Hydrogen Detector for Gas Media

Abstract

A hydrogen detector for a gaseous medium is disclosed. The detector includes an operating element fixed to the upper part of the detector housing by means of sealant. The lower part of the detector is insulated and in contact with a heater that provides operational temperature of the medium supplied to a waterproof membrane of a steam hydrogen compartment. Disturbances introduced by a measurement flow is transferred to the central core of a potential measuring unit through a measuring platinum electrode fixed to the lower part of a ceramic sensing element connected to the metal casing of the sensing element by the sealant. A standard electrode is located in the inner cavity of the ceramic sensing element. The external part of the ceramic sensing element bottom is covered with a porous platinum electrode. The end of the potential measuring unit central core is brought out to the standard electrode.

Claims

1. The hydrogen detector for gas media comprises a waterproof membrane and a housing with a potential measuring unit inside, a ceramic sensing element made of solid electrolyte, the cavity of which contains a reference electrode, a porous platinum electrode, applied on the external layer of the ceramic sensing element, a sealed lead-in tightly fixed inside the housing above the ceramic sensing element, a potential measuring unit that passes through the central core of the sealed lead-in and the lower bushing, wherein the ceramic sensing element is designed as a cylinder interlinked with the bottom located in the lower part of the cylinder. The external cylindrical surface of the ceramic sensing element is tightly connected to the inner side surface of the housing. The standard electrode is located in the inner cavity of the ceramic sensing element. The external part of the bottom of the ceramic sensing element is covered with a layer of the porous platinum electrode. The end of the central core of the potential measuring unit is brought out to the standard electrode, thus the electrical contact is provided between the standard electrode and the lower part of the central core of the potential measuring unit. The lower bushing designed as a tube is connected to the lower part of the housing on the side of the ceramic sensing element. The lower end of the lower bushing has a bottom with a center hole with an attached selective membrane made of at least one tube. The lower free end of the selective membrane is tightly closed with a plug. The cavity limited by the inner surface of the lower bushing, the external part of the bottom of the ceramic sensing element and the inner surfaces of the selective membrane and the plug is made leak-tight by means of glass-ceramic sealant. The detector is equipped with an additional thermally-insulated heater that serves for heating and sustaining stable operating temperature on the sensing part of the operating element.

2. A detector according to claim 1, wherein oxygen sensors are additionally equipped with a compartment of constant vapor pressure of water and a waterproof membrane to measure hydrogen concentration in a gas medium more effectively.

3. A detector according to claim 1, wherein an upper nut is installed in the upper part of the potential measuring unit and the ring-shaped cavity between the inner surface of the nut wall and the external surface of the potential measuring unit is filled with sealant.

4. A detector according to claim 1, wherein its steam hydrogen compartment consisting of a nickel case and a thin-walled waterproof membrane made of a thin-walled nickel tube is welded to the sensing element casing made of corrosion resistant steel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is illustrated with drawings.

[0023] FIG. 1 is a general view of the longitudinal axial cross-section of the detector.

[0024] FIG. 2 is a general view of the longitudinal axial cross-section of the detector operating element.

[0025] FIG. 3 is a general view of the longitudinal axial cross-section of the detector sensing element.

EMBODIMENT OF INVENTION

[0026] The hydrogen detector comprises a reference electrode 1 with immersed central core 2 of the potential measuring unit 3, located in the lower part of the ceramic sensing element 4 connected by means of glass-ceramic 5 with a metal case 6 of the sensing element 7 located inside the steam-water compartment 8. The represented items are included in the operating element 9 that has a bottom with a center hole to which a waterproof membrane 10 is attached. The membrane is made of at least one tube provided with a measuring platinum electrode 11 in its upper part. The operating element is located in the metal housing 12, leak-tightness of which is provided by sealant 3 and nut 14. A heater 15 with thermal insulation 16 serves for heating and sustaining stable operating temperature on the sensing part of the operating element.

[0027] The thermal insulation 16 fills the ring-shaped cavity between the inner surface of the heater wall 15 and the external surface of the housing of the detector that determines hydrogen concentration in gas 12.

[0028] The ceramic sensing element 4 is located in the lower part of the detector and shaped as a cylindrical part interlinked with the bottom.

[0029] The external cylindrical surface of the ceramic sensing element 4 is tightly connected to the inner side surface of the metal housing 12.

[0030] The reference electrode 1 is located in the inner cavity of the ceramic sensing element 4.

[0031] The housing 12 is designed as a tube connected with the metal casing of the sensing element 7.

[0032] The sealant 3 is a glass-ceramic consisting of silicon oxide (SiO.sub.2)−50 weight %, aluminum oxide (Al.sub.2O.sub.3)−5 weight %, boric oxide (B.sub.2O.sub.3)−20 weight %, titanium oxide (TiO.sub.2)−10 weight %, sodium oxide (Na.sub.2O)−12 weight %, potassium oxide (K.sub.2O)−1 weight % and magnesium oxide (MgO)−2 weight %.

[0033] The sealant is necessary to prevent ingress of oxygen from the air into the inner cavity of the detector and to avoid changes in the reference electrode properties.

[0034] The hydrogen detector applies the electrochemical method that allows to determine oxygen concentration by means of oxygen sensor made of solid oxide electrolyte. To measure hydrogen concentration in a gas medium, oxygen detectors are additionally equipped with a compartment of constant vapor pressure of water 8 and a waterproof membrane 10. Hydrogen contained the medium reversibly diffuses into the steam hydrogen compartment 8 through the membrane of the hydrogen detector to the measuring platinum electrode 11 changing the electromotive force of the detector. The electromotive force of the detector occurs due to differences in partial pressure of oxygen in the electrodes of the concentration cell. The scheme of the cell can be presented in the following way: Me-ES (an electrochemical sensor)-solid oxide electrolyte—AE (an actuating element)—H.sub.2O, H.sub.2—H-membrane—the controlled medium.

[0035] The concentration cell includes the ceramic sensing element (CSE) 4 made of solid oxide electrolyte, the reference electrode (RE) 1 and the measuring platinum electrode (MPE) 11.

[0036] Partially stabilized zirconium dioxide (PSZD) based material was chosen to be used as solid oxide electrolyte. PSZD has high thermo-mechanical properties. Ionic conductivity within the temperature range of 300-400° C. may be up to 0.95 and is not less than 0.97 within the temperature range of 400-500° C. Thermal impacts resistance exceeds 20° C./s.

[0037] Bi−Bi.sub.2O.sub.3 is used as a reference electrode 1 due to the stability of its thermodynamic properties.

[0038] Platinum-based porous composite coating is best suitable as a measuring (working) electrode 11 that serves as a catalyst for fast hydrogen oxidation on its surface. A special formula and method of application of this material on raw ceramic of the sensing element followed by annealing allows to produce high-porous working electrode of 30 μm thickness with good adhesive characteristics to ceramic.

[0039] The steam hydrogen compartment 8 is located in the cavity between the measuring platinum electrode 11 and the ceramic sensing element 4 and functions as a converter of hydrogen thermodynamic potential into oxidation potential of steam hydrogen mixture on the platinum electrode 11. Nickel is the most suitable material for the hydrogen membrane 10 due to its hydrogenous permeability and corrosion resistance in lead-bismuth eutectic.

INDUSTRIAL APPLICABILITY

[0040] The detector can be commercially manufactured. Moreover, its manufacturing does not require special equipment.