Exhaust gas post-processing system and control method therefor

Abstract

The present invention relates to a system for controlling an operation of an exhaust gas post-processing device on the basis of operation data of an engine. The system comprises: an exhaust pipe; a post-processing device; a first pipe; a second pipe; a first valve and a second valve installed in the respective pipes; and a processor controlling the same. The processor determines an operation state of the engine, and accordingly, switches an operation mode by opening the first valve so that an exhaust gas flows into the post-processing device or opening the second valve so that the exhaust gas bypasses the post-processing device. Such a configuration may protect the post-processing device in an unstable operation state.

Description

Exhaust gas aftertreatment system and control method thereof

[0001] The present invention relates to an exhaust gas aftertreatment system and a control method thereof, and more specifically, to a system and a control method thereof that protects an aftertreatment device by controlling a valve according to engine load.

[0002] The International Maritime Organization (IMO) has recently been introducing and strengthening regulations on greenhouse gas emissions, including restrictions on sulfur oxide and nitrogen oxide emissions from marine vessels. Furthermore, in the European Union (EU), interest in reducing Greenhouse Gas (GHG) emissions and using eco-friendly fuels in the marine industry is growing due to the expansion of the Emission Trading System (ETS) into the maritime sector and the introduction of eco-friendly policies such as FuelEU Maritime. In particular, LNG is attracting attention as an eco-friendly fuel because it has lower carbon dioxide (CO2) emissions and a higher energy density compared to other fossil fuels used in ships.

[0003] However, in engines that use LNG as fuel, a phenomenon called methane slip occurs during the combustion process, in which some fuel is not completely burned and is emitted. Since methane has a Global Warming Potential approximately 28 times higher than carbon dioxide, methane slip can act as an obstacle to achieving carbon reduction targets.

[0004] Engine exhaust aftertreatment devices are devices designed to remove or reduce harmful substances generated by engines, and are widely used in various internal combustion engine systems, including automobiles, land-based power plants, and propulsion and power generation engines for marine vessels.

[0005] In particular, in the case of gas engines using LNG as fuel, methane slip—a phenomenon in which fuel is emitted without complete combustion inside the combustion chamber—can occur during the combustion process, and technology to reduce this is required.

[0006] The pressure, temperature, and composition of exhaust gases vary depending on the operating environment of the engine. In particular, the engine's combustion environment can become unstable during initial startup, low-load operation, and load fluctuations, and engine exhaust gases emitted under these conditions can cause harmful effects on exhaust gas aftertreatment devices.

[0007] In particular, in the case of a methane slip reduction aftertreatment device using an oxidation catalyst, if exhaust gas containing excessive methane is introduced into the aftertreatment device, the generation of excessive oxidation heat during the methane oxidation process may lead to performance degradation or physical damage to the oxidation catalyst or the methane slip reduction aftertreatment device.

[0008] In other words, the pressure, temperature, and composition of exhaust gas entering the aftertreatment device may vary depending on the engine operating environment, and if there are acceptable limits for the exhaust gas pressure, temperature, and composition of the aftertreatment device, control technology is required to prevent performance degradation, physical damage, or overall loss of function of the aftertreatment device.

[0009] Conventionally, protection logic based on the temperature or pressure of the engine outlet or the inlet of the aftertreatment device was used, but this method has limitations in that it cannot detect changes in the composition of the exhaust gas other than the temperature or pressure of the engine exhaust gas.

[0010] For example, a technology has been proposed to control exhaust gas aftertreatment devices by measuring exhaust gas temperature, pressure, and composition. However, this method has the limitation of not being able to directly detect changes in exhaust gas composition.

[0011] For example, temperature sensors take time to transmit a signal to the controller after a physical reaction, and gas analyzers that analyze exhaust gas composition may experience time delays of several seconds or more during the sampling, analysis, and calculation processes. Due to these delay characteristics, there was a problem in that it was difficult to respond immediately to rapid changes in exhaust gas or instantaneous abnormal conditions.

[0012] On the other hand, when making judgments based on the engine's operating status or performance data, changes in temperature, pressure, and composition can be predicted, which has the advantage of enabling more rapid protection control of the aftertreatment device.

[0013] Therefore, technology is required to protect the device by constantly monitoring the engine's operating status and controlling or blocking the inflow of exhaust gas into the aftertreatment device based on the prediction of the exhaust gas temperature and pressure composition.

[0014] The present invention aims to provide an exhaust gas aftertreatment system capable of protecting an aftertreatment device through control that blocks exhaust gas from flowing into the aftertreatment device according to the engine's operating state.

[0015] Furthermore, the present invention aims to provide a control method for an exhaust gas aftertreatment system that stops the operation of the aftertreatment device in an unstable operating state and automatically determines whether to operate the aftertreatment device according to conditions when returning to a normal operating state.

[0016] The problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0017] The apparatus includes a monitoring device for monitoring engine operation data, a post-treatment device for reducing harmful substances in exhaust gas emitted from the engine's exhaust pipe, a first pipe connecting the exhaust pipe and the inlet of the post-treatment device, a first valve installed in the first pipe, a second pipe branching from the exhaust pipe and formed separately from the first pipe, a second valve installed in the second pipe, a post-treatment device, and a processor for controlling the first valve and the second valve. The processor determines the engine's operation state based on the engine's operation data and can switch to one of a first mode in which the first valve is closed and the second valve is opened, or a second mode in which the second valve is closed and the first valve is opened, based on the determined operation state.

[0018] The engine operation data includes the engine load value, and if the engine load value is less than or equal to a preset value, the processor determines that the engine operation state is unstable and can switch to the first mode.

[0019] The first mode may include a step of stopping the operation of the post-processing device.

[0020] If the processor determines that the engine's operating state is stable, it can switch to a second mode.

[0021] The processor can calculate the instability time during which the first mode is operated and determine the operation process of the post-processing device in the second mode based on the instability time.

[0022] The processor can activate the post-processing device if the instability time is within the first reference time.

[0023] If the instability time exceeds the second reference time, the processor may stop the operation of the post-processing device and generate an alarm.

[0024] If the instability time exceeds the first reference time and is within the second reference time, the processor can proceed with the process of preparing the post-processing device for operation.

[0025] If the processor cannot determine the operating status of the engine, it may stop the operation of the after-processing device.

[0026] The above system can be applied to ships.

[0027] A control method for an exhaust gas aftertreatment system that reduces harmful substances in exhaust gas emitted from an engine may include: receiving engine operation data; determining the engine operation state based on the received operation data; switching to a first mode in which, if the operation state is determined to be unstable, a first valve is closed and a second valve is opened and the aftertreatment device is stopped; and switching to a second mode in which, if the operation state is determined to be stable, a first valve is opened and a second valve is closed and the aftertreatment device is started.

[0028] The engine operation data includes engine load values, and if the engine load value is below a preset value, the engine operation state can be determined to be unstable.

[0029] The instability time until switching from the first mode to the second mode can be calculated, and the operation process of the post-processing device can be determined based on the instability time.

[0030] According to one embodiment of the present invention, the safety and reliability of the aftertreatment device can be ensured by controlling the flow of exhaust gas according to the operating state of the engine.

[0031] In addition, the durability of the device can be improved by determining whether the aftertreatment device operates based on the engine's operating conditions.

[0032] In addition, automated control logic can improve the system's continuous operation and maintenance efficiency.

[0033] Further scopes of the applicability of the present invention will become apparent from the following detailed description. However, since various changes and modifications within the spirit and scope of the present invention are clearly understood by those skilled in the art, specific embodiments, such as the detailed description and preferred embodiments of the present invention, should be understood as being given merely as examples.

[0034] FIG. 1 is a block diagram of an exhaust gas aftertreatment system according to one embodiment of the present invention.

[0035] FIG. 2 is a conceptual diagram of an exhaust gas aftertreatment system according to one embodiment of the present invention.

[0036] FIG. 3 is a flowchart illustrating a control method for an exhaust gas aftertreatment system according to one embodiment of the present invention.

[0037] FIG. 4 is a flowchart illustrating a control method for an exhaust gas aftertreatment system according to another embodiment of the present invention.

[0038] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Identical or similar components regardless of drawing symbols are given the same reference number, and redundant descriptions thereof will be omitted.

[0039] The suffixes "module" and "part" for components used in the following description are assigned or used interchangeably solely for the sake of ease of drafting the specification, and do not inherently possess distinct meanings or roles. Furthermore, in describing the embodiments disclosed in this specification, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions could obscure the essence of the embodiments disclosed in this specification.

[0040] In addition, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that all modifications, equivalents, and substitutions included within the concept and technical scope of the present invention are included.

[0041] Terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0042] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0043] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0044] In this application, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0045]

[0046] The exhaust gas aftertreatment system of the present invention can be applied to marine vessels. Since marine engines are generally large in size and operate under various operating conditions for a long time, changes in the composition of exhaust gas depending on the operating condition of the engine may occur frequently.

[0047] In particular, in large merchant vessels such as dual-fuel ships, container ships, oil tankers, and bulk carriers that use LNG as fuel, post-treatment systems such as methane slip reduction devices or Selective Catalytic Reduction (SCR) devices are applied, and there is a risk that these devices may be damaged depending on operating conditions. The system according to the present invention can be usefully employed to ensure the protection and operational stability of post-treatment devices in these various vessels.

[0048] Hereinafter, with reference to FIGS. 1 and FIGS. 2, an exhaust gas aftertreatment system (100) according to one embodiment of the present invention will be described in detail.

[0049] FIG. 1 is a block diagram showing the schematic configuration of an exhaust gas aftertreatment system (100) according to one embodiment of the present invention.

[0050] The exhaust gas aftertreatment system (100) may include an engine (110), a monitoring device (130), an aftertreatment device (150), a first pipe (171) and a second pipe (172), a first valve (1711) and a second valve (1722), and a processor (190).

[0051] The engine (110) is an internal combustion engine that generates mechanical power through the combustion reaction of fuel and is used for purposes such as propulsion of a ship or driving a generator. Generally, various fuels such as diesel, LNG, and methane are used, and as the fuel burns in a high temperature and high pressure state within the combustion chamber, piston movement occurs, and this movement is converted into rotational power through a crankshaft.

[0052] Exhaust gas is formed during this process, and depending on the type of fuel and combustion conditions, the exhaust gas may contain various harmful substances such as nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), and methane (CH4).

[0053] The engine (110) described in the present invention can be applied, for example, to a dual-fuel engine mainly for ships, particularly to an engine that uses LNG (Liquefied Natural Gas) as fuel.

[0054] Meanwhile, engine operating conditions vary over time, and combustion may be incomplete during initial startup, low load, rapid acceleration, or deceleration, which can cause significant changes in the composition, temperature, and flow rate of exhaust gases.

[0055] The monitoring device (130) can collect operating data of the engine (110) in real time and transmit the data to the processor (190).

[0056] The monitoring device (130) interfaces with various sensors installed in the engine (110) and can process data collected from the sensors in an integrated manner. The collected driving data may include, for example, engine load, rotational speed (RPM), intake and exhaust temperatures, fuel injection timing, fuel type (diesel, gas, etc.), fuel supply amount, turbocharger pressure, pressure and temperature inside the combustion chamber, exhaust gas temperature and oxygen concentration, etc.

[0057] The monitoring device (130) quantitatively analyzes the current operating state of the engine based on this data and transmits it to the processor (190) on a regular or event basis. In some embodiments, data may be transmitted and received via a vehicle communication network such as a CAN (Controller Area Network) bus or Ethernet.

[0058] The monitoring device (130) may not merely measure data but may include some logic for determining abnormal conditions or boundary conditions, in which case the processor (190) can perform control decisions more efficiently.

[0059] The aftertreatment device (150) is a device for removing or reducing harmful substances contained in exhaust gas emitted from the engine (110), and various catalyst-based technologies may be applied to satisfy exhaust gas standards. The aftertreatment device (150) targets pollutants such as hydrocarbons (HC), carbon monoxide (CO), methane (CH4), nitrogen oxides (NOx), etc., and converts the said substances into harmless carbon dioxide (CO2), nitrogen (N2), water vapor (H2O), etc.

[0060] Specifically, the post-treatment device (150) may include an oxidation catalyst, a selective catalytic reduction (SCR) device, a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a methane oxidation catalyst (MOCS), etc., and may be configured alone or in combination depending on the application target and the type of fuel.

[0061] In particular, since methane slip can occur in dual-fuel marine engines using low-carbon fuels such as LNG, a Methane Oxidation Catalytic System (MOCS) may be used. This device operates by inducing a catalytic reaction at high temperatures to oxidize methane into CO2 and H2.

[0062] However, methane is a difficult gas to combust, and if engine operation is unstable, excessive unburned methane may enter through the exhaust gas, triggering a rapid oxidation reaction in the catalyst bed. This causes the catalyst temperature to rise sharply, potentially leading to thermal damage, such as catalyst degradation or performance reduction.

[0063] The system according to the present invention can protect the system by detecting such a situation in advance and switching the flow path so that the exhaust gas bypasses the after-treatment device (150) or by temporarily suspending the operation of the after-treatment device. Accordingly, the after-treatment device (150) of the present invention can be operated in a structure linked to protection control according to operating conditions, going beyond a simple purification function.

[0064] The first pipe (171) connects the exhaust pipe (111) and the inlet of the post-treatment device (150), and a first valve (1711) is installed inside it. The pipe (172) branches off from the exhaust pipe (111) and is formed separately from the first pipe (171), and this also includes a second valve (1722).

[0065] The first valve (1711) and the second valve (1722) can each selectively switch the flow path of the exhaust gas through an opening and closing operation, and these valves are operated according to a control signal of the processor (190).

[0066] Referring to FIG. 2, the engine (110) discharges exhaust gas through the exhaust pipe (111), and the exhaust pipe (111) branches into a first pipe (171) and a second pipe (172). That is, as shown in FIG. 2, the first pipe (171) branches off from the downstream of the exhaust pipe (111) and forms a path connected to the inlet of the post-treatment device (150). A first valve (1711) is installed inside the first pipe (171), and the first valve (1711) can selectively allow or block the inflow of exhaust gas into the post-treatment device (150) through an opening and closing operation.

[0067] The second pipe (172) is a bypass path formed by branching off from the first pipe (171) from the exhaust pipe (111), and has a structure that connects directly to the discharge system without passing through the post-treatment device (150). A second valve (1722) is installed in the second pipe (172), and this valve can also selectively open or close the path through which the exhaust gas flows by bypassing the post-treatment device.

[0068] The first valve (1711) and the second valve (1722) operate independently or in conjunction with each other according to a control signal from the processor (190).

[0069] For example, the processor (190) can control the exhaust gas to flow through the second pipe (172) to the discharge pipe (112) without passing through the aftertreatment device (150) by closing the first valve (1711) and opening the second valve (1722) when it is determined that the operating state is unstable based on engine operating data received from the monitoring device (130). Conversely, when the operating state of the engine is stable, it can control the exhaust gas to pass through the aftertreatment device (150) by closing the second valve (1722) and opening the first valve (1711).

[0070] The processor (190) analyzes the driving data transmitted from the monitoring device (130) to determine the driving state of the engine (110), and by controlling the opening and closing of the first valve (1711) and the second valve (1722) according to the determined driving state, it can select an exhaust gas flow path that passes through or bypasses the aftertreatment device (150).

[0071] A detailed description of the operation of the processor will be given later with reference to FIGS. 3 and FIGS. 4.

[0072] FIG. 2 is a conceptual diagram of an exhaust gas aftertreatment system according to one embodiment of the present invention.

[0073] The engine (110) is an internal combustion engine that generates power by burning fuel, and generates exhaust gas during the combustion process, and the generated exhaust gas is discharged to the outside through the exhaust pipe (111). The exhaust pipe (111) branches into two branches downstream, one is a first pipe (171) that passes through a post-treatment device (150), and the other is a second pipe (172) that bypasses the post-treatment device.

[0074] The first pipe (171) is formed as a path connecting the exhaust pipe (111) and the inlet of the post-treatment device (150), and a first valve (1711) is installed inside it. The first valve (1711) can allow exhaust gas to flow into the post-treatment device (150) or block it through an opening and closing operation.

[0075] The second pipe (172) is a bypass discharge path formed separately from the first pipe (171) by branching off from the exhaust pipe (111), and a second valve (1722) is installed therein. The second valve (1722) selectively opens the path so that exhaust gas can be discharged directly without passing through a post-treatment device.

[0076] Although the second tube (172) is depicted as a simple bypass channel in the configuration shown in FIG. 2, in other embodiments, a separate post-processing device may be additionally provided in the second tube (172).

[0077] For example, if the post-treatment device (150) of the first pipe (171) is a methane oxidation catalyst that oxidizes methane, there may be a risk that the catalyst may be damaged due to a high-temperature reaction while the methane slip is high. In this case, the processor (190) may close the first valve (1711) and open the second valve (1722) to protect the methane oxidation catalyst, thereby diverting the exhaust gas to the second pipe (172).

[0078] And in the second tube (172), a selective catalytic reduction (SCR) device for selectively reducing nitrogen oxides (NOx), for example, may be installed. The selective catalytic reduction device can remove nitrogen oxides from the exhaust gas and discharge them to the outside.

[0079] The post-treatment device (150) purifies harmful substances in the exhaust gas introduced from the first pipe (171) and then discharges the exhaust gas to the outside through the discharge pipe (112).

[0080] At this time, a third valve (1712) may be installed on the outlet side of the post-treatment device (150), and this serves to open and close the connection with the discharge pipe (112). The third valve (1712) establishes a passage so that exhaust gas passing through the post-treatment device (150) can safely flow into the discharge pipe (112). The third valve (1712) can be controlled together with the first valve (1711).

[0081] The monitoring device (130) collects engine operation data through various sensors installed in the engine (110), and the collected data is transmitted to the processor (190). The operation data may include various elements such as engine load, rotational speed, type of fuel, fuel injection amount, temperature, and pressure, and the processor (190) can determine the engine operation status in real time through this data. The processor (190) determines the engine operation status based on the operation data received from the monitoring device (130), and switches the system to either a first mode or a second mode according to the result of the determination, thereby controlling the opening and closing operation of the first valve (1711), the second valve (1722), and the third valve (1712).

[0082] More specifically, the processor (190) can switch the system to a first mode when it is determined that the operating state is unstable, such as when the engine is started, under low load, or under rapid load fluctuations.

[0083] For example, in the first mode, the first valve (1711) and the third valve (1712) can be closed and the second valve (1722) opened so that the exhaust gas bypasses the aftertreatment device (150) and is directly discharged through the discharge pipe (112) along the second pipe (172). This prevents the aftertreatment device (150) from being exposed to high-temperature oxidation reactions or excessive unburned fuel components. Additionally, if necessary, the operation of the aftertreatment device (150) itself can be stopped in the first mode.

[0084] Conversely, if the processor (190) determines from the driving data that the engine's condition is stable, it switches the system to a second mode. In the second mode, the first valve (1711) and the third valve (1712) are opened, and the second valve (1722) is closed, so that exhaust gas flows into the post-treatment device (150) through the first pipe (171), and after being purified, is discharged to the outside through the discharge pipe (112).

[0085] In the second mode, the operation of the post-treatment device (150) is resumed, and emission control following a normal post-treatment path can be performed. Hereinafter, a control method for an exhaust gas post-treatment system according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

[0086] FIG. 3 is a flowchart illustrating a control method for an exhaust gas aftertreatment system according to one embodiment of the present invention.

[0087] First, operating data of the engine (110) is collected in real time through the monitoring device (130) (S3001).

[0088] Driving data may consist of, for example, engine load, rotational speed (RPM), type of fuel, fuel injection amount, intake temperature, exhaust temperature, combustion pressure, etc., and the monitoring device (130) receives these data from various sensors and transmits them to the processor (190).

[0089] The processor (190) examines whether it can determine the current operating state of the engine based on the received operating data (S3002).

[0090] If the operating condition cannot be determined normally, the operation of the post-processing device (150) may be stopped to prevent malfunction of the post-processing device (S3003). This may be applied in cases where normal determination is difficult due to, for example, sensor errors, data anomalies, or communication failures. This control is a protective measure to prevent excessive load from being placed on the catalyst without a clear determination of operating conditions.

[0091] When the driving condition can be determined normally, the processor (190) analyzes the data to determine whether the engine is in an unstable state (S3004).

[0092] An unstable state can be defined as a condition that may affect the aftertreatment device, such as when the engine load decreases rapidly, falls below a set standard, experiences large fluctuations in combustion pressure, or when fuel injection conditions are inconsistent.

[0093] In particular, the present invention may use engine load values ​​as a criterion for determining the operating state of an engine. This is because the judgment can be faster and clearer compared to indirect indicators such as exhaust temperature. Specifically, based on preliminary experimental results showing that combustion becomes unstable and the likelihood of unburned fuel being emitted increases as the engine load decreases, a case where the load is below a certain standard can be considered an unstable state.

[0094] If the engine is determined to be in an unstable state, the system may switch to the first mode (S3005).

[0095] The first mode is defined as a protection mode of the post-treatment device (150), and subsequent control includes blocking the inflow of exhaust gas to the post-treatment device and switching to a bypass path.

[0096] When switched to the first mode, the first valve (1711) is closed and the second valve (1722) is opened (S3006).

[0097] Thus, the exhaust gas is discharged directly to the discharge pipe (112) through the second pipe (172) without passing through the post-treatment device (150), and the inflow into the post-treatment device is blocked.

[0098] Along with this, the operation of the post-treatment device (150) may be stopped (S3007). This measure can prevent unburned components, such as methane, from entering the post-treatment device and causing overheating or abnormal reactions.

[0099] In this first mode state, the accumulated time during which the unstable state persists can be calculated (S3008).

[0100] The instability time is used as a criterion for determining whether and when to restart the post-processing device in the future, and is subsequently linked to the process described in Fig. 4.

[0101] Meanwhile, if the processor (190) determines that the engine state is stable, it switches to the second mode (S3009).

[0102] The second mode is the regular operating mode of the post-treatment device, and the exhaust gas can be controlled to undergo the purification procedure normally.

[0103] In the second mode, by opening the first valve (1711) and closing the second valve (1722) (S3010), exhaust gas flows into the post-treatment device (150) along the first pipe (171).

[0104] The post-treatment device (150) is operated in a normal operating state (S3011), and after purifying harmful substances, it can discharge exhaust gas to the outside through the discharge pipe (112).

[0105] FIG. 4 is a flowchart illustrating a control method for an exhaust gas aftertreatment system according to another embodiment of the present invention. FIG. 4 is a flowchart showing a control flow for determining whether and when to restart the aftertreatment device after a first mode is performed in an exhaust gas aftertreatment system according to an embodiment of the present invention.

[0106] The flowchart illustrated in Fig. 4 may be a control step included in step S3008 of Fig. 3.

[0107] First, as the first mode is performed, the processor (190) calculates the time during which the unstable state persists, i.e., the unstable time, by accumulating it (S4001).

[0108] This instability time is the time during which the post-processing device (150) remains in a protection mode state, and the system determines a subsequent control procedure based on this.

[0109] The unstable time may refer to the accumulated time from the point when the first mode is activated until it is switched to the second mode. That is, it can be calculated based on the continuous time from the point when the processor (190) determines that the operating state of the engine (110) is unstable and switches to the first mode, until it is switched to a stable state and returns to the second mode.

[0110] This instability time corresponds to the time during which the post-treatment device (150) is kept in a stopped state, cut off from exhaust gas, and can be used as a judgment criterion for determining whether and when to restart the post-treatment device.

[0111] For example, if the instability time is short, the post-processing device can be restarted immediately, but if it persists for a long time, protection procedures such as a start-up phase, shutdown, and alarm generation may be performed.

[0112] Meanwhile, it is determined whether the calculated instability time is less than or equal to a preset first reference time (a) (S4002).

[0113] The first reference time (a) can be set, for example, to a time during which the aftertreatment device can determine that it is not affected by a temporary engine instability state.

[0114] If the corresponding condition is satisfied, the processor (190) immediately switches to the second mode (S4003), opens the first valve (1711), closes the second valve (1722), and resumes the operation of the post-processing device (150). This allows the system to quickly return to the normal purification mode.

[0115] On the other hand, if the instability time exceeds the first reference time (a), the processor (190) next determines whether the instability time is greater than or equal to the second reference time (b) (S4004).

[0116] The second reference time (b) can be set to a time when the post-processing device is likely to be exposed to excessive thermal stress or repetitive load.

[0117] If the instability time exceeds this reference time, the processor (190) determines that there is a high probability of damage to the post-processing device and continues to stop the operation of the post-processing device (150) (S4005), and generates an alarm to notify the operator of the system abnormality or stop status (S4006). At this time, restarting the post-processing device requires intervention or inspection by the operator and does not automatically return to operation. At this time, the operator can check the status through system inspection or manual intervention.

[0118] If the instability time exceeds the first reference time (a) but does not reach the second reference time (b), it is determined to be an intermediate condition, and the process of preparing the post-processing device for operation is performed (S4007).

[0119] This operation preparation process may include preheating, exhaust temperature stabilization, catalyst condition check, etc., and the system may be controlled in stages so that the post-treatment device (150) can return to the second mode under sufficiently stable conditions.

[0120] In another embodiment, intermediate conditions may be omitted, and the restart or termination of the post-processing device may be performed based on a preset time.

[0121] This unstable time-based control method can prevent damage caused by thermal overload and repeated operation of the post-processing device, and enable automatic system operation according to operating conditions.

[0122]

[0123] It is obvious to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit and essential features of the invention.

[0124] The foregoing detailed description should not be interpreted restrictively in all respects and should be considered exemplary. The scope of the invention shall be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the invention are included within the scope of the invention.

Claims

1. A monitoring device for monitoring engine operation data; A post-treatment device for reducing harmful substances in exhaust gas emitted from the exhaust pipe of the above-mentioned engine; A first pipe connecting the exhaust pipe and the inlet of the post-treatment device; A first valve installed in the first pipe above; A second pipe branching off from the exhaust pipe and formed separately from the first pipe; A second valve installed in the second pipe above; A processor comprising determining the operating state of the engine based on the operating data of the engine, and controlling the post-processing device, the first valve, and the second valve based on the determined operating state. Exhaust gas aftertreatment system.

2. In Paragraph 1, The operating data of the above engine is characterized by including the load value of the above engine, The above processor An exhaust gas aftertreatment system characterized by determining that the operating state of the engine is unstable when the load value of the engine is less than or equal to a preset value.

3. In Paragraph 1, The above processor An exhaust gas aftertreatment system characterized by switching to a first mode in which the second valve is opened and the first valve is closed when the operating state of the engine is determined to be unstable, and switching to a second mode in which the first valve is opened and the second valve is closed when the operating state of the engine is determined to be stable.

4. In Paragraph 1, The above processor An exhaust gas aftertreatment system characterized by stopping the aftertreatment device when the operating state of the engine is determined to be unstable, and operating the aftertreatment device when the operating state of the engine is determined to be stable.

5. In Paragraph 3, The above processor An exhaust gas aftertreatment system characterized by calculating the instability time during which the first mode is operated and determining whether to operate the aftertreatment device based on the instability time.

6. In Paragraph 5, The above processor An exhaust gas aftertreatment system characterized by operating the aftertreatment device when the above instability time is within a preset time.

7. In Paragraph 5, The above processor An exhaust gas aftertreatment system characterized by terminating the operation of the aftertreatment device and generating an alarm when the above instability time exceeds a preset time.

8. In Paragraph 1, The above processor An exhaust gas aftertreatment system characterized by stopping the operation of the aftertreatment device when the operating state of the above-mentioned engine cannot be determined.

9. An engine comprising an exhaust gas aftertreatment system according to any one of paragraphs 1 through 8.

10. A vessel comprising an exhaust gas aftertreatment system according to any one of paragraphs 1 through 8.

11. A control method for an exhaust gas aftertreatment system that reduces harmful substances in exhaust gas emitted from an engine, A step of receiving driving data of the above engine; A step of determining the operating state of the engine based on the operating data of the engine received above; A step of switching to a first mode in which, if it is determined that the operating state of the above engine is unstable, the first valve is closed, the second valve is opened, and the after-treatment device is stopped; and A control method for an exhaust gas aftertreatment system comprising the step of, when it is determined that the operating state of the engine is in a stable state, opening the first valve, closing the second valve, and switching to a second mode that operates the aftertreatment device.

12. In Paragraph 11, The operating data of the above engine includes the load value of the above engine, and A control method for an exhaust gas aftertreatment system characterized by further including a step of determining that the operating state of the engine is unstable when the load value of the engine is less than or equal to a preset value.

13. In Paragraph 11, A step of calculating the instability time during which the above-mentioned first mode is operated; and A control method for an exhaust gas aftertreatment system, further comprising the step of determining whether to operate a aftertreatment device based on the above instability time.

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