# US 10,865,679 B2 · Method for operating an exhaust after-treatment system comprising an SCR-catalyst

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- Number: US 10,865,679 B2
- Document ID: US10865679B2
- Status: Granted
- Kind: B2
- Application number: 15/742,789
- Filed: 2016-06-28
- Published: 2018-07-19
- Granted: 2020-12-15
- Earliest claimed: 2015-07-07
- Assignees: MTU Friedrichshafen GmbH
- Applicants: Mtu Friedrichshafen GmbH
- Inventors: Klaus Rusch; Jörg Remele; Jens Niemeyer
- Web page: https://patentgrep.com/patent/US10865679B2

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- F01N 11/00: Monitoring or diagnostic devices for exhaust-gas treatment apparatus
- F01N 2550/02: Catalytic activity of catalytic converters
- F01N 2560/026: for measuring or detecting NOx
- F01N 2590/02: for marine vessels or naval applications
- F01N 2590/08: for heavy duty applications, e.g. trucks, buses, tractors, locomotives
- F01N 2590/10: for stationary applications
- F01N 2610/02: the substance being ammonia or urea
- F01N 2900/0402: using adaptive learning
- Y02T 10/12: Improving ICE efficiencies
- Y02T 10/40: Engine management systems
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method for operating an exhaust after-treatment system including an SCR-catalyst, a metering device for dosing a reducing agent being controlled on the basis of a determining variable that influences a nitrogen-oxide concentration downstream of the SCR-catalyst. A breakthrough identification is carried out for the SCR-catalyst, wherein if a breakthrough is identified, the determining variable is altered to a higher nitrogen-oxide concentration downstream of the SCR-catalyst and the metering device is controlled in order to dose the reducing agent on the basis of the altered determining variable.

## Claims

### Claim 1

A method of operating an exhaust gas aftertreatment system comprising an SCR catalyst, the method comprising the steps of:
Actuating a dosage unit for dosage of a reducing agent based on a determining parameter that affects a nitrogen oxide concentration downstream of the SCR catalyst;
Conducting breakthrough recognition for the SCR catalyst;
Changing the determining parameter, when a breakthrough is recognized, toward higher nitrogen oxide concentration downstream of the SCR catalyst; and
actuating the dosage unit for dosage of reducing agent based on the changed determining parameter.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the SCR catalyst in operation is monitored permanently for a breakthrough.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the determining parameter is a target nitrogen oxide concentration downstream of the SCR catalyst, wherein the determining parameter is changed by recalculating the determining parameter based on an adaptation parameter that is a predetermined nitrogen oxide conversion rate of the SCR catalyst, wherein
the adaptation parameter is equal to a predetermined inertial value when an actual nitrogen oxide concentration downstream of the SCR catalyst is equal to the determining parameter, wherein
a decrease in the adaptation parameter leads to an increase in the determining parameter, wherein
the adaptation parameter is reduced when a breakthrough is recognized.

### Claim 4 (depends on 3)

The method according to claim 3, including determining the adaptation parameter over a specific adaptation period in which the SCR catalyst is in a steady state.

### Claim 5 (depends on 4)

The method according to claim 4, including changing the adaptation parameter in the specific adaptation period incrementally toward higher nitrogen oxide concentration downstream of the SCR catalyst when a breakthrough is recognized, wherein the change in the adaptation parameter is ended when no breakthrough is recognized any longer.

### Claim 6 (depends on 4)

The method according to claim 4, including changing the adaptation parameter in the specific adaptation period incrementally toward lower nitrogen oxide concentration downstream of the SCR catalyst when no breakthrough is recognized and the adaptation parameter is not equal to the predetermined inertial value, wherein the change is ended as soon as the adaptation parameter is equal to the predetermined inertial value, or as soon as a breakthrough is recognized, wherein, when a breakthrough is recognized, a last alteration increment is reversed again.

### Claim 7 (depends on 4)

The method according to claim 4, wherein, when the adaptation parameter is equal to the predetermined inertial value, the adaptation parameter in the specific adaptation period is kept equal to the predetermined inertial value when no breakthrough is recognized.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the determining parameter is a target nitrogen oxide concentration downstream of the SCR catalyst, wherein
the change in the determining parameter is conducted by arithmetic combination of the determining parameter with an adaptation parameter that is a predetermined differential nitrogen oxide concentration, wherein
the adaptation parameter is equal to a predetermined inertial value when an actual nitrogen oxide concentration downstream of the SCR catalyst is equal to the determining parameter, wherein
an increase in the adaptation parameter leads to an increase in the determining parameter, wherein
the adaptation parameter is increased when a breakthrough is recognized.

### Claim 9 (depends on 1)

The method according to claim 1, including generating a warning signal and/or initiating a reduction in a nitrogen oxide concentration upstream of the SCR catalyst on attainment or exceedance of a limit in the adaptation parameter or in the actual nitrogen oxide concentration downstream of the SCR catalyst.

### Claim 10 (depends on 1)

The method according to claim 1, including recording data for determination of the adaptation parameter in a overwritable characteristic map during a first adaptation period, wherein the data are provided in a second adaptation period, wherein the second adaptation period follows after the first adaptation period in time.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the overwritable characteristic map is not written with data in predetermined states of operation of the exhaust gas aftertreatment system or units operatively connected thereto.

### Claim 12

An exhaust gas aftertreatment system, comprising:
an SCR catalyst;
a dosage unit; and
a control unit comprising:
a steady state recognition element;
a characteristic map containing predetermined, fixed target values for a nitrogen oxide concentration downstream of the SCR catalyst;
a closed-loop emission control element configured to actuate a dosage unit for dosage of a reducing agent based on a determining parameter from the characteristic map that affects a nitrogen oxide concentration downstream of the SCR catalyst;
a breakthrough recognition element configured to conduct recognition of breakthrough for the SCR catalyst, and, when a breakthrough is recognized, to change the determining parameter toward higher nitrogen oxide concentration downstream of the SCR catalyst;
a calculation element connected to receive inputs from the breakthrough recognition element and the steady-state recognition element; and,
a change element connected to receive inputs from the calculation element and the characteristic map, and connected to output a change parameter to the control element,
wherein the omission control element is configured to actuate the dosage unit for dosage of the reducing agent based on the changed determining parameter.

### Claim 13 (depends on 12)

The exhaust gas aftertreatment system according to claim 12, further comprising an oxidation catalyst connected downstream of the SCR catalyst for prevention of an NH3 emission from the exhaust gas aftertreatment system.