RU2536315C1 - Device for determining oxygen and hydrogen concentration in gas medium - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: device for determining the oxygen and hydrogen concentration in a gas medium relates to measurement instruments and can be used for control of gas media parameters, in particular of those, containing oxygen and hydrogen. The device consists of a channel (7), located at an angle to the horizon, an input hydrogen sensor (2) and an input oxygen sensor (3), located in the input part of the channel (7) cavity, an input catalytically active element (1), installed in the channel (7) cavity above the output sensors of hydrogen (2) and oxygen (3), an output hydrogen sensor (5) and an output oxygen sensor (6), located in the channel (7) cavity between the input (1) and output (4) catalytically active elements. The input (2) and output (4) catalytically active elements are made of highly porous cellular materials with a platinum coating applied on their surface. As the input hydrogen sensor (5) and the output hydrogen sensor (7) used are solid electrolyte sensors of the hydrogen concentration with a ceramic sensitive element, made of oxygen-conducting ceramics.

EFFECT: increased speed of the device performance and sensitivity, provision of protection against erroneous readings of the device.

3 cl, 1 dwg

Description

The invention relates to measuring equipment and can be used to control parameters of gaseous media, in particular containing oxygen and hydrogen.

A device is known "Control system of combustible and explosive gases based on solid electrolyte ceramic sensitive elements" authors P.N. Martynova, M.E. Chernova, A.N. Storozhenko, V.M. Shelemetyeva, R.P. Sadovnichy, A.S. Fomina [University News. Nuclear Energy No. 4, 2011, pp. 3-8], including two oxygen sensors connected to recording instruments, hermetically connected to a pipe through which the analyzed gas is forced to pump. Oxygen sensors based on solid electrolyte ceramic sensitive elements are located in metal cases equipped with heaters and thermal converters to maintain a constant temperature. An input catalytically active element is installed at the input of one of the oxygen sensors.

A disadvantage of the known device is the difficulty of its use in offline mode due to the need for forced pumping of the analyzed gas medium through a channel hermetically connected to oxygen sensors, and the impossibility of measuring oxygen concentration in the presence of hydrogen.

The closest in technical essence to the claimed device is a gas analyzer for determining the concentration of oxygen in a hydrogen-containing gas medium [RF patent for the invention No. 2293972, IPC G01N 27/12, 2004], including gas sensors connected to recording devices, a channel and a catalytically active element, installed in cross section of the middle part of the channel cavity. As gas sensors, the input hydrogen sensor is used, which is installed in the input part of the channel cavity, and the output hydrogen and oxygen sensors located in the output part of the channel cavity. The input and output hydrogen sensors, the oxygen sensor and the catalytically active element are connected to at least one power source.

The disadvantages of this technical solution are the low speed and sensitivity of the device, as well as the lack of protection against erroneous readings that occur when a possible change in the flow direction of the analyzed gas medium in the channel, i.e. in the case when the analyzed gas enters the channel through the outlet of the channel cavity, as a result of which the determination of the true oxygen concentration is erroneous.

The objective of the technical solution is to eliminate these drawbacks, namely increasing speed and sensitivity, providing protection against erroneous readings of the device.

To solve the problem in a device including a rope, an input hydrogen sensor located in the input part of the channel cavity, an input catalytically active element installed in a cross section of the middle part of the channel cavity, an output hydrogen sensor and an output oxygen sensor located in the output part of the channel cavity, moreover, the sensors are connected to the registration and control system, it is proposed:

- additionally equip the device with an input oxygen sensor, placing it in the input part of the channel cavity;

- additionally equip the device with an output catalytically active element by installing it in the upper part of the channel cavity above the output oxygen and hydrogen sensors;

- input and output catalytically active elements to perform from highly porous cellular materials with a platinum coating applied to their surface;

- use a solid-electrolyte hydrogen concentration sensor with a ceramic sensor made of oxygen-conducting ceramics as hydrogen sensors.

A schematic diagram of the device is shown in Figure 1, which uses the following notation: 1 - input catalytically active element, 2 - input hydrogen sensor, 3 - input oxygen sensor, 4 - output catalytically active element, 5 - output hydrogen sensor; 6 - output oxygen sensor, 7 - channel, 8 - heater, 9 - electrical connections.

The device comprises: a channel 7 located at an angle to the horizon, an input hydrogen sensor 2 and an input oxygen sensor 3 located in the input part of the cavity of the channel 7, an input catalytically active element 1 installed in the cavity of the channel 7 above the input sensors of hydrogen 2 and oxygen 3, the output hydrogen sensor 5 and the output oxygen sensor 6 located in the cavity of the channel 7 between the input 1 and output 4 catalytically active elements. Moreover, the input 1 and output 4 catalytically active elements are made of highly porous cellular materials with a platinum coating applied to their surface. As an input hydrogen sensor 2 and an output hydrogen sensor 5, solid electrolyte hydrogen concentration sensors with a ceramic sensing element made of oxygen-conducting ceramic were used. The input oxygen sensor 3 is used as a signaling device of the appearance of hydrogen in the studied gas medium. The change in the signal of the input oxygen sensor 3 occurs when hydrogen appears in the studied gas medium due to the interaction of hydrogen and oxygen and sorption processes on the surface of the ceramic sensitive element of the input oxygen sensor 3.

This device is designed to record the occurrence of ultra-low concentrations of hydrogen (~ 5 × 10 ^-3 vol.%) In the test gas environment in a time interval not longer than a few seconds. Installation of the output catalytically active element, which produces a catalytic afterburning of oxygen and hydrogen, ensures the correct operation of the output oxygen sensor and protection against erroneous readings of the device.

The device operates as follows:

The analyzed gas medium comes into contact with the upstream hydrogen sensor 2 and the upstream oxygen sensor 3 installed in the input part of the channel 7. In this case, the upstream oxygen sensor 3 operates in the mode of signaling the appearance of small and ultra-low concentrations of hydrogen in the analyzed gas medium. The oxygen concentration of the input oxygen sensor 3 in the analyzed gas medium is not determined, since the presence of hydrogen interferes with this measurement.

Further, the analyzed gas medium, due to natural convection formed by the inlet sensors of hydrogen 2 and oxygen 3 heated to a high temperature, and the heater 8, passes in the channel cavity through the inlet catalytically active element 1, made, for example, of highly porous materials coated with platinum coated and heated with a heater 8 to a temperature that ensures the occurrence of a catalytic oxidation of hydrogen on its surface to water vapor with a recombination coefficient equal to Diniz.

Then, the analyzed gas medium comes into contact with the output hydrogen sensor 5 heated to a high temperature and the output oxygen sensor 6 installed in the cavity of the channel after the input catalytically active element 1. Using electrical connections, 9 signals from the input sensors of hydrogen 2 and oxygen 3 and output sensors hydrogen 5 and oxygen 6 can be transferred to the registration system to determine the concentration of hydrogen and oxygen in the analyzed gas medium. Then, the analyzed gas mixture leaves the cavity of the channel 7 through the output catalytically active element 4, and the output catalytically active element 4 is not equipped with a heater, and its heating is carried out due to the analyzed gas medium heated by gas sensors and the input catalytically active element.

To prevent penetration of the analyzed gas medium to the output hydrogen sensor 5 and the output oxygen sensor 6 through the upper part of the channel 7, an output catalytically active element 4 is installed in it, which produces a catalytic afterburning of oxygen and hydrogen in the event of a possible change in the flow direction of the analyzed gas medium in the channel and ensures Thus, the correct operation of the output oxygen sensor 6 and protection against erroneous readings of the device.

The true concentration of oxygen in the analyzed gas medium is determined by the ratio:

$$C_{O_2}^{\mathrm{and}\mathrm{from}t}=C_{O_2}^{\mathrm{at}sx}+{\mathrm{TO}}_{\mathrm{from}t}(C_{H_2}^{\mathrm{at}x}-C_{H_2}^{\mathrm{at}sx}),\begin{array}{cccc}& & & \end{array}\text{(one)}$$

- концентрация кислорода, фиксируемая выходным сенсором кислорода 6; $$C_{H_2}^{вх}$$

- концентрация водорода, фиксируемая входным сенсором водорода 2; $$C_{H_2}^{вых}$$

- концентрация водорода, фиксируемая выходным сенсором водорода 6; К_ст - стехиометрический коэффициент $$\left(K_{ст}\approx \frac{1}{2}\right)$$

.Where $$C_{O_2}^{\mathrm{at}sx}$$

- the oxygen concentration recorded by the output oxygen sensor 6; $$C_{H_2}^{\mathrm{at}x}$$

- hydrogen concentration recorded by the input hydrogen sensor 2; $$C_{H_2}^{\mathrm{at}sx}$$

- hydrogen concentration detected by the output hydrogen sensor 6; To _st - stoichiometric coefficient $$\left(K_{\mathrm{from}t}\approx \frac{\mathrm{one}}{2}\right)$$

.

An example of a specific implementation of the device

Channel 1 is made of stainless corrosion-resistant steel and is positioned so that the axis of the channel forms an angle of 90 ° with the horizontal direction.

As input 3 and output 6 oxygen sensors, solid-state oxygen concentration sensors with a galvanic concentration cell based on an oxygen-conducting solid electrolyte made from partially stabilized zirconia are used [RF Patent No. 2298176, “Solid-Electrolyte Oxygen Concentration Sensor and Methods of Its Production”].

, $$C_{O_2}^{вых}=16об.\%$$

, $$C_{H_2}^{вых}=0$$

. Определенная по формуле (1) истинная концентрация кислорода $$C_{O_2}^{ист}$$

составила 19%.Solid-state hydrogen sensors for gas and liquid media with a galvanic concentration cell based on an oxygen-conducting solid electrolyte made of partially stabilized zirconia, equipped with a camera with constant water vapor pressure and a hydrogen-permeable membrane are used as an input hydrogen sensor 2 and an output hydrogen sensor 5 [RF Patent No. 90907 , “Solid Electrolyte Hydrogen Sensor for Liquid and Gaseous Media”]. Upon receipt of a gas mixture containing 6 vol.% Hydrogen at the input of the device, the readings of the gas sensors were as follows: $$C_{H_2}^{\mathrm{at}x}=6ob.\%$$

, $$C_{O_2}^{\mathrm{at}sx}=16\mathrm{about}b.\%$$

, $$C_{H_2}^{\mathrm{at}sx}=0$$

. The true oxygen concentration determined by formula (1) $$C_{O_2}^{\mathrm{and}\mathrm{from}t}$$

amounted to 19%.

The technical result consists in increasing the speed and sensitivity of the device, providing protection against erroneous readings of the device due to a possible change in the flow direction of the analyzed gas medium in the channel cavity.

Claims (3)

1. A device for determining the concentration of oxygen and hydrogen in a gaseous medium, including a channel, an input hydrogen sensor located in the input part of the channel cavity, an input catalytically active element installed in a cross section of the middle part of the channel cavity, an output hydrogen sensor and an output oxygen sensor located in the output part of the channel cavity, the sensors being connected to a registration and control system, characterized in that the device further comprises an input oxygen sensor located in audio channel portion of the cavity, and the output of the catalytically active element mounted in the upper part of the cavity over the channel output sensors of oxygen and hydrogen. 2. The device according to claim 1, characterized in that the input and output catalytically active elements are made of highly porous cellular materials with a platinum coating applied to their surface. 3. The device according to claim 1, characterized in that a solid electrolyte hydrogen concentration sensor with a ceramic sensor made of oxygen-conducting ceramic is used as hydrogen sensors.