CS274001B1 - Continuous method of hydrogen determination in water - Google Patents

Abstract

The design concerns the continuous method of determination of hydrogen especially in the cooling medium of the primary circuit of nuclear power plants and it does not require calibration by gas standards with hydrogen content. The introduced goal is achieved with the use of indirect determination of hydrogen that is separated from the cooling medium by the stripper gas (air, or mixture of air with nitrogen) from the values of oxygen depletion in the stripper gas, which is used up for catalytic incineration of hydrogen. Oxygen depletion is determined with the use of the oxygen analyser (4), which is equipped with an oxygen sensor with the solid electrolyte with oxygen ionic conduction and which is located in the set consisting of the stripper (1), vessel with a catalyser (2) and gas dehydrator with a cooling spiral (3). The signal of the oxygen sensor, responding by the thermodynamic relation, is processed by means of computer technology, which can at the same time control the activity of the analyser. The design can be used in all fields where it is needed to determine hydrogen that is soluble in water, water solutions or other liquids.<IMAGE>

Description

The invention relates to a continuous method for determining hydrogen, in particular in a refrigerant primary circuit of nuclear power plants, which does not require calibration with hydrogen-containing gas standards.

Current methods of determining hydrogen in the cooling primary circuit of nuclear power plants are either discontinuous, based on manual sampling followed by gas chromatographic analysis, or continuously, based on continuous stripping of hydrogen from the flowing refrigerant followed by analysis either by gas chromatography or by direct measurement (e.g. ) in the stripping gas stream. All of the above procedures require the input signal to be calibrated using pure hydrogen or standard gases containing it. These facts make it more difficult to incorporate these methods into the automated control system of the primary circuit chemical regime. In addition, the relationship between the measured variable and the sensor signal cannot be described by a simple mathematical relationship, which complicates mass data collection using computer technology. The stripping and carrier gases used are not common in the central gas distribution of nuclear power plants. containers.

These disadvantages are solved by the continuous method of determining hydrogen in the cooling water of the primary circuit of nuclear power plants, which is based on indirect determination of hydrogen in the stripped gas using an oxygen sensor with a solid electrolyte to measure the loss of oxygen in the stripping gas. caused by catalytic combustion of hydrogen with a stoichiometric amount of oxygen on the catalyst upstream of the oxygen sensors.

The oxygen sensor signal is precisely defined by the oxygen concentration relative to the Nernst-Peters equation over the voltage of the galvanic cell at atmospheric pressure, with air as the reference gas:

χθ ₂ ~ 0.205 exp where x _Q2 - is the molar fraction of oxygen in E - is the cell voltage (V)

E__ - is the asymmetric voltage of cell (V) and S

T - is the cell temperature (K).

In addition to the simplicity of the analyzer utilizing the present solution, its advantage is in particular that air or air can be used for stripping. a mixture of air with an inert gas (nitrogen), further that the only calibration is the occasional measurement of the asymmetric cell voltage (changes caused by the unevenness of the pressure and temperature fields in the cell) and finally the existence of a simple, well defined relationship between This makes it possible to utilize the present method of determining hydrogen in a system of automatic analyzers for the control of the chemical mode using computer technology for controlling the system and processing the measured results.

In FIG. 1 is a schematic illustration of an automatic hydrogen analyzer assembly utilizing the described hydrogen determination method. In FIG. 2 is an example of an oxygen analyzer arrangement with a solid electrolyte sensor.

The hydrogen dissolved in the coolant primary circuit is quantitatively separated in the stripper 7.

in which the refrigerant passes from top to bottom and the stripping gas from bottom to top. The mixture of stripping gas and hydrogen entering from the top of the stripper passes through a heated catalyst vessel 2 - platinum or palladium black on an inert support or another suitable catalyst - where the hydrogen reacts quantitatively with part of the oxygen from the stripping gas. After

2,154.10 ⁵ T gas

CS 274 001 B1 drying in a dryer 3 equipped with a cooling coil, the gas is fed to an oxygen analyzer 6. The oxygen analyzer consists of an oxygen sensor 5, a oven 6 heated to a temperature above 650 ° C and a thermocouple 6 for monitoring the oven temperature. The oxygen sensor 5 is a solid electrolyte ceramic tube with an oxygen ion conductivity, e.g. made of calcium or yttria-stabilized zirconia, which is provided with platinum electrodes 6 in the form of a porous layer on the surface of the solid electrolyte.

The hydrogen content of the refrigerant is determined from the loss of oxygen by reaction with hydrogen according to:

in the stripping gas caused by its

22 ^{2 V} ^ ^(X ° o2 - ^X 02>)

^G i (i - W where C ^ 2 - hydrogen content in the cooling primary circuit of a nuclear power plant (ml.kg ^-1 )

Χθ02 ^m ° LARNAS fraction of oxygen in the dry stripping gas entering the stripper. This value can preferably be continuously monitored using an oxygen sensor placed parallel to the sensor 5 in the oven 8.

For clean air, X ° ₀₂ ~ θ> 205.

Χθ2 "C ^much the mole fraction of oxygen in the dry gas, the oxygen analyzer detected Elevator £ - is the flow rate of the stripping gas at the stripper £ (ml min ^)

- the flow rate of the analyzed coolant through the stripper δ (kg.min ^).

The analyzer utilizing the method of determining hydrogen according to the invention makes it possible to monitor continuously the hydrogen content of the cooling primary circuit of nuclear power plants without any need for calibration with hydrogen-containing gas mixtures. The analysis of the analyzer and the processing of the measured values can advantageously be performed using computer technology.

Claims (2)

OBJECT OF THE INVENTION Continuous method of determination of hydrogen, especially in the cooling circuit of nuclear power plants, characterized in that the hydrogen content is determined indirectly by stripping gas from the refrigerant by stripping gas by measuring the oxygen loss in the stripping gas consumed for catalytic hydrogen combustion with solid electrolyte.