Method for the quantitative analysis of the composition of a gas mixture and associated measuring device
A method for the quantitative analysis of the composition of a gas mixture is specifically suited for the analysis of the atmosphere of a containment in a nuclear installation. Even under difficult conditions, this method enables the simple, reliable and as direct as possible determination of physical parameters, thereby permitting the characteristic definition of the ignition field and the combustion behavior of the gas mixture. A measuring device is provided with a thermal conductivity detector with a first measuring bridge, a thermal tonality detector with a second measuring bridge, and a common evaluation unit. With reference to bridge voltages present on the two measuring bridges, the hydrogen content and the oxygen content are simultaneously determined in the evaluation unit.
1. A method for quantitative analysis of the composition of a gas mixture, the method comprising:
providing a measuring device with
a thermal conductivity detector having a first measuring bridge;
a reaction heat detector having a second measuring bridge; and
an evaluation unit;
using the evaluation unit for determining a hydrogen content and, at the same time, determining an oxygen content in the gas mixture based on respective bridge voltages present at the first and second measuring bridges.
2. The method according to claim 1 , which comprises analyzing an atmosphere of a containment of a nuclear plant.
3. The method according to claim 1 , which comprises determining two measured values for the hydrogen content in the evaluation unit in diversitary processes based on the bridge voltages present at the first and second measuring bridges.
4. The method according to claim 1 , which comprises, in case of hydrogen concentrations of >10% by volume, determining the oxygen content directly from an empirically determined calibrating curve for the bridge voltage present on the measuring bridge of the reaction heat detector.
5. The method according to claim 1 , which comprises, in case of hydrogen concentrations of <2.5% by volume, determining the oxygen concentration based on
a thermal conductivity of the gas mixture measured on the thermal conductivity detector;
a hydrogen concentration of the gas mixture determined by calibration on the reaction heat detector; and
a temperature of the gas mixture determined by way of a temperature sensor;
wherein a vapor pressure of water vapor present in the gas mixture is determined from the temperature, for the evaluation, assuming a saturation.
6. The method according to claim 1 , which comprises, in case of hydrogen concentrations of <10% by volume, determining the oxygen content redundantly by measuring a galvanic voltage tapped at a heated zirconium dioxide measuring cell.
7. The method according to claim 6 , which comprises switching off a heating of the zirconium dioxide measuring cell if the hydrogen concentration determined by one or both of the thermal conductivity detector or the reaction heat detector is >10% by volume.
8. A measuring device for quantitative analysis of a composition of a gas mixture, the measuring device comprising:
a thermal conductivity detector having a first measuring bridge;
a reaction heat detector having a second measuring bridge; and
a common evaluation unit connected to said thermal conductivity detector and to said reaction heat detector, said evaluation unit being configured for carrying out the method according to claim 1 .
9. The measuring device according to claim 8 , configured for analyzing an atmosphere of a containment of a nuclear plant.
10. The measuring device according to claim 8 , wherein:
said second measuring bridge of said reaction heat detector is formed by two catalytically active measuring cells surrounded by the measuring gas together with two catalytically inactive cells surrounded by the measuring gas; and
said first measuring bridge of said thermal conductivity detector is formed by two catalytically inactive measuring cells isolated from the measuring gas together with said two catalytically inactive cells surrounded by the measuring gas.
11. The measuring device according to claim 8 , comprising a heatable zirconium dioxide measuring cell for a diversitary redundant determination of an oxygen content in said evaluation unit, in case of hydrogen concentrations of <10% by volume.
12. A monitoring system for the atmosphere in a containment of a nuclear plant in case of severe hazardous incidents, the monitoring system comprising a measuring device according to claim 8 .