KR20110030972A - Method for disel oxidation catalyst desulfurization - Google Patents

Abstract

PURPOSE: A method for diesel oxidation catalyst desulfurization is provided to perform desulfurization without an excessive quantity of metal material by additional supplying fuel after comparing catalyst backend temperature and catalyst shear temperature. CONSTITUTION: A method for diesel oxidation catalyst desulfurization comprises the next step. The temperature of a catalyst backend is monitored(S10). The catalyst backend temperature and engine supply exhaust gas temperature are compared. The monitored temperature and the temperature of catalyst shear are compared(S21,S22). The temperature of the catalyst shear is increased by additional supplying fuel in order for desulfurization(S31,S32,S33).

Description

Method for Disel Oxidation Catalyst desulfurization

The present invention relates to a diesel oxidation catalyst. More particularly, the present invention relates to a desulfurization method of a diesel oxidation catalyst which effectively desulfurizes poisoned sulfur in a diesel oxidation catalyst without using a large amount of precious metal catalyst.

In general, the exhaust gas discharged from the engine through the exhaust manifold is guided to a catalytic converter formed in the middle of the exhaust pipe and purified, and the noise is attenuated while passing through the muffler and then released into the atmosphere through the tail pipe. The catalytic converter is a type of diesel particulate filter (DPF) to treat pollutants contained in the exhaust gas. In addition, a catalyst carrier for trapping particulate matter (PM) included in the exhaust gas is formed inside the catalytic converter to purify various exhaust gases discharged from the engine through a chemical conversion process.

One type of catalyst applied to the catalytic converter which plays such a role is Diesel Oxidation Catalyst (DOC). Diesel oxidation catalysts oxidize the hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas.

On the other hand, since the sulfur component contained in the fuel lowers the performance of the oxidation catalyst, an oxidation catalyst coated with a platinum (Pt) having strong sulfur resistance is mainly used in diesel oxidation catalysts. However, platinum has a problem in that manufacturing cost increases when only platinum is coated as a precious metal, and thus, an oxidation catalyst coated with platinum and palladium (Pd) is used.

However, the catalyst coated with platinum and palladium has a problem in that the activity of the oxidation catalyst by sulfur is deteriorated and the catalyst is deteriorated. In order to prevent deterioration of the catalyst by sulfur poisoning, coating a large amount of platinum increases production costs. There is a problem.

Therefore, the present invention has been invented to solve this problem, to provide a desulfurization method of the diesel oxidation catalyst that can be desulfurized without using an excess of precious metal to prevent catalyst deterioration by sulfur poisoning. The purpose is.

The present invention includes a temperature monitoring step of monitoring the temperature of the rear end of the catalyst; A step of determining whether or not sulfur poisoning is determined by comparing the monitored temperature with the catalyst shear temperature; And a desulfurization step of performing desulfurization by increasing the temperature of the front end of the catalyst by additionally supplying fuel when it is determined that the sulfur poisoning is determined as a result of the sulfur poisoning determination step.

The step of determining whether the poisoning poison, if the temperature of the rear end of the catalyst is less than the temperature of the front end of the catalyst may be determined as sulfur poisoning.

The desulfurization method of the diesel oxidation catalyst may further include a catalyst activity determination step of determining whether or not the activity of the catalyst is restored by monitoring the temperature of the rear end of the catalyst at the time when desulfurization is completed after the desulfurization step.

The catalyst activity determination step may be determined as the catalytic activity when the temperature monitored after the desulfurization step is higher than the temperature of the front end of the catalyst, it may be determined that the catalyst is deteriorated.

The additional supply of the fuel is carried out through post-fuel injection or secondary injection so that the temperature of the front end of the catalyst is raised to a predetermined temperature, and the additional supply of the fuel may be performed for a predetermined time.

The temperature monitoring step may be to monitor the temperature through a temperature sensor mounted to the rear end of the oxidation catalyst.

On the other hand, the step of examining whether the temperature of the cooling water is above the reference temperature; Calculating a shear temperature of a catalyst corresponding to the coolant temperature and an operating condition based on previously prepared modeling data when the coolant temperature becomes higher than a reference temperature; A temperature monitoring step of monitoring a temperature at the rear of the catalyst; A sulfur poisoning determination step of determining whether or not sulfur poisoning is performed by comparing a difference between the temperature of the rear end of the catalyst and the shear temperature of the catalyst; And a desulfurization step of performing desulfurization by increasing the temperature of the front end of the catalyst by additionally supplying fuel when it is determined that the sulfur poisoning is determined as a result of the sulfur poisoning determination step.

The determination of whether or not sulfur poisoning may be determined as sulfur poisoning when the temperature difference between the temperature of the rear end of the catalyst and the front end of the catalyst is smaller than a first predetermined reference value.

The desulfurization method of the diesel oxidation catalyst may further include a catalyst activity determination step of determining whether or not the activity of the catalyst is restored by monitoring the temperature of the rear end of the catalyst at the time when desulfurization is completed after the desulfurization step.

The catalyst activity determination step may be determined as a catalyst activity when the difference value between the monitored catalyst rear end temperature and the catalyst front end temperature after the desulfurization step is larger than a second predetermined reference value, and when the catalyst activity decreases, the catalyst deterioration.

According to the desulfurization method of the diesel oxidation catalyst of the present invention, it is possible to perform desulfurization without using excess precious metal, and to determine whether the catalyst caused by sulfur poisoning is activated or deteriorated by monitoring the temperature after the catalyst after desulfurization. .

The present invention includes a temperature monitoring step of monitoring the temperature of the rear end of the catalyst; A step of determining whether or not sulfur poisoning is determined by comparing the monitored temperature with the temperature of the front end of the catalyst; And a desulfurization step of performing desulfurization by increasing the temperature of the front end of the catalyst by additionally supplying fuel when it is determined that the sulfur poisoning is determined as a result of the sulfur poisoning determination step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a layout diagram of a diesel oxidation catalyst apparatus to which the desulfurization method of the present invention is applied, and FIG. 2 is a schematic step diagram according to an embodiment of the desulfurization method of the diesel oxidation catalyst of the present invention, and FIG. 4 is a detailed flowchart of each step, and FIG. 4 is a graph of temperature and time of the rear end of the catalyst according to sulfur poisoning.

As shown in FIG. 1, a diesel oxidation catalyst apparatus (hereinafter, a catalyst) for applying the desulfurization method of the diesel oxidation catalyst of the present invention is connected to an exhaust pipe located at the rear end of the engine 10, and the catalyst 20 At the rear end of the catalyst 20 is installed a temperature sensor for temperature measurement to monitor the temperature of the rear end.

Here, the thermocouple 30 may be used as the temperature sensor. As is well known, the thermocouple is a device made of two kinds of metals for measuring a wide range of temperature using the Seebeck effect. Mainly used to measure the temperature in power plants, steel mills, etc., it is useful for measuring the rear end temperature of the catalyst 20 in a high-temperature atmosphere state because it is widely used in extreme conditions with good durability. Of course, the temperature sensor is not limited to thermocouples and various sensors can be used.

As shown in FIG. 2, the desulfurization method of the diesel oxidation catalyst according to the exemplary embodiment of the present invention includes a temperature monitoring step (S10) of monitoring a temperature of the rear end of the catalyst 20, and the monitored temperature and the engine 10. If it is determined as a result of the sulfur poisoning determination step (S20) and the sulfur poisoning determination step (S20) by comparing the temperature of the catalyst shearing step (S20) and the post-injection or secondary fuel Desulfurization step (S30) of performing desulfurization by raising the temperature of the front end of the catalyst 20 by performing additional supply of fuel such as injection, and catalyst activity determination step of determining whether the catalyst 20 is activated by desulfurization. It may be made, including (S40).

As shown in FIG. 3, the temperature monitoring step S10 monitors the temperature of the rear end of the catalyst 20 by measuring the temperature of the rear end of the catalyst 20 in real time through a thermocouple 30 installed at the rear end of the catalyst 20. do.

The sulfur poisoning determination step (S20) is a step of determining whether the catalyst 20 is in a poisoned state, the temperature of the rear end of the catalyst 20 and the catalyst 20 measured from the temperature monitoring step (S10) ) The temperature of the shear is compared (S21).

And if the temperature of the rear end of the catalyst 20 is less than the temperature of the front end of the catalyst 20 is determined as sulfur poisoning (S21), if the temperature of the rear end of the catalyst 20 is higher than the temperature of the front end of the catalyst 20 Can be determined to be non-poisonous.

If it is determined that the catalyst 20 is sulfur poisoning, the catalyst 20 is deactivated to oxidize oxidizing exhaust gas. The deactivation of the catalyst 20 by sulfur changes depending on the vehicle driving conditions, such as when sulfur poisoning increases at low speed (when the catalyst is low temperature).

In general, deactivation of the catalyst occurs due to heat in the case of high temperature running of the vehicle and sulfur poisoning in the case of low temperature driving, so that the oxidation capacity is reduced. Here, the heat deactivation phenomenon is irreversible, so that the catalyst does not recover activity when damaged by heat, but the deactivation phenomenon by sulfur poisoning is reversible, and the activity of the catalyst is restored when exposed at a high temperature for a predetermined time.

When sulfur poisoning is generated, it is necessary to perform desulfurization in order to improve the oxidation performance of the catalyst 20. The desulfurization step (S30) of the present invention is performed after fuel so that the temperature of the front end of the catalyst 20 can be raised to a predetermined target temperature. Injection or secondary injection is performed (S31) to further supply fuel to restore the deactivated catalyst 20 to the active state, thereby improving the oxidizing ability of the catalyst 20.

On the other hand, the post-fuel injection (S31) is an example of the additional supply of fuel for desulfurization in the present invention is made for a predetermined time, for example, it can be maintained for 10 minutes while the target temperature is 500 ℃ or more. Then, it is determined whether or not the temperature of the front end of the catalyst 20 becomes higher than the set target temperature while the fuel injection is in progress (S32).

That is, if the temperature of the front end of the catalyst 20 does not reach the set target temperature, the fuel post-injection is performed until the target temperature is reached, and if the target temperature is higher than the target temperature, it is determined whether the target holding time has been reached (S33). (S31) can be made.

Here, the first few minutes of the target holding time is used to maintain a high temperature for desulfurization, and the remaining minutes are used to determine the activation of the catalyst 20 by monitoring the temperature of the rear end of the catalyst 20.

After the desulfurization step (S30), at the time when desulfurization is completed, the temperature of the rear end of the catalyst 20 is monitored to determine whether the activity of the catalyst 20 is restored, that is, whether the catalyst 20 that has been deactivated is activated or deteriorated. The determining catalyst activity determining step (S40) is performed.

As shown in the graph of FIG. 5, the catalyst activity determination step (S40) may monitor whether or not the activity of the catalyst 20 is restored or not by monitoring the temperature of the rear end of the catalyst 20 at the time when desulfurization is completed. . {Here, (1) is the rear end temperature of the catalyst when the oxidation capacity of the catalyst is normally maintained, (2) is the rear end temperature of the catalyst deteriorated because the oxidation capacity is not restored even after the desulfurization step, and (3) is after the desulfurization step Means the rear temperature of the catalyst that has been activated by oxidizing ability.

That is, the catalyst activity determining step S40 compares the temperature of the rear end of the catalyst 20 monitored after the desulfurization step S30 with the temperature of the front end of the catalyst 2 (S41), and thus the temperature of the rear end of the catalyst 20. Whether or not the engine 10 exceeds the exhaust gas temperature is checked (S42).

Here, when the temperature of the rear end of the catalyst 20 exceeds the front end of the catalyst 20, desulfurization is preferably performed to determine that the catalyst 20 is activated, and when it is less than the catalyst 20, the catalyst 20 is not activated and the catalyst ( 20 may be determined to be degraded.

As described above, according to the desulfurization method of the diesel oxidation catalyst of the present invention, desulfurization can be carried out without using an excess of precious metal, and after desulfurization, by monitoring the temperature at the rear of the catalyst, it is possible to determine whether the catalyst caused by sulfur poisoning is activated or deteriorated. Can be.

Figure 5 is a flow chart according to another embodiment of the desulfurization method of the diesel oxidation catalyst of the present invention, Figure 6 is a graph of the temperature & vehicle speed and time for the front and rear ends of the catalyst, Figure 7 is a region A of FIG. Is an enlarged view. Hereinafter, a desulfurization method of a diesel oxidation catalyst according to another embodiment of the present invention will be described with reference to the accompanying drawings.

The extent to which the catalyst is poisoned by sulfur and deactivated may vary depending on the exhaust system, operating conditions, fuel conditions, etc. In view of this, it is necessary to determine the regeneration point for sulfur poisoning.

In this aspect, when the coolant of the automotive engine 10 has a predetermined temperature, for example, 80 ° C. or more, the catalyst 20 may be determined to be sufficiently warmed up. In this case, the rear end of the catalyst 20 is generally used. It can be seen that the temperature of is higher than the temperature of the front end of the catalyst (20).

If the state where the front end of the catalyst 20 continues to be lower than the rear end when the cooling water reaches a predetermined temperature as described above, the catalyst 20 may be determined to have lost the oxidation ability and thus diagnosed as sulfur poisoning.

Therefore, in this embodiment, it is possible to specify when the coolant reaches a certain reference temperature or more when determining whether or not the catalyst 20 is poisoned.

As shown in FIG. 4, it is determined whether the coolant temperature is equal to or higher than the reference temperature (S101). When the coolant temperature becomes higher than or equal to the reference temperature, the shear temperature of the catalyst 20 depends on the rpm, load, etc. (hereinafter, operating conditions) of the vehicle. To predict the step (S102). That is, the predicted temperature of the front end of the catalyst 20 may be data (1) modeled in advance according to the operating conditions as shown in FIGS. 6 and 7.

When the front end of the catalyst 20 is predicted as described above, the temperature of the rear end of the catalyst 20 is measured. The temperature measurement after the catalyst 20 may be monitored by the thermocouple 30 as in the above-described embodiment.

And the temperature of the rear end of the catalyst 20 may be an average value of the temperature measured for a predetermined time (t), the temperature of the front end of the catalyst 20 may be an average modeling prediction value for a predetermined time (t).

Subsequently, the temperature difference value between the rear end of the catalyst 20 and the front end of the catalyst 20 is calculated, and whether the difference value is smaller than the first reference value is determined to determine whether sulfur poisoning is performed (S120). The first reference value may be predetermined data in consideration of different driving conditions for each vehicle.

If it is determined that the difference value is smaller than the predetermined first reference value, the after-fuel injection (S130) is performed as in the above-described embodiment, and the oxidation performance of the catalyst 20 is decomposed by desulfurization.

Subsequently, after the desulfurization is completed after the post-fuel injection (S130), the temperature of the rear end of the catalyst 20 is monitored again to determine whether or not the activity of the catalyst 20 is restored, that is, whether the catalyst 20 that has been deactivated is deactivated. A catalyst activity determination step of determining whether or not the state is in the activated state is performed.

The catalyst activity determination step (S140), by calculating the difference between the temperature of the catalyst 20, the rear end of the catalyst 20 monitored after the desulfurization step (S130) and the exhaust gas temperature supplied from the engine 10, the difference value is It is checked whether it is smaller than the set second reference value. Here, the second reference value may also be predetermined data in consideration of different driving conditions for each vehicle.

As illustrated in FIG. 7, data may be compared with each other in a certain region of FIG. 6, that is, within a range considering operation conditions such as time (sec) and temperature (° C.) x vehicle speed (mph).

In this case, when the difference is smaller than the second reference value, desulfurization is preferably performed to determine that the catalyst 20 is activated (S140), and when exceeded, the catalyst 20 may not be activated and may be determined to have lost oxidation capacity. .

As described above, according to the desulfurization method of the diesel oxidation catalyst of the present invention, desulfurization can be carried out without using an excess of precious metal, and after desulfurization, by monitoring the temperature at the rear of the catalyst, it is possible to determine whether the catalyst caused by sulfur poisoning is activated or deteriorated. Can be.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

1 is a configuration diagram of a diesel oxidation catalyst apparatus to which the desulfurization method of the present invention is applied.

Figure 2 is a schematic step according to an embodiment of the desulfurization method of the diesel oxidation catalyst of the present invention.

3 is a detailed flowchart of the step of FIG.

4 is a graph of the temperature and time of the rear end of the catalyst according to the poisoning.

5 is a flow chart according to another embodiment of the desulfurization method of the diesel oxidation catalyst of the present invention.

6 is a graph of temperature & vehicle speed and time for the front and rear ends of the catalyst.

FIG. 7 is an enlarged view of area A of FIG. 6; FIG.

<Description of reference numerals for main parts of the drawings>

10: engine 20: diesel oxidation catalyst 30: thermocouple

S10: temperature monitoring step S20: judging whether or not sulfur poisoning

S30 desulfurization step S40: catalytic activity determination step

Claims (10)

A temperature monitoring step of monitoring the temperature at the rear of the catalyst; A step of determining whether or not sulfur poisoning is determined by comparing the monitored temperature with the temperature of the front end of the catalyst; And And a desulfurization step of performing desulfurization by increasing the temperature of the front end of the catalyst by additionally supplying fuel when it is determined that the sulfur poisoning is determined as a result of the sulfur poisoning determination step. The method of claim 1, The determination of whether or not sulfur poisoning, Desulfurization method of a diesel oxidation catalyst, characterized in that determined as sulfur poisoning if the temperature of the rear end of the catalyst is below the temperature of the front end of the catalyst. The method of claim 2, Desulfurization method of the diesel oxidation catalyst, Desulfurization method of the diesel oxidation catalyst characterized in that it further comprises a catalyst activity determination step of determining whether the activity of the catalyst is restored by monitoring the temperature of the rear end of the catalyst at the time when the desulfurization is completed after the desulfurization step. The method of claim 3, The catalytic activity determination step, Desulfurization method of the diesel oxidation catalyst, characterized in that if the temperature monitored after the desulfurization step is higher than the temperature of the front end of the catalyst is determined as the catalytic activity, and if the temperature is lower than the temperature. The method according to any one of claims 1 to 4, The further supply of the fuel is carried out through post-fuel injection or secondary injection so that the temperature of the front end of the catalyst is raised to a predetermined temperature, and the additional supply of the fuel is carried out for a predetermined time. The method according to any one of claims 1 to 4, The temperature monitoring step Desulfurization method of a diesel oxidation catalyst, characterized in that for monitoring the temperature through a temperature sensor mounted to the rear end of the oxidation catalyst. Examining whether the temperature of the cooling water is higher than or equal to the reference temperature; Calculating a shear temperature of a catalyst corresponding to the coolant temperature and an operating condition based on previously prepared modeling data when the coolant temperature becomes higher than a reference temperature; A temperature monitoring step of monitoring a temperature at the rear of the catalyst; A sulfur poisoning determination step of determining whether or not sulfur poisoning is performed by comparing a difference between the temperature of the rear end of the catalyst and the shear temperature of the catalyst; And And a desulfurization step of performing desulfurization by increasing the temperature of the front end of the catalyst by additionally supplying fuel when it is determined that the sulfur poisoning is determined as a result of the sulfur poisoning determination step. The method of claim 7, wherein The desulfurization method of the diesel oxidation catalyst, characterized in that the step of determining whether the sulfur poisoning is determined as sulfur poisoning if the temperature difference between the temperature of the rear end of the catalyst and the front end of the catalyst is smaller than the first reference value. The method of claim 8, Desulfurization method of the diesel oxidation catalyst, Desulfurization method of the diesel oxidation catalyst characterized in that it further comprises a catalyst activity determination step of determining whether the activity of the catalyst is restored by monitoring the temperature of the rear end of the catalyst at the time when the desulfurization is completed after the desulfurization step. 10. The method of claim 9, The catalytic activity determination step, Desulfurization method of the diesel oxidation catalyst, characterized in that if the difference between the temperature of the catalyst after the step of monitoring the catalyst and the temperature of the front end of the catalyst is greater than the second reference value is determined as the catalyst activity, if the difference is smaller, deterioration of the catalyst .

Images