Procedure for the regeneration of a particle filter and for the desulphurization of an NOx storage catalytic converter

Abstract

The invention concerns a procedure for the regeneration of a particle filter and the desulfurization of a NOx storage catalytic converter in an exhaust gas aftertreatment system of an internal combustion engine; whereby for the regeneration of the particle filter in contrast to a normal operation, the temperature of the particle filter is raised in at least one mode of operation “DPF-heating” and whereby for the desulfurization of the NOx storage catalytic converter, the NOx storage catalytic converter is heated up in at least one mode of operation “NOx storage cat heating” (λ≧1); and in a subsequent mode of operation “NOx storage cat desulfurize”, a Lambda value of λ<1 is set in the exhaust gas; whereby in the case of a regeneration request for the particle filter or in the case of a desulfurization request for the NOx storage catalytic converter, a combined complete or partial regeneration of the particle filter as well as a desulfurization of the NOx storage catalytic converter is initiated. The necessary heating energy and with it the associated fuel consumption can thereby be significantly reduced. Furthermore, an increase in efficiency of the NOx storage catalytic converter results, because the average sulfur absorption is reduced on account of the greater frequency of the desulflurization phases. In so doing, the NOx emissions after the NOx storage catalytic converter can further be reduced.

Description

SHORT DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below using the examples of embodiment depicted in the figures. The following are shown:

FIG. 1 a schematic depiction of an internal combustion engine with an exhaust gas aftertreatment system as an example of application of the procedure,

FIG. 2 the chronological temperature progression in a particle filter and in a NO_x storage catalytic converter,

FIG. 3 the chronological progression for various modes of operation,

FIG. 4 the chronological progression of a mass of sooty particles in the particle filter and

FIG. 5 the chronological progression of a mass of sulfur in the NO_x storage catalytic converter.

FORMS OF EMBODIMENT OF THE INVENTION

FIG. 1 shows a technical layout as an example, in which the procedure according to the invention is operating. In the figure, an internal combustion engine 1, consisting of an engine block 40 and an incoming air duct 10, which provides the engine block 40 with combustion air, is depicted, whereby the amount of air in the incoming air duct 10 can be determined using an incoming air measurement device 20. The exhaust gas of the internal combustion engine 1 is carried in the depiction by way of an emission control system, which has an exhaust gas duct 50 as its main component. A particle filter 70 (DPF) and subsequently a NO_x storage catalytic converter 90 are disposed in the exhaust gas duct 50 in the direction of flow. Provision is additionally made on the engine block 40 for a fuel metering mechanism 30 in the form of a diesel injection system, which is controlled in a closed-loop, respectively actuated, by way of an engine control unit 110. In similar technical layouts, the NO_x storage catalytic converter 90 (NSC) can also be disposed in front of the particle filter 70 (DPF). Furthermore, combinations with an OSC (Oxygen Storage Catalyst), NSC and with a DPF are conceivable. Any mixtures with multiple components of the same type (for example: NSC1, DPF, NSC2, . . . ) are likewise possible.

The closed-loop control of a work mode of the internal combustion engine 1 can result using selected operating parameters. It is therefore conceivable to determine a composition of the exhaust gas by means of Lambda probes 60 and/or NO_x sensors 100 disposed in the exhaust gas duct 50. An exhaust gas temperature can, for example, be additionally determined in the area of the emission control system, for example between the particle filter 70 and the NO_x storage catalytic converter 90 by means of one or several temperature probes 80. From the signals of the different probes 60, 80, 100, which are connected to the engine control unit 110, as well as from the data of the incoming air measurement device 20, the mixture can be calculated and the fuel metering mechanism 30 can be correspondingly actuated to meter the fuel.

Provision is made in the procedure according to the invention for the regeneration of the particle filter 70 as well as the desulfurization of the NO_x storage catalytic converter 90, in that in the case of a regeneration request for the particle filter 70 or a desulfurization request for the NO_x storage catalytic converter 90, a combined regeneration of the particle filter 70 as well as the NO_x storage catalytic converter 90 is initiated. A desulfurization request can, for example, be initiated in the case of an improper fueling or in the case of the diesel fuel containing a high content of sulfur.

Initially the particle filter 70 starting from the normal operation 141 in a mode of operation “DPF-heating” 142 is heated up to the temperature (for example 550 to 650° C.) required for regeneration, and it is maintained at this temperature by a temperature regulator. After a threshold for sooty particles has been undershot during the DPF-regeneration (regeneration of the particle filter 70), the operation is switched to the mode of operation “NO_x storage cat heating” 143; and a new set point temperature (for example 600 to 750° C.) is specified, whereby in order to avoid temperature spikes before switching to the mode of operation “NO_x storage cat heating” 143, conditions for this new set point temperature are tested. During the mode of operation “NO_x storage cat heating” 143, a Lambda value of λ>1 is set in the exhaust gas. If sooty particles are still present in the particle filter 70, burnout is consequently also continued during this phase.

After the new set point temperature has been achieved, changeover occurs between the mode of operation “NO_x storage cat heating” 143 and the mode of operation “NO_x storage cat desulfurize” 144, whereby the changeover alternating between the mode of operation “NO_x storage cat heating” 143 and the mode of operation “NO_x storage cat desulfurize” 144 is specified (typically for, for example, 10 s at a time).

The conditions for a completion of the desulfurization can be different according to the subsequent list, whereby these can also be deployed in combination. The desulfurization can be terminated, if

• • a firmly established time period for the desulfurization is achieved and/or
  • the degree of efficiency of the desulfurization decreases after the particle filter 70 has been regenerated and/or
  • a firmly established threshold value for the sulfur content in the NO_x storage catalytic converter 90 is undershot after the particle filter 70 has been regenerated and/or
  • a firmly established accumulated time period for the desulfurization is exceeded after the particle filter 70 has been regenerated.

Provision is furthermore made in the procedure according to the invention for the desulfurization phase to be terminated and the “DPF-heating” 142 to be continued when a firmly established threshold value for the sulfur content in the NO_x storage catalytic converter 90 has been undershot, and the regeneration of the particle filter 70 has not been completely concluded.

FIG. 2 shows as an example the progression for the temperatures (° C.) in the NO_x storage catalytic converter 90 (NSC-temperature 131) and in the particle filter 70 (DPF-temperature 132) as a function of time 120 (minutes).

In FIG. 3 the various modes of operation 140 are plotted in their chronological sequence, as previously described.

FIG. 4 and FIG. 5 show the progression of the mass of sooty particles 150 (g) in the particle filter 70 as well as that of a mass of sulfur 160 (g) in the NO_x storage catalytic converter 90 as a function of time 120 (minutes).

As can be recognized in FIG. 2, the temperature in the particle filter 70 and in the NO_x storage catalytic converter 90 initially rise above 500° C. on account of the changeover to the mode of operation “DPF-heating” 142. After achieving this optimal temperature for the burnout of the sooty particles, the burnout of the sooty particles begins, which makes itself known by the reduction of the mass of sooty particles 150 in FIG. 4. A status “Particle filter empty” 151 is achieved, if the mass of sooty particles 150 has achieved a certain threshold value (here for example 5 g). Already before this point in time, the operation has been switched over to the mode of operation “NO_x storage cat heating” 143. During this mode of operation, an additional burnout of sooty particles is registered. Only with the repeatedly occurring changeover to the mode of operation “NO_x storage cat desulfurize” 144, a significant decrease in the mass of sulfur 160 occurs in the NO_x storage catalytic converter 90.

With the indicated procedure the necessary heating energy and with it the associated fuel consumption can be significantly reduced. Furthermore, an increase in efficiency of the NO_x storage catalytic converter 90 results, because the average sulfur absorption is reduced by the greater frequency of the desulfurization phases, whereby the NO_x emissions after the NO_x storage catalytic converter 90 can further be reduced.

Claims

1. Procedure for the regeneration of a particle filter (70) and for the desulfurization of a NOx storage catalytic converter (90) in an exhaust gas aftertreatment system of an internal combustion engine (1), whereby for the regeneration of the particle filter (70) in contrast to a normal operation (141), the temperature of the particle filter (70) is raised in at least one mode of operation “DPF-heating” (142) and whereby for the desulfurization of the NOx storage catalytic converter (90), the NOx storage catalytic converter (90) is heated up in at least one mode of operation “NOx storage cat heating” (143) (λ≧1); and in a subsequent mode of operation “NOx storage cat desulfurize” (144), a Lambda value of λ<1 is set in the exhaust gas, is thereby characterized, in that when a regeneration is requested for the particle filter (70) or a desulfurization is requested for the NOx storage catalytic converter, a combined complete or partial regeneration of the particle filter (70) as well as a desulflurization of the NOx storage catalytic converter (90) is initiated.

2. Procedure according to claim 1 is thereby characterized; in that initially starting from the normal operation (141) in a mode of operation “DPF-heating” (142), the particle filter (70) is heated up to the temperature required for regeneration and is maintained at this temperature by means of a temperature regulator.

3. Procedure according to claim 1 or 2 is thereby characterized, in that after or during the mode of operation “DPF-heating” (142), the operation is switched to the mode of operation “NOx storage cat heating” (143), and a new set point temperature is specified.

4. Procedure according to claim 3 is thereby characterized, in that conditions for the new set point temperature are tested before switching to the mode of operation “NOx storage cat heating” (143).

5. Procedure according to claim 3 is thereby characterized; in that during the mode of operation “NOx storage cat heating” (143), a Lambda value of λ>1 is set in the exhaust gas.

6. Procedure according to one of the claims 1 to 5 is thereby characterized; in that after the achievement of the new set point temperature, an operational changeover is made between the mode of operation “NOx storage cat heating” (143) and the mode of operation “NOx storage cat desulflurize”.

7. Procedure according to claim 6 is thereby characterized, in that the changeover between the mode of operation “NOx storage cat heating” (143) and the mode of operation “NOx storage cat desulfurize” (144) is specified alternately for certain time intervals, which, for example, can depend on the operating point of the internal combustion engine (1) or the conditions of the NOx storage catalytic converter (90).

8. Procedure according to one of the claims 1 to 7 is thereby characterized, in that the time period of the desulflurization is firmly established and is terminated after the expiration of this time.

9. Procedure according to one of the claims 1 to 7 is thereby characterized, in that the desulfurization phase is terminated when the particle filter (70) is completely or partially regenerated and when the degree of efficiency of the desulfurization decreases.

10. Procedure according to one of the claims 1 to 7 is thereby characterized; in that the desulfurization phase is terminated, when the particle filter (70) is completely or partially regenerated and when a firmly established threshold value for the sulfur content in the NOx storage catalytic converter (90) is undershot.

11. Procedure according to one of the claims 1 to 7 is thereby characterized; in that the desulfurization phase is terminated, when the particle filter (70) is completely or partially regenerated and when a firmly established accumulated time period for the desulfurization is achieved.

12. Procedure according to one of the claims 8 to 11 is thereby characterized, in that the conditions for a termination of the desulfurization phase are combined.

13. Procedure according to one of the claims 1 to 12 is thereby characterized; in that the desulflurization phase is terminated and the mode of operation “DPF-heating” (142) is continued, when a firmly established threshold value for the sulfur content in the NOx storage catalytic converter (90) is undershot and when the regeneration of the particle filter (70) is still not completely concluded.