KR102563490B1 - Regeneration control method for improving durability of exhaust gas purification system - Google Patents

Abstract

The present invention relates to a regeneration control method of an exhaust purification device, and more particularly, to minimize damage to an exhaust system caused by ammonia (NH ₃ ) that may be caused by injection of a reducing agent such as a urea solution, reducing agent injection amount and A regeneration control method of an exhaust purification apparatus for improving the durability of the exhaust purification apparatus, which changes and controls a regeneration entry point according to an exhaust temperature condition after a reducing agent is injected.

Description

Regeneration control method of exhaust purification device for improving durability of exhaust purification device

The present invention prevents damage to the exhaust purification device due to ammonia (NH ₃ ), which may be caused by injection of a reducing agent such as urea solution during the exhaust purification process in an internal combustion engine operating under lean combustion conditions and equipped with an exhaust purification device. A regeneration control method of an exhaust purification apparatus for improving the durability of an exhaust purification apparatus for changing and controlling a regeneration entry point according to a reducing agent injection amount and an exhaust temperature condition after reducing agent injection in order to minimize a regeneration control method.

As emission regulations are strengthened, the application of exhaust purification devices is expanding to remove nitrogen oxides (NOx) generated during the operation of lean-burn internal combustion engines.

Among exhaust purification systems, the Urea-SCR system, which uses urea as a reducing agent, can expect high nitrogen oxide reduction efficiency without deteriorating fuel economy, and technology development is being actively conducted. Specifically, the Urea-SCR system purifies nitrogen oxides by using an in-vehicle urea aqueous solution injection system and a SCR (Selective Catalytic Reduction) catalyst. In this process, in order to improve the nitrogen oxide purification performance of the SCR catalyst, a mixer is generally installed at the rear end of the urea aqueous solution injection system so that the urea aqueous solution flowing into the SCR catalyst can be evenly distributed, and nitrogen oxide is purified according to the shape of the mixer. Performance may vary.

A part of the urea aqueous solution colliding with the mixer is converted into ammonia (NH ₃ ) form by the heat of the exhaust gas. However, not all of the injected urea aqueous solution or converted ammonia can be delivered to the SCR catalyst, so some of it remains in the mixer, pipe, or canning located at the rear end of the urea aqueous solution injection device. As a result, if ammonia exhibiting a strong alkalinity of about pH 12 is not removed for a long time during vehicle operation or after the engine is turned off, corrosion of the exhaust purification device by ammonia may occur. As a result, if the exhaust purification device is damaged, it may cause deterioration in nitrogen oxide purifying performance and deterioration in quality.

In this way, in order to minimize or suppress the canning corrosion phenomenon caused by ammonia generated in the process of purifying nitrogen oxides, materials with strong corrosion resistance that can withstand strong bases have been used. However, this method is merely a means of delaying the occurrence of corrosion and cannot be an ultimate solution, and there is also a problem of cost increase caused by using an expensive corrosion-resistant material.

US Patent Publication No. 2010-0317823

In order to solve the above problems, the present invention changes the regeneration entry time of the exhaust system according to the cumulative injection amount of the used reducing agent after exposure to the high-temperature exhaust gas operating conditions of 400 ° C. or higher and the exhaust gas temperature condition after the reducing agent is injected to change the regeneration process. An object of the present invention is to provide a control method capable of improving the durability of an exhaust purification device by removing ammonia components that cause corrosion remaining in the exhaust system using a high-temperature atmosphere generated from the exhaust system.

In order to achieve the above object, the regeneration control method of the exhaust purification apparatus of the present invention provides the cumulative injection amount information of the reducing agent, the exhaust temperature information, the amount of particulate matter (soot) and the amount of sulfur oxide (S) in the exhaust purification apparatus during operation. Detecting information detection step, weight calculation step of calculating a first weight based on the cumulative injection amount information of the reducing agent and calculating a second weight based on the exhaust temperature information, the amount of particulate matter (soot) and sulfur oxides (S) Determining a regeneration entry condition by comparing the amount of with a regeneration reference value reset by multiplying the first weight and the second weight, if the regeneration entry condition is satisfied, particulate matter (soot) is removed or sulfur oxides in the exhaust purification device ( S) a regeneration execution step to effect removal.

In the information detection step, the cumulative reducing agent injection amount (m _Urea ) is a value that satisfies Equation 1 below, and the cumulative reducing agent injection amount is calculated by checking the reducing agent injection change amount (dm _Urea ) according to the time change (dt).

[Equation 1]

In the first weight, when the cumulative reducing agent injection amount is equal to or greater than the predetermined cumulative reducing agent injection amount reference value, the weight for the reducing agent cumulative injection amount m _Urea is f(m _Urea )<1, and the reducing agent cumulative injection amount is less than the preset reducing agent injection amount reference value. , the weight for the cumulative injection amount m _Urea of the reducing agent is f(m _Urea )=1.

For the second weight, if the exhaust temperature T is 400°C or more, the weight for the exhaust temperature T is f'(T)=1, and if the exhaust temperature T is less than 400°C, the weight for the exhaust temperature T is f '(T) < 1. The step of determining the regeneration entry condition includes resetting the regeneration reference value by multiplying a predetermined regeneration reference value by the weight, and comparing the reset regeneration reference value with the amount of particulate matter (soot) and the amount of sulfur oxide (S), respectively. and determining a regeneration entry condition.

The resetting of the regeneration reference value may include a first weight value (f(m _Urea )) and a second weight value (m _soot , _set ) for the amount (m _soot ) of the particulate matter (soot). _The first _regeneration reference value may be reset by multiplying f′(T)) _, and the first weight value f( The second reproduction reference value may be reset by multiplying m _Urea )) and the second weight f'(T).

In the step of resetting the reproduction reference value, a value obtained by multiplying the first weight by the second weight may have a value equal to or less than 1.

The step of determining the regeneration entry condition may include the amount of particulate matter (soot) (m _soot ) equal to or greater than the reset first regeneration reference value, or the amount (m _S ) of sulfur oxide (S) of the reset second regeneration reference value. If it is equal to or greater than the regeneration reference value, it may be determined that regeneration is entered. In the reproduction entry condition determination step, if the reproduction entry condition is not satisfied, the process may return to the information detection step and perform the following steps again.

It is preferable that a value obtained by multiplying the first weight and the second weight in the step of determining the reproduction entry condition is equal to or less than 1. In the regeneration execution step, in order to remove particulate matter from a diesel particulate filter (hereinafter referred to as 'DPF') or remove sulfur oxides from a nitrogen oxide storage catalyst (LNT), the temperature of the exhaust purification device is set to a predetermined level. It is characterized by raising the temperature. At this time, in the regeneration execution step, the temperature of the exhaust purification device may be increased to 400°C or higher.

In the information detection step, the exhaust temperature information is the exhaust temperature measured in real time, and the reducing agent is a urea reducing agent or an ammonia reducing agent.

According to the regeneration control method of the exhaust purification device of the present invention, ammonia (NH ₃ ) has the advantage of minimizing damage to the exhaust purification device caused by ammonia (NH ₃ ) by changing and controlling the regeneration entry point according to the amount of the reducing agent injection and the exhaust temperature conditions after the reducing agent injection so that the exhaust gas can be properly removed.

1 shows a configuration diagram of a regeneration control device of an exhaust purification system.
2 is a flow chart showing a regeneration control method of the exhaust purification device of the present invention.
3 is a detailed flowchart illustrating a regeneration control method of an exhaust purification apparatus according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of a regeneration control method of an exhaust purification device according to the present invention will be described in detail with reference to the accompanying drawings, but this is an example and various modifications and changes may be made by those skilled in the art to which the present invention belongs. Since it can be implemented by doing, it is not limited to what is described herein.

On the other hand, terms such as “include” or “add” used in this specification should not be construed as necessarily including all of the various components or steps described in the specification, and some of the components or It should be construed that some steps may not be included and may further include additional components or steps.

In addition, in this specification, terms such as 'first' and 'second' are used to distinguish the objects or components to be referred to, and are not construed as limiting to specify a certain order or importance.

In addition, the number of repetitions of each step to be described, process conditions, etc. are not particularly limited as long as they do not deviate from the object of the present invention.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, are the same as those commonly understood by one of ordinary skill in the art to which the present invention belongs.

1 schematically shows the configuration of an exhaust purification device, and such an exhaust purification device is installed on the exhaust side of an engine.

As shown in FIG. 1, the exhaust purification device includes a nitrogen oxide removal catalyst (Lean NOx Trap, LNT) 10 at the front end and a diesel particulate matter filter (DPF) that collects particulate matter contained in exhaust and burns them by exhaust heat. ) 20 is installed, and an SCR (Selective Catalytic Reduction) catalyst 40 is installed at the rear end to reduce nitrogen oxides contained in the exhaust to nitrogen using a catalyst and urea aqueous solution or ammonia.

The nitrogen oxide removal catalyst 10 installed at the front part supplies reducing agents such as hydrocarbons, hydrogen monoxide, etc. to react with nitrogen oxides (NOx) to remove nitrogen oxides, and the SCR catalyst device at the rear end of the diesel particulate matter filter 20 ( 40) reacts and reduces the nitrogen oxides that have not been purified at the front end by injecting the reducing agent (30) with ammonia.

In the exhaust purification device installed on the exhaust side of the internal combustion engine configured as above, the present invention purifies ammonia (NH ₃ ) generated in the exhaust purification process and remaining in the device according to the cumulative injection amount of the injected reducing agent and the exhaust temperature condition after the reducing agent is injected. It can be removed by raising the temperature inside the exhaust purification device to 400° C. or more by adjusting the regeneration entry point of the device.

The 'reducing agent' refers to a reducing agent injected to remove nitrogen oxides from the SCR catalyst device, and a urea reducing agent or an ammonia reducing agent may be used as the reducing agent.

2 and 3 are flowcharts showing a regeneration control method of the exhaust purification apparatus of the present invention.

As shown in FIGS. 2 and 3, the regeneration control method of the exhaust purification apparatus of the present invention includes information detection step (S100), weight calculation step (S200), regeneration entry condition determination step (S300) among general operating conditions, regeneration control method It may be composed of a reproduction execution step (S400) of performing reproduction when the entry condition is satisfied, and a reproduction completion step (S500).

Specifically, in the information detection step (S100), information necessary for determining whether or not regeneration is entered in a subsequent regeneration control method is detected, and through a detection sensor provided inside the exhaust purification device, reduction agent cumulative injection amount information of the exhaust purification device during operation, Exhaust temperature information, amount of particulate matter (soot) and amount of sulfur oxide (S) can be detected.

The detection sensor includes an exhaust temperature sensor for detecting the temperature of the exhaust gas discharged from the engine, an exhaust temperature sensor for detecting the temperature inside the exhaust purifying device, and detecting the internal temperature of the nitrogen oxide removal catalyst (LNT) and the diesel particulate matter filter (DPF). It may include an internal temperature sensor that

In addition, the nitrogen oxide removal catalyst (LNT) is provided with a detection sensor for detecting the concentration of nitrogen oxides (NOx), and a detection sensor capable of detecting the concentration of sulfur oxides (S) and nitrogen oxides (NOx) and sulfur oxides. A weight sensor capable of measuring the amount of (S) is provided, the diesel particulate matter filter (DPF) collects particulate material (PM) contained in the exhaust, and a PM sensor detects the amount of such particulate matter. In addition, the SCR catalyst is provided with a reducing agent detection sensor capable of measuring the cumulative injection amount of the reducing agent injected through the reducing agent injection nozzle, and determines whether regeneration is entered through the sensors provided inside the exhaust purification device. You will find the information you need. The detection sensor presented here is just an example, and may be changed to another sensor or detect information through a model as needed.

The accumulated reducing agent injection amount (m _Urea ) detected in the information detection step is a value calculated according to Equation 1 below, and as shown in Equation 1, it is calculated by numerically integrating the reducing agent injection change amount (dm _Urea ) according to the reducing agent injection time. The cumulative injection amount of the reducing agent may be calculated by checking the amount of change in injection of the reducing agent (dm _Urea ) according to the change in time (dt).

[Formula 1]

In this specification, the 'cumulative injection amount of reducing agent' means the amount of reducing agent used after exposure to high-temperature exhaust over 400 °C. The reason why it is mentioned here after exposure to high-temperature exhaust of 400°C or higher is that ammonia (NH ₃ ), which corrodes the exhaust purification device, can be all removed when exposed to high-temperature exhaust conditions of 400°C or higher for about 3 minutes or more.

The next weight calculation step (S200) is a step of calculating weights for changing the regeneration entry condition standard to determine whether or not regeneration of the exhaust purification device is executed, and the weights calculated here are the information detection step (S100) by a weight function. ), a first weight value may be calculated based on the cumulative injection amount information of the reducing agent measured in ), and a second weight value may be calculated based on the exhaust temperature information.

As for the weight used in the regeneration control method of the present invention, the weight for the cumulative injection amount of the reducing agent is referred to as a first weight, and the weight according to the exhaust temperature is referred to as a second weight.

Specifically, for the first weight, when the cumulative injection amount of the reducing agent is equal to or greater than the reference value for the cumulative injection amount of the reducing agent, the weight f (m _Urea ) for the cumulative injection amount of the reducing agent m _Urea has a value of less than 1, and the cumulative injection amount of the reducing agent has a preset cumulative injection amount of the reducing agent. If the cumulative injection amount is less than the reference value, the weight f(m _Urea ) for the cumulative injection amount m _Urea of the reducing agent is 1.

In addition, the second weight, which is a weight according to the exhaust temperature, has a weight f'(T) for the exhaust temperature T of 1 when the measured exhaust temperature T inside the exhaust purification device is 400°C or more, and when the exhaust temperature T is less than 400°C. The weight f'(T) for the exhaust temperature T has a value less than 1.

In this specification, the function f'(T) representing the second weight represents a new function for distinguishing from the function f (m _Urea ) representing the first weight, and is an inverse function of the first weight function in relation to the first weight function. It should be noted that it does not represent

The regeneration entry condition determination step (S300) compares the regeneration entry condition value based on the amount of the particulate matter (soot) and the amount of sulfur oxide (S) measured in the information detection step (S100) to determine whether regeneration is entered. In the step of doing so, it is possible to determine whether or not to enter regeneration by comparing the amount of particulate matter (soot) and the amount of sulfur oxide (S) with a regeneration reference value reset by multiplying the first weight and the second weight.

In the step of determining a regeneration entry condition (S300), a regeneration reference value is reset by multiplying a predetermined regeneration reference value by the weight, and the amount of the particulate matter (soot) and the amount of sulfur oxide (S) are respectively determined by setting the reset regeneration reference value. It is possible to determine whether or not to enter reproduction, including the step of determining a reproduction proceeding condition by comparing to .

The resetting of the regeneration reference value is a step of resetting the regeneration progress reference value using the first weight and the second weight calculated from the preset regeneration reference value to determine whether or not to enter regeneration, and the amount of particulate matter (m _soot The first regeneration reference value may be reset by multiplying the first regeneration reference value (m _soot , _set ) for ) by the first weight (f(m _Urea )) and the second weight (f'(T)), and sulfuric acid Second reproduction by multiplying a first weight value (f(m _Urea )) and a second weight value (f'(T)) by a preset reproduction reference value (m _S , _set ) for the amount ₍ m S ) of the cargo (S). The reference value can be reset.

In this case, a value obtained by multiplying the first weight by the second weight may be less than or equal to 1.

That is, since the value obtained by multiplying the first weight by the second weight has a value of 1 or less, the reference value for determining the progress of regeneration can be set to be smaller than the preset reference value. Depending on the change, the regeneration entry condition can be made to be reached quickly.

Based on the reset reference value, the amount of particulate matter (m _soot ) is greater than the reset first regeneration reference value or the amount of sulfur oxide (S) (m _S ) is greater than the reset second regeneration reference value. , playback can be performed.

If the reproduction reference value is not satisfied in the reproduction entry condition determination step (S300), the process returns to the information detection step and the following steps are performed.

As shown in FIG. 2 , in the regeneration entry condition determination step (S300), when it is determined that the regeneration entry condition is satisfied after comparing the first regeneration reference value and the second regeneration reference value, regeneration is performed (S400).

In the regeneration execution step (S400), particulate matter is removed from the diesel particulate matter filter (DPF) in the exhaust purification device or sulfur oxide (S) is removed from the nitrogen oxide storage catalyst (LNT).

In this regeneration process, the exhaust temperature is increased to burn the particulate matter (PM) collected in the diesel particulate matter filter (DPF).

Alternatively, the nitrogen oxide removal catalyst (LNT) collects nitrogen oxides (NOx) and sulfur oxides (S) at the same time. Since it deteriorates the performance, the collected sulfur oxides (S) need to be removed by the nitrogen oxide removal catalyst (LNT). For this, desulfurization of the nitrogen oxide removal catalyst (LNT) is performed, and Desulfurization of the nitrogen oxide removal catalyst (LNT) can be carried out by heating the exhaust gas with sulfur oxides (S) and enriching the exhaust gas atmosphere.

Exhaust temperature can be raised to a high temperature of 400° C. or higher to perform exhaust purification device regeneration.

When the exhaust temperature is maintained at a high temperature of 400° C. or more in the regeneration execution step (S400), most of the ammonia (NH ₃ ) component remaining in the exhaust purifying device is removed, ultimately improving the durability of the exhaust purifying device.

The regeneration process described herein refers to a regeneration process in which an electronic control unit (hereinafter referred to as 'ECU') automatically proceeds without a driver's manipulation when a regeneration requirement is satisfied.

Meanwhile, in the process of regenerating the diesel particulate matter filter (DPF) and the nitrogen oxide removal catalyst (LNT), the exhaust gas may be maintained in a rich state.

In the regeneration completion step (S500), when the existing regeneration completion condition of the exhaust purification device is satisfied after the regeneration execution step (S400), particulate matter (soot) that has been progressed in the diesel particulate matter filter (DPF) and the nitrogen oxide removal catalyst (LNT) is removed. Alternatively, it is a step of ending the sulfur oxide (S) removal process and returning to the information detection step again.

As described above, the regeneration control method of the exhaust purification apparatus of the present invention is exhaust purification by adjusting the regeneration reference value for determining the progress of the regeneration process according to the cumulative injection amount of the reducing agent and the exhaust temperature measured in the exhaust purification apparatus by applying a weight. It is possible to control when the device performs regeneration.

Therefore, as a method of changing and controlling the regeneration entry point according to the amount of reducing agent injection and the exhaust temperature condition after injection of the reducing agent, ammonia (NH ₃ ) remaining inside the exhaust purification device and causing corrosion of the exhaust purification device is efficiently removed. Therefore, damage to the exhaust purification device caused by ammonia (NH ₃ ) can be minimized.

10: nitrogen oxide removal catalyst
20: diesel particulate matter filter
30: reducing agent injection device
40: SCR catalyst
110: front end lambda sensor
120: rear lambda sensor
130: front end nitrogen oxide (NOx) sensor
140: rear nitrogen oxide (NOx) sensor
150: PM sensor

Claims (14)

As a regeneration control method of an exhaust purification device,
an information detection step of detecting cumulative injection amount information of a reducing agent, exhaust temperature information, amount of particulate matter and amount of sulfur oxides of the exhaust purification system during operation;
a weight calculation step of calculating a first weight based on the cumulative injection amount information of the reducing agent and calculating a second weight based on the exhaust temperature information;
determining a regeneration entry condition by comparing the amount of particulate matter and the amount of sulfur oxide with a regeneration reference value reset by multiplying the first weight and the second weight;
A regeneration control method of an exhaust purification apparatus comprising: a regeneration execution step of performing a particulate matter removal or sulfur oxide removal process in the exhaust purification apparatus when a regeneration entry condition is satisfied. According to claim 1,
The regeneration control method of the exhaust purification device, characterized in that the cumulative injection amount of the reducing agent (m _Urea ) satisfies Equation 1 below.
[Formula 1]
According to claim 1,
The first weight is,
If the cumulative injection amount of the reducing agent is equal to or greater than the preset cumulative injection amount of the reducing agent, the weight for the cumulative injection amount m _Urea of the reducing agent is f(m _Urea )<1,
If the cumulative reducing agent injection amount is less than a predetermined cumulative reducing agent injection amount reference value, the weight for the cumulative reducing agent injection amount m _Urea is f(m _Urea )=1. According to claim 1,
The second weight is,
When the exhaust temperature is 400° C. or higher, the weight for the exhaust temperature T is f′(T)=1,
If the exhaust temperature is less than 400 ° C, the weight for the exhaust temperature T is f' (T) < 1. According to claim 1,
The step of determining the regeneration entry condition,
resetting a reproduction reference value by multiplying a preset reproduction reference value by the weight; and
A method for controlling regeneration of an exhaust purification apparatus comprising: comparing the reset regeneration reference value with the amount of particulate matter (soot) and the amount of sulfur oxides (S), respectively, to determine a regeneration starting condition. According to claim 5,
The step of resetting the regeneration reference value,
A first weight value (f(m _Urea )) and a second weight value ₍ f'(T)) are multiplied by a predetermined regeneration reference value (m _{soot , set} ) for the amount (m soot ) of the particulate matter (soot). A regeneration control method of an exhaust purification device, characterized in that the regeneration reference value is reset. According to claim 5,
The step of resetting the regeneration reference value,
A second regeneration reference value obtained by multiplying the first regeneration reference value (m _{S , set} ) for the amount of sulfur oxide (m _S ) by the first weight value (f(m _Urea )) and the second weight value (f'(T)). Regeneration control method of an exhaust purification device, characterized in that for resetting. According to claim 1,
The step of determining the regeneration entry condition,
Exhaust purification characterized in that it is determined that regeneration is entered when the amount of particulate matter (m _soot ) is greater than the reset first regeneration reference value or the amount of sulfur oxides (m _S ) is greater than the reset second regeneration reference value. How to control the device's playback. According to claim 1,
and returning to the information detection step when the regeneration entry condition is not satisfied in the step of determining the regeneration entry condition. According to claim 1,
The regeneration control method of the exhaust purification apparatus, characterized in that in the step of determining the regeneration entry condition, a value obtained by multiplying the first weight and the second weight is a value less than or equal to 1. According to claim 1,
The replay execution step,
Regeneration control of an exhaust purification system characterized in that the temperature of the exhaust purification system is raised to a predetermined temperature by removing particulate matter from a diesel particulate filter or removing sulfur oxides from a nitrogen oxide storage catalyst (LNT). method. According to claim 1,
The replay execution step,
A method for controlling regeneration of an exhaust purification device, characterized in that the temperature of the exhaust purification device is raised to 400° C. or higher. According to claim 1,
In the information detection step, the exhaust temperature information is the exhaust temperature measured in real time. According to claim 1,
The regeneration control method of the exhaust purification device, characterized in that the reducing agent is a urea reducing agent or an ammonia reducing agent.

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