A dual-fuel engine methane escape aftertreatment system

Abstract

The present invention belongs to the technical field of engines, and discloses a post-treatment system for escaped methane of a dual-fuel engine, which includes a turbocharger, a dual-fuel engine, and a methane catalytic oxidation reactor. The turbocharger is provided with an intake passage and an exhaust passage. The dual-fuel engine is provided with engine cylinders. The intake port of the engine cylinders is communicated with the outlet of the intake passage. The intake port of the methane catalytic oxidation reactor is communicated with the outlet of the engine cylinders. The outlet of the methane catalytic oxidation reactor is communicated with the intake port of the exhaust passage. By arranging the methane catalytic oxidation reactor upstream of the exhaust passage of the turbocharger and using the flue gas before the turbocharger to carry out the methane catalytic oxidation reaction, there is no need to set up a heating device to heat the flue gas, which saves costs and avoids waste of the heat energy of the flue gas.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and particularly to a post-treatment system for escaped methane of a dual-fuel engine. Background Art

[0002] With the continuous development of internal combustion engine technology, the requirements for the economy of internal combustion engines have been continuously improved and international emission regulations have become increasingly strict. The research and development of alternative fuels for engines have become an important topic. Compared with existing fuels, natural gas fuel has lower emission pollution, is cleaner and has rich reserves. Due to the dual influence of economic and environmental benefits, natural gas has gradually become the most promising alternative fuel in the shipping industry. Natural gas is a gaseous fuel mainly composed of methane (CH4), and has advantages such as low emissions, relatively low price, rich reserves and high octane number. A marine dual-fuel engine is an engine that uses natural gas as fuel. In recent years, the market proportion of marine dual-fuel engines has gradually increased, resulting in a large amount of escaped methane emissions. Methane has an impact on the global atmospheric greenhouse effect that is 25 times that of carbon dioxide, and it is the second largest greenhouse gas, causing greater harm to port atmosphere and the global marine environment. The methane molecule is very stable, and the minimum oxidation temperature requirement is above 600 - 700 °C. The exhaust gas temperature of existing marine dual-fuel engines after the turbocharger is about 200 - 250 °C, which is far lower than the requirement of the methane oxidation temperature. It is necessary to heat the exhaust gas after the turbocharger to carry out the oxidation reaction, increasing the post-treatment cost and causing waste of the heat energy of the exhaust gas emitted by the dual-fuel engine. Therefore, it is necessary to design a post-treatment system for escaped methane of a dual-fuel engine to solve the above problems. Summary of the Invention

[0003] The purpose of the present invention is to provide a post-treatment system for escaped methane of a dual-fuel engine to solve the problem that the exhaust gas temperature of existing marine dual-fuel engines after the turbocharger is far lower than the requirement of the methane oxidation temperature, and it is necessary to heat the exhaust gas after the turbocharger to carry out the oxidation reaction, increasing the post-treatment cost and causing waste of the heat energy of the exhaust gas emitted by the dual-fuel engine.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] A post-treatment system for escaped methane of a dual-fuel engine, comprising:

[0006] A turbocharger, which is provided with an intake passage and an exhaust passage;

[0007] A dual-fuel engine, which is provided with an engine cylinder, and the intake port of the engine cylinder is communicated with the outlet of the intake passage;

[0008] A methane catalytic oxidation reactor, the inlet of the methane catalytic oxidation reactor is communicated with the outlet of the engine cylinder, and the outlet of the methane catalytic oxidation reactor is communicated with the inlet of the exhaust passage.

[0009] Preferably, a turbine bypass valve is connected in parallel to the exhaust passage. One end of the turbine bypass valve is communicated with the inlet of the exhaust passage, and the other end of the turbine bypass valve is communicated with the outlet of the exhaust passage.

[0010] Preferably, a reactor bypass valve is communicated between the outlet of the engine cylinder and the inlet of the exhaust passage.

[0011] Preferably, a reactor inlet valve is communicated between the outlet of the engine cylinder and the inlet of the methane catalytic oxidation reactor, and a reactor outlet valve is communicated between the outlet of the methane catalytic oxidation reactor and the inlet of the exhaust passage.

[0012] Preferably, a ventilation pipe is communicated between the reactor inlet valve and the inlet of the methane catalytic oxidation reactor, and a reactor ventilation valve is arranged on the ventilation pipe.

[0013] Preferably, a reactor relief valve is communicated between the outlet of the methane catalytic oxidation reactor and the outlet of the exhaust passage.

[0014] Preferably, a scavenging header is communicated between the outlet of the intake passage and the inlet of the engine cylinder.

[0015] Preferably, the outlet of the engine cylinder is communicated with an exhaust header. The exhaust header is provided with 1 inlet and 2 outlets. The inlet of the exhaust header is communicated with the outlet of the engine cylinder. One outlet of the exhaust header is communicated with the inlet of the methane catalytic oxidation reactor, and the other outlet of the exhaust header is communicated with the inlet of the exhaust passage.

[0016] Preferably, a heater is arranged at the inlet of the methane catalytic oxidation reactor.

[0017] Preferably, a first sensor assembly is arranged at the inlet of the methane catalytic oxidation reactor, and a second sensor assembly is arranged at the outlet of the methane catalytic oxidation reactor. Both the first sensor assembly and the second sensor assembly are connected to a methane state monitoring and control system.

[0018] Advantages of the present invention: The present invention provides a post-treatment system for escaping methane in a dual-fuel engine. By arranging a methane catalytic oxidation reactor upstream of the exhaust passage of the turbocharger, the flue gas before the turbocharger (with a temperature of 300 - 450 °C and a pressure of 1.5 - 4.5 bar, a) can be used for methane catalytic oxidation reaction. That is, the flue gas after the engine cylinder combustion will directly enter the methane catalytic oxidation reactor for methane catalytic oxidation reaction, eliminating the need to set up a heating device to heat the flue gas, saving costs and avoiding waste of flue gas thermal energy. The gas treated by the methane catalytic oxidation reactor enters the exhaust passage of the turbocharger to drive the turbine to rotate, and the turbine drives the impeller in the intake passage to rotate through the rotating shaft, ensuring the air demand of the engine cylinder. Brief Description of the Drawings

[0019] Figure 1 is a schematic diagram of the post-treatment system for escaping methane in a dual-fuel engine provided by the present invention.

[0020] In the figure:

[0021] 10. Turbocharger; 101. Intake passage; 102. Exhaust passage; 11. Engine cylinder; 12. Methane catalytic oxidation reactor; 13. Turbo bypass valve; 14. Reactor bypass valve; 15. Reactor inlet valve; 16. Reactor outlet valve; 17. Reactor ventilation valve; 18. Reactor relief valve; 19. Scavenging header; 20. Exhaust header; 21. Methane status monitoring and control system; 211. First sensor assembly; 2111. First temperature sensor; 2112. First differential pressure sensor; 212. Second sensor assembly; 2121. Methane concentration sensor; 2122. Second temperature sensor; 2123. Second differential pressure sensor; 2124. Pressure sensor. Detailed Embodiments

[0022] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only for explaining the present invention and not for limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0023] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the present invention, unless otherwise clearly specified and defined, the first feature being “above” or “below” the second feature may include direct contact between the first and second features, or may also include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being “above”, “over” and “on top of” the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being “below”, “under” and “beneath” the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0025] In the description of this embodiment, the orientation or positional relationships such as “above”, “below”, “left” and “right” are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of description and simplifying the operations, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms “first” and “second” are only used for distinction in description and have no special meanings.

[0026] The present invention provides a dual-fuel engine methane escape aftertreatment system, which includes a turbocharger 10, a dual-fuel engine and a methane catalytic oxidation reactor 12. The turbocharger 10 is provided with an intake passage 101 and an exhaust passage 102. The dual-fuel engine is provided with an engine cylinder 11. The intake port of the engine cylinder 11 is communicated with the outlet of the intake passage 101. The intake port of the methane catalytic oxidation reactor 12 is communicated with the outlet of the engine cylinder 11. The outlet of the methane catalytic oxidation reactor 12 is communicated with the intake port of the exhaust passage 102. Air enters the engine cylinder 11 through the intake passage 101 of the turbocharger 10 and burns with methane. The flue gas generated after combustion enters the methane catalytic oxidation reactor 12 from the engine cylinder 11 for catalytic oxidation reaction, and finally the flue gas after the catalytic oxidation reaction flows into the exhaust passage 102 of the turbocharger 10 through the outlet of the methane catalytic oxidation reactor 12 and is discharged.

[0027] Optionally, a turbine bypass valve 13 is connected in parallel to the exhaust passage 102. One end of the turbine bypass valve 13 communicates with the inlet of the exhaust passage 102, and the other end of the turbine bypass valve 13 communicates with the outlet of the exhaust passage 102. A turbine is provided in the exhaust passage 102, and an impeller is provided in the intake passage 101. The turbine and the impeller are connected by a rotating shaft. The flue gas flowing through the exhaust passage 102 will drive the turbine to rotate, and the rotation of the turbine drives the impeller connected to the turbine by the rotating shaft to rotate. When the temperature of the flue gas upstream of the methane catalytic oxidation reactor 12 is lower than the preset temperature, the turbine bypass valve 13 is opened, and a part of the flue gas will flow through the turbine bypass valve 13 and be discharged. At this time, the amount of flue gas flowing into the exhaust passage 102 is reduced, and the rotational speed of the turbine decreases, causing the rotational speed of the impeller in the intake passage 101 to decrease, so as to reduce the pressure of the air entering the engine cylinder 11, thereby reducing the amount of air entering the engine cylinder 11, increasing the temperature of the discharged flue gas, and meeting the temperature conditions for the operation of the methane catalytic oxidation reactor 12.

[0028] Optionally, a reactor bypass valve 14 is connected between the outlet of the engine cylinder 11 and the inlet of the exhaust passage 102. When the pressure drop of the methane catalytic oxidation reactor 12 is higher than the preset pressure drop, the reactor bypass valve 14 is opened, and a part of the flue gas will flow into the exhaust passage 102 of the turbocharger 10 through the reactor bypass valve 14, avoiding the influence of excessive flue gas backpressure on the operation of the dual-fuel engine. Here, the flue gas backpressure refers to the resistance pressure of the discharged flue gas. The greater the flue gas backpressure, the greater the resistance of the discharged flue gas, and the power of the dual-fuel engine will be reduced.

[0029] Further, a reactor inlet valve 15 is connected between the outlet of the engine cylinder 11 and the inlet of the methane catalytic oxidation reactor 12, and a reactor outlet valve 16 is connected between the outlet of the methane catalytic oxidation reactor 12 and the inlet of the exhaust passage 102. When the dual-fuel engine is in the fuel mode, there is no escaping methane emission in the flue gas, so the flue gas does not need to flow through the methane catalytic oxidation reactor 12. At this time, the reactor bypass valve 14 is opened, the reactor inlet valve 15 and the reactor outlet valve 16 are closed, and the methane treatment bypass mode is entered. The flue gas discharged from the engine cylinder 11 will flow through the reactor bypass valve 14 into the exhaust passage 102 and then be discharged, improving the flue gas emission efficiency, avoiding equipment loss of the methane catalytic oxidation reactor 12, and saving the equipment maintenance cost.

[0030] Furthermore, a ventilation pipe is connected between the reactor inlet valve 15 and the air inlet of the methane catalytic oxidation reactor 12. The ventilation pipe is provided with a reactor ventilation valve 17. When the dual-fuel engine is in the fuel mode, to ensure the sealing of the methane catalytic oxidation reactor 12, compressed air higher than the flue gas pressure can be introduced into the methane catalytic oxidation reactor 12 through the reactor ventilation valve 17, so that the flue gas cannot enter the interior of the methane catalytic oxidation reactor 12 through the reactor inlet valve 15 and the reactor outlet valve 16, avoiding the loss of equipment and the waste of catalyst caused by the leakage of flue gas into the methane catalytic oxidation reactor 12.

[0031] Optionally, a reactor relief valve 18 is connected between the air outlet of the methane catalytic oxidation reactor 12 and the air outlet of the exhaust passage 102. When the internal pressure of the methane catalytic oxidation reactor 12 is higher than the preset pressure after the ventilation valve 17 is opened, the reactor relief valve 18 is opened, and a part of the compressed air in the methane catalytic oxidation reactor 12 will flow out through the reactor relief valve 18, reducing the pressure in the methane catalytic oxidation reactor 12, so that the internal pressure of the methane catalytic oxidation reactor 12 is controlled within the design allowable range, avoiding the danger caused by the damage of the methane catalytic oxidation reactor 12 due to excessive internal pressure.

[0032] Optionally, a scavenging header 19 is connected between the air outlet of the intake passage 101 and the air inlet of the engine cylinder 11. During the operation of the dual-fuel engine, air is inhaled, pressurized by the turbocharger 10 and flows into the scavenging header 19, and then flows into the engine cylinder 11 to participate in the combustion in the engine cylinder 11.

[0033] Furthermore, the air outlet of the engine cylinder 11 is connected to an exhaust header 20. The exhaust header 20 is provided with 1 air inlet and 2 air outlets. The air inlet of the exhaust header 20 is connected to the air outlet of the engine cylinder 11. One air outlet of the exhaust header 20 is connected to the air inlet of the methane catalytic oxidation reactor 12, and the other air outlet of the exhaust header 20 is connected to the air inlet of the exhaust passage 102. During the operation of the dual-fuel engine, the flue gas discharged from the engine cylinder 11 is collected in the exhaust header 20. When the dual-fuel engine is in the gas mode, the flue gas in the exhaust header 20 flows into the methane catalytic oxidation reactor 12 for catalytic oxidation reaction. When the dual-fuel engine is in the fuel mode, the flue gas in the exhaust header 20 flows into the exhaust passage 102 of the turbocharger 10 and then is discharged.

[0034] Optionally, a heater is provided at the inlet of the methane catalytic oxidation reactor 12. The heater serves as a backup device. When the temperature of the flue gas is too low to reach the minimum temperature for methane catalytic oxidation in the methane catalytic oxidation reactor 12, the heater is turned on to heat the flue gas so that the temperature of the flue gas flowing into the methane catalytic oxidation reactor 12 meets the temperature for catalytic oxidation, ensuring that the methane catalytic oxidation reactor 12 can continuously carry out the catalytic oxidation reaction, that is, ensuring the working efficiency.

[0035] A first sensor assembly 211 is provided at the inlet of the methane catalytic oxidation reactor 12. The first sensor assembly 211 measures the temperature and differential pressure of the inlet gas of the methane catalytic oxidation reactor 12. A second sensor assembly 212 is provided at the outlet of the methane catalytic oxidation reactor 12. The second sensor assembly 212 measures the temperature, differential pressure, methane concentration, and pressure of the exhaust gas of the methane catalytic oxidation reactor 12. Both the first sensor assembly 211 and the second sensor assembly 212 are connected to the methane status monitoring and control system 21. By setting up the methane status monitoring and control system 21, the working status of the methane catalytic oxidation reactor 12 can be monitored in real time.

[0036] Further, the first sensor assembly 211 includes a first temperature sensor 2111 and a first differential pressure sensor 2112. The second sensor assembly 212 includes a methane concentration sensor 2121, a second temperature sensor 2122, a second differential pressure sensor 2123, and a pressure sensor 2124. The first temperature sensor 2111, the first differential pressure sensor 2112, the methane concentration sensor 2121, the second temperature sensor 2122, the second differential pressure sensor 2123, and the pressure sensor 2124 are all connected to the methane status monitoring and control system 21. By setting up the first temperature sensor 2111, the first differential pressure sensor 2112, the methane concentration sensor 2121, the second temperature sensor 2122, the second differential pressure sensor 2123, and the pressure sensor 2124 connected to the methane status monitoring and control system 21, the methane status monitoring and control system 21 can monitor the methane concentration, the pressure of methane, the temperature of methane before and after the reaction, and the differential pressure of methane before and after the reaction inside the methane catalytic oxidation reactor 12.

[0037] Furthermore, the methane status monitoring and control system 21 is connected to the reactor bypass valve 14, the turbine bypass valve 13, and the reactor relief valve 18. When the dual-fuel engine is in the gas mode, when the methane status monitoring and control system 21 monitors that the pressure drop of the methane catalytic oxidation reactor 12 is higher than the preset pressure drop through the first differential pressure sensor 2112 and the second differential pressure sensor 2123, the methane status monitoring and control system 21 gives a prompt alarm and controls the reactor bypass valve 14 to open. A part of the flue gas will flow into the exhaust passage 102 of the turbocharger 10 through the reactor bypass valve 14 to avoid the influence of excessive flue gas back pressure on the operation of the dual-fuel engine. When the methane status monitoring and control system 21 monitors that the upstream flue gas temperature of the methane catalytic oxidation reactor 12 is lower than the preset temperature through the first temperature sensor 2111, the methane status monitoring and control system 21 controls the turbine bypass valve 13 to open, thereby reducing the amount of air entering the engine cylinder 11 and increasing the flue gas temperature discharged by the dual-fuel engine. When the dual-fuel engine is in the fuel mode, when the methane status monitoring and control system 21 monitors that the internal pressure of the methane catalytic oxidation reactor 12 is higher than the preset pressure through the pressure sensor 2124, the methane status monitoring and control system 21 controls the reactor relief valve 18 to open, and a part of the compressed air in the methane catalytic oxidation reactor 12 will flow out through the reactor relief valve 18 to release the pressure in the methane catalytic oxidation reactor 12.

[0038] The working process of the dual-fuel engine escape methane post-treatment system provided by the present invention is as follows:

[0039] When the dual-fuel engine is in the gas mode, air flows into the scavenging manifold 19 through the intake passage 101 of the turbocharger 10 and then into the engine cylinder 11 to participate in combustion. The flue gas generated by combustion flows into the exhaust manifold 20, and then flows into the methane catalytic oxidation reactor 12 through the reactor inlet valve 15 for catalytic oxidation reaction. The flue gas after the reaction flows into the exhaust passage 102 of the turbocharger 10 through the reactor outlet valve 16 and is finally discharged through the exhaust passage 102.

[0040] When the dual-fuel engine is in the fuel mode, air flows into the scavenging manifold 19 through the intake passage 101 of the turbocharger 10 and then into the engine cylinder 11 to participate in combustion. The flue gas generated by combustion flows into the exhaust manifold 20, and then the flue gas flows into the exhaust passage 102 of the turbocharger 10 through the reactor bypass valve 14 and is finally discharged through the exhaust passage 102.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A dual-fuel engine methane escape aftertreatment system, characterized in that, Comprising: A turbocharger (10) provided with an intake passage (101) and an exhaust passage (102); A dual-fuel engine provided with an engine cylinder (11), and an intake port of the engine cylinder (11) is communicated with an outlet of the intake passage (101); A methane catalytic oxidation reactor (12), an intake port of the methane catalytic oxidation reactor (12) is communicated with an outlet of the engine cylinder (11), and an outlet of the methane catalytic oxidation reactor (12) is communicated with an intake port of the exhaust passage (102); A turbine bypass valve (13) is connected in parallel to the exhaust passage (102), one end of the turbine bypass valve (13) is communicated with the intake port of the exhaust passage (102), and the other end of the turbine bypass valve (13) is communicated with the outlet of the exhaust passage (102); A reactor inlet valve (15) is communicated between an outlet of the engine cylinder (11) and an intake port of the methane catalytic oxidation reactor (12), and a reactor outlet valve (16) is communicated between an outlet of the methane catalytic oxidation reactor (12) and an intake port of the exhaust passage (102); A ventilation pipe is communicated between the reactor inlet valve (15) and the intake port of the methane catalytic oxidation reactor (12), and the ventilation pipe is provided with a reactor ventilation valve (17); When the dual-fuel engine is in the fuel mode, to ensure the sealing of the methane catalytic oxidation reactor (12), compressed air higher than the flue gas pressure is introduced into the methane catalytic oxidation reactor (12) through the reactor ventilation valve (17), so that the flue gas cannot enter the interior of the methane catalytic oxidation reactor (12) through the reactor inlet valve (15) and the reactor outlet valve (16).

2. The post-treatment system for escaping methane of the dual-fuel engine according to claim 1, wherein A reactor bypass valve (14) is communicated between an outlet of the engine cylinder (11) and an intake port of the exhaust passage (102).

3. The post-treatment system for escaping methane of the dual-fuel engine according to claim 1, characterized in that, A reactor relief valve (18) is communicated between an outlet of the methane catalytic oxidation reactor (12) and an outlet of the exhaust passage (102).

4. The dual-fuel engine methane escape aftertreatment system according to claim 1, characterized in that A scavenging header (19) is communicated between an outlet of the intake passage (101) and an intake port of the engine cylinder (11).

5. The dual-fuel engine methane escape aftertreatment system according to claim 4, characterized in that, An exhaust header (20) is communicated with an outlet of the engine cylinder (11), the exhaust header (20) is provided with 1 intake port and 2 outlet ports, the intake port of the exhaust header (20) is communicated with the outlet of the engine cylinder (11), one outlet of the exhaust header (20) is communicated with the intake port of the methane catalytic oxidation reactor (12), and the other outlet of the exhaust header (20) is communicated with the intake port of the exhaust passage (102).

6. The dual-fuel engine methane escape aftertreatment system according to claim 1, characterized in that, A heater is provided at the intake port of the methane catalytic oxidation reactor (12).

7. The dual-fuel engine methane escape aftertreatment system according to any one of claims 1-6, characterized in that, A first sensor assembly (211) is provided at the air inlet of the methane catalytic oxidation reactor (12), a second sensor assembly (212) is provided at the air outlet of the methane catalytic oxidation reactor (12), and both the first sensor assembly (211) and the second sensor assembly (212) are connected to the methane state monitoring and control system (21).

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