KR101480644B1 - METHOD FOR DETECTING AGED OF LEAN NOx TRAP CATALYST - Google Patents

Abstract

The present invention relates to a deterioration detection method for a lean NOx trap catalyst. According to the present invention, DeSOx regeneration time is controlled based on the time required for lambda signals at front and back ends of a diesel oxidation catalyst to become equal to each other so that desulfurization efficiency can be improved. Provided are a first lambda sensor that is disposed between an engine downstream side and a lean NOx trap catalyst upstream side and a second lambda sensor that is disposed on a downstream side of a diesel particle filter disposed on a lean NOx trap downstream side. If a difference value between a signal generated in the first lambda sensor and a signal generated in the second lambda sensor is equal to or less than a predetermined value during the richness control for the DeNOx of the catalyst, the richness control is terminated, and the DeSOx execution time or DeSOx execution cycle is controlled based on the time of the termination.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for detecting a deterioration of a catalyst,

The present invention relates to a method of detecting deterioration of a Lean NOx Trap catalyst, and more particularly, to a method of detecting degradation of a Lean NOx Trap catalyst by controlling the DeSOx regeneration time based on the time required until the lambda signals before and after the diesel oxidation catalyst become equal, And to a deterioration detection method of a linox trap catalyst capable of increasing the efficiency.

Generally, the harmful substances contained in the exhaust gas generated during operation of the internal combustion engine include CO (carbon monoxide), HC (hydrocarbon) and soluble organic fraction (SOF) ) Is used.

The oxidation catalyst reacts with a platinum catalyst coated on a ceramic carrier with CO and HC to purify it in the form of CO2 (carbon dioxide) and H2O (water).

Oxidation catalysts have two degradation mechanisms, one is irreversible deterioration in which the specific surface area is reduced by high temperature exposure, and the other is reversible sulfur poisoning in which the reaction site is reduced by the sulfur component.

The reversible sulfur poisoning is a reaction in which the activity of the oxidation catalyst is lowered due to the sulfur component contained in the fuel or the engine oil. Since the reaction is a reversible reaction, it is possible to restore the activity of the oxidation catalyst whose performance has deteriorated.

The process of reactively restoring the oxidation catalyst from reversible sulfur poisoning is referred to as desulfurization, and a method of exposing the oxidation catalyst to a high temperature (for example, 450 ° C or higher) for a certain period of time is mainly used.

The desulfurization of the oxidation catalyst can solve the problem of deactivation due to sulfur poisoning by exposing the oxidation catalyst to the acid of the oxidation catalyst when a period of a predetermined interval set by the running distance or the running time arrives.

However, in order to create a high-temperature environment in the oxidation catalyst in the desulfurization process, additional fuel is consumed by a method such as post-fuel injection, which causes deterioration of fuel efficiency.

Korean Patent Publication No. 10-2012-0047386

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a deSOx regeneration catalyst and a deoxidation catalyst which are capable of controlling the DeSOx regeneration time based on the time taken until the lambda signals before and after the diesel oxidation catalyst become equal, Or deoxidation efficiency by increasing or decreasing the DeSOx cycle.

In order to accomplish the above object, the method of detecting a deterioration of a linox trap catalyst according to an embodiment of the present invention is characterized in that the lambda value of the first and second lambda sensors before and after the LNT catalyst is equalized A reference time setting step of setting a reference time, a time determination step of determining whether the difference between the time required for the lambda value of the first and second lambda sensors to become the same in the current LNT catalyst and the reference time is higher than the pre- And a DeSOx execution time increasing step of increasing the DeSOx execution time by the execution time increase / decrease constant when the difference value is higher than the preset required time in the time determination step, and in the time determination step, Time is shorter than the predetermined time, the step of determining the required time is performed again.

Further, in the step of increasing the DeSOx performance time, a time required for the lambda value of the first and second lambda sensors to be equal in the present LNT catalyst immediately after DeSOx is performed is measured, and a time required to determine whether the required time is higher than the reference time Re-determining the DeSOx execution time and re-determining the DeSOx execution time when the required time is higher than the reference time in the re-determining time.

If the required time is less than the reference time, the DeSOx execution time is restored to the initial DeSOx time.

Also, the DeSOx performance control accumulation step of accumulating the number of times of execution every time the DeSOx performance time increasing step is performed is performed.

Performing a DeSOx performance control determination step of determining whether the number of times of execution is higher than a predetermined number of times of execution, restoring the DeSOx performance time to an initial DeSOx performance time if the number of performance times is higher than a preset number of times, The DeSOx performance control number determination step is repeatedly performed.

In the meantime, a reference time setting step of setting a reference time required for the lambda values of the first and second lambda sensors before and after the LNT catalyst to become the same when the LNT catalyst is not deteriorated, Determining whether a difference between the time required for obtaining the lambda value of the reference time and the reference time is higher than a preset required time; The DeSOx execution period reduction step of decreasing the DeSOx execution period by a period increase / decrease constant, and if the difference value is less than the preset required time in the required time determination step, the time determination step may be performed again.

In the step of decreasing the DeSOx performance period, the time required for the lambda value of the first and second lambda sensors to be equal in the present LNT catalyst immediately after DeSOx is performed is measured, and the time required to determine whether the required time is higher than the reference time Re-determination step, and if the required time is higher than the reference time in the required time re-determination step, performing the DeSOx execution cycle reducing step to perform the DeSOx execution cycle reducing step again.

In addition, if the required time is less than the reference time, the DeSOx execution period may be restored to the initial DeSOx execution period.

Further, it is possible to perform the DeSOx performance control accumulation step of accumulating the execution count every time the DeSOx performance period decreasing step is performed.

Also, it is preferable to perform a DeSOx performance control determination step of determining whether the number of times of execution is higher than a predetermined number of times of execution, and to restore the DeSOx performance period to an initial DeSOx performance period if the number of performance is higher than a predetermined performance number, If it is lower than the pre-set number of times, the DeSOx performance control count determination step can be repeated.

As described above, according to the deterioration detection method of the linox trap catalyst according to the present invention, it is possible to determine the sulfur poisoning effect based on the time required for the signals from the lambda sensors before and after the diesel oxidation catalyst to be equalized during DeNOx operation immediately after DeSOx And the effect of increasing the DeSOx efficiency as well as increasing the DeSOx efficiency through shortening the DeSOx time or shortening the DeSOx regeneration cycle.

FIG. 1 schematically shows the structure of a linox trap and a diesel particulate filter applied to a deterioration detecting method of a linox trap catalyst according to an embodiment of the present invention. Referring to FIG.
FIG. 2 shows the front and rear lambda signals according to the steady state and deterioration state of the Linnox trap catalyst represented by the system of FIG.
FIG. 3 is a flowchart illustrating DeSOx time control applied to a method for detecting deterioration of a Linnox trap catalyst according to an embodiment of the present invention. Referring to FIG.
FIG. 4 is a graph showing a state in which the DeSOx execution time is controlled by FIG. 3. FIG.
FIG. 5 is a flowchart illustrating DeSOx periodic control applied to a method for detecting deterioration of a linox trap catalyst according to an embodiment of the present invention. Referring to FIG.
FIG. 6 is a graph showing a state in which the DeSOx cycle is controlled by FIG.
FIG. 7 is a flowchart illustrating the recovery of the DeSOx cycle shortening time or the DeSOx time increase count, which is applied to the method of detecting the deterioration of the linox trap catalyst according to an embodiment of the present invention, to a normal cycle or time when the predetermined number of times is more than a predetermined number.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 schematically shows the structure of a linox trap and a diesel particulate filter applied to a deterioration detecting method of a linox trap catalyst according to an embodiment of the present invention. Referring to FIG. As shown in FIG. 1, the LNT catalyst and the DPF system applied to the method of detecting the deterioration of the linox trap catalyst according to an embodiment of the present invention include an engine, an LNT catalyst, and a DPF, 1 temperature sensor 100 and a first lambda sensor 200. A second temperature sensor 110 is installed between the LNT catalyst and the DPF and a second lambda sensor 210 is installed downstream of the DPF Thereby measuring the temperature and oxygen concentration at each site.

FIG. 2 shows the front and rear lambda signals according to the steady state and deterioration state of the Linnox trap catalyst represented by the system of FIG. As shown in FIG. 2 (a), signals of the first lambda sensor 200 and the second lambda sensor 210 can be known during DeNOx of the normal LNT catalyst. Here, if the lambda value difference between the first lambda sensor 200 and the second lambda sensor 210 is less than a predetermined value (e.g., 0.04), the execution of DeNOx may be terminated preferentially.

2 (a), the time taken until the lambda values of the first lambda sensor 200 and the second lambda sensor 210 become equal due to the consumption of oxygen occluded in the LNT catalyst over a certain level is 8.7 And this time is proportional to the OSC (oxidation storage capacity) performance of the LNT catalyst, and the OSC performance is a deterioration index of the LNT catalyst.

The OSC performance is determined by the heat and sulfur poisoning levels applied to the LNT catalyst. That is, as shown in FIG. 2 (b), the LNT catalyst is deteriorated by sulfur poisoning, and the time required for the first lambda sensor 200 and the second lambda sensor 210 to have the same lambda value is 4 seconds. That is, 4.7 seconds less than the normal LNT catalyst, the normal LNT catalyst uses 10 ppm sulfur fuel, and the abnormal LNT catalyst uses 100 ppm sulfur fuel.

Therefore, it can be seen that the LNT rich time is shortened by sulfur poisoning. At this time, since the poisoning is caused by the high concentration of sulfur, the amount of NOx storage is reduced and the control time of the rich is also shortened, so that the NOx purification performance of the LNT catalyst is drastically reduced. Further, it is determined that the rich control time is reduced due to the sulfur poisoning based on the time required for the lambda value of the first lambda sensor 200 and the second lambda sensor 210 to become equal to each other as described above. do.

FIG. 3 is a flowchart illustrating DeSOx time control applied to a method of detecting detoxification of a Linnox trap catalyst according to an embodiment of the present invention, and FIG. 4 is a graph illustrating a state in which DeSOx execution time is controlled by FIG.

As shown in FIG. 3 and FIG. 4, the standard time required for the lambda values of the first and second lambda sensors on the upstream and downstream sides of the LNT catalyst to be equal to each other in the state that the LNT catalyst is not deteriorated at the time of performing DeNOx is set at step S100.

Then, it is determined whether the difference between the time required for the lambda value of the first and second lambda sensors to become the same in the current LNT catalyst and the reference time is higher than the preset required time (S110). Here, the time taken for the measured values from the first and second lambda sensors 200 and 210 to be equal in the normal condition (when the catalyst is not significantly deteriorated) varies depending on the catalyst volume and the aging state, 12 seconds appear.

If it is determined that the difference is greater than the preset required time, the DeSOx execution time increasing step is performed to increase the DeSOx execution time by the execution time increase / decrease constant at step S120. May be set based on experimental values such that the execution time increasing and decreasing constants a and c are mutually proportional.

If it is determined that the difference is less than the preset required time (a) in the elapsed time determination step, the elapsed time determination step (S110) is performed again.

Therefore, when the time required for the measured values from the first and second lambda sensors 200 and 210 at the time of performing the present DeNOx is shortened, the DeSOx regeneration time is increased by increasing the regeneration time by a constant c, Performance can be enhanced.

On the other hand, in the step of increasing the DeSOx performance time, the time required for the lambda value of the first and second lambda sensors to be equal in the present LNT catalyst immediately after DeSOx is performed is measured and it is re-judged whether the required time is higher than the reference time ). Here, Ra means the time required for the lambda values of the first and second lambda sensors 200 and 210 to become equal to each other at the time of DeNOx immediately after DeSOx.

If the required time is higher than the reference time in the required time re-determination step, the DeSOx execution time increasing step may be performed again (S131).

If the required time is less than the reference time, the DeSOx execution time is restored to the initial DeSOx time (S132). That is, if the required time is less than the reference time in the re-determining time after DeSOx, it means that the toxic toxicity is removed by DeSOx and the catalytic activity is restored, so that the regeneration cycle is restored to the normal DeSOx time.

FIG. 5 is a flowchart illustrating a DeSOx periodic control applied to a method for detecting deterioration of a Linnox trap catalyst according to an embodiment of the present invention, and FIG. 6 is a graph illustrating a state in which the DeSOx period is controlled by FIG. As shown in FIGS. 5 and 6, the reference time required for the lambda values of the first and second lambda sensors 200 and 210 on the upstream and downstream sides of the LNT catalyst to be identical in a state where the LNT catalyst is not deteriorated is set (S200) .

Then, the time from the rich control start time for DeNOx to the time tr required until the lambda values of the first and second lambda sensors 200 and 210 become equal is calculated. At this time, the difference between the lambda values of the first and second lambda sensors 200 and 210 may be added (S210). Also, the tr is variable depending on the volume and aging state of the LNT catalyst, for example, 5 to 10 seconds.

In step S220, it is determined whether the difference between the time required for the lambda values of the first and second lambda sensors 200 and 210 to be the same in the current LNT catalyst and the reference time is higher than the preset required time a. Here,? Base is the time required for the lambda values of the first and second lambda sensors 200 and 210 to become the same in the case where the base lambda is not seriously deteriorated,? B is the lambda value of the first and second lambda sensors 200 and 210 The sum of the lambda value differences of the first and second lambda sensors 200 and 210 is equal to the time required for the values to become the same.

If it is determined in step S220 that the difference value is higher than the preset required time (a), the DeSOx execution cycle decreasing step is performed to reduce the DeSOx execution cycle by a cycle increment / decrement constant (S230). Here, satisfying Δbase-Δb> a means that the deterioration of the catalyst in the current condition has progressed.

If it is determined in the elapsed time determination step S220 that the difference value is less than the preset required time, the elapsed time determination step S220 is performed again.

Then, in the step of decreasing the DeSOx performance period (S230), the time (Delta a) required for the lambda values of the first and second lambda sensors 200 and 210 to be equal in the LNT catalyst immediately after DeSOx is measured is measured, And judges whether or not the time is higher than the reference time. Here, Δa is the sum of the lambda value differences of the first and second lambda sensors 200 and 210 until the time required for the lambda values of the first and second lambda sensors 200 and 210 to become the same immediately after DeSOx, will be.

If the required time is higher than the reference time, the DeSOx execution time reducing step is performed again by repeating the DeSOx execution cycle decreasing step by multiplying the required time by an arbitrary constant b (S241)

If the required time is less than the reference time, the DeSOx execution period is restored to the initial DeSOx execution period I (S242).

That is, FIG. 7 is a flowchart showing the restoration of the DeSOx cycle shortening time or the DeSOx time increase count applied to the method of detecting the deterioration of the Linnox trap catalyst according to an embodiment of the present invention to a normal cycle or time, As shown in FIG. 7, the execution count is accumulated every time the DeSOx execution time increasing step and the DeSOx execution cycle decreasing step are performed.

A DeSOx performance control time determination step of determining whether the number of times of execution is higher than a predefined number of times of execution, and if the number of times of execution is higher than the predetermined execution number, performing the DeSOx execution cycle or DeSOx execution time, If the number of times of execution is less than the preset number of times of execution, the DeSOx execution control determination step is repeated.

That is, after DeSOx, as shown in FIG. 3 and FIG. 5, when Rbase-Ra> a or Δbase-Δa> a, the time required for the lambda values of the first and second lambda sensors 200 and 210 to become equal due to sulfur poisoning It can be judged that permanent deterioration such as heat has occurred. Therefore, it is necessary to perform a step of restoring to a normal deSOx execution time t or a normal DeSOx period I.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

100: first temperature sensor
110: second temperature sensor
200: 1st lambda sensor
210: second lambda sensor

Claims (10)

A reference time setting step of setting a reference time required for the lambda values of the first and second lambda sensors before and after the LNT catalyst to become equal in a state where the LNT catalyst is not deteriorated;
Determining whether the difference between the time required for the lambda value of the first and second lambda sensors to become the same in the current LNT catalyst and the reference time is higher than the preset required time; And
Wherein when the difference value is higher than the preset required time, the DeSOx execution time increase step of increasing the DeSOx execution time by the execution time increase / decrease constant is performed in the elapsed time determination step, and in the elapsed time determination step, And if it is lower than the predetermined time, the step of determining the required time is performed again. The method according to claim 1,
The time required for the lambda value of the first and second lambda sensors to be equal in the present LNT catalyst immediately after the execution of DeSOx is measured in the step of increasing the DeSOx execution time and the time required for judging whether the required time is higher than the reference time step;
Wherein the step of performing the deoxidization step further comprises the step of re-increasing the DeSOx performance time when the required time is higher than the reference time, Way. 3. The method of claim 2,
Wherein the DeSOx execution time is restored to the initial DeSOx time if the required time is less than the reference time in the time re-determination step. The method of claim 3,
And performing DeSOx performance control accumulation step of accumulating the number of times of execution every time the DeSOx performance time increase step is performed. 5. The method of claim 4,
Performing a DeSOx performance control number determination step of determining whether the number of performance times is higher than a preset performance number, restoring the DeSOx performance time to an initial DeSOx performance time if the performance number is higher than a preset performance number, Wherein the step of determining the number of times of DeSOx performance control is repeatedly performed when the number of times of performing the DeSOx performance control is less than the number of times of performing the setting. A reference time setting step of setting a reference time required for the lambda values of the first and second lambda sensors before and after the LNT catalyst to become equal in a state where the LNT catalyst is not deteriorated;
Determining whether the difference between the time required for the lambda value of the first and second lambda sensors to become the same in the current LNT catalyst and the reference time is higher than the preset required time; And
Wherein when the difference value is higher than the preset required time, the DeSOx execution period decreasing step of decreasing the DeSOx execution period by a period increase / decrease constant is performed in the elapsed time determination step, And if the temperature is lower than the predetermined temperature, the step of determining the required time is performed again. The method according to claim 6,
The time required for the lambda value of the first and second lambda sensors to become the same in the LNT catalyst immediately after the execution of DeSOx is measured in the step of decreasing the DeSOx performance period and the time required for judging whether the required time is higher than the reference time step;
And if the required time is longer than the reference time, performing the DeSOx execution cycle reducing step to perform the DeSOx execution cycle decreasing step again. 8. The method of claim 7,
Wherein when the required time is less than the reference time, the DeSOx execution cycle is restored to the initial DeSOx execution cycle. 9. The method of claim 8,
And performing a DeSOx performance control accumulation step of accumulating the number of times of execution every time the DeSOx performance period decreasing step is performed. 10. The method of claim 9,
Performing a DeSOx execution control determination step of determining whether the execution number is higher than a predetermined execution number, restoring the DeSOx execution period to an initial DeSOx execution period when the execution number is higher than a predetermined execution number, Wherein the step of determining the number of times of DeSOx performance control is repeatedly performed.

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