# US 10,480,385 B2 · Apparatus for measuring combustible-gas concentration, system for measuring combustible-gas concentration, system for treating exhaust gas, method for measuring combustible-gas concentration, and method for deriving constant

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- Number: US 10,480,385 B2
- Document ID: US10480385B2
- Status: Granted
- Kind: B2
- Application number: 15/673,766
- Filed: 2017-08-10
- Published: 2018-04-26
- Granted: 2019-11-19
- Earliest claimed: 2016-10-24
- Assignees: NGK Insulators, Ltd.
- Applicants: Ngk Insulators, Ltd.
- Inventors: Taku Okamoto; Yoshinobu Nakada; Kosuke Monna
- Web page: https://patentgrep.com/patent/US10480385B2

## CPC

- F01N 13/008: {Mounting or arrangement of exhaust sensors in or on exhaust apparatus (sensor arrangements for engine control F02D41/1439)}
- B01D 53/30: Controlling by gas-analysis apparatus (regulating non electrical variables in general G05D)
- B01D 53/9431: {Processes characterised by a specific device}
- B01D 53/9477: {with catalysts positioned on separate bricks, e.g. exhaust systems}
- G01N 27/4067: {Means for heating or controlling the temperature of the solid electrolyte}
- G01N 27/4074: {for detection of gases other than oxygen}
- G01N 27/4075: {Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts}
- G01N 27/4077: {Means for protecting the electrolyte or the electrodes}
- G01N 27/419: Measuring voltages or currents with a combination of oxygen pumping cells and oxygen concentration cells
- B01D 53/9418: {for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas}
- B01D 53/9436: {Ammonia}
- B01D 53/944: {Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts (three-way-catalysts [TWC] B01D53/9445)}
- B01D 2255/904: Multiple catalysts
- F01N 3/021: by means of filters
- F01N 3/103: {Oxidation catalysts for HC and CO only}
- F01N 3/106: {Auxiliary oxidation catalysts}
- F01N 3/2066: {Selective catalytic reduction [SCR]}
- F01N 13/009: {having two or more separate purifying devices arranged in series}
- F01N 2560/02: the means being an exhaust gas sensor
- F01N 2560/023: for measuring or detecting HC
- F01N 2560/025: for measuring or detecting O2, e.g. lambda sensors
- F01N 2560/20: Sensor having heating means
- F01N 2570/18: Ammonia
- F01N 2610/02: the substance being ammonia or urea
- 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)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A apparatus 70 for measuring combustible-gas concentration includes an electromotive force acquisition section 75 configured to acquire information about an electromotive force of a mixed potential cell 55 while a detection electrode 51 is exposed to a target gas, an oxygen concentration acquisition section 76 configured to acquire information about oxygen concentration pO2 in the target gas, and a control section 72. The control section 72 derives combustible-gas concentration pTHC in the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration pO2, and the relationship represented by formula (1): EMF=α loga(pTHC)−β logb(pO2)+B (1) where α, β, and B each represent a constant, and a and b each represent any base (provided that a≠1, a>0, b≠1, and b>0).

## Claims

### Claim 1

An apparatus for measuring combustible-gas concentration serving as carbon-equivalent concentration of a combustible gas in a target gas with a sensor element including a mixed potential cell that includes a solid electrolyte body, a detection electrode arranged on the solid electrolyte body, and a reference electrode arranged on the solid electrolyte body, the apparatus comprising:
an electromotive force acquisition section configured to acquire information about an electromotive force of the mixed potential cell while the detection electrode is exposed to the target gas;
an oxygen concentration acquisition section configured to acquire information about oxygen concentration in the target gas; and
a combustible gas concentration derivation section configured to determine the combustible-gas concentration in the target gas based on the acquired information about the electromotive force, the acquired information about the oxygen concentration, and a relationship represented by formula (1):
EMF=α loga(pTHC)−β logb(pO2)+B (1)
(where
EMF: the electromotive force of the mixed potential cell,
α, β, and B: constants,
a and b: any base (provided that a≠1, a>0, b≠1, and b>0),
pTHC: the combustible-gas concentration in the target gas, and
pO2: the oxygen concentration in the target gas).

### Claim 2 (depends on 1)

A system for measuring combustible-gas concentration, comprising:
apparatus for measuring combustible-gas concentration according to claim 1; and
the sensor element.

### Claim 3 (depends on 2)

The system for measuring combustible-gas concentration according to claim 2,
wherein the detection electrode is composed of a Au—Pt alloy as a main component.

### Claim 4 (depends on 3)

The system for measuring combustible-gas concentration according to claim 3,
wherein the detection electrode has a degree of concentration (=amount of Au present [atom %]/amount of Pt present [atom %]) of 0.3 or more, the degree of concentration being measured by at least one of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

### Claim 5 (depends on 2)

The system for measuring combustible-gas concentration according to claim 2,
wherein the sensor element includes a heater configured to heat the mixed potential cell to an operating temperature of 450° C. or higher and 600° C. or lower.

### Claim 6 (depends on 2)

The system for measuring combustible-gas concentration according to claim 2,
wherein the sensor element includes a protective layer that covers the detection electrode, the protective layer having a porosity of 28% or more by volume.

### Claim 7 (depends on 2)

A system for treating an exhaust gas, comprising:
the system for measuring combustible-gas concentration according to claim 2; and
an exhaust gas path through which an exhaust gas serving as the target gas from an internal combustion engine flows, the sensor element being arranged in the exhaust gas path.

### Claim 8 (depends on 7)

The system for treating an exhaust gas according to claim 7, further comprising:
one or more supply sections arranged in the exhaust gas path, the one or more supply sections being configured to supply at least one of urea and ammonia,
wherein the internal combustion engine is a diesel engine, and
the sensor element is arranged upstream of the most upstream supply section of the one or more supply sections arranged in the exhaust gas path.

### Claim 9

A method for measuring combustible-gas concentration serving as a carbon-equivalent concentration of a combustible gas in a target gas with a sensor element including a mixed potential cell that includes a solid electrolyte body, a detection electrode arranged on the solid electrolyte body, and a reference electrode arranged on the solid electrolyte body, the method comprising:
an electromotive force acquisition step of acquiring information about an electromotive force of the mixed potential cell while the detection electrode is exposed to the target gas;
an oxygen concentration acquisition step of acquiring information about oxygen concentration in the target gas; and
a combustible gas concentration derivation step of determining the combustible-gas concentration in the target gas based on the acquired information about the electromotive force, the acquired information about the oxygen concentration, and a relationship represented by formula (1):
EMF=α loga(pTHC)−β logb(pO2)+B (1)
(where
EMF: the electromotive force of the mixed potential cell,
α, β, B: constants,
a and b: any base (provided that a≠1, a>0, b≠1, and b>0),
pTHC: the combustible-gas concentration in the target gas, and
pO2: the oxygen concentration in the target gas).

### Claim 10

A method for deriving a constant in a relational formula used to measure combustible-gas concentration serving as carbon-equivalent concentration of a combustible gas in a target gas with a sensor element including a mixed potential cell that includes a solid electrolyte body, a detection electrode arranged on the solid electrolyte body, and a reference electrode arranged on the solid electrolyte body, the method comprising:
(a) a step of multiple times of executing electromotive force measurement processing that measures an electromotive force of the mixed potential cell in a state in which the detection electrode is exposed to the target gas while at least one of oxygen concentration and the carbon-equivalent concentration of at least one combustible gas of one or more combustible gases in the target gas is changed, a gas containing oxygen and the one or more combustible gases being used as the target gas; and
(b) a step of deriving constants α, β, and B in formula (1) from results of the electromotive force measurement processing executed multiple times:
EMF=α loga(pTHC)−β logb(pO2)+B (1)
(where
EMF: the electromotive force of the mixed potential cell,
α, β, and B: constants,
a and b: any base (provided that a≠1, a>0, b≠1, and b>0),
pTHC: the combustible-gas concentration in the target gas, and
pO2: the oxygen concentration in the target gas).

### Claim 11 (depends on 10)

The method for deriving a constant according to claim 10,
wherein step (a) includes:
(a1) a substep of executing the electromotive force measurement processing multiple times at a constant oxygen concentration and different carbon-equivalent concentrations of a particular hydrocarbon in the target gas, the particular hydrocarbon being defined as one or more kinds of hydrocarbons, excluding alkanes, among hydrocarbons having 3 or more carbon atoms, and the target gas being defined as a gas containing the particular hydrocarbon; and
(a2) a substep of executing the electromotive force measurement processing multiple times at a constant carbon-equivalent concentration of a particular hydrocarbon and different oxygen concentrations in the target gas, the particular hydrocarbon being defined as one or more kinds of hydrocarbons, excluding alkanes, among hydrocarbons having 3 or more carbon atoms, and the target gas being defined as a gas containing the particular hydrocarbon, and
step (b) includes:
(b1 ) a substep of deriving the constant α in formula (1) from the results of the electromotive force measurement processing executed multiple times in substep (a1) by regarding the carbon-equivalent concentration of the particular hydrocarbon as the combustible-gas concentration pTHC;
(b2) a substep of deriving the constant β in formula (1) from the results of the electromotive force measurement processing executed multiple times in substep (a2) by regarding the carbon-equivalent concentration of the particular hydrocarbon as the combustible-gas concentration pTHC; and
(b3) a substep of deriving the constant B in formula (1) from the derived constants α and β and the results of the electromotive force measurement processing executed one or more times in at least one of substeps (a1) and (a2).

### Claim 12 (depends on 11)

The method for deriving a constant according to claim 11,
wherein in substep (a1), the particular hydrocarbon comprises one or more kinds of hydrocarbons among hydrocarbons that have 3 or more carbon atoms, that have a double bond, and that do not have a triple bond, and
in substep (a2), the particular hydrocarbon comprises one or more kinds of hydrocarbons among hydrocarbons that have 3 or more carbon atoms, that have a double bond, and that do not have a triple bond.

### Claim 13 (depends on 11)

The method for deriving a constant according to claim 11,
wherein in substep (a1), the target gas is a gas containing only a single kind of hydrocarbon, and
in substep (a2), the target gas is a gas containing only a single kind of hydrocarbon.