Exhaust gas after treatment system and ship having the same

Abstract

The exhaust gas aftertreatment system may include a catalyst chamber comprising an upstream catalyst configured to reduce the sulfur content of the exhaust gas discharged from the upstream catalyst by adsorbing sulfur components in the exhaust gas, and a downstream catalyst located downstream of the upstream catalyst.

Description

Technology Field

[0001] The present invention relates to an exhaust gas aftertreatment system, and more specifically, to an exhaust gas aftertreatment system capable of extending the service life of a methane oxidation catalyst by removing sulfur oxides, hydrocarbons, etc. contained in the exhaust gas by a diesel oxidation catalyst before the exhaust gas comes into contact with the methane oxidation catalyst, and to a ship including the same. Background Technology

[0002] The vessel includes a multi-fuel engine that uses two or more different types of fuel, such as gaseous fuel (natural gas, methane, etc.) and liquid fuel (diesel fuel).

[0003] Gas fuels contain methane, and because methane exists in a highly stable state due to strong carbon-hydrogen bonds, if it is not completely consumed by the engine and is emitted, it does not naturally oxidize under exhaust gas temperature conditions and is released into the atmosphere in an untreated state.

[0004] Meanwhile, methane (CH4) is a greenhouse gas that exhibits a stronger greenhouse effect than an equivalent amount of carbon dioxide (CO2). To solve the problem of global warming, the amount of methane emitted from exhaust gases must be reduced. Recently, with the strengthening of regulations to reduce GHG (Greenhouse Gas) emissions by the International Maritime Organization (IMO) and the European Union (EU), carbon taxes and regulations on GHG emissions, including carbon dioxide (CO2), are being discussed, and technologies that prevent methane from being emitted into the atmosphere are required. In response to these demands, various studies are underway on methods to efficiently remove methane, which is contained in large quantities in exhaust gases, in order to efficiently purify the exhaust gases of multi-fuel engines, which act as a major cause of environmental pollution.

[0005] Marine exhaust gas aftertreatment systems utilize methane oxidation catalysts (MOCs) to efficiently remove methane. The methane oxidation catalyst can achieve appropriate performance when its temperature is higher than the temperature of the exhaust gas. Furthermore, the performance of the methane oxidation catalyst can be easily degraded by sulfur oxides and hydrocarbons.

[0006] The matters described in this background technology section are written to enhance understanding of the background of the invention and may include matters that are not prior art already known to those skilled in the art to which this technology belongs. The problem to be solved

[0007] The present invention has been devised in consideration of the above points, and aims to provide an exhaust gas aftertreatment system capable of extending the service life of a methane oxidation catalyst by reducing or removing sulfur oxides, hydrocarbons, etc. contained in the exhaust gas by a diesel oxidation catalyst before the exhaust gas comes into contact with the methane oxidation catalyst, and a ship including the same.

[0008] The problems intended to be solved in the embodiments are not limited thereto, and may also include objectives or effects that can be identified from the means of solving the problems or the forms of implementation described below. means of solving the problem

[0009] An exhaust gas aftertreatment system according to an embodiment of the present invention for achieving the above-mentioned purpose may include: an upstream catalyst configured to reduce the sulfur content of the exhaust gas by adsorbing sulfur components within the exhaust gas; and a downstream catalyst located downstream of the upstream catalyst.

[0010] The size of the upstream catalyst may be smaller than the size of the downstream catalyst.

[0011] The upstream catalyst may be at least one catalyst among a diesel oxidation catalyst and a methane oxidation catalyst, or a combination thereof, and the downstream catalyst may be at least one catalyst among a methane oxidation catalyst and a diesel oxidation catalyst, or a combination thereof.

[0012] According to one embodiment, the content of the catalyst composition of the upstream catalyst may be relatively higher than the content of the catalyst composition of the downstream catalyst.

[0013] According to one embodiment, the precious metal content of the upstream catalyst may be relatively higher than the precious metal content of the downstream catalyst.

[0014] The above catalyst chamber can be located downstream of the turbocharger.

[0015] An exhaust gas aftertreatment system according to an embodiment of the present invention may further include a multi-fuel engine, an inlet exhaust gas line connected from the multi-fuel engine to the inlet of the catalyst chamber, and an outlet exhaust gas line connected to the outlet of the catalyst chamber. An exhaust gas aftertreatment system for a ship according to an embodiment of the present invention may further include an inlet valve disposed in the inlet exhaust gas line and an outlet valve disposed in the outlet exhaust gas line.

[0016] An exhaust gas aftertreatment system according to an embodiment of the present invention may further include a bypass line that branches off from the inlet exhaust gas line and joins the outlet exhaust gas line so that the exhaust gas discharged from the multi-fuel engine bypasses the catalyst chamber.

[0017] An exhaust gas aftertreatment system according to an embodiment of the present invention may further include a bypass valve disposed in the bypass line.

[0018] The above catalyst chamber may be located upstream of the turbocharger.

[0019] An exhaust gas aftertreatment system according to an embodiment of the present invention may further include a multi-fuel engine, an inlet exhaust gas line connected from the multi-fuel engine to the inlet of the catalyst chamber, and an outlet exhaust gas line connected from the outlet of the catalyst chamber to the inlet of the turbine of the turbocharger.

[0020] A vessel according to an embodiment of the present invention may include an exhaust gas aftertreatment system according to the above-described embodiment. Effects of the invention

[0021] According to the present invention, as the exhaust gas reacts first with the upstream catalyst, an exothermic reaction may occur in the upstream catalyst, and the temperature of the internal space of the catalyst chamber may rise relatively, and through this, the temperature of the downstream catalyst rises, thereby allowing the downstream catalyst to more effectively remove methane contained in the exhaust gas (i.e., the reactivity of the downstream catalyst increases at high temperatures).

[0022] According to the present invention, the upstream catalyst can be configured to be relatively smaller in size than the downstream catalyst, and thus, when the performance of the upstream catalyst that first comes into contact with the exhaust gas deteriorates as it removes hydrocarbons and sulfur, etc. in advance, it is easy to replace only the upstream catalyst, and the replacement cost of the upstream catalyst can be relatively low.

[0023] According to the present invention, the content of the catalyst composition of the upstream catalyst may be relatively higher than that of the downstream catalyst, and thus, an exothermic reaction can be induced in the upstream catalyst during the process in which the exhaust gas reacts with the upstream catalyst. Through this, the temperature of the internal space of the catalyst chamber may rise relatively, and as the temperature of the downstream catalyst rises above the temperature of the exhaust gas, the downstream catalyst can more effectively remove methane contained in the exhaust gas.

[0024] According to the present invention, the precious metal content of the upstream catalyst may be relatively higher than that of the downstream catalyst. Consequently, the upstream catalyst experiences no or minimized performance degradation due to hydrocarbon poisoning, sulfur poisoning, etc., and can induce an exothermic reaction in the upstream catalyst during the process in which the exhaust gas reacts with the upstream catalyst. Through this, the temperature of the internal space of the catalyst chamber may rise relatively, and as the temperature of the downstream catalyst rises above the temperature of the exhaust gas, the downstream catalyst can more effectively remove methane contained in the exhaust gas.

[0025] For example, in a catalyst chamber, the upstream catalyst is composed of a diesel oxidation catalyst and the downstream catalyst is composed of a methane oxidation catalyst, thereby allowing sulfur oxides, hydrocarbons, etc. contained in the exhaust gas to be removed in advance before the exhaust gas comes into contact with the methane oxidation catalyst, and thereby extending the service life of the methane oxidation catalyst. Brief explanation of the drawing

[0026] FIG. 1 is a schematic diagram illustrating the overall structure of an exhaust gas aftertreatment system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a catalyst arrangement structure arranged in the internal space of a catalyst chamber of an exhaust gas aftertreatment system according to one embodiment of the present invention. FIG. 3 is a diagram illustrating a catalyst arrangement structure arranged in the internal space of a catalyst chamber of an exhaust gas aftertreatment system according to another embodiment of the present invention. FIG. 4 is a drawing illustrating a diesel injector mechanism mounted in a catalyst chamber of an exhaust gas aftertreatment system according to one embodiment of the present invention and a water injection mechanism disposed within the catalyst chamber. FIG. 5 is a drawing illustrating a diesel injector mechanism mounted in a catalyst chamber of an exhaust gas aftertreatment system according to another embodiment of the present invention and a water injection mechanism disposed within the catalyst chamber. FIG. 6 is a drawing illustrating a diesel injector mechanism mounted on the inlet side exhaust gas line of an exhaust gas aftertreatment system according to one embodiment of the present invention and a water injection mechanism disposed within a catalyst chamber. FIG. 7 is a drawing illustrating a diesel injector mechanism mounted on the inlet side exhaust gas line of an exhaust gas aftertreatment system according to another embodiment of the present invention and a water injection mechanism disposed within a catalyst chamber. FIG. 8 is a drawing illustrating a urea injector mechanism mounted in a catalyst chamber of an exhaust gas aftertreatment system according to one embodiment of the present invention and a water injection mechanism disposed within the catalyst chamber. FIG. 9 is a drawing illustrating a urea injector mechanism mounted in a catalyst chamber of an exhaust gas aftertreatment system according to another embodiment of the present invention and a water injection mechanism disposed within the catalyst chamber. FIG. 10 is a drawing illustrating a urea injector mechanism mounted on the inlet side exhaust gas line of an exhaust gas aftertreatment system according to one embodiment of the present invention and a water injection mechanism disposed within a catalyst chamber. FIG. 11 is a drawing illustrating a urea injector mechanism mounted on the inlet side exhaust gas line of an exhaust gas aftertreatment system according to another embodiment of the present invention and a water injection mechanism disposed within a catalyst chamber. FIG. 12 is a drawing illustrating a regenerated gas supply device connected to an exhaust gas aftertreatment system according to an embodiment of the present invention. FIG. 13 is a schematic diagram illustrating the overall structure of an exhaust gas aftertreatment system according to another embodiment of the present invention. Specific details for implementing the invention

[0027] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0028] In describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc., may be used. These terms are used merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms used.

[0029] In an embodiment of the present invention, the singular form may include the plural form unless specifically mentioned in the text, and when described as "at least one of A and B and C (or more than one)," it may include one or more of all combinations that can be formed from A, B, and C.

[0030] And, where it is stated that a component is 'connected', 'combined', or 'connected' to another component, this may include not only cases where the component is directly connected, combined, or connected to the other component, but also cases where it is 'connected', 'combined', or 'connected' due to another component located between the component and the other component.

[0031] Furthermore, when described as being formed or placed "above or below" each component, "above" or "below" includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or placed between the two components. Additionally, when expressed as "above or below," it may include the meaning of a downward direction as well as an upward direction relative to a single component.

[0032] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0033] Referring to FIG. 1, an exhaust gas aftertreatment system according to an embodiment of the present invention may include a catalyst chamber (11).

[0034] The catalyst chamber (11) may include a plurality of catalysts disposed therein, and the plurality of catalysts may be configured to remove various harmful substances contained in the exhaust gas discharged from the multi-fuel engine (1). The catalyst chamber (11) may have an inlet (11a) into which exhaust gas is introduced and an outlet (11b) into which exhaust gas is discharged, and the plurality of catalysts may be arranged so as to be spaced apart along the direction of exhaust gas flow within the internal space of the catalyst chamber (11).

[0035] FIG. 1 illustrates a low-pressure exhaust gas aftertreatment system in which a catalyst chamber (11) is located downstream of a turbocharger (4). That is, the exhaust gas aftertreatment system illustrated in FIG. 1 may be a low-pressure exhaust gas aftertreatment system in which low-pressure exhaust gas discharged from a turbocharger (4) flows into a catalyst chamber (11).

[0036] Referring to FIG. 1, an inlet exhaust gas line (2) can be connected from a multi-fuel engine (1) to an inlet (11a) of a catalyst chamber (11), and an outlet exhaust gas line (3) can be connected to an outlet (11b) of a catalyst chamber (11). Exhaust gas discharged from a multi-fuel engine (1) and a turbocharger (4) is introduced into the inlet (11a) of a catalyst chamber (11) through the inlet exhaust gas line (2), harmful substances contained in the exhaust gas passing through the catalyst chamber (11) are removed by a plurality of catalysts, and the exhaust gas from which harmful substances have been removed can be discharged to the outside through the outlet exhaust gas line (3) from the outlet (11b) of the catalyst chamber (11).

[0037] A turbocharger (4) may be positioned in the inlet side exhaust gas line (2), and the turbocharger (4) may include a turbine (4a) that rotates by exhaust gas and a compressor (4b) that compresses intake air. The turbine (4a) of the turbocharger (4) may be positioned in the inlet side exhaust gas line (2). Accordingly, exhaust gas discharged from the multi-fuel engine (1) may flow into the inlet (11a) of the catalyst chamber (11) after passing through the turbine (4a) of the turbocharger (4).

[0038] The low-pressure exhaust gas aftertreatment system according to the embodiment of FIG. 1 may further include a bypass line (12) that branches off from a branch point (2a) of an inlet exhaust gas line (2) and joins at a merging point (3a) of an outlet exhaust gas line (3) so that exhaust gas discharged from a multi-fuel engine (1) bypasses the catalyst chamber (11). The branch point (2a) of the inlet exhaust gas line (2) may be located downstream of the turbine (4a) of the turbocharger (4), and the inlet of the bypass line (12) may be connected to the inlet exhaust gas line (2) at a downstream point of the turbine (4a) of the turbocharger (4).

[0039] Referring to FIG. 1, an inlet valve (13) may be placed in the inlet exhaust gas line (2), and an outlet valve (14) may be placed in the outlet exhaust gas line (3). By selectively opening and closing the inlet valve (13) and / or the outlet valve (14), the exhaust gas may or may not pass through the catalyst chamber (11).

[0040] Referring to FIG. 1, a bypass valve (15) may be placed in a bypass line (12), and the exhaust gas may or may not pass through the bypass valve (15) by selectively opening and closing the bypass valve (15).

[0041] For initial performance verification, a methane meter may be optionally installed, and after performance verification is completed, the methane meter (16, 17) may be separated. For example, as illustrated in FIG. 1, the inlet methane meter (16) may be detachably installed in the inlet exhaust gas line (2), and the inlet methane meter (16) may measure the methane concentration in the exhaust gas flowing into the inlet (11a) of the catalyst chamber (11). The outlet methane meter (17) may be detachably installed in the outlet exhaust gas line (3), and the outlet methane meter (17) may measure the methane concentration in the exhaust gas discharged from the outlet (11b) of the catalyst chamber (11).

[0042] Referring to FIG. 1, an inlet temperature sensor (T1) may be positioned in a portion adjacent to the inlet (11a) of the catalyst chamber (11), and the inlet temperature sensor (T1) may be configured to measure the upstream temperature of the catalysts in the catalyst chamber (11). An outlet temperature sensor (T2) may be positioned in a portion adjacent to the outlet (11b) of the catalyst chamber (11), and the outlet temperature sensor (T2) may be configured to measure the downstream temperature of the catalysts in the catalyst chamber (11). An intermediate temperature sensor (T3) may be positioned in the middle of the catalyst chamber (11) and may be configured to measure the temperature of the space between the chambers placed within the catalyst chamber (11). A differential pressure gauge (PDT) may be mounted on the catalyst chamber (11), and the differential pressure gauge (PDT) may be configured to measure the pressure difference between the inlet pressure and the outlet pressure of the catalyst chamber (11).

[0043] The controller (20) can control the operation of the inlet side valve (13), outlet side valve (14), bypass valve (15), etc. based on the methane concentration in the exhaust gas measured by the inlet side methane meter (16), the methane concentration of the exhaust gas measured by the outlet side methane meter (17), the temperature measured by the inlet side temperature sensor (T1), the temperature measured by the outlet side temperature sensor (T2), the temperature measured by the intermediate side temperature sensor (T3), the pressure measured by the differential pressure gauge (PDT), etc.

[0044] Referring to FIG. 1, an engine system according to an embodiment of the present invention may include a catalyst chamber (11) and a multi-fuel engine (1) disposed upstream of the catalyst chamber (11).

[0045] The multi-fuel engine (1) may be configured to selectively use two or more different types of fuel, such as gaseous fuel (natural gas, methane, etc.) and liquid fuel (diesel fuel). For example, the multi-fuel engine (1) may operate in at least one of the following modes: a gaseous fuel operation mode in which only gaseous fuel is used for combustion, a liquid fuel operation mode in which only liquid fuel is used for combustion, and a mixed fuel operation mode in which a mixture of gaseous fuel and liquid fuel is used for combustion.

[0046] FIG. 2 is a diagram illustrating a type of catalyst arrangement structure disposed in the internal space of a catalyst chamber (11) of an exhaust gas aftertreatment system according to an embodiment of the present invention. Referring to FIG. 2, the catalyst chamber (11) may include an upstream catalyst (21) disposed adjacent to the inlet of the catalyst chamber (11) and a downstream catalyst (31) disposed adjacent to the outlet of the catalyst chamber (11). The upstream catalyst (21) and the downstream catalyst (31) may be oxidation catalysts. The upstream catalyst (21) may be at least one catalyst or a combination thereof among a diesel oxidation catalyst and a methane oxidation catalyst, and the downstream catalyst (31) may be at least one catalyst or a combination thereof among a methane oxidation catalyst and a diesel oxidation catalyst.

[0047] According to the embodiment of FIG. 2, the upstream catalyst (21) may be a diesel oxidation catalyst (DOC) configured to adsorb sulfur components in the exhaust gas and reduce the sulfur components of the exhaust gas discharged from the upstream catalyst (21).

[0048] According to the embodiment of FIG. 2, the downstream catalyst (31) may be a methane oxidation catalyst configured to remove methane generated from the unburned gas fuel.

[0049] According to one embodiment, the catalyst composition content of the upstream catalyst (21) may be relatively lower than that of the downstream catalyst (31), and the upstream catalyst (21) may be configured to be relatively smaller in size than the downstream catalyst (31). Accordingly, when the performance of the upstream catalyst (21), which first comes into contact with the exhaust gas, deteriorates as it reduces or removes hydrocarbons and sulfur, etc., it may be easier to replace only the upstream catalyst (21), and the replacement cost of the upstream catalyst (21) may be relatively low. The replacement cycle of the upstream catalyst (21) can be appropriately determined through various methods that can directly or indirectly verify the performance of the upstream catalyst (21), such as a counting method of operating time, methane oxidation reduction performance, and temperature rise.

[0050] According to another embodiment, the catalyst composition content of the upstream catalyst (21) may be relatively higher than the catalyst composition content of the downstream catalyst (31), and thus, an exothermic reaction may be induced in the upstream catalyst (21) during the process in which the exhaust gas reacts with the upstream catalyst (21). Through this, the temperature of the exhaust gas passing through the upstream catalyst (21) may rise relatively due to the exothermic reaction of the upstream catalyst (21), and thus the temperature of the downstream catalyst (31) rises to the reaction temperature by the exhaust gas discharged from the upstream catalyst (21), thereby allowing the downstream catalyst (31) to more effectively remove methane contained in the exhaust gas.

[0051] According to another embodiment, the precious metal content of the upstream catalyst (21) may be relatively higher than the precious metal content of the downstream catalyst (31), so that the upstream catalyst (21) does not experience or minimizes performance degradation due to hydrocarbon poisoning, sulfur poisoning, etc., and can induce an exothermic reaction in the upstream catalyst (21) during the process in which the exhaust gas reacts with the upstream catalyst (21). Through this, the temperature of the exhaust gas passing through the upstream catalyst (21) can be relatively raised by the exothermic reaction of the upstream catalyst (21), and the temperature of the downstream catalyst (31) rises to the reaction temperature required by the exhaust gas discharged from the upstream catalyst (21), thereby allowing the downstream catalyst (31) to more effectively remove methane contained in the exhaust gas.

[0052] FIG. 3 is a diagram illustrating a different type of catalyst arrangement structure disposed in the internal space of a catalyst chamber (11) of an exhaust gas aftertreatment system according to an embodiment of the present invention. Referring to FIG. 3, the catalyst chamber (11) may include an upstream catalyst (21) disposed adjacent to the inlet of the catalyst chamber (11) and a plurality of downstream catalysts (31, 32) located downstream of the upstream catalyst (21). The plurality of downstream catalysts (31, 32) may include a first downstream catalyst (31) located downstream of the upstream catalyst (21) and a second downstream catalyst (32) located downstream of the first downstream catalyst (31). The second downstream catalyst (32) may be disposed adjacent to the outlet (11b) of the catalyst chamber (11). The upstream catalyst (21) and the downstream catalysts (31, 32) may be oxidation catalysts. The upstream catalyst (21) may be at least one catalyst among a diesel oxidation catalyst and a methane oxidation catalyst, or a combination thereof, and the downstream catalyst (31, 32) may be at least one catalyst among a methane oxidation catalyst and a diesel oxidation catalyst, or a combination thereof.

[0053] According to the embodiment of FIG. 3, the upstream catalyst (21) may be a diesel oxidation catalyst (DOC) configured to adsorb sulfur components in the exhaust gas and reduce the sulfur components of the exhaust gas discharged from the upstream catalyst (21).

[0054] According to the embodiment of FIG. 3, the first downstream catalyst (31) and the second downstream catalyst (32) may be methane oxidation catalysts configured to remove methane generated from the unburned gas fuel.

[0055] According to one embodiment, the amount of catalyst composition of the first downstream catalyst (31) may be equal to the amount of catalyst composition of the second downstream catalyst (32), the amount of catalyst composition of the upstream catalyst (21) may be relatively less than the amount of catalyst composition of each downstream catalyst (31, 32), and the upstream catalyst (21) may be configured to be relatively smaller in size than each downstream catalyst (31, 32). Accordingly, when the performance of the upstream catalyst (21) deteriorates as it removes hydrocarbons and sulfur, etc., it may be easier to replace only the upstream catalyst (21), and the cost of replacing the upstream catalyst (21) may be relatively low.

[0056] According to another embodiment, the catalyst composition content of the upstream catalyst (21) may be relatively higher than the catalyst composition content of each downstream catalyst (31, 32), and thus, an exothermic reaction may be induced in the upstream catalyst (21) during the process in which the exhaust gas reacts with the upstream catalyst (21). Through this, the temperature of the exhaust gas passing through the upstream catalyst (21) may rise relatively due to the exothermic reaction of the upstream catalyst (21), and thus the temperature of the downstream catalyst (31) rises to the reaction temperature required by the exhaust gas discharged from the upstream catalyst (21), thereby allowing each downstream catalyst (31, 32) to more effectively remove methane contained in the exhaust gas.

[0057] According to another embodiment, the precious metal content of the upstream catalyst (21) may be relatively higher than the precious metal content of each downstream catalyst (31, 32), and thus the upstream catalyst (21) may not have its performance degraded due to hydrocarbon poisoning, sulfur poisoning, etc., or may minimize it, and may induce an exothermic reaction in the upstream catalyst (21) during the process in which the exhaust gas reacts with the upstream catalyst (21). Through this, the temperature of the exhaust gas passing through the upstream catalyst (21) may rise relatively due to the exothermic reaction of the upstream catalyst (21), and thus the temperature of the downstream catalyst (31) rises to the reaction temperature required by the exhaust gas discharged from the upstream catalyst (21), thereby allowing each downstream catalyst (31, 32) to more effectively remove methane contained in the exhaust gas.

[0058] The inlet temperature sensor (T1) can measure the upstream temperature of the upstream catalyst (21), the outlet temperature sensor (T2) can measure the downstream temperature of the downstream catalyst (31, 32), and the intermediate temperature sensor (T3) can measure the temperature of the space between the upstream catalyst (21) and the downstream catalyst (31, 32). As the intermediate temperature sensor (T3) measures the temperature of the space between the upstream catalyst (21) and the downstream catalyst (31, 32), the increased temperature of the exhaust gas caused by the upstream catalyst (21) can be substantially detected.

[0059] As described above, since the upstream catalyst (21) is located upstream of the downstream catalyst (22), the upstream catalyst (21) can come into contact with and react with the exhaust gas before the downstream catalyst (22). Accordingly, the exhaust gas, in which hydrocarbons (HC) and sulfur, etc., have been reduced or removed in advance by the upstream catalyst (21), comes into contact with and reacts with the downstream catalyst (31, 32), thereby allowing the methane contained in the exhaust gas to be efficiently removed or reduced by the downstream catalyst (31, 32), which is a methane oxidation catalyst, and the service life of the downstream catalyst (31, 32), which is a methane oxidation catalyst, to be extended.

[0060] Additionally, as the exhaust gas reacts first with the upstream catalyst (21), an exothermic reaction may occur in the upstream catalyst (21), and the temperature of the exhaust gas passing through the upstream catalyst (21) may rise relatively due to the exothermic reaction of the upstream catalyst (21), and the temperature of the downstream catalyst (31) rises to the reaction temperature required by the exhaust gas discharged from the upstream catalyst (21), thereby allowing the downstream catalyst (31, 32) to more effectively remove methane contained in the exhaust gas.

[0061] A ship exhaust gas aftertreatment system (10) according to an embodiment of the present invention may further include an injector mechanism configured to inject an oxidizable substance into the upstream catalyst (21) from the upstream side of the upstream catalyst (21). According to the embodiment, the oxidizable substance may be at least one or a combination of two or more of diesel fuel, LNG, methanol, ethanol, and urea. As the oxidizable substance reacts with the upstream catalyst (21) and is oxidized, the temperature of the exhaust gas passing through the upstream catalyst (21) may be relatively raised by the oxidation reaction of the oxidizable substance, and the downstream catalyst (31, 32) may be raised to the required reaction temperature by the exhaust gas discharged from the upstream catalyst (21). That is, the temperature of the downstream catalyst (31, 32) may be induced by the exhaust gas raised by the upstream catalyst (21), and the methane reduction efficiency by the downstream catalyst (31, 32) may be significantly improved. The injector mechanism may be positioned upstream of the upstream catalyst (21). For example, the injector mechanism may be positioned in a part of the catalyst chamber (11) adjacent to the inlet (11a) of the catalyst chamber (11) or in a part of the inlet exhaust gas line (2) adjacent to the catalyst chamber (11). The controller (20) may be configured to control the injector mechanism, the upstream valve (13), the downstream valve (14), and the bypass valve (15) based on the temperature of the downstream catalyst (31, 32) and whether gas stripping occurs in the multi-fuel engine.

[0062] According to the embodiments of FIGS. 4 to 7, the injector mechanism may be a diesel injector mechanism (40) that injects diesel fuel into an upstream catalyst (21).

[0063] Referring to FIGS. 4 to 7, the diesel injector mechanism (40) may include a diesel injector (41) that injects diesel fuel into an upstream catalyst (21), a diesel fuel tank (43) fluidly connected to the diesel injector (41) through a diesel fuel line (42), a fuel pump unit (44) configured to supply diesel fuel to the diesel injector (41), and a fuel dosing unit (45) configured to control the flow rate of the diesel fuel. The fuel pump unit (44) may be composed of a fuel pump and peripheral devices, and the fuel dosing unit (45) may be composed of a fuel flow meter, a fuel flow control valve, and peripheral devices.

[0064] Referring to FIGS. 4 and 5, a diesel injector (41) can be mounted in the catalyst chamber (11) adjacent to the inlet (11a) of the catalyst chamber (11).

[0065] Referring to FIGS. 6 and 7, the diesel injector (41) can be mounted on the inlet side exhaust gas line (2).

[0066] As diesel fuel is injected into the upstream catalyst (21) by the diesel injector (41), the diesel fuel is oxidized, and the temperature of the exhaust gas passing through the upstream catalyst (21) can rise relatively due to the oxidation reaction of the diesel fuel, and the temperature of the downstream catalyst (31) can rise to the reaction temperature by the exhaust gas discharged from the upstream catalyst (21). According to one example, the controller (20) can control the fuel pump unit (44) to determine the amount of diesel fuel injected by the diesel injector (41) based on the target temperature (e.g., 300~500℃) of the downstream catalyst (31, 32) that can optimize the methane removal efficiency.

[0067] According to another example, the controller (20) can determine whether the temperature of the downstream catalyst (31, 32) exceeds an acceptable temperature based on the upstream temperature of the upstream catalyst (21) measured by the inlet temperature sensor (T1), the downstream temperature of the downstream catalyst (31, 32) measured by the outlet temperature sensor (T2), and the temperature of the space between the upstream catalyst (21) and the downstream catalyst (31, 32) measured by the intermediate temperature sensor (T3). The controller (20) can control the fuel pump unit (44) to reduce the injection amount of diesel fuel when the temperature of the downstream catalyst (31, 32) exceeds an allowable temperature, adjust the opening amount of the bypass valve (15) so that some exhaust gas passes through the bypass line (12), and close the upstream valve (13) and downstream valve (14) to block the exhaust gas from passing through the catalyst chamber (11). According to another example, when a gas trip occurs in the multi-fuel engine (1), the controller (20) can stop the fuel pump unit (44) to stop the injection of diesel fuel, close the upstream valve (13) and downstream valve (14) to block the exhaust gas from passing through the catalyst chamber (11), and fully open the bypass valve (15) so that the exhaust gas passes through the bypass line (12). When the gas fuel operation mode of the multi-fuel engine (1) is incomplete, misfires in the combustion chamber may occur above a certain level, and the multi-fuel engine (1) is converted to a liquid fuel operation mode; this situation is called a gas strip. When such a gas strip occurs, the controller (20) stops the fuel pump unit (44) so ​​that the injection of diesel fuel is stopped, and the controller (20) completely opens the bypass valve (15) and closes the upstream valve (13) and downstream valve (14), so that the exhaust gas passes only through the bypass line (12) and does not pass through the catalyst chamber (11).

[0068] According to the embodiments of FIGS. 8 to 11, the injector mechanism may be a urea injector mechanism (50) configured to inject urea from upstream of the upstream catalyst (21) to the upstream catalyst (21).

[0069] Referring to FIGS. 8 to 11, the urea injector mechanism (50) may include a urea injector (51) that injects urea into an upstream catalyst (21) and a urea dosing unit (53) fluidly connected to the urea injector (51) through a urea line (52). By connecting the urea dosing unit (53) to the urea supply system of the SCR catalyst mechanism, the urea dosing unit (53) can utilize the urea supply system of the SCR catalyst mechanism.

[0070] Referring to FIGS. 8 and 9, a urea injector (51) can be mounted in the catalyst chamber (11) adjacent to the inlet (11a) of the catalyst chamber (11).

[0071] Referring to FIGS. 10 and 11, the urea injector (51) can be mounted in a portion adjacent to the catalyst chamber (11) of the inlet side exhaust gas line (2).

[0072] As urea is injected into the upstream catalyst (21) by the urea injector (51), the urea is oxidized, and the temperature of the exhaust gas passing through the upstream catalyst (21) can be relatively raised by the oxidation reaction of the urea, and as the temperature of the downstream catalyst (31) rises to the reaction temperature by the exhaust gas discharged from the upstream catalyst (21), the temperature of the downstream catalyst (31, 32) can be raised.

[0073] According to one example, the controller (20) can control the urea dosing unit (53) to determine the amount of urea injected by the urea injector (51) based on the target temperature (e.g., 300 to 500°C) of the downstream catalyst (31, 32) that can optimize the removal efficiency of methane.

[0074] According to another example, the controller (20) can determine whether the temperature of the downstream catalyst (31, 32) exceeds an acceptable temperature based on the upstream temperature of the upstream catalyst (21) measured by the inlet temperature sensor (T1), the downstream temperature of the downstream catalyst (31, 32) measured by the outlet temperature sensor (T2), and the temperature of the space between the upstream catalyst (21) and the downstream catalyst (31, 32) measured by the intermediate temperature sensor (T3). The controller (20) can control the urea dosing unit (53) to reduce the amount of urea injected when the temperature of the downstream catalyst (31, 32) exceeds an allowable temperature, adjust the opening amount of the bypass valve (15) so that some exhaust gas passes through the bypass line (12), and close the upstream valve (13) and downstream valve (14) to block the exhaust gas from passing through the catalyst chamber (11).

[0075] According to another example, when a gas trip occurs in a multi-fuel engine (1), the controller (20) may stop the urea dosing unit (53) to stop the injection of urea, close the upstream valve (13) and downstream valve (14) to block exhaust gas from passing through the catalyst chamber (11), and fully open the bypass valve (15) to allow exhaust gas to pass through the bypass line (12). If the gas fuel operation mode of the multi-fuel engine (1) is incomplete, misfires in the combustion chamber may occur above a certain level, and the multi-fuel engine (1) is switched to a liquid fuel operation mode; this situation is called a gas trip. When such a gas strip occurs, the controller (20) stops the urea dosing unit (53), thereby stopping the fuel injection of urea, and the controller (20) completely opens the bypass valve (15) and closes the upstream valve (13) and downstream valve (14), so that the exhaust gas passes only through the bypass line (12) and does not pass through the catalyst chamber (11).

[0076] According to the embodiments of FIGS. 4 to 11, the upstream catalyst (21), which is a diesel oxidation catalyst, may have a relatively lower precious metal content than the downstream catalyst (31, 32), which is a methane oxidation catalyst, and thereby the upstream catalyst (21) may be relatively cheaper than the downstream catalyst (31, 32). Accordingly, the upstream catalyst (21), which is a diesel oxidation catalyst, can extend the service life of the downstream catalyst (31, 32), which is a methane oxidation catalyst, by primarily reducing or removing hydrocarbons (HC), sulfur (S), etc., which are catalyst poisoning components.

[0077] An exhaust gas aftertreatment system according to an embodiment of the present invention may include a water injector mechanism (60) configured to regenerate an upstream catalyst (21) and a downstream catalyst (31, 32) by spraying water onto the upstream catalyst (21) and the downstream catalyst (31, 32). By directly spraying water onto the upstream catalyst (21) and the downstream catalyst (31, 32) through the water injector mechanism (60), adsorbed substances adsorbed on the upstream catalyst (21) and the downstream catalyst (31, 32) can be washed, thereby allowing the upstream catalyst (21) and the downstream catalyst (31, 32) to be regenerated smoothly.

[0078] Referring to FIGS. 4 to 11, a water injector mechanism (60) may be positioned downstream of an upstream catalyst (21) and downstream of each downstream catalyst (31, 32) within the internal space of a catalyst chamber (11). The water injector mechanism (60) may include a water pipe (61) extending downstream of the upstream catalyst (21) and downstream of each downstream catalyst (31, 32), and a plurality of water injectors (62) positioned toward the upstream catalyst (21) and each downstream catalyst (31, 32) from the water pipe (61). A water supply source may be connected to the water pipe (61) through a water supply line, and a water pump may be positioned in the water supply line to supply water to the water pipe (61). Each water injector (62) can directly spray water onto the upstream catalyst (21) and downstream catalyst (31, 32), thereby removing adsorbed material adsorbed on the upstream catalyst (21) and downstream catalyst (31, 32), and thereby increasing the regeneration efficiency of the upstream catalyst (21) and downstream catalyst (31, 32).

[0079] Referring to FIG. 1, the exhaust gas aftertreatment system according to an embodiment of the present invention may further include a regeneration gas supply device (70) configured to supply regeneration gas to the inlet (11a) of the catalyst chamber (11).

[0080] According to an embodiment, the regeneration gas may include a reducing agent for reducing the catalyst (21, 31, 32) and an inert gas for creating a reducing atmosphere in the internal space of the catalyst chamber (11). According to a specific embodiment, the reducing agent may be CH4, H2, etc., and the inert gas may be N2 as a balance gas for creating a reducing atmosphere.

[0081] Referring to FIG. 12, the regenerative gas supply device (70) may include a reducing agent supply unit (71) that supplies a reducing agent and an inert gas supply unit (74) that supplies an inert gas.

[0082] The reducing agent supply unit (71) may be configured to supply a reducing agent into the internal space of the catalyst chamber (11) to reduce an oxidizing agent poisoned on the surface of the catalyst (21, 31, 32). According to a specific embodiment, the reducing agent supply unit (71) may be fluidly connected to the inlet exhaust gas line (2) through the reducing agent supply line (72), and the reducing agent source (73) may be located upstream of the reducing agent supply unit (71), and the reducing agent supply unit (71) may be configured to supply the reducing agent from the reducing agent source (73) to the inlet exhaust gas line (2).

[0083] The inert gas supply unit (74) may be configured to supply inert gas into the internal space of the catalyst chamber (11) to create an oxygen-free reducing atmosphere inside the catalyst chamber (11). According to a specific embodiment, the inert gas supply unit (74) may be fluidly connected to the inlet exhaust gas line (2) through the inert gas supply line (75), and the inert gas source (77) may be located upstream of the inert gas supply unit (74), and the inert gas supply unit (74) may be configured to supply inert gas from the inert gas source (77) to the inlet exhaust gas line (2).

[0084] According to an embodiment, the inert gas supply unit (74) may further include a heater (76) configured to heat the inert gas to a set temperature. The heater (76) may be located downstream of the inert gas supply unit (74), and the high-temperature inert gas heated by the heater (76) may be supplied to the internal space of the catalyst chamber (11) through the inlet side exhaust gas line (2).

[0085] The reducing agent supply line (72) and the inert gas supply line (75) can be joined to the inlet of the regeneration gas supply line (78), and the outlet of the regeneration gas supply line (78) can be fluidly connected to a portion adjacent to the catalyst chamber (11) of the inlet-side exhaust gas line (2). The reducing agent supplied by the reducing agent supply line (72) and the inert gas supplied by the inert gas supply line (75) can be supplied to the inlet-side exhaust gas line (2) through the regeneration gas supply line (78). A reducing agent and an inert gas can be supplied to the inlet (11a) of the catalyst chamber (11) through the inlet side exhaust gas line (2), and thus the internal space of the catalyst chamber (11) is created with a reducing atmosphere by the reducing agent and the high-temperature inert gas, and the oxide substances poisoned on the surface of each catalyst (21, 31, 32) are reduced by the reducing agent, thereby allowing each catalyst (21, 31, 32) to be efficiently regenerated by the reducing agent and the inert gas.

[0086] The catalyst arrangement structure of the catalyst chamber (11), the diesel injector mechanism, the urea injector mechanism, the water injector mechanism, the regenerative gas supply device, etc., according to the embodiments of FIGS. 2 to 11 are not limited to the low-pressure exhaust gas aftertreatment system of FIG. 1 and can be applied in the same way to the high-pressure exhaust gas aftertreatment system of FIG. 13.

[0087] FIG. 13 illustrates a high-pressure exhaust gas aftertreatment system in which a catalyst chamber (11) is located upstream of a turbocharger (4). That is, the exhaust gas aftertreatment system illustrated in FIG. 13 may be a high-pressure exhaust gas aftertreatment system in which high-pressure exhaust gas discharged from a multi-fuel engine (1) passes through a catalyst chamber (11) or a bypass line (12) and then flows into the inlet of a turbine (4a) of a turbocharger (4).

[0088] Referring to FIG. 13, an exhaust gas reservoir (1a) may be positioned downstream of a multi-fuel engine (1), and the exhaust gas reservoir (1a) may receive exhaust gas discharged from the multi-fuel engine (1).

[0089] Referring to FIG. 13, the inlet exhaust gas line (2) can be connected from the exhaust gas reservoir (1a) to the inlet (11a) of the catalyst chamber (11), and the outlet exhaust gas line (3) can be connected from the outlet (11b) of the catalyst chamber (11) to the inlet (4a) of the turbocharger (4). Exhaust gas discharged from the multi-fuel engine (1) flows into the inlet (11a) of the catalyst chamber (11) through the exhaust gas reservoir (1a) and the inlet exhaust gas line (2), harmful substances contained in the exhaust gas passing through the catalyst chamber (11) are removed by a plurality of catalysts, and the exhaust gas from which harmful substances have been removed can be discharged to the outside after passing through the turbine (4a) of the turbocharger (4) via the outlet exhaust gas line (3) from the outlet (11b) of the catalyst chamber (11).

[0090] The high-pressure exhaust gas aftertreatment system according to the embodiment of FIG. 13 may further include a bypass line (12) that branches off from an inlet exhaust gas line (2) or an exhaust gas reservoir (1a) and joins to an outlet exhaust gas line (3) so that the exhaust gas bypasses the catalyst chamber (11).

[0091] Referring to FIG. 13, an inlet valve (13) may be placed in the inlet exhaust gas line (2), and an outlet valve (14) may be placed in the outlet exhaust gas line (3). By selectively opening and closing the inlet valve (13) and / or the outlet valve (14), the exhaust gas may or may not pass through the catalyst chamber (11).

[0092] Referring to FIG. 13, a bypass valve (15) may be placed in a bypass line (12), and the exhaust gas may or may not pass through the bypass valve (15) by selectively opening and closing the bypass valve (15).

[0093] A methane meter may be optionally installed for initial performance verification, and the methane meter may be removed after the performance verification is completed. According to one example, only the outlet-side methane meter (17) may be placed in the outlet-side exhaust gas line (3). For instance, a probe may be installed on one side of the outlet-side exhaust gas line (3), and the outlet-side methane meter (17) may be detachably mounted on the probe. Furthermore, the methane meter (17) may check the upstream and downstream measurement levels of methane in the exhaust gas passing through the catalyst chamber (11) with a time difference by the operation of the inlet-side valve (13), the outlet-side valve (14), and the bypass valve (15). According to another example, an inlet methane meter (16) may be placed in the inlet exhaust gas line (2), and the inlet methane meter (16) may measure the methane concentration in the exhaust gas flowing into the inlet (11a) of the catalyst chamber (11). An outlet methane meter (17) may be placed in the outlet exhaust gas line (3), and the outlet methane meter (17) may measure the methane concentration in the exhaust gas discharged from the outlet (11b) of the catalyst chamber (11).

[0094] Referring to FIG. 13, an inlet temperature sensor (T1) may be positioned in a portion adjacent to the inlet (11a) of the catalyst chamber (11), and the inlet temperature sensor (T1) may be configured to measure the upstream temperature of the catalysts in the catalyst chamber (11). An outlet temperature sensor (T2) may be positioned in a portion adjacent to the outlet (11b) of the catalyst chamber (11), and the outlet temperature sensor (T2) may be configured to measure the downstream temperature of the catalysts in the catalyst chamber (11). An intermediate temperature sensor (T3) may be positioned in the middle of the catalyst chamber (11) and may be configured to measure the temperature of the space between the chambers placed within the catalyst chamber (11). A differential pressure gauge (PDT) may be mounted on the catalyst chamber (11), and the differential pressure gauge (PDT) may be configured to measure the pressure difference between the inlet pressure and the outlet pressure of the catalyst chamber (11).

[0095] The controller (20) can control the operation of the inlet valve (13), outlet valve (14), bypass valve (15), etc. based on the methane concentration in the exhaust gas measured by the inlet methane meter (16), the methane concentration in the exhaust gas measured by the outlet methane meter (17), the temperature measured by the inlet temperature sensor (T1), the temperature measured by the outlet temperature sensor (T2), the temperature of the space between the upstream catalyst (21) and the downstream catalyst (31, 32) measured by the intermediate temperature sensor (T3), and the pressure measured by the differential pressure gauge (PDT).

[0096] In addition, a vessel according to an embodiment of the present invention may include an exhaust gas aftertreatment system and an engine system according to the above-described embodiment.

[0097] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention.

[0098] Accordingly, the embodiments disclosed in this invention are intended to illustrate, not limit, the technical concept of the invention, and the scope of the technical concept of the invention is not limited by these embodiments. The scope of protection of this invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this invention. Explanation of the symbols

[0099] 1: Multi-fuel engine 2: Inlet side exhaust gas line 3: Exit-side exhaust line 4: Turbocharger 11: Catalytic Chamber 12: Bypass line 13: Inlet valve 14: Outlet valve 15: Bypass valve 16: Inlet methane meter 17: Outlet-side methane meter 20: Controller 21: Upstream catalyst 31, 32: Downstream catalyst 40: Diesel injector mechanism 41: Diesel injector 42: Diesel fuel line 43: Diesel fuel tank 44: Pump 50: Urea injector mechanism 51: Urea injector 52: Urea Line 53: Urea Dosing Unit 60: Water injector mechanism 61: Water pipe 62: Water injector 70: Regeneration gas supply device 71: Reducing agent supply unit 72: Reducing agent supply line 73: Reducing agent source 74: Inert gas supply unit 75: Inert gas supply line 76: Heater 77: Inert gas source 78: Renewable gas supply line

Claims

Claim 1 An exhaust gas aftertreatment system comprising: an upstream catalyst configured to reduce the sulfur content of the exhaust gas by adsorbing the sulfur content of the exhaust gas, and a catalyst chamber including a downstream catalyst located downstream of the upstream catalyst. Claim 2 An exhaust gas aftertreatment system according to claim 1, wherein the size of the upstream catalyst is smaller than the size of the downstream catalyst. Claim 3 The exhaust gas aftertreatment system according to claim 1, wherein the downstream catalyst is configured to remove methane contained in the exhaust gas discharged from the upstream catalyst. Claim 4 An exhaust gas aftertreatment system according to claim 1, wherein the catalyst composition content of the upstream catalyst is relatively higher than the catalyst composition content of the downstream catalyst. Claim 5 An exhaust gas aftertreatment system according to claim 1, wherein the precious metal content of the upstream catalyst is relatively higher than the precious metal content of the downstream catalyst. Claim 6 In claim 1, the catalyst chamber is an exhaust gas aftertreatment system located downstream of a turbocharger. Claim 7 An exhaust gas aftertreatment system according to claim 6, further comprising a multi-fuel engine, an inlet exhaust gas line connected from the multi-fuel engine to the inlet of the catalyst chamber, and an outlet exhaust gas line connected to the outlet of the catalyst chamber. Claim 8 An exhaust gas aftertreatment system according to claim 7, further comprising an inlet valve disposed in the inlet exhaust gas line and an outlet valve disposed in the outlet exhaust gas line. Claim 9 An exhaust gas aftertreatment system according to claim 7, further comprising a bypass line branched from the inlet exhaust gas line and joined to the outlet exhaust gas line so that exhaust gas discharged from the multi-fuel engine bypasses the catalyst chamber. Claim 10 An exhaust gas aftertreatment system according to claim 9, further comprising a bypass valve disposed in the bypass line. Claim 11 An exhaust gas aftertreatment system according to claim 1, wherein the catalyst chamber is located upstream of the turbocharger. Claim 12 An exhaust gas aftertreatment system according to claim 1, further comprising a multi-fuel engine, an inlet exhaust gas line connected from the multi-fuel engine to the inlet of the catalytic chamber, and an outlet exhaust gas line connected from the outlet of the catalytic chamber to the inlet of the turbine of a turbocharger. Claim 13 A vessel comprising an exhaust gas aftertreatment system according to claim 1.

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