# US 10,480,373 B2 · Techniques for control of an SCR aftertreatment system in response to an ammonia slip condition

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,480,373 B2
- Document ID: US10480373B2
- Status: Granted
- Kind: B2
- Application number: 15/187,061
- Filed: 2016-06-20
- Published: 2016-10-06
- Granted: 2019-11-19
- Earliest claimed: 2014-01-20
- Assignees: Cummins Inc.
- Applicants: Cummins Inc.
- Inventors: Michael Haas
- Web page: https://patentgrep.com/patent/US10480373B2

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- F01N 3/021: by means of filters
- F01N 11/00: Monitoring or diagnostic devices for exhaust-gas treatment apparatus
- F01N 2560/026: for measuring or detecting NOx
- F01N 2610/02: the substance being ammonia or urea
- F01N 2900/1402: Exhaust gas composition
- F01N 2900/1616: NH3-slip from catalyst
- F01N 2900/1621: Catalyst conversion efficiency
- F01N 2900/1812: Flow rate
- Y02T 10/12: Improving ICE efficiencies
- 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

An exhaust aftertreatment system includes a selective catalytic reduction (SCR) catalyst is disposed in an exhaust gas system of an internal combustion engine. A reductant injector is coupled to the exhaust gas stream at a position upstream of the SCR catalyst. A controller is configured to determine an NH3 slip condition and control operation of the exhaust aftertreatment system in response to the NH3 slip condition to improve deNOx efficiency and reduce NH3 slip.

## Claims

### Claim 1

A method, comprising:
operating an internal combustion engine to produce an exhaust gas flow into an exhaust system including a selective catalytic reduction (SCR) catalyst disposed in the exhaust gas flow, the exhaust system including:
a reductant injector coupled to the exhaust system at a position upstream of the SCR catalyst;
a first NOx sensor upstream of the SCR catalyst;
a second NOx sensor downstream of the SCR catalyst;
determining a target deNOx efficiency for the SCR catalyst;
injecting a first amount of reductant into the exhaust gas flow in response to the target deNOx efficiency;
determining a current deNOx efficiency of the SCR catalyst in removing NOx from the exhaust gas flow as a function of a first output from the first NOx sensor and a second output from the second NOx sensor;
determining the current deNOx efficiency is less than the target deNOx efficiency;
detecting an NH3 slip condition;
in response to detecting the NH3 slip condition, determining a temporary target deNOx efficiency for the SCR catalyst; and
injecting a second amount of the reductant in response to the temporary target deNOx efficiency while increasing the temporary target deNOx efficiency toward the target deNOx efficiency until at least one deNOx efficiency adjustment condition is satisfied, wherein the second amount of reductant is less than the first amount of reductant.

### Claim 2 (depends on 1)

The method of claim 1, wherein the second amount of reductant is determined by an ammonia to NOx ratio upstream of the SCR catalyst that achieves the temporary target deNOx efficiency.

### Claim 3 (depends on 1)

The method of claim 1, wherein the current deNOx efficiency of the SCR catalyst is determined by:
current ηSCR=(CNOx,in−CNOx,out)/CNOx,in;
wherein current ηSCR is the current deNOx efficiency of the SCR catalyst, CNox,in is the NOx measurement indicated by the first NOx sensor, and CNOx,out is the NOx measurement indicated by the second NOx sensor.

### Claim 4 (depends on 1)

The method of claim 1, wherein detecting the NH3 slip condition includes determining an NH3 presence in the exhaust gas flow downstream of the SCR catalyst.

### Claim 5 (depends on 1)

The method of claim 1, wherein the exhaust system includes an ammonia oxidation catalyst downstream of the SCR catalyst, and detecting the NH3 slip condition includes determining the AMOX catalyst is converting NH3 to NOx.

### Claim 6 (depends on 1)

The method of claim 1, wherein the temporary target deNOx efficiency is determined as a function of the current deNOx efficiency.

### Claim 7 (depends on 6)

The method of claim 6, wherein the at least one deNOx efficiency adjustment includes at least one of:
the NH3 slip condition is no longer present;
an elapse of a time period since detecting the NH3 slip condition;
a threshold increase in the temporary target deNOx efficiency; and
the temporary target deNOx efficiency is the same as the target deNOx efficiency.

### Claim 8 (depends on 1)

The method of claim 1, wherein determining the temporary target deNOx efficiency for the SCR catalyst includes setting the temporary target deNOx efficiency equal to the current deNOx efficiency.

### Claim 9 (depends on 1)

The method of claim 1, wherein the first NOx sensor is a virtual NOx sensor.

### Claim 10

A system, comprising:
an internal combustion engine operable to produce an exhaust gas flow into an exhaust system, the exhaust system including:
a selective catalytic reduction (SCR) catalyst disposed in the exhaust gas flow;
a reductant injector operationally coupled to the exhaust gas flow at a position upstream of the SCR catalyst;
a first NOx sensor upstream of the SCR catalyst;
a second NOx sensor downstream of the SCR catalyst;
a controller connected to the first NOx sensor, the second NOx sensor and the internal combustion engine, the controller being configured to determine:
a target deNOx efficiency in response to one or more operating conditions of the system and a current deNOx efficiency from a first output of the first NOx sensor and a second output of the second NOx sensor;
a reductant injector command that provides a feedback controlled NH3 amount in response at least in part to a deviation of the current deNOx efficiency from the target deNOx efficiency;
the controller further being configured, in response to detection of an NH3 slip condition, to determine:
a temporary target deNOx efficiency; and
a modified reductant injection command to provide a reduced NH3 amount in response to the temporary target deNOx efficiency while increasing the temporary target deNOx efficiency toward the target deNOx efficiency.

### Claim 11 (depends on 10)

The system of claim 10, wherein the controller is configured to determine the feedback controlled NH3 amount and the reduced NH3 amount as a function of an ammonia to NOx ratio upstream of the SCR catalyst.

### Claim 12 (depends on 10)

The system of claim 10, wherein the controller is configured to detect the NH3 slip condition in response to an NH3 presence in the exhaust gas flow downstream of the SCR catalyst.

### Claim 13 (depends on 10)

The system of claim 10, wherein the temporary target deNOx efficiency for the SCR catalyst is set to the current deNOx efficiency.

### Claim 14 (depends on 10)

The system of claim 10, further comprising at least one of an oxidation catalyst upstream of the SCR catalyst, a particulate filter upstream of the SCR catalyst, and an ammonia oxidation catalyst downstream of the SCR catalyst.

### Claim 15 (depends on 10)

The system of claim 10, wherein the controller is configured to, in response to detection of an NH3 slip condition, suspend providing the feedback controlled NH3amount via the reductant injector command until a deNOx efficiency adjustment condition is satisfied.

### Claim 16 (depends on 15)

The system of claim 15, wherein the deNOx efficiency adjustment condition includes at least one of:
the NH3 slip condition is no longer present;
an elapse of a time period since detection of the NH3 slip condition;
a threshold increase in the temporary target deNOx efficiency; and
the temporary target deNOx efficiency being the same as the target deNOx efficiency.

### Claim 17 (depends on 10)

The system of claim 10, wherein the first NOx sensor is one of a physical constituent gas sensor and a virtual gas constituent sensor, and wherein the second NOx sensor is one of a physical constituent gas sensor and a virtual gas constituent sensor.

### Claim 18

An apparatus, comprising:
a controller connected to a first NOx sensor upstream of a selective catalytic reduction (SCR) catalyst in an exhaust system and a second NOx sensor downstream of the SCR catalyst, wherein the exhaust system receives an exhaust gas flow produced by operation of an internal combustion engine, the controller including:
a deNOx efficiency target module configured to determine a target deNOx efficiency for injection of an NH3 amount to achieve the target deNOx efficiency;
a deNOx efficiency feedback module configured to determine a current deNOx efficiency in response to NOx amounts from the first NOx sensor and the second NOx sensor;
an NH3 slip detection module configured to detect an NH3 slip condition;
in response to the NH3 slip condition, the controller suspending injection of the NH3amount for achieving the target deNOx efficiency; and
further comprising an NH3 correction module configured to determine a temporary target deNOx efficiency in response to the NH3 slip condition for injection of a reduced NH3 amount and to increase the temporary target deNOx efficiency toward the target deNOx efficiency during injection of the reduced NH3 amount.

### Claim 19 (depends on 18)

The apparatus of claim 18, wherein the NH3 correction module is configured to determine the temporary target deNOx efficiency as a function of the current deNOx efficiency and a reductant injector command in response to the temporary target deNOx efficiency, the reductant injector command providing the reduced NH3 amount that is less than the NH3 amount provided in response to the target deNOx efficiency.

### Claim 20 (depends on 18)

The apparatus of claim 18, further comprising a deNOx efficiency tracking module that is configured to determine a reductant injector command in response to a deviation of the current deNOx efficiency from the target deNOx efficiency.

### Claim 21 (depends on 18)

The apparatus of claim 18, wherein the controller is configured to suspend injection of the NH3 amount to achieve the target deNOx efficiency until a deNOx efficiency adjustment condition is satisfied, the deNOx efficiency adjustment condition including at least one of the NH3 slip condition no longer being present; an elapse of a time period since detection of the NH3 slip condition; a threshold increase in the temporary target deNOx efficiency; and the temporary target deNOx efficiency being the same as the target deNOx efficiency.

### Claim 22 (depends on 18)

The apparatus of claim 18, wherein the first NOx sensor is one of a physical constituent gas sensor and a virtual gas constituent sensor, and wherein the second NOx sensor is one of a physical constituent gas sensor and a virtual gas constituent sensor.