Gas analyzer purpose. Gas analyzers what it is and why are they needed

Analysis of gas mixtures in order to establish their quality and quantitative composition is called gas analysis.

Devices with which to produce gas analysis are called gas analyzers. They are manual and automatic. Among the first, the most common are chemical absorption, in which the components of the gas mixture are sequentially absorbed by various reagents.

Automatic gas analyzers measure any physical or physicochemical characteristic of a gas mixture or its individual components.

Currently, the most common automatic gas analyzers.

According to the principle of operation, they can be divided into three main groups:

1. Devices, the action of which is based on physical methods of analysis, including auxiliary chemical reactions. With the help of such gas analyzers, the change in the volume or pressure of a gas mixture as a result of chemical reactions of its individual components is determined.

2. Devices, the operation of which is based on physical methods of analysis, including auxiliary physical and chemical processes (thermochemical, electrochemical, photocolorimetric, etc.). Thermochemical ones are based on measuring the thermal effect of the catalytic oxidation (combustion) reaction of a gas. Electrochemical ones make it possible to determine the concentration of gas in a mixture by the value of the electrical conductivity of the electrolyte that has absorbed this gas. Photocolorimetric based on the change in the color of certain substances, when they react with the analyzed component of the gas mixture.

3. Devices, the operation of which is based on purely physical methods of analysis (thermoconductometric, thermomagnetic, optical, etc.). The principle of operation of thermal conductometric gas analyzers is based on measuring the thermal conductivity of gases. Thermomagnetic gas analyzers are mainly used to determine the concentration of oxygen, which has a high magnetic susceptibility. The operation of optical gas analyzers is based on measuring the optical density, absorption spectra or emission spectra of a gas mixture.

Each of the methods mentioned has its pros and cons, the description of which will take a lot of time and space, and is beyond the scope of this article. Manufacturers of gas analyzers currently use almost all of the listed methods of gas analysis, but electrochemical gas analyzers are the most widely used, as the cheapest, universal and simplest ones. Disadvantages of this method: low selectivity and measurement accuracy; short service life of sensitive elements exposed to aggressive impurities.

All gas analysis devices can also be classified:

• by functionality (indicators, leak detectors, alarms, gas analyzers);
• by design (stationary, portable, portable);
• by the number of measured components (one-component and multicomponent);
• by the number of measurement channels (single-channel and multi-channel);
• as intended (to ensure the safety of work, to control technological processes, to control industrial emissions, for vehicle exhaust gas control, for environmental control).

Functionality classification

1. Indicators are devices that give a qualitative assessment of a gas mixture by the presence of a controlled component (according to the principle "a lot - a little"). As a rule, information is displayed using a ruler of several point indicators. All indicators are on - there are many components, one is on - few. This also includes leak detectors. Leak detectors equipped with a probe or sampler can be used to locate a leak from a pipeline, for example a refrigerant gas.

2. Alarms also give a very rough estimate of the concentration of the monitored component, but at the same time they have one or more alarm thresholds. When the concentration reaches the threshold value, the alarm elements are triggered (optical indicators, sound devices, relay contacts are switched).

3. The pinnacle of the evolution of gas analysis devices is the gas analyzers themselves. These devices not only quantify the concentration of the measured component with indication of readings (by volume or by mass), but can also be equipped with any auxiliary functions: threshold devices, output analog or digital signals, printers, and so on.

Design classification

Like most control and measuring devices, gas analysis devices can have different weight and size indicators and modes of operation. These properties determine the division of devices by design. Heavy and bulky gas analyzers designed for long-term continuous operation are stationary. Smaller products that can easily move from one object to another, and can be quite simply put into operation - portable. Small and lightweight designed for personal safety - portable.

Classification by the number of measured components

Gas analyzers can be designed to analyze multiple components at once. Moreover, the analysis can be carried out both simultaneously for all components, and alternately, depending on design features device.

Classification by the number of measurement channels

Gas analysis devices can be either single-channel (one sensor or one sampling point) or multi-channel. As a rule, the number of measurement channels per device varies from 1 to 16. It should be noted that modern modular gas analysis systems allow increasing the number of measurement channels almost indefinitely. The measured components for different channels can be either the same or different, in an arbitrary set. For gas analyzers with sensor flow-through type(thermoconductometric, thermomagnetic, optical-absorption) the problem of multi-point control is solved with the help of special auxiliary devices - gas distributors, which provide alternate supply of the sample to the sensor from several sampling points.

Classification by purpose

Unfortunately, it is impossible to create a single universal gas analyzer, with the help of which it would be possible to solve all the problems of gas analysis, for the reason that none of the known methods allows measurements with the same accuracy in the widest possible range of concentrations. The control of different gases, in different concentration ranges, is performed by different methods and methods. Therefore, manufacturers design and manufacture devices for solving specific tasks measurements. The main tasks are: control of the atmosphere of the working area (safety), control of industrial emissions (ecology), control of technological processes (technology), control of atmospheric pollution of the residential area (ecology), control of vehicle exhaust gases (ecology and technology), control of human exhaled air ( healthcare) ... Separately, we can highlight the control of gases dissolved in water and other liquids. In each of these areas, even more narrowly specialized groups of devices can be distinguished.

As you probably noticed, the material of this article cannot claim to be 100% scientific reliability, but only expresses the author's point of view on the issues under consideration, and the author may be mistaken or sincerely mistaken. However, we hope that the material we have proposed may turn out to be useful topics who are interested in gas analysis issues ...

Gas analyzers are equipment that helps to accurately measure the qualitative and quantitative composition of a gas. The principle of operation of the gas analyzer is not very complicated, but each type of equipment has its own characteristics. Best of all, these moments can be reflected by the diagram of the gas analyzer. In this article, we will consider both the general principle of operation and the operation of some models of gas analyzers.

General working principle

The principle of operation is based on the absorption of constituent substances by special reagents. This happens in a special sequence. If the principle of operation is automatic, then the measurement takes place constantly, which means that no interruptions occur. This is convenient because the physicochemical parameters of the gas mixture are recorded accurately, which is also possible when interacting with individual components of the substance.

The analysis of various gas mixtures is used by enterprises in the metallurgical, chemical and heat generating industries. The data that make it clear about the number of certain components is needed to control the process in order to subsequently optimize and debug its work.

Gas measuring equipment includes models different types... They differ from each other in some parameters and in the principle of operation.

Their work is based on the fact that the thermal conductivity of a gas mixture depends on what components are included in its composition. Such a gas analyzer has the following main parts:

1. The measuring cell is in the form of a cylindrical channel, which is made of a material of high thermal conductivity and is filled with the analyzed gas.
2. A heating element located inside the channel and powered from a voltage source.

The cell is filled with air. If the current value is stable, then a heating element will have a certain temperature, in which case the heat received by the element and the heat that it gives to the channel material will be equal to each other.

If the duct is filled not with air, but with gas, which differs in thermal conductivity, the heating element will have a different temperature. In the event that the thermal conductivity of the gas exceeds the thermal conductivity of air, the temperature of the element will be lower; if it does not exceed, but becomes lower, then the temperature of the element will increase.

Optical devices

Basis of work of this type the device consists in the fact that the radiation flux is absorbed by various gases in a selective way. In the infrared part of the spectrum, a change in selective absorption is usually carried out, since it is in this place that absorption selectivity is observed.

Such a gas analyzer has:

1. A source infrared radiation;
2. Cameras of two optical channels, which differ only in their internal content: the comparison chamber is full clean air, and the working chamber constantly blows the controlled gas mixture; a stream of infrared radiation enters these cameras.
3. Filter chambers.

The radiation flux when passing through the volume of the second, working chamber, loses part of its energy. This does not happen when crossing the comparison chamber. Both fluxes of radiation then enter the filter chambers, where the unmeasurable components of the gas mixture are located. At this point, the energy corresponding to the spectrum is completely absorbed.

Thermochemical gas analyzers

Such devices determine the energy of the generated heat when a chemical reaction takes place in a mixture of gases. The principle of operation is based on the oxidation process of gas components. However, additional catalysts are used, such as fine platinum and manganese-copper catalyst.

A special thermistor helps measure the temperature that occurs. This device changes its resistance, which depends on the temperature, which contributes to a change in the passing current.

Electrochemical gas analyzers

This model is designed to detect toxic gases. Its peculiarity is that it can be used in hazardous areas. This device is compact, energy-saving and insensitive to mechanical stress.

The basis of these gas analyzers is the phenomenon of electrochemical compensation. This means that a special reagent is released that reacts with some specific component of the mixture. There are several types of electrochemical gas analyzers:

• potentiometric; their purpose is to measure the ratio of the field strength;
• electro-conductometric; they respond to changes in tension and current;
• electroplating; sensitive to changes in electrical conductivity.

As you can see, the principle of operation of gas analyzers is not complicated, however, one type of device differs from another, since it has different goals. Gas analyzers are useful devices that allow you to determine the state of gas on this moment indoors, which will maintain human health at an acceptable level.

In modern industrial conditions, the work area - a place where people are periodically or constantly during a work shift - can be increased by a dangerous area.

In connection with technological processes or during accidental releases, the air in the work area is contaminated with toxic, flammable and explosive gas components.

Gas analyzers- devices with the help of which the composition of the gas mixture is determined, both qualitative (which gases are present) and quantitative (how many specific gases are in the mixture).

First of all, gas analyzers are equipped with fire, explosion and chemically hazardous industries, as well as mines where there are accumulations of firedamp (methane).

Be sure to use gas analyzers before carrying out hot work in basements and wells, as well as to certify jobs in hazardous industries.

Application for personal protection

Portable gas analyzers small size, which employees of hazardous industries are supplied can be considered primary personal protective equipment.

They promptly signal an increased content of harmful impurities in the air, at which it is necessary to leave the working area or apply. The gas analyzer is shown in the photo:

The way the device works

Handheld analyzers, which are activated by the operator, are based on the fact that individual gaseous components are absorbed by special reagents.

The air in the production area is passed through an absorber that binds a specific gas. After that, the initial volume of the mixture is reduced. By reducing the volume, it is calculated how much gas bound by the absorber was initially contained there. Depending on the qualifications of the operator, measurement takes five to ten minutes.

Operation of automatic analyzers continuous action based on physical and chemical processes, as well as their combination.

The physical principle of measuring the result of the auxiliary chemical reaction ensures the operation of volumetric or chemical analyzers. In these devices measures how much the volume or pressure of a gas mixture has changed after its components have entered into certain chemical reactions.

The physicochemical principle of action, combined with the physical one, has the following devices:

The following automatic gas analyzers have purely physical principles of operation:

Varieties

In addition to the difference in the mode of operation (manual or automatic) and the principle of operation, gas analyzers for air in the working area are divided into types:

• Stationary... Such devices automatically monitor the concentration of gases. V industrial performance if the permissible content of the hazardous gas component is exceeded, they give light and sound signals, and also include ventilation and other security systems;
• Portable... Designed to determine the concentration of gas impurities in different parts of the production area;
• Portable... Individual devices. They have small dimensions and weight, measure the concentration of harmful impurities directly where the worker is.

In addition, by the amount of measured impurities, these devices are single and multicomponent, and according to the number of channels (sensors or sampling points) - single and multichannel.

Selection rules

To choose the right device for monitoring the air in the working area, you need, first of all, proceed from the list of impurities to be defined. It also has value hazard class of impurities: there are modifications of devices for explosive and explosion-proof environment.

Samples of models of industrial gas analyzers are shown in the photo:

Depending on the tasks set, this is general control, local or individual, choose stationary, portable or portable models of gas analyzers. And, finally, devices with different operating principles have inherent Advantages and disadvantages.

So, thermochemical devices have a low cost, but at the same time a short service life of the gas analyzer sensor, low speed and sensitivity, a small range of measured concentrations. Thermochemical analyzers used primarily for air control the production area for the content of flammable gases, for example, CO.

Electrochemical analyzers occupy an average price position. They have high sensitivity, a wide range of analytes, and low energy consumption. At the same time, they are large in size and difficult to maintain.

Optical instruments have excellent performance, high selectivity and sensitivity. The range of their measurement covers almost the entire spectrum of possible contamination. At the same time, the cost of optical gas analyzers is the highest.

Operation manual and storage

Installation, use and verification of gas analyzers for air in the working area must be carried out in strict accordance with the conditions specified by the manufacturer.

Storage requirements depend on the analyzer design... For example, electrochemical devices are stored in the supplier's packaging in a heated storage facility. at temperatures from + 5 ° C to + 40 ° C and can withstand high humidity.

Optical devices allow a temperature range from -50 ° C to + 50 ° C, however, they are sensitive to sudden changes in temperature and humidity, as well as to dust, aggressive vapors and other harmful impurities.

The guaranteed shelf life is usually 12 months, and the warranty service period does not exceed one and a half years.

Adequately sized, serviceable and properly used gas analyzer provides accurate and timely information on the air composition of the working area... This information may be not only necessary, but also vital for the employee.

In conclusion, we suggest watching a video review of how the FP11.2K gas analyzer works:

Devices with which gas mixtures are analyzed in order to establish their qualitative and quantitative composition are called gas analyzers.

According to the principle of operation, they can be divided into three main groups.

1. Devices, the action of which is based on physical methods of analysis, including auxiliary chemical reactions. With the help of such gas analyzers, the change in the volume or pressure of a gas mixture as a result of chemical reactions of its individual components is determined.
2. Devices, the operation of which is based on physical methods of analysis, including auxiliary physicochemical processes (thermochemical, electrochemical, photocolorimetric, etc.). Thermochemical ones are based on measuring the thermal effect of the catalytic oxidation (combustion) reaction of a gas. Electrochemical ones make it possible to determine the concentration of gas in a mixture by the value of the electrical conductivity of the electrolyte that has absorbed this gas. Photocolorimetric based on the change in the color of certain substances, when they react with the analyzed component of the gas mixture.
3. Devices, the operation of which is based on purely physical methods of analysis (thermoconductometric, thermomagnetic, optical, etc.). Thermal conductivity measurements are based on measuring the thermal conductivity of gases. Thermomagnetic gas analyzers are mainly used to determine the concentration of oxygen, which has a high magnetic susceptibility. Optical gas analyzers are based on measuring optical density, absorption spectra or emission spectra of a gas mixture.

Gas analyzers can be divided into several types depending on the tasks performed - these are combustion gas analyzers, gas analyzers for determining the parameters of the working area, gas analyzers for monitoring technological processes and emissions, gas analyzers for purifying and analyzing water, etc. execution on portable, portable and stationary, according to the number of measured components (can be measurement of one or several substances), according to the number of measurement channels (single-channel and multi-channel), according to functionality (indicators, alarms, gas analyzers).

Combustion gas analyzers are designed for setting up and monitoring boilers, furnaces, gas turbines, burners and other fuel combustion installations. They also allow monitoring emissions of hydrocarbons, carbon oxides, nitrogen, sulfur.

Gas analyzers (gas alarms, gas detectors) for monitoring the air parameters of the working area. Monitor for hazardous gases and vapors in working area, indoors, mines, wells, collectors.

Stationary gas analyzers are designed to control the composition of gas during technological measurements and control emissions in metallurgy, energy, petrochemistry, cement industry. Gas analyzers measure the content of oxygen, nitrogen and sulfur oxides, freon, hydrogen, methane and other substances.

Firms offering gas analyzers for Russian market: Kane International (Great Britain), Testo GmbH (Germany), FSUE Analitpribor (Russia), Eurotron (Italy), LLC Ditangaz (Russia).

Gas analyzers - devices that measure the content (concentration) of one or more components in gas mixtures. Each gas analyzer is designed to measure the concentration of only certain components against the background of a specific gas mixture under specified conditions. Along with the use of separate gas analyzers, gas monitoring systems are being created that combine dozens of such devices.

Gas analyzers are classified by type into pneumatic, magnetic, electrochemical, semiconductor, etc.

Thermal conductometric gas analyzers. Their action is based on the dependence of the thermal conductivity of the gas mixture on its composition.

Thermal conductometric gas analyzers do not have high selectivity and are used if the controlled component differs significantly from the others in terms of thermal conductivity, for example. to determine the concentrations of H 2, He, Ar, CO 2 in gas mixtures containing N 2, O 2, etc. Measurement range - from units to tens of percent by volume.

Thermochemical gas analyzers. These devices measure the thermal effect of a chemical reaction in which the determined component is involved. In most cases, oxidation of the component with atmospheric oxygen is used; catalysts - manganese-copper (hopcalite) or fine Pt deposited on the surface of a porous support. The change in t-ry during oxidation is measured using metal. or a semiconductor thermistor. In some cases, a platinum thermistor is used as a catalyst. The value is related to the number of molesM of the oxidized component and the thermal effect by the ratio:

Magnetic gas analyzers. This type is used to determine O 2. Their action is based on the dependence of the magnetic susceptibility of a gas mixture on the concentration of O 2, the volumetric magnetic susceptibility of which is two orders of magnitude greater than that of most other gases. Such gas analyzers allow the selective determination of O 2 in complex gas mixtures. The range of measured concentrations is 10 -2 - 100%. The most common magnetics. and thermomagn. gas analyzers.

In magnetomechanical gas analyzers, the forces acting in an inhomogeneous magnet are measured. field on a body (usually a rotor) placed in the analyzed mixture.

Gas analyzers made according to the compensation scheme are more accurate. In them, the moment of rotation of the rotor, which is functionally related to the concentration of O 2 in the analyzed mixture, is balanced by the known moment, for the creation of which magnetoelectric is used. or electrostatic. systems. Rotary gas analyzers are unreliable in industrial environments and are difficult to align.

Pneumatic gas analyzers. Their action is based on the dependence of the density and viscosity of the gas mixture on its composition. Changes in density and viscosity are determined by measuring the hydromech. stream parameters. Three types of pneumatic gas analyzers are common.

Gas analyzers with throttle converters measure hydraulics. the resistance of the throttle (capillary) when the analyzed gas is passed through it. At constant flow gas pressure drop across the throttle is the density function (turbulent throttle), viscosity (laminar throttle), or both at the same time.

Jet gas analyzers measure dynamic. the head of the gas jet flowing out of the nozzle. They are used, for example, in the nitrogen industry to measure the H2 content in nitrogen (measurement range 0-50%), in the chlorine industry - to determine C1 2 (0-50 and 50-100%). The settling time of the readings of these gas analyzers does not exceed several. seconds, therefore they are also used in gas detectors of pre-explosive concentrations of gases and vapors of certain substances (for example, dichloroethane, vinyl chloride) in industrial air. premises.

Infrared gas analyzers. Their action is based on selective absorption by molecules of gases and vapors of infrared radiation in the range of 1-15 microns. This radiation is absorbed by all gases, the molecules of which consist of at least two different atoms. The high specificity of the molecular absorption spectra of various gases determines the high selectivity of such gas analyzers and their wide application in laboratories and industry. The range of measured concentrations is 10 -3 -100%. Dispersive gas analyzers use radiation of one wavelength, obtained using monochromators (prisms, diffraction gratings). In non-dispersive gas analyzers, due to the features of the optical. device circuits (use of light filters, special radiation detectors, etc.), use non-monochromatic. radiation.

Ultraviolet gas analyzers. Their principle of operation is based on the selective absorption of radiation by molecules of gases and vapors in the range of 200-450 nm. The selectivity of the determination of monatomic gases is very high. Di- and polyatomic gases have a continuous absorption spectrum in the UV region, which reduces the selectivity of their determination. However, the absence of a UV absorption spectrum for N 2, O 2, CO 2 and water vapor makes it possible, in many practically important cases, to carry out rather selective measurements in the presence. these components. The range of determined concentrations is usually 10 -2 -100% (for Hg vapors the lower limit of the range is 2.5-10 -6%).

Ultraviolet gas analyzers use Ch. way for automatic control of the content of C1 2, O 3, SO 2, NO 2, H 2 S, C1O 2, dichloroethane, in particular in emissions industrial enterprises, as well as for the detection of Hg vapors, less often Ni (CO) 4, in indoor air.

Luminescent gas analyzers. Chemiluminescent gas analyzers measure the intensity of luminescence excited due to the chemical reaction of a controlled component with a reagent in a solid, liquid or gaseous phase. An example is interaction. NO with О 3 used for the determination of nitrogen oxides:

N0 + 0 3 -> N0 2 + + 0 2 -> N0 2 + hv + 0 2

Photocolorimetric gas analyzers. These devices measure the color intensity of the products chosen. p-tion between the determined component and a specially selected reagent. The reaction is carried out, as a rule, in solution (liquid gas analyzers) or on a solid carrier in the form of a tape, tablet, or powder (correspondingly tape, tablet, powder gas analyzers).

Photocolorimetric gas analyzers are used to measure the concentrations of toxic impurities (for example, nitrogen oxides, O 2, C1 2, CS 2, O 3, H 2 S, NH 3, HF, phosgene, a number of organic compounds) in the atmosphere of industrial. zones and in the air prom. premises. Portable instruments are widely used in air pollution control. periodic action... A large number of photo colorimetric gas analyzers are used as gas detectors.

Electrochemical gas analyzers... Their action is based on the relationship between the electrochemical parameter. system and the composition of the analyzed mixture entering this system.

In conductometric gas analyzers, the electrical conductivity of a solution is measured with selective absorption of the component being determined. The disadvantages of these gas analyzers are low selectivity and the duration of the establishment of indications when measuring low concentrations. Conductometric gas analyzers are widely used to determine O 2, CO, SO 2, H 2 S, NH 3, etc.

Ionization gas analyzers. The action is based on the dependence of the electrical conductivity of gases on their composition. The appearance of impurities in the gas has an additional effect on the formation of ions or on their mobility and, consequently, recombination. The resulting change in conductivity is proportional to the content of impurities.

All ionisation gas analyzers contain flow-through ionisation. a chamber, on the electrodes of which a certain potential difference is imposed. These devices are widely used to control trace impurities in the air, as well as detectors in gas chromatographs.