Escape methane post-treatment system and method based on low-temperature catalytic oxidation method

Abstract

The invention discloses an escape methane post-treatment system and method based on a low-temperature catalytic oxidation method. The escape methane post-treatment system comprises a heat compensation combustor, a premixer, a low-temperature catalytic oxidation device, an energy saver, an air fan, a waste heat boiler, a tail gas fan and a chimney. An outlet of the heat compensation combustor is communicated with an inlet of the premixer through a one-way valve II, and an outlet of the LNG engine is communicated with the inlet of the premixer through a one-way valve I; an outlet of the premixer is communicated with the left end of the low-temperature catalytic oxidizer, and the right end of the low-temperature catalytic oxidizer is communicated with an inlet of one flow channel of the energy saver, so that high-temperature tail gas and air in the other flow channel of the energy saver are subjected to primary heat exchange for cooling; a runner outlet of the energy saver is communicated with an inlet of the waste heat boiler, an outlet of the waste heat boiler is communicated with the exhaust chimney through a pipeline and a tail gas fan, then tail gas is guided into the waste heat boiler for secondary heat exchange cooling, and the cooled tail gas is exhausted through the exhaust chimney. According to the method, the escape amount of methane is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ship engine exhaust treatment, in particular to an escaped methane aftertreatment system and method based on low-temperature catalytic oxidation. BACKGROUND

[0002] As the core transportation mode that accounts for 80% of global freight volume, the marine industry is accelerating the transition of its power system to liquefied natural gas (LNG) engines.

[0003] Although natural gas has advantages such as high carbon-hydrogen ratio and clean combustion products, the problem of methane escape has become a core bottleneck for the low-carbonization of ships. During the operation of a ship engine, 50%-70% of the unburned methane comes from the combustion chamber dead zone, especially the wall quenching effect. In addition, the crankcase can cause up to 20% of the total amount of methane escape. Finally, the fuel short circuit during valve overlap period constitutes the remaining methane escape. The methane escape rate of a typical medium-speed Otto cycle engine is as high as 5.5 g / kWh, resulting in a carbon emission cost accounting for 21% of the total operating cost, while the greenhouse effect of methane is 28 times that of CO2, further exacerbating the carbon compliance pressure of the marine industry.

[0004] In the field of catalytic oxidation of ship methane escape, the core bottleneck of existing technologies is concentrated on the dual challenges of low-temperature activity and sulfur resistance of the catalyst. Although traditional Pt / Al2O3 catalysts are widely used for land-based methane treatment, their light-off temperature of 600℃ is far higher than the typical exhaust temperature range of 200-280℃ of ship engines, resulting in almost zero catalytic efficiency under low-temperature conditions. More seriously, the sulfur content of 0.5% in the pilot diesel and lubricating oil composition can cause permanent sulfur poisoning of the catalyst, with active sites being irreversibly occupied by sulfides and deactivated. Currently, although Wuxilan has developed a noble metal catalyst that can achieve 90% methane conversion, its reliance on high Pd load (3-6 g / L) results in high costs, and the system is still at the bench test stage. BASF and Umicore attempt to use TiO2 carriers to improve the activity of Pd catalysts, although the light-off temperature is reduced to 429℃ (90% conversion requires 460℃), but the long-term stability problem in a sulfur-containing environment has not been solved, and the temperature threshold is still higher than the low-load exhaust temperature of ships. The catalytic system of Yanmar Power has been certified by the ship classification society, but the actual measured residual methane escape amount is >2.8 g / kWh, and it deliberately avoids publishing low-temperature sulfur resistance performance data. Other alternative technologies such as the plasma catalysis of Daphne Technology require continuous consumption of 3%-5% of engine power, resulting in a negative net emission reduction benefit, and the land-based regenerative thermal oxidizer (RTO) increases CO2 emissions by 15%-20% due to its large size and reliance on auxiliary fuel heating.

[0005] Therefore, the above problems need to be solved urgently. SUMMARY

[0006] The technical problem solved by the present application is to provide an escaped methane aftertreatment system and method based on low-temperature catalytic oxidation method, which actively heats to break through the low-temperature catalytic activation bottleneck, optimizes the reactor structure to improve the catalytic efficiency, and innovatively combines the step-by-step recovery of waste heat to reduce the energy consumption of the system, thereby constructing an energy closed-loop utilization chain of "combustion heating-catalytic conversion-waste heat recovery", so as to significantly reduce the amount of methane escape to ≤1.0 g / kWh to meet the stringent standards, and also significantly improve the overall energy utilization efficiency of the system.

[0007] To solve the above technical problems, the present application adopts the following technical scheme: the escaped methane aftertreatment system based on low-temperature catalytic oxidation method, the innovation of which lies in that it comprises a heat-supplementing combustor, a premixer, a low-temperature catalytic oxidizer, an economizer, an air blower, a waste heat boiler, an exhaust gas blower, and an exhaust chimney; the outlet of the heat-supplementing combustor is communicated with the inlet of the premixer through a pipeline and a one-way valve II, and the outlet of the LNG engine is communicated with the inlet of the premixer through a pipeline and a one-way valve I; the outlet of the premixer is communicated with the left end of the low-temperature catalytic oxidizer through a pipeline, and the right end of the low-temperature catalytic oxidizer is communicated with the inlet of one flow channel of the economizer, so that the high-temperature exhaust gas is subjected to one-time heat exchange and cooling with the air in the other flow channel of the economizer; the outlet of one flow channel of the economizer is communicated with the inlet of the waste heat boiler through a pipeline, and the outlet of the waste heat boiler is communicated with the exhaust chimney through an exhaust gas blower, so that the exhaust gas subjected to one-time heat exchange and cooling is introduced into the waste heat boiler for two-time heat exchange and cooling, and the exhaust gas subjected to two-time cooling is discharged through the exhaust chimney.

[0008] Preferably, it further comprises an air blower and a reversing valve; the reversing valve is a two-position three-way reversing valve, the outlet of the air blower is communicated with the inlet P of the reversing valve through a pipeline, and the air blower sends normal-temperature air to the reversing valve; the working port A of the reversing valve is communicated with the inlet of the other flow channel of the economizer through a pipeline, and the outlet of the other flow channel of the economizer and the FGSS system are respectively communicated with the inlet of the heat-supplementing combustor through pipelines, so that the heat-supplementing combustor is heated; the working port B of the reversing valve is communicated with the pipeline between the one-way valve II and the premixer through a pipeline, and when the heat-supplementing combustor does not work, the normal-temperature air is introduced into the premixer for mixing and cooling through the switching of the reversing valve.

[0009] Preferably, the flow direction of the one-way valve II needs to ensure that the high-temperature exhaust gas in the premixer can be actively heated by the supplementary heater, and the flow direction of the one-way valve I needs to ensure that the high-temperature exhaust gas discharged from the LNG engine can enter the premixer.

[0010] Preferably, the low-temperature catalytic oxidizer is a square-section catalytic reactor optimized in fluid dynamics, and the full length thereof is 2628 mm; the left end of the low-temperature catalytic oxidizer is a conical inlet with an expansion angle of 60°, and the high-temperature exhaust gas is guided to smoothly transition to a round-hole-shaped flow guide plate with a hole diameter of 72 mm through the conical inlet, and a rectangular catalytic layer loaded with catalysts is arranged inside the low-temperature catalytic oxidizer, so that the high-speed exhaust gas is uniformly distributed throughout the low-temperature catalytic oxidizer through the double cooperation of the conical inlet and the round-hole-shaped flow guide plate, and the direct impact pressure of the high-speed exhaust gas on the rectangular catalytic layer is reduced through pressure division.

[0011] Preferably, the catalyst adopts a Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst, and is arranged in a 3 × 3 × 3 array, and the total number of the catalysts is 27; 18 of them are standard blocks with a size of 150 mm × 150 mm × 150 mm, and the other 9 are thin blocks with a size of 150 mm × 150 mm × 70 mm, and the total volume is 75L; all the catalysts are packaged in a detachable frame, and the blocks of adjacent catalysts are sealed with 3 mm high-temperature-resistant gaskets to prevent leakage, so as to be maintained and replaced; the catalyst adopts a high-geometric-surface-area design with a noble metal platinum loading of 3 g / L and a pore density of 300 cpsi, and realizes high-efficiency catalytic oxidation conversion of methane in combination with the physical isolation effect of the core-shell structure on active sites.

[0012] The post-processing method of the escape methane post-processing system based on the low-temperature catalytic oxidation method, and the innovation point lies in the following steps: (1) First, according to the exhaust gas temperature discharged from the LNG engine, a heating mode or a cooling mode is selected to ensure that the exhaust gas temperature entering the low-temperature catalytic oxidizer is ≥300℃, the catalyst activation threshold, and the exhaust gas temperature entering the low-temperature catalytic oxidizer is lower than 400℃; (2) Then, the high-temperature exhaust gas discharged from the LNG engine enters the premixer through the one-way valve I, and the exhaust gas temperature is optimized in the premixer through the heating mode or the cooling mode, and the exhaust gas temperature is optimized to 320~380℃; (3) Then, the temperature-optimized exhaust gas uniformly flows through the round-hole-shaped flow guide plate, is uniformly distributed in the rectangular catalytic layer, and realizes high-efficiency conversion of methane of more than 85% under the low-temperature regulation of the Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst at 320~380℃, and in this process, the core-shell structure effectively isolates the toxic effect of sulfides on active components; (4) Then the valve core of the reversing valve moves downward, so that the inlet P of the reversing valve is connected to its working port A, and the air at normal temperature is sent into the other flow channel of the economizer through the air blower. At the same time, the high-temperature exhaust gas generated after catalytic oxidation enters the one flow channel of the economizer and undergoes a heat exchange with the air in the other flow channel of the economizer to cool down. (5) The air heated by the primary heat exchange enters the supplementary heat burner to reduce the consumption of methane fuel supplied by the FGSS system; and the high-temperature exhaust gas cooled by the primary heat exchange is introduced into the waste heat boiler for secondary heat exchange cooling. When the exhaust gas temperature after the secondary heat exchange cools down to below 150°C, it is discharged through the exhaust chimney through the exhaust fan.

[0013] Preferably, in the above step (1), the supplementary heat mode is to inject methane fuel supplied by the FGSS system when the exhaust gas temperature of the LNG engine is lower than 300°C due to idling, and actively heat the exhaust gas in the premixer to the catalyst activation threshold through the supplementary heat burner.

[0014] Preferably, in the above step (1), the cooling mode is that when the temperature of the exhaust gas discharged by the LNG engine is higher than 400°C, the economizer and the supplementary heat burner both stop working, and then the valve core of the reversing valve moves upward to connect the inlet P of the reversing valve with its working port B. At this time, normal temperature air is introduced through the air blower to mix and cool the exhaust gas in the premixer to prevent the rectangular catalytic layer from overheating to above 450°C and causing sintering of the Pt active component.

[0015] Preferably, in the above step (4), the temperature of the high-temperature exhaust gas generated after catalytic oxidation is 400-450°C.

[0016] Beneficial effects of the present invention: The present invention uses an innovative combination of active heating to break through the bottleneck of low-temperature catalytic activation, optimizing the reactor structure to improve catalytic efficiency, and cascade recovery of waste heat to reduce system energy consumption, thereby constructing a closed-loop energy utilization chain of "combustion heating-catalytic conversion-waste heat recovery", thereby significantly reducing the methane escape amount to ≤1.0 g / kWh to meet stringent standards, and significantly improving the overall energy utilization efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 The figure is a schematic structural diagram of a fugitive methane post-treatment system based on a low-temperature catalytic oxidation method according to the present invention.

[0019] Among them, 1-LNG engine; 2-supplementary heat burner; 3-premixer; 4-low-temperature catalytic oxidizer; 5-economizer; 6-air fan; 7-waste heat boiler; 8-exhaust fan; 9-exhaust chimney; 10-reversing valve; 11-check valve I; 12-check valve II. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below through specific implementation methods.

[0021] The methane slip of existing LNG engines at exhaust temperatures of 250-400°C is as high as about 2.5 g / kWh, making it difficult to meet stringent emission standards (≤1.0 g / kWh). To address the above issues, the present invention provides a methane slip aftertreatment system based on low-temperature catalytic oxidation, comprising a supplementary heat burner 2, a premixer 3, a low-temperature catalytic oxidizer 4, an economizer 5, an air blower 6, a waste heat boiler 7, an exhaust blower 8, and an exhaust chimney 9. The specific structure is as follows: Figure 1 As shown, the outlet of the supplementary heat burner 2 is connected to the inlet of the premixer 3 through a pipeline via a one-way valve II 12, and the outlet of the LNG engine 1 is connected to the inlet of the premixer 3 through a pipeline via a one-way valve I 11; the outlet of the premixer 3 is connected to the left end of the low-temperature catalytic oxidizer 4 through a pipeline, and the right end of the low-temperature catalytic oxidizer 4 is connected to the inlet of a flow channel of the economizer 5, thereby causing the high-temperature exhaust gas to undergo a heat exchange and cooling with the air in the other flow channel of the economizer 5; the outlet of the one flow channel of the economizer 5 is connected to the inlet of the waste heat boiler 7 through a pipeline, and the outlet of the waste heat boiler 7 is connected to the exhaust chimney 9 through a pipeline via an exhaust fan 8, thereby introducing the exhaust gas after the primary heat exchange and cooling into the waste heat boiler 7 for a secondary heat exchange and cooling, and the exhaust gas after the secondary cooling is discharged through the exhaust chimney 9. Among them, the flow direction of the one-way valve II 12 needs to ensure that the high-temperature exhaust gas in the premixer 3 can be actively heated by the heat supplement burner 2, and the flow direction of the one-way valve I 11 needs to ensure that the high-temperature exhaust gas discharged from the LNG engine 1 can enter the premixer 3.

[0022] like Figure 1 As shown, the reversing valve 10 is a two-position three-way reversing valve 10, and the outlet of the air blower 6 is connected to the inlet P of the reversing valve 10 through a pipeline, and the normal temperature air is sent to the reversing valve 10 through the air blower 6; the working port A of the reversing valve 10 is connected to the inlet of another flow channel of the economizer 5 through a pipeline, and the outlet of the other flow channel of the economizer 5 and the FGSS system are respectively connected to the inlet of the supplementary heat burner 2 through pipelines, and then supplementary heat is performed through the supplementary heat burner 2; the working port B of the reversing valve 10 is connected to the pipeline located between the one-way valve II 12 and the premixer 3 through a pipeline, and when the supplementary heat burner 2 is not working, the normal temperature air is passed into the premixer 3 for mixing and cooling by switching the reversing valve 10.

[0023] The low-temperature catalytic oxidizer 4 of the application is a square-section catalytic reactor optimized in fluid dynamics, and its total length is 2628 mm; as shown in Figure 1 The left end of the low-temperature catalytic oxidizer 4 is a conical inlet with an expansion angle of 60°, and the high-temperature exhaust gas is smoothly guided through the conical inlet to a round-hole guide plate with a hole diameter of 72 mm, and a rectangular catalytic layer loaded with catalysts is arranged inside the low-temperature catalytic oxidizer 4, and then through the double cooperation of the conical inlet and the round-hole guide plate, the high-speed exhaust gas is uniformly distributed throughout the low-temperature catalytic oxidizer 4, and the direct impact pressure of the high-speed exhaust gas on the rectangular catalytic layer is reduced by pressure division. The round-hole guide plate has the effects of flow division and flow regulation, eliminates the central high-speed area and the edge wall low-speed area, ensures that the velocity uniformity index of the high-speed exhaust gas at the inlet of the rectangular catalytic layer is >0.9, and at the same time reduces the impact pressure on the rectangular catalytic layer, avoiding the risk of catalyst damage caused by particle blockage.

[0024] The catalyst of the application adopts a Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst, which is arranged in a 3 × 3 × 3 array and a total of 27 pieces; among them, 18 pieces are standard blocks of 150 mm × 150 mm × 150 mm, and the other 9 pieces are thin blocks of 150 mm × 150 mm × 70 mm, and the total volume is ensured to be 75L; all the catalysts are packaged in a detachable frame, and the blocks of adjacent catalysts are sealed with 3 mm high-temperature-resistant gaskets to prevent leakage for maintenance and replacement; the catalyst adopts a high-geometric-surface-area design with a noble metal platinum loading of 3 g / L and a pore density of 300 cpsi, and in combination with the physical isolation effect of the core-shell structure on the active sites, high-efficiency catalytic oxidation conversion of methane is realized. The Pt active sites are coated on the outer layer of the CeO2-ZrO2 carrier, thereby forming a unique core-shell structure, and with the uniform flow field and high-activity catalyst, high-efficiency catalytic oxidation conversion of methane >85% can be realized, and the poisoning of the Pt active sites by sulfides in the exhaust gas can be physically blocked, thereby improving the anti-sulfide poisoning ability.

[0025] A post-processing method of an escape methane post-processing system based on a low-temperature catalytic oxidation method according to the application, as shown in Figure 1 The method comprises the following steps: (1) First, according to the exhaust gas temperature discharged by the LNG engine 1, select the heat supplement mode or the temperature reduction mode to ensure that the exhaust gas temperature entering the low-temperature catalytic oxidizer 4 is ≥300℃, the catalyst activation threshold, and the exhaust gas temperature entering the low-temperature catalytic oxidizer 4 is lower than 400℃. In the above steps, the heat supplement mode is that when the LNG engine 1 causes the exhaust gas temperature to be lower than 300℃ due to idling, the methane fuel supplied by the FGSS system is injected and actively heated to the catalyst activation threshold by the heat supplement combustor 2.

[0026] In the above steps, the cooling mode is that when the exhaust temperature of the LNG engine 1 is higher than 400 DEG C, the economizer 5 and the heat supplement burner 2 are both stopped, then the valve core of the reversing valve 10 is moved upwards, the inlet P of the reversing valve 10 is communicated with the working port B, at this time, the air at normal temperature is introduced by the air blower 6 to mix and cool the exhaust in the premixer 3, so as to prevent the rectangular catalytic layer from being overheated to above 450 DEG C to cause sintering of the Pt active component.

[0027] (2) Then the high-temperature exhaust of the LNG engine 1 enters the premixer 3 through the one-way valve I 11, and the exhaust temperature is optimized in the premixer 3 through the heat supplement mode or the cooling mode, and the exhaust temperature is optimized to 320~380 DEG C.

[0028] (3) Then the exhaust with optimized temperature uniformly flows through the round-hole-shaped guide plate, is uniformly distributed in the rectangular catalytic layer, and is adjusted at a low temperature of 320~380 DEG C through the Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst, so that the high-efficiency conversion of methane greater than 85% is realized, and in the process, the poisoning effect of sulfide on the active component is effectively isolated through the core-shell structure.

[0029] (4) Then the valve core of the reversing valve 10 is moved downwards, the inlet P of the reversing valve 10 is communicated with the working port A, and the air at normal temperature is sent into the other flow channel of the economizer 5 through the air blower 6, and the high-temperature exhaust generated after catalytic oxidation enters one flow channel of the economizer 5, and is once heat-exchanged and cooled with the air in the other flow channel of the economizer 5. In the above steps, the temperature of the high-temperature exhaust generated after catalytic oxidation is 400~450 DEG C.

[0030] (5) The air once heat-exchanged and heated is preheated to about 280 DEG C, enters the heat supplement burner 2, so as to reduce the consumption of methane fuel supplied by the FGSS system, and the high-temperature exhaust once heat-exchanged and cooled is cooled to about 320 DEG C, and is introduced into the waste heat boiler 7 to be twice heat-exchanged and cooled, and when the exhaust temperature after twice heat-exchanged and cooled is reduced to below 150 DEG C, the exhaust is discharged through the exhaust chimney 9 by the exhaust blower 8.

[0031] The application forms the path of "preheating combustion-supporting air (first-stage recovery) -> reducing combustion energy consumption -> waste heat secondary recovery", and innovatively constructs an efficient energy closed-loop utilization chain, so that the deep energy-saving effect is realized.

[0032] The application has the beneficial effects that the application adopts the innovative combination of active heating, breaking the low-temperature catalytic activation bottleneck, optimizing the reactor structure to improve the catalytic efficiency, and waste heat gradient recovery to reduce the system energy consumption, constructs the energy closed-loop utilization chain of "combustion heating-catalytic conversion-waste heat recovery", thereby significantly reduces the methane escape amount to ≤1.0 g / kWh to meet the strict standard, and also significantly improves the overall energy utilization efficiency of the system.

[0033] The above-described embodiments are merely preferred embodiments of the application and are not intended to limit the concept and scope of the application. Without departing from the design concept of the application, various modifications and improvements to the technical solutions of the application made by ordinary engineering technicians in the art shall fall within the protection scope of the application. The technical content claimed by the application has been fully recorded in the technical requirements.

Claims

1. A low-temperature catalytic oxidation method-based post-treatment system for escaped methane, characterized by: The application relates to a LNG engine exhaust heat recovery system which comprises a heat-supplementing burner, a premixer, a low-temperature catalytic oxidizer, an economizer, an air blower, a waste heat boiler, an exhaust gas blower and an exhaust chimney; the outlet of the heat-supplementing burner is connected with the inlet of the premixer through a pipeline and a one-way valve II, and the outlet of an LNG engine is connected with the inlet of the premixer through a pipeline and a one-way valve I; the outlet of the premixer is connected with the left end of the low-temperature catalytic oxidizer through a pipeline, and the right end of the low-temperature catalytic oxidizer is connected with the inlet of a flow channel of the economizer, so that the high-temperature exhaust gas is subjected to one-time heat exchange and cooling with air in another flow channel of the economizer; the outlet of the flow channel of the economizer is connected with the inlet of the waste heat boiler through a pipeline, and the outlet of the waste heat boiler is connected with the exhaust chimney through the exhaust gas blower, so that the exhaust gas subjected to one-time heat exchange and cooling is introduced into the waste heat boiler to be subjected to two-time heat exchange and cooling, and the exhaust gas subjected to two-time heat exchange and cooling is discharged through the exhaust chimney.

2. The system according to claim 1, wherein the system is a low-temperature catalytic oxidation-based post-treatment system for escaped methane. The application further comprises an air blower and a reversing valve; the reversing valve is a two-position three-way reversing valve, the outlet of the air blower is connected with the inlet P of the reversing valve through a pipeline, and the air blower sends normal-temperature air to the reversing valve; the working port A of the reversing valve is connected with the inlet of another flow channel of the economizer through a pipeline, and the outlet of another flow channel of the economizer and the FGSS system are respectively connected with the inlet of the heat-supplementing burner through pipelines, so that the heat-supplementing burner is used for heat supplementing; the working port B of the reversing valve is connected with the pipeline between the one-way valve II and the premixer through a pipeline, and when the heat-supplementing burner does not work, the normal-temperature air is introduced into the premixer through the switching of the reversing valve for mixing and cooling.

3. The system of claim 1, wherein the system is a low-temperature catalytic oxidation system. The flow direction of the one-way valve II should ensure that the high-temperature exhaust gas in the premixer can be actively heated by the heat-supplementing burner, and the flow direction of the one-way valve I should ensure that the high-temperature exhaust gas discharged from the LNG engine can enter the premixer.

4. The system of claim 1, wherein the system is a low-temperature catalytic oxidation system. The low-temperature catalytic oxidizer is a square-section catalytic reactor optimized by fluid dynamics, and the full length of the low-temperature catalytic oxidizer is 2628 mm; the left end of the low-temperature catalytic oxidizer is a conical inlet with an expansion angle of 60 degrees, the high-temperature exhaust gas is guided to pass through the conical inlet and then to a round-hole guide plate with a hole diameter of 72 mm, a rectangular catalytic layer loaded with a catalyst is arranged in the low-temperature catalytic oxidizer, so that the high-speed exhaust gas is uniformly distributed in the whole low-temperature catalytic oxidizer through the double cooperation of the conical inlet and the round-hole guide plate, and the direct impact pressure of the high-speed exhaust gas on the rectangular catalytic layer is reduced through pressure division.

5. The low-temperature catalytic oxidation-based slip methane aftertreatment system of claim 4, wherein: The catalyst adopts a Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst, and is arranged in a 3 × 3 × 3 array, and the total number of blocks is 27; 18 blocks are standard blocks with a size of 150 mm × 150 mm × 150 mm, and the other 9 blocks are thin blocks with a size of 150 mm × 150 mm × 70 mm, and the total volume is ensured to be 75L; all the catalysts are packaged in a detachable frame, and the blocks of adjacent catalysts are sealed with 3 mm high-temperature-resistant gaskets to prevent leakage, so as to be maintained and replaced; the catalyst adopts a high geometric surface area design with a noble metal platinum loading of 3 g / L and a pore density of 300 cpsi, and realizes efficient catalytic oxidation conversion of methane in combination with the physical isolation effect of the core-shell structure on the active sites.

6. The method according to any one of claims 1 to 5, wherein the method is a method for treating the escaped methane using a low-temperature catalytic oxidation method. It comprises the following steps: (1) First, according to the exhaust gas temperature of the LNG engine, select the heat supplement mode or the temperature reduction mode to ensure that the exhaust gas temperature entering the low-temperature catalytic oxidizer is greater than or equal to the catalyst activation threshold of 300℃, and ensure that the exhaust gas temperature entering the low-temperature catalytic oxidizer is less than 400℃; (2) Then, the high-temperature exhaust gas discharged by the LNG engine enters the premixer through the one-way valve I, and the exhaust gas temperature is optimized in the premixer through the heat supplement mode or the temperature reduction mode, and the exhaust gas temperature is optimized to 320~380℃; (3) Then, the temperature-optimized exhaust gas uniformly flows through the round-hole guide plate and is uniformly distributed in the rectangular catalytic layer, and through the Pt / CeO2-ZrO2 core-shell structure honeycomb ceramic catalyst, efficient conversion of methane greater than 85% is realized under the low-temperature regulation of 320~380℃, and in this process, the poisoning effect of sulfides on active components is effectively isolated by the core-shell structure; (4) Then, the valve core of the reversing valve moves down, so that the inlet P of the reversing valve is connected with the working port A, and the normal-temperature air is sent into the other flow channel of the energy saver through the air blower, while the high-temperature exhaust gas after catalytic oxidation enters the flow channel of the energy saver, and exchanges heat with the air in the other flow channel of the energy saver to reduce the temperature; (5) The air after the first heat exchange is introduced into the heat supplement combustor to reduce the consumption of methane fuel supplied by the FGSS system, and the high-temperature exhaust gas after the first heat exchange is introduced into the waste heat boiler for the second heat exchange to reduce the temperature, and when the temperature of the exhaust gas after the second heat exchange is reduced to below 150℃, the exhaust gas is discharged through the exhaust chimney by the exhaust gas blower.

7. A method of aftertreatment according to claim 6, characterized in that: In the above step (1), the heat supplement mode is that when the exhaust gas temperature of the LNG engine is lower than 300℃ due to idling, the methane fuel supplied by the FGSS system is injected, and the exhaust gas in the premixer is actively heated to the catalyst activation threshold through the heat supplement combustor.

8. The method of claim 6, wherein the low-temperature catalytic oxidation method is a catalytic oxidation method using a catalyst having a temperature of 200-400°C. In the above step (1), the temperature reduction mode is that when the exhaust gas temperature of the LNG engine is higher than 400℃, the energy saver and the heat supplement combustor stop working, then the valve core of the reversing valve moves up, so that the inlet P of the reversing valve is connected with the working port B, at this time, the normal-temperature air is introduced through the air blower to mix and reduce the temperature of the exhaust gas in the premixer, so as to prevent the rectangular catalytic layer from overheating to above 450℃ to cause sintering of the Pt active component.

9. The method of claim 6, wherein the low-temperature catalytic oxidation method is a catalytic oxidation method using a catalyst having a temperature of 200-400°C. In the above step (4), the temperature of the high-temperature tail gas generated after catalytic oxidation is 400-450°C.

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