# US 9,435,244 B1 · System and method for injection control of urea in selective catalyst reduction

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- Number: US 9,435,244 B1
- Document ID: US9435244B1
- Status: Granted
- Kind: B1
- Application number: 14/686,350
- Filed: 2015-04-14
- Granted: 2016-09-06
- Earliest claimed: 2015-04-14
- Assignees: General Electric Company
- Applicants: General Electric Company
- Inventors: Maruthi Narasinga Rao Devarakonda
- Web page: https://patentgrep.com/patent/US9435244B1

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- F01N 3/2066: {Selective catalytic reduction [SCR]}
- F01N 9/00: Electrical control of exhaust gas treating apparatus (monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00)
- F01N 11/00: Monitoring or diagnostic devices for exhaust-gas treatment apparatus
- F01N 2560/021: for measuring or detecting ammonia NH3
- F01N 2560/026: for measuring or detecting NOx
- F01N 2560/12: Other sensor principles, e.g. using electro conductivity of substrate or radio frequency
- F01N 2560/14: having more than one sensor of one kind
- F01N 2570/18: Ammonia
- F01N 2610/02: the substance being ammonia or urea
- F01N 2610/146: Control thereof, e.g. control of injectors or injection valves
- F01N 2900/0601: being estimated
- F01N 2900/1404: Exhaust gas temperature
- F01N 2900/1411: Exhaust gas flow rate, e.g. mass flow rate or volumetric flow rate
- F01N 2900/1622: Catalyst reducing agent absorption capacity or consumption amount
- 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

A system includes an exhaust aftertreatment system configured to treat emissions from a combustion engine. The exhaust aftertreatment system includes a selective catalytic reduction (SCR) catalyst assembly and at least one radio frequency (RF) probe disposed within the SCR catalyst assembly. A controller is coupled to the exhaust aftertreatment system and utilizes an NH3 storage estimate measured by the at least one RF probe and an NH3 storage estimate determined by an NH3 storage estimate model to output a control action for a reductant injection system. The NH3 storage estimate model utilizes measured concentrations of nitrogen oxides (NOx) in the fluid upstream or downstream of the SCR catalyst and/or measured concentrations of NH3 in the fluid upstream or downstream of the SCR catalyst, and the NH3 storage measurement from the at least one RF probe to determine the NH3 storage estimate.

## Claims

### Claim 1

A system, comprising:
an exhaust aftertreatment system configured to treat emissions from a combustion engine, wherein the exhaust aftertreatment system comprises:
a selective catalytic reduction (SCR) catalyst assembly configured to receive a fluid from the combustion engine, wherein the SCR catalyst assembly has an inlet and an outlet;
at least one radio frequency (RF) probe disposed within the SCR catalyst and configured to measure ammonia (NH3) storage of the SCR catalyst;
an injection system configured to inject NH3 or urea into the fluid upstream of the inlet of the SCR catalyst;
a controller communicatively coupled to the exhaust aftertreatment system, wherein the controller is configured to control operations of the exhaust aftertreatment system and to receive signals representative of the measured concentrations of nitrogen oxides (NOx) or NH3 in the fluid upstream of the SCR catalyst, to receive signals representative of the measured concentrations of NOx or NH3 in the fluid downstream of the SCR catalyst, or any combination thereof; and a signal representative of the NH3 storage measurement from the at least one RF probe; and
an NH3 storage estimate model configured to determine an NH3 storage estimate based on at least the signals representative of the measured concentrations of NOx or NH3 in the fluid upstream of the SCR catalyst or the signals representative of the measured concentrations of NOx or NH3 in the fluid downstream of the SCR catalyst, or any combination thereof;
wherein the controller is configured to utilize at least both the estimated NH3 storage estimate and the NH3 storage measurement to output a control action for the injection system.

### Claim 2 (depends on 1)

The system of claim 1, comprising a first NOx sensor disposed upstream of the inlet of the SCR catalyst and configured to measure the concentration of NOx in the fluid upstream of the inlet, or disposed downstream of the outlet of the SCR catalyst and configured to measure the concentration of NOx in the fluid downstream of the outlet.

### Claim 3 (depends on 1)

The system of claim 1, comprising a first NH3 sensor disposed upstream of the inlet of the SCR catalyst and configured to measure the concentration of NH3 in the fluid upstream of the inlet, or disposed downstream of the outlet of the SCR catalyst and configured to measure the concentration of NH3 in the fluid downstream of the outlet.

### Claim 4 (depends on 1)

The system of claim 1, comprising one or more sensors configured to measure the operating parameters of the combustion engine.

### Claim 5 (depends on 4)

The system of claim 4, wherein the controller receives the operating parameters of the combustion engine and utilizes the NH3 storage estimate model to determine the NH3 storage estimate based at least in part on the operating parameters.

### Claim 6 (depends on 1)

The system of claim 1, wherein the control action comprises adjusting an amount of NH3 or urea injected into the fluid upstream of the inlet of the SCR catalyst.

### Claim 7 (depends on 1)

The system in claim 1, wherein the controller is configured to receive signals representative of the measured concentrations of (NOx) and NH3 in the fluid upstream of the SCR catalyst.

### Claim 8 (depends on 1)

The system of claim 1, comprising the combustion engine coupled to the exhaust aftertreatment system.

### Claim 9 (depends on 1)

The system of claim 1, wherein the controller is configured to determine an NH3 storage error value between the NH3 storage estimate and the NH3 storage measurement and to output the control action based on the NH3 storage error value.

### Claim 10

A system, comprising:
a controller of an exhaust aftertreatment system configured to treat emissions from a combustion engine, wherein the controller is configured to receive signals representative of measured concentrations of ammonia (NH3) or nitrogen oxides (NOx) within a fluid upstream of a selective catalytic reduction (SCR) catalyst assembly or to receive signals representative of the measured concentrations of NH3 or (NOx) in the fluid downstream of the SCR catalyst, or any combination thereof, to utilize an NH3 storage estimate model to determine an NH3 storage estimate of the SCR catalyst based on the measured concentrations of NOx in the fluid upstream or downstream of the SCR catalyst and/or the measured concentrations of NH3 in the fluid upstream or downstream of the SCR catalyst, to receive a signal representative of an NH3 storage measurement of the SCR catalyst from at least one radio frequency (RF) probe disposed within the SCR catalyst, and to control an amount of urea or ammonia injected by an injection system into the fluid upstream of an inlet of the SCR catalyst assembly based at least on both the NH3 storage measurement and the NH3 storage estimate.

### Claim 11 (depends on 10)

The system of claim 10, wherein the controller is configured to receive signals representative of the measured parameters of the combustion engine.

### Claim 12 (depends on 11)

The system of claim 11, wherein the controller is configured to utilize the NH3 storage estimate model to determine an NH3 storage estimate based at least in part on the measured operating parameters.

### Claim 13 (depends on 10)

The system of claim 10, wherein the controller is a proportional-integral-derivative controller.

### Claim 14 (depends on 10)

The system of claim 10, wherein the controller is configured to determine an NH3 storage error value between the NH3 storage estimate and the NH3 storage measurement and to output the control action based on the NH3 storage error value.

### Claim 15

A method for controlling urea or ammonia (NH3) injection into a fluid upstream of an inlet of a selective catalytic reduction (SCR) catalyst assembly coupled to a combustion engine, comprising:
utilizing a controller to:
receive signals representative of measured concentrations of nitrogen oxides (NOx) and/or NH3 upstream and/or downstream of the SCR catalyst assembly; and
receive signals representative of an NH3 storage measurement of the SCR catalyst assembly from at least one radio frequency (RF) probe disposed within the SCR catalyst;
utilize an NH3 storage estimate model to determine an NH3 storage estimate based on at least the signals representative of the measured concentrations of NOx in the fluid upstream or downstream of the SCR catalyst and/or the signals representative of the measured concentrations of NH3 in the fluid upstream or downstream of the SCR catalyst to determine the NH3 storage estimate; and
output a control action for an injection system, based at least in part on the NH3 storage estimate and the NH3 storage measurement, wherein the injection system injects an amount of NH3 or urea into the fluid upstream of the inlet of the SCR catalyst assembly.

### Claim 16 (depends on 15)

The method of claim 15, comprising utilizing the controller to:
determine a NH3 storage error value between the NH3 storage estimate and the NH3 storage measurement; and
output the control action based on the NH3 error value.

### Claim 17 (depends on 15)

The method of claim 15, wherein the control action comprises generating an NH3 or urea injection command that adjusts an injection rate of NH3 or urea to achieve a desired NOx emission level exiting the SCR assembly.

### Claim 18 (depends on 15)

The method of claim 15, wherein the control action comprises receiving signals representative of measured operating parameters of the combustion engine.

### Claim 19 (depends on 18)

The method of claim 18, wherein the control action comprises utilizing the NH3 storage estimate model to determine the NH3 storage estimate based at least in part of the operating parameters.

### Claim 20 (depends on 18)

The method of claim 18, wherein the operating parameters comprise an exhaust flow rate and a temperature of an exhaust exiting the combustion engine.