CN111102052B

CN111102052B - Exhaust gas aftertreatment system and control method thereof

Info

Publication number: CN111102052B
Application number: CN201910759009.3A
Authority: CN
Inventors: 李康洪; 李良鲁; 安启沅; 崔殷锡
Original assignee: Ceracomb Co ltd
Current assignee: Ceracomb Co ltd; CERACOMB株式会社
Priority date: 2018-10-26
Filing date: 2019-08-16
Publication date: 2021-11-26
Anticipated expiration: 2039-08-16
Also published as: KR102054214B1; CN111102052A

Abstract

The present invention provides an exhaust gas aftertreatment system which is mounted in an exhaust pipe of an internal combustion engine and in which a particulate trap device and a selective catalytic reduction device are provided in this order from an upstream side, the exhaust gas aftertreatment system comprising: a burner, located upstream of the particulate trap device, for raising a temperature of exhaust gas of the internal combustion engine; a hydrocarbon injector located on an upstream side of the particulate trap device and configured to inject hydrocarbon into the exhaust gas; and a control unit that controls the burner and the hydrocarbon injector according to a first mode for removing nitrogen oxides or a second mode for removing particulates, wherein the control unit operates the burner according to the first mode to raise the temperature of the exhaust gas to the operating temperature of the selective catalytic reduction device when the temperature of the exhaust gas does not affect the operating temperature of the selective catalytic reduction device, or operates the burner simultaneously with injecting hydrocarbons by the hydrocarbon injector according to the second mode to raise the temperature to the particulate removal temperature of the particulate trap device.

Description

Exhaust gas aftertreatment system and control method thereof

The present application claims priority from korean patent application No. 10-2018-0128750, filed on 26.10.2018, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates to an exhaust gas aftertreatment system and a control method thereof, and more particularly, to an exhaust gas aftertreatment system for purifying exhaust gas discharged from an internal combustion engine mounted on a vehicle and a control method thereof.

Background

In general, there is an increasing demand for a diesel engine that can achieve high-efficiency and high-output operation in a vehicle, a ship, a generator, and the like. This is because diesel oil is inexpensive and has an advantage in terms of fuel economy or efficiency.

When such a diesel engine is driven, nitrogen oxides (NOx) and Particulate Matter (PM) causing air pollution are discharged together with exhaust gas, and therefore, it is necessary to install a soot reduction device in an obligatory manner in order to reduce such exhaust gas.

Typically, the Particulate Filter may be a Particulate Filter (DPF) for collecting Particulate Matter (PM) for purifying exhaust gas discharged from the internal combustion engine, a Selective Catalytic Reduction (SCR) for purifying nitrogen oxides (NOx) using ammonia or the like generated in urea as a reducing agent, or the like.

The particulate trap device or the selective catalytic reduction device operates based on the catalyst function, and therefore operates depending on the temperature of the exhaust gas discharged from the engine of the internal combustion engine. Therefore, in a high-speed high-load operating environment, the catalyst activity is extremely large, and therefore, the exhaust gas purification function will be normally performed, but in the case of a low-speed high-load vehicle or a vehicle with frequent start and stop (stop & go), it is difficult to normally operate the aftertreatment system due to the low temperature of the exhaust gas, and the discharge of harmful exhaust gas will increase.

Therefore, various methods for raising the temperature of the exhaust gas have been developed and used, but in order to raise the temperature of the exhaust gas using a burner, the fuel injection amount is large and the flame is also large, so that the size and structure of the burner become complicated, and the operation and mounting become difficult, and thus, failure and abnormal operation of the components occur frequently.

In the case of a large vehicle with a large exhaust gas flow rate, the control of the initial slip (slip) or the like becomes difficult due to a large fuel injection amount, and it is difficult to achieve stable restart efficiency.

Therefore, there is a need for a technique that can solve such a problem.

Documents of the prior art

Patent document

Patent document 1: KR10-1826556B1

Disclosure of Invention

The present invention is intended to provide an exhaust gas aftertreatment system and a control method thereof, which can expand the operating region of the exhaust gas aftertreatment system to a low temperature region using a low capacity burner and hydrocarbon injection.

In order to solve the above problems, the present invention provides an exhaust gas aftertreatment system which is attached to an exhaust pipe of an internal combustion engine and in which a particulate matter trapping device and a selective catalytic reduction device are provided in this order from an upstream side, the exhaust gas aftertreatment system comprising: a burner, located upstream of the particulate trap device, for raising a temperature of the exhaust gas of the internal combustion engine; a hydrocarbon injector located upstream of the particulate trap device and configured to inject hydrocarbon into the exhaust gas; and a control unit that controls the burner and the hydrocarbon injector according to a first mode for removing nitrogen oxides or a second mode for removing particulates, wherein the control unit operates the burner according to the first mode to raise the temperature of the exhaust gas to an operating temperature of the selective catalytic reduction device when the temperature of the exhaust gas does not affect the operating temperature of the selective catalytic reduction device, or operates the burner to raise the temperature to a particulate removal temperature of the particulate collection device while injecting hydrocarbons by the hydrocarbon injector according to the second mode.

According to an embodiment, when the temperature of the exhaust gas is equal to or higher than the operating temperature of the selective catalytic reduction device, the controller may deactivate the burner and the hydrocarbon injector in the first mode, or increase the temperature to the particulate matter removal temperature of the particulate matter trapping device by the burner and/or the hydrocarbon injector in the second mode.

According to one embodiment, in the second mode, the control unit may increase the temperature of the exhaust gas only by injecting the hydrocarbon by the hydrocarbon injector when the hydrocarbon does not flow, and increase the temperature of the exhaust gas by the burner and the hydrocarbon injector when the hydrocarbon flow occurs.

According to an embodiment, in the first mode, the control unit may increase the temperature of the front end of the particulate trap device to 300 ℃ or higher by the exhaust gas using the burner.

According to an embodiment, the burner may be a mini burner capable of raising the temperature of the exhaust gas to 100 ℃.

According to an embodiment, in the second mode, the control unit may increase the temperature of the front end of the particulate trap device to 400 ℃ or higher in the exhaust gas by using the burner and the hydrocarbon injector.

The present invention also provides an exhaust gas aftertreatment system including an exhaust pipe attached to an internal combustion engine and provided with a particulate matter trapping device and a selective catalytic reduction device in this order from an upstream side, the exhaust gas aftertreatment system including a control unit that controls the burner to be positioned on the upstream side of the particulate matter trapping device and to raise a temperature of the exhaust gas of the internal combustion engine, and the hydrocarbon injector to be positioned on the upstream side of the particulate matter trapping device and to inject hydrocarbon into the exhaust gas, according to a first mode for removing nitrogen oxides or a second mode for removing particulate matter, wherein in the control unit, the burner is operated to raise the temperature of the exhaust gas to an operating temperature of the selective catalytic reduction device according to the first mode when the temperature of the exhaust gas does not affect the operating temperature of the selective catalytic reduction device, alternatively, according to the second mode, the temperature of the particulate matter removal device is raised to the particulate matter removal temperature by injecting the hydrocarbon by the hydrocarbon injector and operating the burner at the same time.

The exhaust gas aftertreatment system and the control method thereof according to the present invention have an effect that the operation region of the exhaust gas aftertreatment system can be expanded to a low temperature region using a low capacity burner and hydrocarbon injection.

According to the control mode, the burner operates the mini burner at the maximum power in the forced restart mode, and operates the mini burner at the minimum power in the nox reduction mode, so that the fuel economy of the mini burner can be minimized.

In the high-speed running mode of the engine, that is, in the high-load state, the restart of the particulate matter trapping device and the reduction of nitrogen oxides can be induced only by the hydrocarbon injection, and in the low-speed running mode, that is, in the low-load state, the exhaust gas is heated to a temperature at which the particulate matter can be forcibly restarted by operating the hydrocarbon injection and the mini-burner simultaneously, thereby reducing the particulate matter.

Drawings

FIG. 1 is a block diagram of an exhaust aftertreatment system according to an embodiment of the invention.

FIG. 2 is a graph illustrating temperatures measured at the exhaust aftertreatment system when in a low speed driving mode.

FIG. 3 is a graph illustrating temperatures measured at the exhaust aftertreatment system when in a particulate trap restart mode of operation at low speed.

FIG. 4 is a graph illustrating temperatures measured by the exhaust aftertreatment system operating at low speed when in the NOx reduction mode.

FIG. 5 is a flow chart illustrating various steps of a method of operation of an exhaust aftertreatment system in accordance with an embodiment of the invention.

Description of reference numerals

10: the engine 21: burner with a burner head

22: diesel oxidation catalyst device 23: particulate trap device

31: selective catalytic reduction device 41: hydrocarbon injector

42: the urea injector 50: control unit

Detailed Description

Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. The suffixes "module" and "section" of the constituent elements used in the following description are given or mixed in consideration of simplicity of the specification, and do not have meanings or functions distinguished from each other. In describing the embodiments disclosed in the present specification, if it is judged that the detailed description of the related known art makes the gist of the embodiments disclosed in the present specification unclear, the detailed description thereof will be omitted. The drawings are only for easy understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited to the drawings, but includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

It is to be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. In contrast, when a structural element is "directly connected" or "directly coupled" to other structural elements, there are no other structural elements present therebetween.

Singular expressions include plural expressions as long as they are not explicitly shown in context.

In the present specification, the terms "including" or "having" and the like are used to designate the presence of the features, numerals, steps, actions, structural elements, components or combinations thereof described in the specification, and are not intended to preclude the presence or addition of one or more other features or numerals, steps, actions, structural elements, components or combinations thereof.

Exhaust gas aftertreatment system

FIG. 1 is a block diagram of an exhaust aftertreatment system according to an embodiment of the invention. As shown in fig. 1, the exhaust gas aftertreatment system according to an embodiment of the present invention is mounted in an exhaust pipe of an engine 10 as an internal combustion engine, and may include a particulate trap device 23 and a selective catalytic reduction device 31 provided in this order from an upstream side: a burner 21 located upstream of the particulate trap device 23 and configured to increase the temperature of the exhaust gas of the engine 10; a hydrocarbon injector 41 located upstream of the particulate trap device 23 and configured to inject Hydrocarbon (HC) into the exhaust gas; and a control unit 50 for controlling the burner 21 and the hydrocarbon injector 41 according to a first mode for removing the nitrogen oxides or a second mode for removing the particulates.

The structural elements shown in fig. 1 are not essential, and therefore, an exhaust aftertreatment system having more or fewer structural elements may be embodied.

Hereinafter, each component will be described.

The Particulate trap device 23 is attached to an exhaust pipe through which exhaust gas discharged from the engine 10 passes, and the Particulate trap device 23 traps most of Particulate Matter (PM) included in the exhaust gas to purify the exhaust gas discharged to the outside through the exhaust pipe.

For example, the particulate trap device 23 may be a filter in which the inlet and outlet of the porous ceramic honeycomb unit are alternately plugged in order to trap particulate matter contained in the exhaust gas. The cell walls trap Particulate Matter (PM) in the course of the exhaust gas flowing into the inlet of an unblocked cell and flowing into the outlet of the unblocked cell through the Particulate Matter (PM) trapping cell walls formed at the boundary with the unblocked adjacent cell.

That is, the particulate matter in the exhaust gas of the engine 10 is physically trapped by the particulate trap device 23 using a filter, and the trapping amount that can be trapped is limited, so that the particulate matter trapping ability can be recovered by forcibly restarting the combustion removal of the particulate matter trapped by the high-temperature exhaust gas in the particulate trap device 23.

The burner 21 is located upstream of the particulate trap device 23, and heats the exhaust gas flowing into the particulate trap device 23 to raise the temperature thereof. For heating the exhaust gas, electricity or microwaves may be used, but the type is not particularly limited.

In this case, the burner 21 according to an embodiment of the present invention may raise the temperature of the exhaust gas to about 100 to 150 ℃, and therefore, the burner 21 is preferably a mini burner having a small combustion injection amount and a relatively small flame size. In the present specification, "about" means a temperature exceeding a small amount or a small amount less than a full range based on the corresponding temperature, and temporarily includes a temperature within the above range.

According to an embodiment, a Diesel Oxidation Catalyst (DOC) 22 may be provided on the upstream side of the particulate trap device 23.

The diesel oxidation catalyst device 22 is a catalyst device that oxidizes Hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas or oxidizes Soluble Organic components (SOF) contained in particulate matter to water (H2O) and carbon dioxide (CO2) using a precious metal such as platinum (Pt), palladium (Pd), or rhodium (Rh) as a catalyst on a honeycomb-structured carrier or the like made of ceramic using cordierite or the like as a raw material, and converts the precious metal into water (H2O) or carbon dioxide (CO 2).

A hydrocarbon injector 41 may be provided on the upstream side of the diesel oxidation catalyst device 22, and the hydrocarbon injector 41 injects Hydrocarbons (HC) into the exhaust pipe, and the increased carbon monoxide and hydrogen components generate heat by oxidation of the exhaust gas flowing into the diesel oxidation catalyst device 22, thereby raising the temperature of the exhaust gas flowing into the selective catalytic reduction device 31. Accordingly, the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 is maintained at the activation temperature or higher under low temperature and low load conditions, whereby the flow of ammonia can be reduced and the selective catalytic reduction purification performance can be improved.

On the other hand, a selective catalytic reduction device 31 may be provided at the rear end of the particulate trap device 23 (or on the downstream side of the exhaust gas).

The selective catalytic reduction device 31 loads catalytic zeolite such as aluminosilicate coated with iron on a carrier such as a ceramic honeycomb, converts urea (urea) as a reducing agent injected by a urea injector 42 located in an upstream side exhaust pipe into ammonia by heat of exhaust gas, and reduces nitrogen oxides (NOx) in the exhaust gas into nitrogen (N2) and water (H2O) by a catalytic reaction of the nitrogen oxides (NOx) and ammonia (NH3) by selective catalytic reduction.

Therefore, a urea injector 42 may be provided at the rear end of the particulate trap device 23, and the operation of the urea injector 42 is controlled by the control unit 50, so that the urea aqueous solution may be injected into the exhaust pipe for the purpose of purifying nitrogen oxides (NOx) in the selective catalytic reduction device 31. In this case, the urea injector 42 may inject ammonia directly, and according to another embodiment, other reducing agents than ammonia may be injected, in which case it may also be injected together with ammonia.

Note that, by providing a nox sensor (not shown) at each of the front end and the rear end of the selective catalytic reduction device 31, the amount of nox before and after the exhaust gas passes through the selective catalytic reduction device 31 can be measured.

According to an embodiment, an ammonia flow catalyst (not shown) is further provided at the rear end of the selective catalytic reduction device 31, whereby ammonia (NH3) in the exhaust gas is oxidized and converted into nitrogen (N2) and water (H2O), thereby purifying the ammonia flowing out of the selective catalytic reduction device 31 and preventing the ammonia from flowing out to the atmosphere.

The ammonia flow catalyst device described above is configured by using a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) as a catalyst in a honeycomb-structured carrier or the like made of ceramic using cordierite or the like as a raw material, similarly to the diesel oxidation catalyst device 22.

On the other hand, according to an embodiment of the present invention, the method may include: a first temperature sensor for detecting a temperature T1 of exhaust gas flowing into the diesel oxidation catalyst device 22; a second temperature sensor for detecting a temperature T2 of the exhaust gas flowing into the particulate trap device 23; and a third temperature sensor for detecting a temperature T3 of the exhaust gas flowing out of the particulate trap device 23.

The controller 50 receives the values T1 to T3 detected by the first to third temperature sensors, and based on the received values, can control the combustor 21 or the hydrocarbon injector 41.

A control temperature sensor may be added to control the combustor 21, and a temperature sensor may be added to monitor the temperature of the rear end of the selective catalytic reduction device 31. Further, a monitoring pressure sensor may be provided upstream of the combustor 21 in order to monitor the particulate matter accumulated in the particulate trap device 23.

The control unit 50 executes the control operation in two modes according to the level of the exhaust gas temperature. The first mode is control for reducing nitrogen oxides, and the second mode is control for removing particulate matter.

The switching operation between the first mode and the second mode of the control unit 50 may be performed automatically according to a direct input from an external user or a set condition (time, temperature of exhaust gas, flow rate of exhaust gas, concentration of nitrogen oxide, etc.), and is not particularly limited.

Specifically, when the temperature T1 of the exhaust gas discharged from the engine 10 is too low and the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 cannot affect the activation temperature, the burner 21 is operated to maintain the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 at the activation temperature or higher and reduce the discharged nitrogen oxides (NOx) according to the first mode, or the burner 21 and the hydrocarbon injector (41) are operated to induce the forced restart of the particulate matter trapping device 23 and simultaneously maintain the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 at the activation temperature or higher according to the second mode, and thereby the discharged nitrogen oxides (NOx) can be reduced.

As shown in fig. 2, in the case of a low-speed and low-load vehicle or a vehicle that is frequently started, the temperature T1 of the exhaust gas discharged from the engine 10 is maintained at 300 ℃ or lower, so that it is difficult for the particulate trap device 23 to achieve natural restart based on the exhaust gas temperature, and since the exhaust gas temperature T3 on the downstream side of the particulate trap device 23 is 200 ℃ or lower, the Urea injection (Urea Dosing) condition cannot be satisfied, and the discharged nitrogen oxides (NOx) will not be reduced.

In this case, when the control unit 50 operates according to the first mode, that is, the nitrogen oxide reduction mode, the burner 21 is operated to raise the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 to the operating temperature of the selective catalytic reduction device 31, that is, the temperature T3 of the exhaust gas flowing out of the particulate matter trapping device 23 reaches about 200 ℃. The temperatures measured at the exhaust aftertreatment system when in the nox reduction mode of low speed operation are shown in fig. 4.

That is, by the operation of the burner 21, the exhaust gas of about 150 ℃ discharged from the engine 10 is raised to the temperature T2 of about 300 ℃ or higher at the front end of the particulate matter trapping device 23, so that the particulate matter trapping device 23 can be naturally restarted based on the exhaust gas temperature, and the temperature at the front end of the selective catalytic reduction device 31 is about 200 ℃ or higher so as to satisfy the urea charging condition, whereby the nox reduction rate can be made 60% or higher by the activation of the selective catalytic reduction device 31.

When the control unit 50 operates in the second mode, that is, in the particulate trap device restart mode, the hydrocarbon injector 41 injects the hydrocarbon into the exhaust gas so that the temperature T2 of the exhaust gas flowing into the particulate trap device 23 becomes about 400 ℃, and the burner 21 is operated to raise the temperature of the exhaust gas. The temperatures measured in the exhaust aftertreatment system when in the particulate trap device restart mode of low speed operation are shown in fig. 3.

That is, the burner 21 is operated and hydrocarbons are injected at the same time, so that the temperature of the exhaust gas of about 150 ℃ discharged from the engine 10 is raised to a temperature T2 of about 400 ℃ or higher in the front end of the particulate matter trapping device 23 to forcibly restart the combustion of the particulate matter by the particulate matter trapping device 23, and the front end of the selective catalytic reduction device 31 is brought to a temperature of about 200 ℃ or higher to satisfy the charging condition, so that the nitrogen oxide reduction rate can be made 60% or higher by the activation of the selective catalytic reduction device 31.

According to an embodiment of the present invention, the restart of the particulate trap device 23 is realized by raising the temperature of the exhaust gas by the stable flame of the mini burner during the low speed running, and according to the mode, the mini burner is operated at the maximum power in the forced restart mode of the particulate trap device 23 and at the minimum power in the nox reduction mode, so that the fuel economy of the burner can be minimized.

In contrast, when the temperature T1 of the exhaust gas discharged from the engine 10 is too high and the temperature of the exhaust gas flowing into the selective catalytic reduction device 31 becomes equal to or higher than the activation temperature, the selective catalytic reduction device 31 is activated only by the heat of the exhaust gas discharged from the engine 10 without operating the burner 21 and the hydrocarbon injector 41 in accordance with the nitrogen oxide reduction mode as the first mode, or the exhaust gas at the tip of the particulate matter trapping device 23 is heated up to the particulate matter removal temperature of the particulate matter trapping device 23 by the burner 21 and/or the hydrocarbon injector 41 in accordance with the Particulate Matter (PM) removal mode as the second mode.

Specifically, when the temperature T1 of the exhaust gas discharged from the engine 10 is too high, the control unit 50 operates the hydrocarbon injector 41 to bring the exhaust gas at the front end of the particulate matter trapping device 23 to a temperature T2 of approximately 400 ℃ or higher by injecting only hydrocarbons to realize forced restart of the particulate matter trapping device 23 by combustion when there is no flow of hydrocarbons. According to another embodiment, since the temperature of the exhaust gas can be raised to about 150 ℃ by the hydrocarbon injection and can be raised to about 100 ℃ by the operation of the burner 21, the controller 50 operates only the burner 21 when the deviation between the temperature T1 of the exhaust gas discharged from the engine 10 and the temperature T2 of the front end of the particulate matter trapping device 23 is about 100 ℃ or less, and operates only the hydrocarbon injector 41 when the deviation is about 100 to 150 ℃.

That is, in the case where the engine 10 is in the high speed running mode, that is, the temperature of the exhaust gas is excessively high, the particulate trap device restart and the nitrogen oxide reduction may be induced only by the hydrocarbon injection.

In contrast, when the hydrocarbon flow occurs, the combustor 21 is operated and the hydrocarbon is injected by the operation of the hydrocarbon injector 41 to make the temperature of the exhaust gas reach a temperature T2 of about 400 ℃ or higher at the tip of the particulate trap device 23, thereby forcibly restarting the particulate trap device 23 by combustion.

The occurrence or non-occurrence of the flow of hydrocarbons may be directly calculated by the control unit 50 by calculating the heat or loss of the inflow and outflow in each and/or the whole of the components (the diesel oxidation catalyst device 22, the particulate matter trapping device 23, and the selective catalytic reduction device 31) of the exhaust gas aftertreatment system or may receive the result calculated by an external device, and the present invention is not particularly limited.

Exhaust gas aftertreatment method

As shown in fig. 5, the method for controlling the exhaust aftertreatment system according to the embodiment of the invention has an exhaust aftertreatment system that is installed in an exhaust pipe of an internal combustion engine and in which the particulate matter trapping device 23 and the selective catalytic reduction device 31 are provided in this order from the upstream side, and may include control steps S10 to S2222 in which the control portion 50 controls the burner 21 and the hydrocarbon injector 41 in accordance with the first mode for removing nitrogen oxides or the second mode for removing particulate matter.

In the control step, when the temperature T3 of the exhaust gas at the front end of the selective catalytic reduction device 31 or the rear end of the particulate matter trapping device 23 is a low temperature that does not mutually affect the operating temperature of the selective catalytic reduction device 31, the burner 21 is operated according to the first mode (step S2211) to raise the temperature of the exhaust gas at the front end of the selective catalytic reduction device 31 or the rear end of the particulate matter trapping device 23 to the operating temperature of the selective catalytic reduction device 31 and activate the selective catalytic reduction device 31 (step S2212), or according to the second mode, the burner 21 is operated while injecting hydrocarbons by the hydrocarbon injector 41 (step S2221) to raise the temperature to the particulate matter removal temperature of the particulate matter trapping device 23, whereby all of the particulate matter trapping device 23 and the selective catalytic reduction device 31 can be activated (step S2222).

Further, according to an embodiment, when the temperature T3 of the exhaust gas at the front end of the selective catalytic reduction device 31 or the rear end of the particulate matter trapping device 23 is equal to or higher than the operating temperature of the selective catalytic reduction device 31, the control portion 50 activates the selective catalytic reduction device 31 without operating the burner 21 and the hydrocarbon injector 41 according to the first mode (step S2111) (step S2112), or activates all of the particulate matter trapping device 23 and the selective catalytic reduction device 31 by raising the temperature to the particulate matter removal temperature of the particulate matter trapping device 23 by the burner 21 and/or the hydrocarbon injector 41 according to the second mode (step S2222).

Specifically, according to the second mode, the control unit 50 increases the temperature of the exhaust gas only by the hydrocarbon injection by the hydrocarbon injector 41 when no hydrocarbon flows, and increases the temperature of the exhaust gas by the burner 21 and the hydrocarbon injector 41 when a hydrocarbon flow occurs.

However, the steps shown in FIG. 5 or the steps of one embodiment of the present invention described above are not required, and a method of controlling an exhaust aftertreatment system having more or fewer steps may be embodied.

The description of each step is repeated as above, and thus, the description thereof will be omitted and replaced with the above description.

Computer readable recording medium

The control method of the exhaust gas aftertreatment system according to the embodiment of the invention described above is embodied in the form of program instructions executable by various computer structural elements, and is recorded in a computer-readable recording medium.

The above-mentioned computer-readable recording media may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable recording medium are specifically designed and configured for the present invention, and may be those commonly used by those skilled in the art of computer software. Examples of the computer-readable recording medium include a magnetic medium such as a hard disk, a floppy disk, and a magnetic disk, an optical recording medium such as a CD-ROM and a DVD, a magneto-optical medium (magnetic-optical medium) such as an optical disk (magnetic disk), and a specially configured hardware device such as a ROM, a RAM, a flash memory, and the like, which stores and executes program instructions. Examples of the program instructions include a mechanical code formed by a compiler and a high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above operate as one or more software modules for performing the processes of the present invention, and vice versa.

The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, and the description of the present invention is for illustrative purposes, and it will be apparent to those skilled in the art that the present invention may be modified into other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is indicated by the above description rather than by the detailed description, and all modifications and variations derived from the meaning and scope of the claims and their equivalents are intended to fall within the scope of the present invention.

Claims

1. An exhaust gas aftertreatment system which is mounted in an exhaust pipe of an internal combustion engine and in which a particulate trap device and a selective catalytic reduction device are provided in this order from an upstream side,

the method comprises the following steps:

a burner, located upstream of the particulate trap device, for raising a temperature of the exhaust gas of the internal combustion engine;

a hydrocarbon injector located upstream of the particulate trap device and configured to inject hydrocarbon into the exhaust gas; and

a control unit for controlling the burner and the hydrocarbon injector according to a first mode for removing nitrogen oxides or a second mode for removing particulates,

the control unit may operate the burner to raise the temperature of the exhaust gas to the operating temperature of the selective catalytic reduction device in accordance with the first mode, or may operate the burner to raise the temperature to the particulate matter removal temperature of the particulate matter trapping device while injecting the hydrocarbon by the hydrocarbon injector in accordance with a second mode, when the temperature of the exhaust gas does not affect the operating temperature of the selective catalytic reduction device;

when the temperature of the exhaust gas is equal to or higher than the operating temperature of the selective catalytic reduction device, the controller may deactivate the burner and the hydrocarbon injector in the first mode, or increase the temperature to the particulate matter removal temperature of the particulate matter trapping device by the burner and/or the hydrocarbon injector in the second mode;

when the temperature of the exhaust gas is equal to or higher than the operating temperature of the selective catalytic reduction device, the control unit may operate only the burner when a deviation between the temperature of the exhaust gas discharged from the internal combustion engine and the temperature of the front end of the particulate matter trapping device is 100 ℃ or lower in a case where no hydrocarbon flows, operate only the hydrocarbon injector when the deviation is 100 to 150 ℃, and increase the temperature of the exhaust gas by the burner and the hydrocarbon injector when a hydrocarbon flow occurs, when the control unit performs control according to the second mode.

2. The exhaust aftertreatment system according to claim 1, wherein, according to the first mode, the control portion causes the exhaust gas to raise a temperature of a tip end of the particulate trap device to 300 ℃ or higher by the burner.

3. The exhaust aftertreatment system of claim 2, wherein the burner is a mini burner capable of raising the temperature of the exhaust gas to 100 ℃ or less.

4. The exhaust gas aftertreatment system according to claim 1, wherein according to the second mode, the control portion causes the exhaust gas to raise a temperature of a tip end of the particulate trap device to 400 ℃ or higher by using the burner and the hydrocarbon injector.

5. A method of controlling an exhaust gas aftertreatment system having an exhaust pipe mounted on an internal combustion engine and provided with a particulate matter trapping device and a selective catalytic reduction device in this order from an upstream side,

comprising a control step of controlling, in accordance with a first mode for removing nitrogen oxides or a second mode for removing particulates, a burner to raise a temperature of an exhaust gas of the internal combustion engine on the upstream side of the particulate trap device, and a hydrocarbon injector to inject hydrocarbons into the exhaust gas on the upstream side of the particulate trap device,

in the control step, when the temperature of the exhaust gas does not affect the operating temperature of the selective catalytic reduction device, the burner is operated to raise the temperature of the exhaust gas to the operating temperature of the selective catalytic reduction device according to the first mode, or the burner is operated to raise the temperature to the particulate matter removal temperature of the particulate matter trapping device while injecting hydrocarbons by the hydrocarbon injector according to the second mode;

in the control step, when the temperature of the exhaust gas is equal to or higher than the operating temperature of the selective catalytic reduction device, the burner and the hydrocarbon injector are not operated in the first mode, or the temperature of the burner and/or the hydrocarbon injector is raised to the particulate matter removal temperature of the particulate matter trapping device in the second mode;

in the control step, when the temperature of the exhaust gas is equal to or higher than the operating temperature of the selective catalytic reduction device, the control unit may operate only the burner when the deviation between the temperature of the exhaust gas discharged from the internal combustion engine and the temperature of the front end of the particulate matter trapping device is 100 ℃ or lower when no hydrocarbon flow is present, operate only the hydrocarbon injector when the deviation is 100 to 150 ℃, and increase the temperature of the exhaust gas by the burner and the hydrocarbon injector when a hydrocarbon flow is generated, in the control according to the second mode.