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

Patent metadata

Field	Value
Publication number	US-10480385-B2
Application number	US-201715673766-A
Country	US
Kind code	B2
Filing date	Aug 10, 2017
Priority date	Oct 24, 2016
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

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 p O2 in the target gas, and a control section 72 . The control section 72 derives combustible-gas concentration p THC in the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration p O2 , and the relationship represented by formula (1):

EMF=α log a ( p THC )−β log b ( p O2 )+ 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).

First claim

What is claimed is:

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 log a ( p THC )−β log b ( p O2 )+ 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),
p THC : the combustible-gas concentration in the target gas, and
p O2 : the oxygen concentration in the target gas).

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

3. 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.

4. 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).

5. 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.

6. 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.

7. 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.

8. 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.

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 log a ( p THC )−β log b ( p O2 )+ 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),
p THC : the combustible-gas concentration in the target gas, and
p O2 : the oxygen concentration in the target gas).

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 log a ( p THC )−β log b ( p O2 )+ 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),
p THC : the combustible-gas concentration in the target gas, and
p O2 : the oxygen concentration in the target gas).

11. 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 p THC ;
(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 p THC ; and
(b3) a substep of deriving the constant B in formula (1) from the derived constants α and β and the

Assignees

• Ngk Insulators Ltd

Inventors

• Okamoto Taku
• Nakada Yoshinobu
• MONNA Kosuke

Classifications

• B01D53/944

  Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts (three-way-catalysts [TWC] B01D53/9445) · CPC title

• G01N27/4074

  for detection of gases other than oxygen · CPC title

• F01N2560/025

  for measuring or detecting O2, e.g. lambda sensors · CPC title

• F01N2570/18

  Ammonia · CPC title

• G01N27/4077

  Means for protecting the electrolyte or the electrodes · CPC title