KR100980875B1 - Exhaust post processing apparatus of diesel engine and regeneration method thereof - Google Patents

Abstract

The present invention is a post-treatment apparatus of a diesel vehicle, and includes a performance degrading factor of the SCR catalyst as a regeneration indicator in the CPF regeneration criterion for stable removal of NOx contained in exhaust gas.

The present invention is a process of detecting the overall driving state information of the vehicle, SCR catalyst shear temperature, NOx purification efficiency, the process of determining the poisoning of the SCR catalyst under the influence of hydrocarbon (HC) / soot, SCR catalyst If poisoning, the process includes performing CPF regeneration for SCR regeneration.

Aftertreatment unit, hydrocarbon (HC), soot, SCR catalyst, CPF

Description

Post-processing device and regeneration method of diesel vehicle {EXHAUST POST PROCESSING APPARATUS OF DIESEL ENGINE AND REGENERATION METHOD THEREOF}

The present invention relates to a post-treatment apparatus for a diesel vehicle, and more particularly, to deterioration of the performance of a selective catalytic reduction (SCR) catalyst in accordance with a criterion for regeneration of a catalyzed particulate filter (CPF) for stable removal of NOx contained in exhaust gas. It relates to a post-processing device and a regeneration method of a diesel vehicle comprising a as a regeneration instruction factor.

Diesel engines with low compression ratio technology reduce NOx by more than 30% compared to engines with conventional compression methods, but CO and THC emissions are increased by two to three times.

Vehicles with diesel engines can remove harmful substances such as NOx, CO, THC, soot, and particulate matter contained in the exhaust according to North American diesel Tier 2 BIN5 regulation or Euro 6 emission regulations. The aftertreatment device is mounted.

The post-treatment device is disposed on the upstream side of the exhaust pipe to carry out the main function of NMHC conversion, DOC (Diesel Oxidation Catalyst 1), and on the downstream side of the DOC, to collect soot and particulate matter (PM), urea It is composed of DM (Urea Dosing Module) for spraying, and SCR catalyst disposed on the downstream side of CPF.

The DOC oxidizes CO, HC, and NO, which are harmful substances contained in the exhaust gas, through a reaction with a platinum-based catalyst coated on a ceramic carrier to purify CO 2 and H 2 O, and simultaneously reduce the concentration of NO ₂ by the reaction of Formula 1. Increase.

NO + 1/2 O ₂ → NO ₂

The CPF physically collects soot and particulate matter (PM) contained in the exhaust gas, and naturally regenerates the CPF by reaction of NO ₂ discharged from the DOC with Chemical Formula 2.

C + 2NO ₂ → CO ₂ + 2NO

The SCR catalyst purifies NOx by the reaction of ammonia (NH3) and NO ₂ produced by decomposition of an aqueous urea (Urea) solution injected through DM.

NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O

4NO + O ₂ + 4NH ₃ → 4N ₂ + 6H ₂ O

6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O

In the post-treatment device of the above-described configuration, the NO ₂ concentration (NO ₂ / NO x concentration ratio = 20 to 90%) of the front end of the SCR catalyst determines the performance of the SCR catalyst.

As the soot (Soot) and particulate matter (PM) is increased to be occluded in the CPF concentration ratio of NO ₂ / NOx in the natural regeneration by the reaction of NO ₂ it falls rapidly, so that performance of the SCR catalyst are substantially reduced.

Therefore, the regeneration timing is determined by integrating information such as the soot and particulate matter (PM) occlusion, driving distance, and driving time detected by the differential pressure sensor installed at the front and rear ends of the CPF. Perform post-injection regeneration of the CPF.

In addition, NO ₂ / NOx is affected by the poisoning caused by hydrocarbon (HC) or sulfur (S) and the soot and particulate matter (PM) deposition in CPF. The concentration is reduced.

However, in determining the regeneration of the CPF in the conventional diesel vehicle, only the soot and particulate matter (PM) deposition information is applied, which causes a problem that the performance of the SCR catalyst cannot be stably maintained.

The present invention has been invented to solve the above problems, the object of which is the poisoning of hydrocarbon (HC) which is a performance deterioration factor of the SCR catalyst and the amount of soot and particulate matter (PM) trapped in the CPF By controlling the regeneration of CPF, the performance of SCR catalyst is maintained stably.

The after-treatment apparatus of a diesel vehicle composed of DOC, CPF, DM, and SCR catalysts according to the characteristics of the present invention for realizing the above object is characterized in that the deposition of poisoning and soot by hydrocarbon (HC) And controlling the CPF regeneration for regenerating the SCR catalyst by determining whether the deterioration of the purification performance is affected.

In addition, a method for regenerating a post-processing apparatus for a diesel vehicle according to another aspect of the present invention includes: detecting general driving state information, SCR catalyst front end temperature, and NOx purification efficiency of a vehicle; Determining whether the SCR catalyst is poisoned by the influence of hydrocarbon (HC) / soot; If poisoning of the SCR catalyst, a process of performing CPF regeneration for SCR regeneration is included.

According to the above-described configuration, the present invention can be expected to have an effect of stably maintaining the performance of the SCR catalyst by controlling the regeneration of the CPF as a factor for reducing the performance of the SCR catalyst in the after-treatment apparatus of a diesel vehicle.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Since the present invention can be implemented in various different forms, the present invention is not limited to the exemplary embodiments described herein, and parts not related to the description are omitted in the drawings in order to clearly describe the present invention.

1 is a view showing a schematic configuration of a post-treatment apparatus of a diesel vehicle according to an embodiment of the present invention.

The after-treatment apparatus of a diesel vehicle according to the present invention is disposed on the most upstream side of the exhaust pipe to oxidize CO, HC, and NO contained in the exhaust gas to perform main functions of NMHC conversion. CPF 200 disposed downstream and collecting soot and particulate matter (PM), DM 300 spraying urea according to the purification rate of NOx, downstream downstream of CPF 200 to NOx SCR catalyst 400 to purify, the control unit 500 for controlling the overall operation of the exhaust gas purification and regeneration of the after-treatment device.

First and second temperature sensors 110 and 120 for detecting the temperature of the exhaust gas are disposed at both ends of the DOC 100 to provide the controller 500 with activation state information of the DCO 100.

First and second differential pressure sensors 210 and 220 and third and fourth temperature sensors 230 and 240 are disposed at both ends of the CPF 200, respectively, and are connected to the control unit 500. Estimate the amount of occlusion collected from the temperature and the differential pressure between the CPF (200).

In addition, a first NOx sensor 250 is disposed at the rear end of the CPF 200 and connected to the control unit 500.

A temperature sensor 410 for detecting the temperature of the exhaust gas is disposed at the front of the SCR catalyst 400 to provide the controller 500 with the temperature of the exhaust gas flowing into the SCR catalyst 400.

In addition, a 2NOx sensor 430 is disposed at the rear end of the SCR catalyst 400 and connected to the control unit 500, and the control unit 500 receives signals of the first NOx sensor 250 and the second NOx sensor 250 and 430. Determining the NOx purification efficiency of the SCR 400 by analyzing the, and controls the injection of urea through the DM 300 according to the purification efficiency of the NOx.

Referring to FIG. 2, the operation of executing the reproduction of the CPF in the present invention including the above-described functions will be described.

First, the characteristics of the SCR catalyst 400 were measured under various conditions, and the following results were confirmed.

As shown in FIG. 3, when the temperature of the exhaust gas is 340 ° C. or higher under the condition that hydrocarbons HC exist in the exhaust gas, the SCR catalyst 400 has no effect on the purification performance of NOx.

In addition, after poisoning the hydrocarbon (HC) to the SCR catalyst 400 and confirming the time required for the desorption of the hydrocarbon (HC) according to the temperature of the SCR catalyst 400, as shown in FIG. Able to know.

Therefore, it can be seen that the degradation of the performance of the SCR catalyst 400 by the hydrocarbon (HC) occurs in the region below 300 ° C.

In addition, sulfur poisoning occurs gradually over a long period of time, and when the temperature of the SCR catalyst 400 is maintained at 350 ° C. or higher, the effect of the sulfur appears to be less and SCR performance is restored at 400 ° C. or higher, thereby forcibly regenerating the CPF 200. Each time this was carried out, the effect of sulfur (S) poisoning was confirmed to disappear.

The post-treatment apparatus according to the present invention applies the characteristics of the SCR catalyst 400 described above to perform the regeneration operation according to the poisoning of the hydrocarbon (HC) and the storage of soot and particulate matter (PM) in the CPF 200. It is executed as follows.

When the operation of the diesel vehicle according to the present invention is started, the control unit 500 controls the air amount, the engine speed (RPM), the displacement of the TPS, the coolant temperature, the fuel amount, the injection timing, the boost pressure, the exhaust gas temperature, and the first and second differential pressure sensors. General vehicle state information such as differential pressure between the both ends of the CPF 200 is detected from the information of the 210 and 220 (S101).

Then, the temperature of the exhaust gas flowing into the SCR catalyst 400 is detected from the temperature sensor 410 disposed in front of the SCR catalyst 400 (S102), and the first NOx sensor disposed at the rear end of the CPF 200 ( 250 and the information of the second NOx sensor 430 disposed at the rear end of the SCR 400 are analyzed to detect the NOx purification efficiency of the SCR catalyst 400 (S103), and the travel distance is detected from the totalizer (not shown) ( S104).

In order to detect the degradation of the performance of the SCR catalyst 400 by poisoning of the hydrocarbon (HC), for example, by measuring the shear temperature of the SCR catalyst 400 every 50 km or more at 300 ℃ or more 8 minutes or more or 350 ℃ or more At 4 minutes, at least 400 minutes, at least 1.6 minutes, or at least 450 minutes.

When exposed to the temperature conditions set above the set time is not affected by the poisoning of hydrocarbons (HC), if the temperature conditions and time conditions are not satisfied poisoning by hydrocarbons (HC) purifying NOx of the SCR catalyst 400 I think it affects performance.

In addition, in order to detect the degradation of the performance of the SCR catalyst 400 due to the deposition of soot (soot), for example, by measuring the shear temperature of the SCR catalyst 400 during every 50 km for 15 minutes at 350 ℃ or more It detects whether it exposes more than 10 minutes at 400 degreeC or more and 5 minutes or more at 450 degreeC or more.

It is determined that the soot does not affect the NOx purification when exposed to the temperature set in the above setting time or more, and when it is not exposed above the above temperature and time conditions, the NOx purification performance is not affected. I judge it.

If it is determined that the purification performance of NOx is affected by poisoning or soot of hydrocarbons (HC), the NOx purification efficiency is analyzed from the signals of the first NOx sensor 250 and the second NOx sensor 430 to determine whether the performance is deteriorated. do.

The determination of the occurrence of degradation of the NOx purification performance is determined by the influence of hydrocarbon (HC) or soot when a degradation of about 10% is detected compared to the normal performance.

The temperature measurement conditions may be reset according to engine operating conditions, that is, temperature, flow rate, exhaust gas composition, and the like.

The information is analyzed to determine whether the CPF 200 is regenerated due to the influence of hydrocarbon (HC) or soot (Soot), which is a performance deterioration factor of the SCR catalyst 400 (S105).

When determining the regeneration time of the CPF 200, it is first determined whether the hydrocarbon (HC) is poisoned, and then the influence of soot (Soot).

When the degradation of the SCR catalyst 400 due to poisoning of the hydrocarbon (HC) is predicted, the NOx purification efficiency is measured using the information of the first NOx sensor 250 and the second NOx sensor 430, and the set reference value is 10% or more. When it is determined that the performance is deteriorated, it is determined that the deterioration of the performance of the SCR catalyst 400 is caused by the poisoning effect of the hydrocarbon HC.

In addition, the purification efficiency of the NOx is calculated through the information of the first NOx sensor 250 and the second NOx sensor 430, and then it is determined whether the performance degradation of the SCR catalyst 400 is caused by the influence of soot.

If it is determined that the performance degradation of the SCR catalyst 400 is caused by the influence of hydrocarbon (HC) or soot in S105, the current operating area is determined (S106) and the SCR catalyst 400 is regenerated according to the operating area. The reproduction of the CPF 200 is executed (S107).

If the operation range determined above is a low speed low load, the temperature of the exhaust gas is increased by increasing the post injection control and the boost pressure. Rise control.

The regeneration mode of the CPF 200 under the influence of the hydrocarbon (HC) is composed of a sub-loop in the forced regeneration mode, and less than 10 minutes at 300 ° C or more based on the shear temperature of the SCR catalyst 400. To perform.

For example, if the shear temperature of the SCR catalyst 400 is 400 ° C., it is maintained for about 1 minute.

In addition, the regeneration mode of the CPF 200 under the influence of soot is configured as a sub loop in the existing forced regeneration mode, and is associated with the first stage regeneration loop.

Regeneration operation conditions are carried out at a holding time of 30 minutes or less at 350 ℃ or more based on the shear temperature of the SCR catalyst 400.

For example, if the shear temperature of the SCR catalyst 400 is 450 ° C., 10 minutes is maintained.

It is determined whether the regeneration operation of the CPF 200 is completed (S108). When the completion of the regeneration operation is detected, the regeneration operation of the CPF 200 is terminated and then normal combustion is controlled (S109).

In addition, in the determination of S105, if it is not the regeneration condition of the CPF 200 due to the influence of hydrocarbon (HC) or soot (soot), it is determined whether the time of forced regeneration of the CPF (200) (S110).

The determination of the forced regeneration time of the CPF 200 may analyze the information of the first NOx sensor 250 and the second NOx sensor 430 at predetermined set distances, for example, every 100 km to determine the NOx purification efficiency of the SCR catalyst 400. Measure and judge

If it is determined in S110 that the CPF 200 is not at the forced regeneration time, the process returns to S105. If the CPF is at the forced regeneration time, the current operation area is determined at step S111 (S111). Force playback (S112).

For example, in the low speed low load operation area, the main injection and post injection control and the intake air volume are adjusted. In the high speed low load operation area, the main injection and post injection control and the booster pressure reduction control are used to control the temperature of the exhaust gas. Based on the front end of the catalyst 400 is maintained at less than 10 minutes at 300 ℃ or more, and maintained for 1 minute at 400 ℃ or more based on the shear temperature of the SCR catalyst 400.

It is determined whether the regeneration of the CPF 200 is completed by the above operation (S108). When it is determined that the regeneration is completed, the forced regeneration operation of the CPF 200 is terminated, and then normal combustion is controlled (S109).

Degradation detection of the SCR catalyst 400 in the above can be adjusted according to the performance of the post-processing system.

 That is, the performance deterioration criteria of the SCR catalyst for regeneration are set according to the difference between the performance of the aftertreatment system and the regulation value.

For example, if the NOx regulation value is 0.05g / mile, the performance of the SCR catalyst is adjusted in the range of 25% reduction of NOx reduction when 0.04g / mile is the reference performance.

In addition, when the NOx regulation value is 0.05g / mile, the performance of the SCR catalyst is adjusted in the range of 67% NOx reduction reduction when 0.03g / mile is the reference performance.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It is included in the scope of rights.

1 is a view schematically showing a post-treatment apparatus of a diesel vehicle according to an embodiment of the present invention.

2 is a view showing a regeneration procedure of the after-treatment apparatus in a diesel vehicle according to an embodiment of the present invention.

3 is a graph illustrating a relationship between exhaust gas temperature and NOx purification performance in a diesel vehicle according to an exemplary embodiment of the present invention.

4 is a graph showing the relationship between the temperature of the exhaust gas and HC poisoning in the diesel vehicle according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: DOC 200: CPF

300: DM 400: SCR

410 temperature sensor

Claims (12)

In the after-treatment device of a diesel vehicle composed of a CPF and SCR catalyst, By determining the temperature and temperature exposure time of the front end of the SCR catalyst at set mileage intervals, it is determined whether the purification performance of the SCR catalyst is degraded by poisoning and soot deposition by hydrocarbon (HC), and the first and second NOx sensors And a control unit for controlling CPF regeneration for SCR catalyst regeneration by determining NOx purification efficiency from the information. delete delete delete The method of claim 1, The controller determines the purification performance of the SCR catalyst due to poisoning of the hydrocarbon (HC) as the primary, and determines the purification performance of the SCR catalyst under the influence of soot as secondary, and then applies the operating conditions to perform the SCR catalyst regeneration. After-treatment device of a diesel vehicle for controlling CPF regeneration. The method of claim 1, And the control unit controls the forced regeneration of the CPF by measuring the purification efficiency of NOx at a set mileage interval when hydrocarbons and soot do not affect the purification performance of the SCR catalyst. Analyzing the shear temperature and exposure time of the SCR catalyst at a set mileage interval to determine whether the SCR catalyst is poisoned by the influence of hydrocarbon (HC) / soot; If the SCR catalyst is not poisoned with hydrocarbon (HC) / soot, the information of the first and second NOx sensors is analyzed at set mileage intervals to determine the NOx purification efficiency of the SCR catalyst, and to determine the time of forced CPF regeneration. Forcibly regenerating the CPF; And regenerating CPF for SCR regeneration if the SCR catalyst is poisoned by hydrocarbon (HC) / soot. delete delete delete The method of claim 7, wherein And a mileage for determining poisoning of the hydrocarbon (HC) / soot is set at a distance of 50 km. The method of claim 7, wherein And a mileage for measuring the purification efficiency of NOx is set at 100 km intervals to determine the CPF forced regeneration time point.

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