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Hydrogen sensing apparatus and method

a technology of sensing apparatus and water, applied in the direction of liquid/fluent solid measurement, instruments, electrochemical variables of materials, etc., can solve the problems of unable to achieve a breakthrough in this technology, the use of reference gas is awkward, and the chemical stability of the electrolyte/reference interface is not guaranteed.

Inactive Publication Date: 2005-11-17
CAMBRIDGE ENTERPRISE LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an apparatus and methods for measuring hydrogen concentration using a proton-conducting solid electrolyte and a metal / hydrogen reference standard. The invention ensures that the hydrogen concentration is measured accurately and reproducibly by using a chemically stable reference standard that does not affect the performance of the electrolyte. The invention also ensures that the interface between the electrolyte and the reference material is stable, preventing any chemical reaction that could affect the measurement. The sensor can be used to determine the hydrogen content in a fluid medium by adjusting the composition of the medium until the required signal is recorded.

Problems solved by technology

The monitoring and control of hydrogen concentration in gaseous and liquid media is an important technological issue.
The incorporation of a hydrogen reference standard into the sensor unit constitutes a scientific and technological problem.
However, the use of a reference gas has been found awkward, and no breakthrough with this technology has been achieved.
However, incorporation of hydrates fixes the water rather than the hydrogen partial pressure and, even though some response behaviour to hydrogen has been observed in a few cases, these sensors require calibration and their signal stability is insufficient for practical applications.
However, this combination was only found to work at comparatively low temperatures, i.e., below 600° C., and for relatively short times, i.e., a few hours, otherwise a continuous drift of the sensor signal towards zero was observed.
The reason for the failure was identified to be the chemical instability of the electrolyte / reference interface.
This causes a chemical reaction between the highly reducing reference material and the oxide-based solid electrolyte, which gradually converts the ion (proton) conductor into a mixed conductor and renders sensor readings impossible to interpret.
Overall, no hydrogen sensor relying on a solid reference material has as yet proven to be viable in any practical application.

Method used

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Examples

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example 1

[0034] 40 mg of titanium metal pieces, cut from a grit-blasted sheet of commercial grade 4 titanium metal with a known bulk oxygen content of 3600 ppm by mass, were placed inside a ceramic calcium zirconate thimble. (Grit-blasting was carried out to clean the surfaces of the as-received titanium metal specimen.) The interior of the thimble was then filled with undoped calcium zirconate powder which is inert and acts as a packing material. This was covered with a layer of a laboratory-made, silicon-free, sealing glass powder, which has a melting point of approximately 930° C. To melt the glass and form the seal, the arrangement was heated to around 940° C. in an alumina tube under pure hydrogen. Prior to application, the hydrogen was passed through calcium sulphate to remove traces of moisture and through a suitable metal scrubber to ensure low residual oxygen content. The unit was then exposed to a 1% by volume hydrogen in argon gas mixture at 700° C. and coulometric titration was p...

example 2

[0037] About 100 mg of zirconium metal were cut from a commercial zirconium wire with a known bulk oxygen content of 1500 ppm by mass and placed inside a ceramic calcium zirconate thimble. The interior of the thimble was filled with yttrium oxide powder, which acts as an inert packing material, and this was covered with a layer of silicon-free sealing glass powder as described in example 1. To melt the glass and form the seal, the arrangement was heated to around 940° C. in an alumina tube under pure hydrogen. By way of this procedure, a zirconium to hydrogen ratio inside the β-zirconium / δ-zirconium two-phase area was established directly. Preconditioning of the sensor was carried out as described in example 1. Sensor measurements were performed between 500° C. and 800° C. in hydrogen / argon mixtures with hydrogen contents of 1, 10 and 100% by volume. Measured emfs are shown in FIG. 3. Agreement with thermodynamic expectations, signal stability and comparability between individual se...

example 3

[0039] About 200 mg of hafnium metal were cut from a commercial hafnium wire with a known oxygen content of 230 ppm by mass and placed inside a ceramic calcium zirconate thimble. 1.0 mg of titanium dioxide was added. The interior of the thimble was filled with yttrium oxide powder, which acts as an inert packing material, and this was covered with a layer of a laboratory-made silicon-free sealing glass powder, which has a melting point of approximately 970° C. To melt the glass and form the seal, the arrangement was heated to around 980° C. in an alumina tube under pure hydrogen. By way of this procedure, a hafnium to hydrogen ratio inside the α-hafnium / δ-hafnium two-phase area was established directly. Preconditioning of the sensor was carried out as described in example 1. Sensor measurements were performed between 600 and 800° C. in hydrogen / argon mixtures with hydrogen contents of 1, 10 and 100% by volume. Measured emfs are shown in FIG. 4. Sensor performance was again found to ...

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Abstract

An apparatus and methods are provided for the accurate determination of hydrogen content in fluid media at elevated temperatures. The apparatus consists of a proton conducting solid electrolyte in contact with an internal metal / hydrogen reference standard, in which the electrolyte and the reference material are in a chemically stable contact. The electrical signal generated is a function of the hydrogen concentration on the measuring side.

Description

FIELD OF INVENTION [0001] The present invention relates to apparatus and a method for measuring the concentration of hydrogen in fluid media at elevated temperatures using a high temperature proton-conducting solid electrolyte in conjunction with an internal hydrogen standard. BACKGROUND OF THE INVENTION [0002] The monitoring and control of hydrogen concentration in gaseous and liquid media is an important technological issue. Fields of application include, for instance, the analysis of gas composition on the fuel side of hydrogen-based fuel cells and the determination of dissolved hydrogen content in molten metals like aluminium. It is therefore desirable to develop simple, easily applicable, reliable and inexpensive sensors having high sensitivity and selectivity. [0003] One concept of constructing hydrogen sensors for operation at elevated temperatures is to utilise a proton conducting solid electrolyte that compares the hydrogen partial pressure on the measuring side with a know...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01N27/407G01N33/00
CPCG01N27/4074G01N33/005
Inventor FRAY, DEREK JOHNSCHWANDT, CARSTEN
Owner CAMBRIDGE ENTERPRISE LTD
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