Patent ID: 6482650
Filing Date: 2002-11-19
Classification: F01N,G01N,Y02T,Y10T

Abstract:
A method for detecting the deterioration of a treatment catalyst which oxidizes a combustible gas in a gas to be treated, the method consisting essentially of:(1) providing a combustible gas sensor which consists essentially of a base member having a first temperature sensor section and a second temperature sensor section, wherein the first temperature sensor section includes a first temperature sensitive portion of a dense ceramic material and the second temperature sensor section includes a second temperature sensitive portion of a dense ceramic material; a first resistor buried in the first temperature sensitive portion and having a positive resistance temperature coefficient; a first pair of current leads for providing current to the first resistor; a first pair of voltage leads for detecting a voltage across the first resistor; a second resistor buried in the second temperature sensitive portion and having a positive resistance temperature coefficient; a second pair of current leads for providing current to the second resistor; a second pair of voltage leads for detecting a voltage across the second resistor; and a porous oxidation catalyst layer which covers at least a part of a surface of the second temperature sensitive portion in which said second resistor is buried to catalyze oxidation of a combustible gas; (2) passing the gas to be treated through the treatment catalyst to obtain a treated gas; (3) contacting the treated gas with said sensor; (4) applying a current I1 to the first resistor to determine a voltage V1 of the first resistor; (5) applying a current I2 to the second resistor to determine a voltage V2 of the second resistor; (6) determining a difference between temperatures of the first resistor and the second resistor or a difference between electric power fed to the first resistor and the second resistor on the basis of the current I1, the current I2, the voltage V1 and the voltage V2; (7) determining the concentration of the combustible gas in the treated gas based on said temperature difference or said electric power difference; and (8) comparing the concentration of the combustible gas determined in (7) with a predetermined value of concentration representative of deterioration of said treatment catalyst.