas scrubber of a large two-cycle diesel engine, comprising using waste water of a scavenging humidification unit of an engine or waste water of a fresh water generator for the exhaust gas scrubber. Is achieved by providing

  Further objects, features, advantages and characteristics of the engine and method according to the present invention will become apparent from the detailed description.

In the following detailed part of the description, the invention will be described in more detail with reference to exemplary embodiments shown in the drawings.
1 is a diagram of an intake system and an exhaust system of an internal combustion engine according to a first embodiment of the present invention. FIG. 3 is a diagram of an intake system and an exhaust system of an internal combustion engine according to a second embodiment of the present invention.

Detailed Description of the Preferred Embodiment

  In the following detailed description, the present invention will be described using preferred embodiments. FIG. 1 is a diagram illustrating a crosshead type large turbocharged two-cycle diesel engine 1 including the intake system and the exhaust system. The engine 1 has an air supply receiver 2 and an exhaust gas receiver 3. An exhaust valve belonging to the combustion chamber is indicated by 4. The engine 1 can be used, for example, as a stationary engine for operating a main engine of an open-sea vessel or a power generator of a power plant. The total output of the engine is, for example, in the range of 5,000 kW to 110,000 kW. Since the engine 1 is operated with heavy oil, a heavy oil system including a heated heavy oil tank and a heated heavy oil pipe (not shown) is provided. These heating elements of the fuel injection system are also heated when the engine is stopped because heavy oil is extremely viscous at ambient temperature. Further, the heavy oil system (not shown) is provided with a recirculation system that keeps heavy oil flowing from the components of the heavy oil system while the engine is stopped. Recirculation makes it possible to reliably warm the components of the heavy oil system that do not have its own heating means even when the engine is stopped, and also helps to degas the heavy oil system.

  Scavenging proceeds from the scavenging pan 2 to the scavenging ports (not shown) of the individual cylinders. When the exhaust valve 4 is opened, the exhaust gas flows into the exhaust receiver 3 through the first exhaust pipe, further proceeds, and flows into the turbine 7 of the turbocharger 6 from the first exhaust pipe 5, From there, the exhaust gas flows out through the second exhaust pipe 20. By means of the shaft 8, the turbine 7 drives a compressor 9 that is supplied via the inlet 10. The compressor 9 supplies pressurized air to the air supply pipe 11 that leads to the air supply receiver 2.

  The intake air in the tube 11 humidifies the supply air (scavenging) (which is released from the compressor at about 200 ° C.) and also reduces the scavenging temperature from a level of 36 ° C. to 80 ° C. Therefore, it passes through the humidification unit 12. In this embodiment, the humidification unit 12 is a scrubber, and a large amount of water is injected and evaporated in the scrubber. The injected water is preferably relatively warmed, for example, by heating seawater with waste heat from a (water) cooling system (not shown) of the engine 1. Alternatively, water that is not pre-warmed may be used, but the resulting absolute moisture level is slightly lower than when warm seawater is supplied to the scavenging humidification unit 12.

  In a preferred embodiment, the humidification unit is a scrubber 12, which causes air having a relative humidity of approximately 100% and a temperature of about 70 ° C. to exit the humidification unit. The absolute humidity of this intake (scavenging) is about 5 times higher than the scavenging exiting the conventional engine intercooler. Therefore, the amount of energy contained in the scavenging and contained in the exhaust gas is significantly higher than that of the conventional engine (non-humidified scavenging engine). Therefore, there is a lot of energy that can be extracted from the exhaust gas and used at a high load level. The high absolute water content during scavenging allows the peak and average combustion temperatures to be lowered, resulting in a decrease in NOx production during combustion.

  The humidified air supply is guided to the air supply receiver 2 by the auxiliary blower 16 driven by the electric motor 17. The auxiliary blower 16 pressurizes the supply air flow to a low load state or a partial load state. At higher load conditions, the turbocharger compressor 9 provides sufficient compressed scavenging and the auxiliary blower 16 is bypassed by the check valve 15.

  A controllable valve 19 is provided in the exhaust pipe 5 upstream of the turbine 7. Through the controllable valve, part of the exhaust gas (about 10%) bypasses the turbine 7. The control valve 19 is connected to the controller 50. The controller 50 controls the operation of the controllable valve 19 so that a certain amount of exhaust gas is branched to the power turbine 31. The energy escaping through the controllable valve 19 recovers relatively efficiently in the power turbine 31, so that the overall fuel efficiency can be made higher.

  In some embodiments, the power turbine 31 drives a generator 32. Accordingly, surplus energy in the exhaust gas stream is converted into electric power, that is, energy having high exergy.

  In the present embodiment, high-pressure seawater is supplied to the scavenging humidification unit 12 that is a scrubber by a pipe 21 and a pump 22. The scavenging and humidifying unit 12 has a relatively high pressure and generates high salinity waste water. This waste water leaves the scavenging / humidifying unit 12 via the outlet of the scavenging / humidifying unit 12 and travels toward the pipe 23. The pipe 23 guides the high-salt waste water to the inlet of the exhaust gas purification scrubber 24.

  The exhaust gas purification scrubber 24 is disposed in the second exhaust pipe 20 so that the exhaust gas passes through the exhaust gas purification scrubber 24. The exhaust gas purification scrubber 24 has a salt water recirculation circuit 27 provided with a pump 28.

  The recirculation circuit 27 includes a valve 25 for controlling the amount of high salinity water introduced into the recirculation circuit 27, and a valve 29 for controlling the amount of used brine discharged from the recirculation circuit 27. Have Valve 25 and valve 29 are connected to controller 50, which controls the amount of high salinity water supplied to recirculation circuit 27 and the wastewater discharged from recirculation circuit 27 and directed to piping 26. Adjust the amount. Since the high salinity waste water from the scavenging humidification unit 12 maintains a relatively high pressure, it can be led to the recirculation circuit 27 without further pumping.

The SO ₂ in the exhaust gas reacts with alkali ions in high salinity water injected as steam into the scrubber 24. SO ₂ absorbed by the high salinity water is removed via the waste pipe 26.

  FIG. 2 shows another embodiment of the present invention. The engine according to this second embodiment is essentially the same as the embodiment described in connection with FIG. 1 except that it does not comprise a scavenging humidification unit. Instead, high salinity wastewater is obtained from the freshwater generator 43. Seawater is supplied to the fresh water generator 43 via the pipe 42 and the pump 40. Seawater is guided to the inlet of the fresh water generator 43 and is evaporated and re-solidified in the fresh water generator 43 by the vacuum heat and waste heat from the engine 1. The fresh water thus obtained is guided to a fresh water tank (not shown) through a pipe 44 connected to the outlet of the fresh water generator 43. Another outlet of the fresh water generator 43 is connected to the exhaust gas purification scrubber 24 via a pipe 23. In the present embodiment, the operation of the exhaust gas purification scrubber 24 is the same as the operation of exhaust gas purification in the embodiment described with respect to FIG.

The present invention has a number of advantages. Different embodiments or implementations may provide one or more of the following advantages. It should be noted that this is not a comprehensive list and that there may be other benefits that are not described herein. One advantage of the present invention is that the amount of energy required to pump salt water into the exhaust gas purification scrubber can be significantly reduced to reduce the SO ₂ content of the exhaust gas of a large two-cycle diesel engine. It can be mentioned.

  The term “comprising”, used in the claims, does not exclude other elements or steps. The singular terms in the claims do not exclude the plural.

  Any reference signs used in the claims shall not be construed as limiting the scope.

  In the foregoing specification, attempts have been made to note features of the present invention that are considered to be of particular importance, but with respect to any patentable feature or combination of features referenced and / or illustrated herein. It is to be understood that the Applicant claims protection regardless of whether or not particular emphasis has been given. Further, those skilled in the art may make modifications and / or improvements on the apparatus of the present invention in view of the present disclosure, but within the scope and spirit of the invention as set forth in the following claims I want you to understand.

Claims (3)

A large two-cycle diesel engine (1) fueled with heavy oil,
An turbocharger (6) having an exhaust gas driven turbine (7) for supplying scavenging gas to an engine cylinder and a compressor (9) driven by the turbine (7);
A seawater-operated scavenging humidification unit (12) having a seawater inlet and a return water outlet, which is arranged downstream of the compressor (9);
A brine-operated exhaust gas purification scrubber (24) disposed downstream of the turbine (7) and having a salt water intake for passing the exhaust gas to reduce the SO ₂ content of the exhaust gas. An exhaust gas purification scrubber (24) that produces salt water vapor;
A pipe (23) for returning water from the scavenging and humidification unit (12) to the intake of the exhaust gas purification scrubber (24);
The return water from the scavenging / humidifying unit (12), which is returned to the intake port of the exhaust gas purification scrubber (24), is introduced into the scavenging / humidifying unit (12). that having a salinity substantially greater than the, engine.   The engine according to claim 1, wherein the exhaust gas purification scrubber (24) comprises a salt water recirculation system (27, 28).   A method of operating an exhaust gas scrubber (24) of a large two-cycle diesel engine (1), comprising using waste water of a scavenging and humidification unit (12) of the engine for the exhaust gas scrubber (23). .

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