Exhaust gas aftertreatment device

Abstract

The invention relates to an exhaust gas aftertreatment device. The invention further relates to a soot blower unit (20) for an exhaust gas aftertreatment device (10) of an internal combustion engine (1), to an internal combustion engine (1) and to a method for blowing soot from a catalyst (30). The soot blower unit (20) comprises a supply line (21) for providing pressurized air and at least one injection device (22) having a soot blower valve (23), in particular a diaphragm valve, fluidly connected or fluidly connectable to the supply line (21) for providing pressurized air. The soot blower unit (20) comprises a pipe (24) for providing backup seal air fluidly connected or fluidly connectable to the supply line (21) for providing pressurized air upstream of the at least one injection device (22).

Description

Technical Field

[0001] The present invention relates to a soot blower unit for an exhaust gas aftertreatment device, an exhaust gas aftertreatment device for an internal combustion engine, an internal combustion engine, and a method for blowing soot off a catalyst.

[0002] This invention preferably relates to an internal combustion engine, such as a large ship or vessel engine or a stationary engine, whose cylinder has an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine can be a diesel engine or a gas engine, a dual-fuel engine or a multi-fuel engine. Liquid and / or gaseous fuels can be burned in such an engine, and it can be self-ignited or forced-ignited.

[0003] An internal combustion engine can be a longitudinally flushing two-stroke engine. Background Technology

[0004] The term "internal combustion engine" also refers to a large engine capable of operating not only in diesel mode (characterized by the self-ignition of fuel) but also in Otto mode (characterized by the forced ignition of fuel), or a combination of both. Furthermore, the term "internal combustion engine" specifically includes dual-fuel engines and large engines in which the self-ignition of one fuel is used for the forced ignition of another fuel.

[0005] The engine speed is preferably below 800 RPM, especially for 4-stroke engines, more preferably below 200 RPM, especially for 2-stroke engines, which indicates the name of a low-speed engine.

[0006] The fuel can be diesel or marine diesel or heavy fuel oil or emulsion or slurry or methanol or ethanol, as well as gases such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG).

[0007] Other possible fuels that can be added as needed are: LBG (liquefied biogas), biofuels (such as oil made from algae or seaweed), ammonia, hydrogen, and synthetic fuels derived from CO2 (such as those made from electricity to gas or electricity to liquid).

[0008] Large ships, especially those used for transporting cargo, are typically powered by internal combustion engines, particularly diesel and / or gas engines, primarily two-stroke crosshead engines.

[0009] SCR (Selective Catalytic Reduction) technology is used to reduce the level of nitrogen oxides (NOx) in the exhaust gases of combustion engines. SCR is commonly used in land-based engines, such as heavy vehicles, industrial equipment, and other applications. SCR technology is also being used in marine environments with two-stroke diesel engines. The demand for effective SCR systems is increasing due to regulatory requirements for both marine and land-based diesel engines.

[0010] The catalytic elements of an SCR reactor are exposed to an exhaust gas stream containing soot. The SCR reactor may therefore include an SCR cleaning system for cleaning the SCR catalyst, particularly for removing soot deposited on the front region of the catalyst layer. To prevent excessive deposition and clogging of the catalytic elements, the deposited soot is periodically blown away by means of specially arranged soot blowing units that blow compressed air transversely to the exhaust flow direction.

[0011] Typically, a soot blowing unit includes an arrangement of soot blowing valves, one or more air tanks, and piping.

[0012] These valves are typically diaphragm valves with a large flow area and a very short opening time. In high-pressure SCR installations, the sootblowing system must be pressurized (e.g., with pressurized air) for the entire engine operating time to prevent the diaphragm valve from being pushed open by exhaust gas pressure and to prevent hot exhaust gas from flowing back into the sootblowing unit. Backflow of hot exhaust gas can cause thermal damage to the valve diaphragm, leading to valve failure and potentially exhaust gas leakage.

[0013] KR101818262B1 discloses a soot blowing unit comprising an air supply line, a spraying device for spraying air onto an SCR catalyst, a control unit for controlling the air supply, and an exhaust gas auxiliary inflow line that independently connects the spraying device to the engine's exhaust manifold, such that a portion of the exhaust gas is used to clean the SCR catalyst. However, the exhaust gas may cause additional soot buildup at the SCR catalyst. Summary of the Invention

[0014] The objective of this invention is to provide a soot blower unit, an exhaust gas aftertreatment device, an internal combustion engine, and a method for blowing soot away from a catalyst, which avoids known disadvantages and, in particular, provides reliable and durable removal of soot from the catalyst.

[0015] According to the present invention, the sootblower unit of the exhaust aftertreatment device for an internal combustion engine includes a supply line for providing pressurized air and at least one injection device. The injection device includes a sootblower valve, particularly a diaphragm valve, fluidly connected to or potentially fluidly connected to the supply line for providing pressurized air.

[0016] The soot blowing valve can open in a very short time, typically less than 1 second, to release pressurized air onto the surface of the catalyst, thereby removing any soot that has accumulated.

[0017] The injection device may include at least one nozzle that is directed toward the surface of the catalyst, particularly toward the portion of the surface that tends to trap soot, as they are arranged transversely to the direction of exhaust gas flow.

[0018] Preferably, the spraying device includes at least one nozzle, with one nozzle corresponding to each catalyst surface to be sprayed.

[0019] The sootblower unit includes a conduit for providing backup sealing air. The conduit is fluidly connected, or potentially fluidly connected, upstream of at least one injection device to a supply line for providing pressurized air. Therefore, the sootblower valve can be pressurized with backup sealing air, which prevents hot exhaust gas from flowing back into the sootblower unit.

[0020] Typically, the pressure of the backup sealed air is kept too low to blow away the soot.

[0021] If the exhaust gas pressure is higher than the pressure supplied by the supply line, there is a risk that the exhaust gas will open the soot blowing valve and that the exhaust gas can be directed through the soot blowing valve. In particular, when the main soot blowing valve is closed, no pressurized air can be supplied to the injection unit.

[0022] Even if the supply line does not provide pressure or provides too low a pressure, the pipeline used to provide backup sealing air can maintain pressure on the injection device.

[0023] Specifically, the backup sealing air is diverted from the turbine of the turbocharger or from the scavenging air inlet manifold of the internal combustion engine.

[0024] In two-stroke internal combustion engines, the scavenging air pressure is typically higher than the exhaust gas pressure, and by pressurizing the soot blowing unit with the scavenging air, hot exhaust gas does not flow back into the soot blowing unit. The soot blowing valves, especially the diaphragm valves, are protected.

[0025] In an SCR reactor, the pressure supplied by the exhaust gas can be as high as 4 bar, typically 3.5 to 3.6 bar. The pressure of the scavenging air can be 0.3 bar or higher.

[0026] The soot blower unit may include a soot blowing air compressor for producing compressed air typically 8 to 10 bar.

[0027] Alternatively or additionally, the sootblower unit may include a pressure vessel for maintaining compressed air, which is located, for example, downstream of an air compressor. The pressure vessel may have a volume of 200-250 liters.

[0028] The container can withstand pressures of up to 8 to 10 bar.

[0029] Preferably, the conduit for providing backup sealing air can be pressurized by a pressure of at least 4 bar.

[0030] The sootblower unit preferably includes a main sootblowing valve arranged in the supply line. The line may be fluidly connected downstream of the main sootblowing valve to, or fluidly connected to, a supply line for providing pressurized air.

[0031] Backup sealing air, such as scavenging air, can only be used for protection.

[0032] During engine operation without SCR function, such as when only Tier II standards must be met, the sootblowing main valve can remain closed. In this mode, exhaust gas typically bypasses the SCR reactor, instead passing through a bypass. However, the SCR reactor can still be pressurized by exhaust gas pressure. Similarly, in this case, the pressure of the backup sealing air prevents the sootblowing valve from opening. Therefore, it is not necessary to pressurize the injection system with pressurized air generated in the sootblowing air compressor.

[0033] This reduces the operating costs of the ship's sootblowing air compressor. The SCR catalyst is ready for use when SCR operation resumes.

[0034] A check valve can be placed in a conduit used to provide backup sealing air. It can prevent hot exhaust gases or pressurized air from flowing into the air inlet of, for example, a turbocharger compressor or an internal combustion engine.

[0035] Additionally or alternatively, a check valve may be placed in the supply line for providing pressurized air, preferably downstream of the main sootblowing valve. This prevents hot exhaust gas or backup sealing air, which may contain water, from flowing to, for example, the sootblowing air compressor.

[0036] Check valves typically provide an opening pressure of 0.02 bar.

[0037] A check valve can be installed to prevent air leakage into the supply system.

[0038] The sootblower unit does not require a regulating valve located in the duct used to provide backup sealing air. The turbocharger can generate backup sealing air as long as the engine is running.

[0039] In an advantageous embodiment of the sootblower unit, the sootblower unit includes a control unit. The control unit may be designed to set at least one sootblowing valve and / or to set the main sootblowing valve.

[0040] The control unit can be designed to receive data from sensors, such as pressure data collected and provided by a pressure sensor downstream of the compressor. The control unit can be designed to open the soot blowing valve and / or the main soot blowing valve only when the measured pressure is above a predetermined pressure value. The opening frequency of the soot blowing valve can depend on the fuel quality and the resulting soot load.

[0041] The soot blowing valves are preferably opened continuously, so that each of the valves provides full pressure.

[0042] The soot blowing valve can be opened once a day, up to once every quarter hour.

[0043] The control unit can be designed to receive data from sensors representing the soot load on the catalyst. One or more pressure sensors may be arranged in the SCR reactor and may, for example, provide data showing the pressure drop of the exhaust gas along the SCR reactor. The control unit can be designed to open only the soot blowing valve and / or the main soot blowing valve whenever the data exceeds a predetermined value.

[0044] If the pressure of the main soot blowing pressurized air is lower than the pressure of the backup sealing air, the supply of backup sealing air can be activated automatically.

[0045] The control unit can be designed to open the soot blowing main valve, located in the supply line for providing pressurized air, when the internal combustion engine is to operate in TIER III mode. The control unit can also be designed to close the regulating valve in other ways.

[0046] When TIER III standards must be met, exhaust aftertreatment systems operate using SCR catalysts. In this case, it is important to keep the catalyst free of soot.

[0047] The problem is also addressed by an exhaust aftertreatment device for internal combustion engines, which includes at least one SCR catalyst and at least one soot blower unit as described above.

[0048] The exhaust gas aftertreatment device may include multiple SCR catalysts and at least one injection device for each of the catalysts. The catalysts may be arranged in the SCR reactor.

[0049] The sootblower unit is preferably arranged such that the airflow from the jetting device flows in a direction different from the main flow direction of the exhaust gas, particularly laterally or transversely to the exhaust flow direction. Therefore, the sootblower valve is arranged such that the main flow direction of the exhaust gas does not directly face the valve.

[0050] However, when the exhaust gas pressure is high, back pressure may be required to keep the sootblower valve closed. This back pressure can be provided by compressed air via a supply line and / or by backup sealing air via a pipeline.

[0051] The problem can also be solved by an internal combustion engine that includes at least one cylinder and at least one exhaust aftertreatment device as described above.

[0052] The internal combustion engine preferably includes a turbocharger.

[0053] The exhaust aftertreatment system can be located upstream of the turbocharger's turbine. In this case, the exhaust gas typically has relatively high pressure as it passes through the SCR catalyst. Back pressure may be required to keep the sootblower valve closed.

[0054] The conduit for providing backup sealing air can be fluidly connected to, or is capable of being fluidly connected to, the compressor of the turbocharger. Preferably, the conduit is fluidly connected to, or is capable of being fluidly connected to, the turbocharger downstream of the compressor, for example, downstream of the cooler. Thus, scavenging air can be provided as backup sealing air at a sufficiently high pressure, typically higher than the pressure of the exhaust gases in the catalyst.

[0055] The problem is also addressed by a method for blowing away soot from the catalyst of an exhaust aftertreatment device for internal combustion engines, preferably an exhaust aftertreatment device as described above.

[0056] Pressurized air is supplied in the supply line. The pressurized air is blown toward the catalyst via at least one injection device, which includes at least one soot blowing valve, particularly a diaphragm valve. The injection device is fluidly connected to the supply line for supplying the pressurized air.

[0057] Specifically, pressurized air is blown in a direction different from the main flow direction of the exhaust gas in the catalyst.

[0058] A backup sealing air is provided in a pipeline, which is fluidly connected upstream of at least one injection device to a supply line for providing pressurized air.

[0059] Therefore, the soot blowing valve is pressurized by the backup sealing air.

[0060] Backup sealing air can be provided in the compressor of the turbocharger of an internal combustion engine, so the backup sealing air can be scavenging air. Attached Figure Description

[0061] Other advantageous aspects of the invention will now be explained with the aid of exemplary embodiments and accompanying drawings. In the drawings, in an illustrative manner:

[0062] Figure 1 A schematic diagram of an internal combustion engine is shown;

[0063] Figure 2 An example of a soot blowing valve is shown.

[0064] Figure Labels

[0065] Internal combustion engine (1)

[0066] Exhaust gas after-treatment device (10)

[0067] Soot blower unit (20)

[0068] Supply pipeline (21)

[0069] Spraying device (22)

[0070] Soot blowing valve (23)

[0071] Piping used to provide backup sealing air (24)

[0072] Soot blowing air compressor (25)

[0073] Soot blowing main valve (26)

[0074] Check valves (27a, 27b)

[0075] Control unit (29)

[0076] SCR catalyst (30)

[0077] Turbocharger (31)

[0078] Turbine (32)

[0079] Compressor (33)

[0080] Direction 34

[0081] Direction 35

[0082] Exhaust manifold 36

[0083] SCR reactor 37

[0084] Compressed air container 38

[0085] Sensor 39

[0086] Entrance 49

[0087] Exports 40

[0088] Membrane 41

[0089] Spring 42

[0090] Cavity 43

[0091] Solenoid 44

[0092] The other membrane 45

[0093] Second Exit 46 Detailed Implementation

[0094] The internal combustion engine 1 includes a cylinder 2 and an exhaust aftertreatment device 10.

[0095] The exhaust gas aftertreatment device 10 includes multiple SCR catalysts 30 and soot blower units 20.

[0096] Exhaust gas exits cylinder 2, passes through exhaust manifold 36, and is guided through SCR reactor 37, which hosts SCR catalyst 30. The exhaust gas carries carbon particles that can accumulate on catalyst 30 to form a soot layer. The soot can be removed by a stream of pressurized air.

[0097] Pressurized air can be generated in the soot blowing air compressor 25 and stored in the pressurized air container 38.

[0098] When the main soot blowing valve 26 is opened, pressurized air can be directed from the supply line 21 to the injection device 22. One injection device 22 is provided for each catalyst 30. Each injection device 22 includes a soot blowing valve 23. When the soot blowing valve 23 is opened, the airflow from the injection device 22 is blown onto the corresponding catalyst 30 in a direction 35 perpendicular to the main flow direction 34 of the exhaust gas. Soot is removed from the catalyst 30.

[0099] A conduit 24 for providing backup sealing air is fluidly connected upstream of the jetting device 22 and downstream of the soot blowing main valve 26 to a supply line 21 for providing pressurized air.

[0100] The backup sealing air is diverted from the scavenging air from the compressor 33 of the turbocharger 31. The backup sealing air pressurizes the soot blow valves 23 so that they cannot be unintentionally opened by exhaust gas, since the pressure of the scavenging air is usually higher than that of the exhaust gas.

[0101] A check valve 27A is arranged in pipe 24. A check valve 27b is arranged in the supply line downstream of the soot blowing main valve 26 and upstream of the fluid connection between supply line 21 and pipe 24.

[0102] Compressed air may not be directed to compressor 33.

[0103] The turbocharger 31 also includes a turbine 32 driven by exhaust gas exiting the SCR reactor 37.

[0104] The soot blower unit 20 includes a control unit 29 for setting the soot blowing valve 23 and the soot blowing main valve 26.

[0105] Pressure sensor 39 is disposed in supply line 21. Based on the pressure in supply line 21, the control unit may allow the soot blowing valve 23 to be opened.

[0106] Figure 2 An example of soot blowing valve 23 is shown.

[0107] The soot blowing valve includes an inlet 49, which can be connected to the supply line 21 (see...). Figure 1 The sootblowing valve also includes an outlet 40 that points to the surface of the SCR catalyst 30 (see...). Figure 1 ).

[0108] In this example, the soot blowing valve 23 includes a diaphragm 41. A spring 42 is used to keep the soot blowing valve 23 normally closed when it is not activated.

[0109] When the air compressor for blowing soot is 25 (see) Figure 1 When pressure is applied, a pinhole (not shown) through the diaphragm 41 allows pressurized air to enter the cavity 43 located behind the diaphragm 41, making the pressure equal on both sides of the diaphragm 41. The spring 42 provides a net downward force.

[0110] If current flows through solenoid 44, the other membrane 45 is retracted by magnetic force. Some of the pressurized air can escape through the second outlet 46, and the pressure in cavity 43 decreases. The force of spring 42 is not strong enough to keep membrane 41 downward. Soot valve 23 opens, and pressurized air can escape through outlet 40.

[0111] When solenoid 44 is deactivated, pressure immediately builds up again in cavity 43, and diaphragm 41 is pressed down to close valve 23.

[0112] When the pressure on the outlet 40 side is higher than the pressure on the inlet 49 side, the spring 42 may not be able to provide enough force to keep the membrane 41 closed.

[0113] Therefore, even when the soot blowing main valve 26 (see Figure 1 When shutting down, sufficient pressure must also be provided on the inlet side. Exhaust gas pressurized at outlet 40 will not be able to open membrane 41.

[0114] The greater force of spring 42 could theoretically keep membrane 41 closed even during periods of pressure in outlet 40. However, the greater force of spring 42 would alter the dynamics of sootblowing valve 23. Opening valve 23 would take longer.

[0115] To blow away the soot, a short pressure pulse is required. Therefore, valve 23 should respond very quickly, which is only possible with a relatively weak spring force.

Claims

1. A soot blower unit (20) for an exhaust gas aftertreatment device (10) for an internal combustion engine (1), the internal combustion engine including a turbocharger, the soot blower unit having: - Supply line (21), the supply line being used to provide pressurized air - Soot blowing air compressor (25), the soot blowing air compressor being used to generate the pressurized air. - At least one injection device (22), said at least one injection device comprising a soot blowing valve (23) fluidly connected to or capable of being fluidly connected to said supply line (21) for providing pressurized air, characterized in that, The soot blower unit (20) includes: - Pipe (24), the pipe being used to provide backup sealing air, the pipe being fluidly connected to or capable of being fluidly connected to the supply line (21) for providing pressurized air. - wherein the conduit (24) is fluidly connected to or can be fluidly connected to the compressor of the turbocharger of the internal combustion engine, such that the spare sealing air is diverted from the turbine of the turbocharger or from the scavenging air from the inlet manifold of the internal combustion engine.

2. The soot blower unit (20) according to claim 1, wherein, The soot blower unit (20) includes a soot blowing main valve (26) arranged in the supply line.

3. The soot blower unit (20) according to claim 1, wherein, Check valves (27a, 27b) are arranged in at least one of the conduit (24) for providing backup sealing air and the supply line (21) for providing pressurized air.

4. The soot blower unit (20) according to claim 3, wherein, The check valves (27a, 27b) are located downstream of the soot blowing main valve (26).

5. The soot blower unit (20) according to claim 1, wherein, The soot blower unit (20) includes a control unit (29) for setting at least one of the soot blowing main valve (26) and at least one soot blowing valve (23).

6. The soot blower unit (20) according to claim 5, wherein, The control unit is designed to receive data from a sensor representing the soot load of the catalyst (30), and the control unit is designed to open at least one of the soot valve (23) and the soot main valve (26) only when the data is higher than a predetermined data.

7. The soot blower unit (20) according to claim 5, wherein, The control unit (29) is designed such that when the internal combustion engine (1) is to operate in TIER III mode, the soot blowing main valve (26) arranged in the supply line (21) for providing pressurized air is opened.

8. An exhaust aftertreatment device (10) for an internal combustion engine (1), the exhaust aftertreatment device comprising at least one SCR catalyst (30) and at least one soot blower unit (20) according to claim 1.

9. The waste gas aftertreatment device (10) according to claim 8, wherein, The soot blower unit (20) is arranged such that the airflow from the jetting device (22) flows in a direction (35) different from the main flow direction (34) of the exhaust gas.

10. An internal combustion engine (1) comprising a turbocharger (31), at least one cylinder (2) and at least one exhaust aftertreatment device (10) according to claim 8.

11. The internal combustion engine (1) according to claim 10, wherein, The exhaust gas aftertreatment device (10) is arranged upstream of the turbine (32) of the turbocharger (31).

12. A method for blowing away soot from a catalyst (30) of an exhaust gas aftertreatment device (10), said exhaust gas aftertreatment device (10) according to claim 8, wherein, -Pressurized air is generated in the soot blowing air compressor (25), -The pressurized air is supplied in the supply line (21), - The pressurized air is blown to the catalyst (30) via at least one injection device (22), the injection device including a soot blowing valve (23) fluidly connected to the supply line (21) for providing pressurized air, wherein backup sealing air is provided in a pipe (24) fluidly connected upstream of the at least one injection device (22) to the supply line (21) for providing pressurized air, wherein the backup sealing air is scavenging air provided in the compressor (33) of the turbocharger (31) of the internal combustion engine (1).

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