RU174760U1 - Multi-way track gas analyzer - Google Patents

Multi-way track gas analyzer Download PDF

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RU174760U1
RU174760U1 RU2016144462U RU2016144462U RU174760U1 RU 174760 U1 RU174760 U1 RU 174760U1 RU 2016144462 U RU2016144462 U RU 2016144462U RU 2016144462 U RU2016144462 U RU 2016144462U RU 174760 U1 RU174760 U1 RU 174760U1
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optical radiation
gas analyzer
characterized
made
radiation
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RU2016144462U
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Russian (ru)
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Александр Михайлович Баранов
Владимир Владимирович Слепцов
Алексей Владимирович Савкин
Сергей Сергеевич Фанченко
Андрей Сергеевич Сомов
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Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский авиационный институт (национальный исследовательский университет)"
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/01Arrangements or apparatus for facilitating the optical investigation

Abstract

The utility model relates to monitoring systems for multicomponent mixtures of toxic and combustible gases in the air. The gas analyzer of multicomponent gas mixtures is made in the form of two blocks - an optical radiation source made on the basis of LEDs and an optical radiation receiver made on the basis of a photodiode located on the same axis at a distance from each other. Moreover, the optical radiation source is configured to emit at three or more wavelengths in the range 1.3-2.3 μm, and the optical radiation receiver unit is made with a semiconductor photodiode with the ability to receive radiation waves in the range 1.3-2.3 μm. The technical result consists in expanding the capabilities and applications of infrared gas analyzers. 7 c.p. f-ly, 5 ill.

Description

The utility model relates to monitoring systems of mixtures of toxic and combustible gases in the air, namely to infrared (IR) gas analyzers of the “open path”, and can be used to continuously monitor the presence of mixtures of hydrocarbons and other gases in the air by measuring the absorption of a multiwave optical radiation passing through the gas "cloud".

A multicomponent gas analyzer is known (US Patent, # 4914719), in which the concentration of a multicomponent mixture is determined by measuring absorption at three wavelengths. A thermal heater emitting in the IR region acts as a radiation source. Infrared radiation from sources passes through a cuvette containing the test gas and is detected by a detector. The intensity of transmitted radiation at a particular wavelength depends on the concentration of gases in the cell. The gas concentration in the cell is calculated by solving a system of three algebraic equations.

The disadvantage of this method and device for measurements is the following features. Since the absorption spectra of the studied gases overlap, the measurements at three working wavelengths make it possible to determine the concentration of only previously known gases. If the type of gas is unknown, then it is impossible to calculate their concentration in this way. In addition, a thermal (heated) source with a wide radiation spectrum (in the far IR range of 8.7–12.3 μm) is used as a radiation source, from which the desired length is cut out using a rotary filter located in front of the radiation detector. This requires the use of a special engine.

The patent also describes a technical solution with three independent detectors, but it requires the use of three translucent optical dividers, which greatly complicates the design of the measuring device.

It is also important to note that the filter bandwidth is comparable to the radiation spectrum width of modern IR LEDs, but LEDs have advantages in miniature sizes and lower power consumption by several orders of magnitude.

Closest to the described device is a methane gas analyzer (Utility Model Patent of the Russian Federation, No. 157463), made in the form of two blocks - an optical radiation source and an optical radiation receiver, located on the same axis at a distance from each other. The optical radiation unit includes an optical circuit for the formation of a parallel beam with low divergence and an electronic circuit for controlling and powering the radiation source (s). The optical radiation receiver unit includes a photodetector, an optical circuit for focusing the incoming radiation on the sensitive element of the photodetector, an electronic control and data processing circuit, and a photodetector power circuit. To exclude the influence of uncontrolled atmospheric factors (the presence of water vapor, temperature, changes in illumination, etc.) on the measurement results, the gas analyzer is made using a two-wave optical system with measuring and reference beams of 2.3 μm and 1.7 μm, respectively. This route gas analyzer can be used to control the concentrations of methane or other combustible gases in the air, due to the absorption of optical radiation passing through the gas "cloud".

The disadvantage of this device is that it is possible to control the content of only one gas in the air, for example methane. Measuring the concentration of multicomponent mixtures is not possible due to the use of only one measuring beam.

Utility Model Disclosure

The utility model is based on the task of expanding the spectrum of capabilities of infrared gas analyzers of the “open” path through the use of multi-wave radiation passing through the gas “cloud”. The use of multiwave radiation makes it possible to determine the concentration of individual components in air in the case of monitoring multicomponent gas mixtures and vapors.

The problem is solved in that in a gas analyzer of multicomponent gas mixtures containing an optical radiation source unit made on the basis of LEDs and an optical radiation receiver unit made on the basis of a photodiode located on one optical axis at a distance from each other, the optical radiation source is made with the possibility of radiation at three or more wavelengths in the range 1.3-2.3 μm, and the optical radiation receiver unit is made with a semiconductor photodiode with the possibility of radiation emitted by him in the range 1.3–2.3 μm. In this case, it may be that the source of optical radiation is an LED matrix placed in the housing of the source unit; LED matrix is placed in the source casing with a parabolic reflector; light-emitting diodes are made in the form of discrete elements placed in the transmitter housing; light-emitting diodes are made in separate cases with parabolic reflectors and placed in the transmitter case; the LED matrix is placed on the cooled base, the photodiode is located on the cooled base, and the photodiode is located in a parabolic case collecting optical radiation.

Since the optical radiation source is configured to emit at three or more wavelengths in the range 1.3-2.3 μm, and the optical radiation receiver unit is made with a semiconductor photodiode with the ability to receive radiation waves in the range 1.3-2.3 μm, it may be that the source optical radiation is an LED matrix placed in the body of the source unit; LED matrix is placed in the source casing with a parabolic reflector; light-emitting diodes of the LED matrix are made in separate cases; light emitting diodes are made in separate cases with parabolic reflectors; the LED matrix is placed on the cooled base, the photodiode is located on the cooled base and the photodiode is located in a parabolic case collecting optical radiation, and the possibilities and applications of infrared gas analyzers are expanded in the case of monitoring multicomponent gas mixtures and vapors and determining the concentration of individual components of the mixture in air.

Brief Description of the Drawings

In FIG. 1 shows a schematic diagram of a multi-wave path gas analyzer consisting of a source 1 and a receiver 2 of optical radiation; in FIG. 2 shows the appearance of a 6-element LED array; in FIG. 3 shows the dependence of the sensitivity of the photodiode on the wavelength; in FIG. 4 shows the emission spectra of a 6-element LED matrix in the wavelength range 1.3-2.3 μm and the absorption spectra of water vapor (H 2 O), carbon dioxide (CO 2 ), carbon monoxide (CO) and methane (CH 4 ) in air; in FIG. 5 is a schematic diagram of a multi-wave path gas analyzer with a discrete set of LEDs, each of which has a parabolic reflector.

Utility Model Implementation

The device operates as follows.

Both blocks, the source 1 and the receiver 2 of optical radiation, are mounted on the same optical axis at a predetermined distance from each other (Fig. 1). An LED matrix 5 consisting of more than 2 LEDs is used as a radiation source, for example, the 6-element LED matrix shown in FIG. 2.

LEDs are selected in such a way that the maximum of their radiation is in the IR wavelength range 1.3-2.3 μm. Smaller than 1.1 μm, the wavelength corresponds to the LEDs in the visible range. A wavelength of more than 2.5 μm requires forced cooling of the LEDs to negative temperatures, due to the small band gap of the LED semiconductor material and the predominance of nonradiative recombination over radiative recombination. The measuring unit uses a Lms24PD-20-TEM semiconductor photodiode.

Monitoring the composition of the gas composition of the medium is carried out on the basis of successive measurements of the transmittance of radiation from all the LEDs of the LED matrix. For this purpose, the LEDs are sequentially switched on and emit infrared optical radiation. The radiation leaves block 1 through a glass 7 transparent in the IR region, propagates in the atmosphere being analyzed, and is recorded by the photodetector as photodiode 6. In this case, the different sensitivity of the photodiode at different wavelengths (Fig. 3) in the range is taken into account. To increase the collection of radiation, a collecting lens is installed in front of the photodiode 4. A decrease in transmittance at the measured wavelength indicates the presence of an absorbing corresponding gas.

The choice of wavelengths of LEDs is determined based on the position of the absorption bands of the gases under study, the maximums of the emission lines should fall (approximately) on the main absorption bands, and the number of LEDs should be at least one greater than the number of gases in the gas mixture. The wavelength of the reference LED is selected so that its wavelength is not absorbed by the gaseous medium of a given composition. To reduce the divergence of radiation, a parabolic reflector 8 is used.

To reduce the influence of temperature, the LEDs and photodiode their temperature is stabilized due to their location on the cooled base 3.

The signals received by the photodiode are filtered from noise, amplified, converted into digital signals and processed in order to obtain the concentration of the target gases in the air. Depending on the installed software, only data on the concentration of gases in the air or warning signals about different levels of danger associated with exceeding the established norms and requirements for individual gases can be received at the control console.

Example. Measurement of the concentration of exhaust gases. The content of H 2 O, CO 2 , CO and CH 4 in the air is detected.

The choice of wavelengths of LEDs for the detection of H 2 O, CO 2 , CO, and CH 4 in air is determined based on the position of the absorption bands of the studied gases. The method of choosing wavelengths is based on the following. First, at least one characteristic absorption band of each gas must be covered by one of all the lines of the LED matrix. If the absorption bands of various gases do not overlap, then this is enough. If the absorption bands of various gases overlap, then you need to add another wavelength that covers the second absorption band of one of the gases. If the probability of overlapping one band for several gases is high enough, then two and with the same absorption coefficient are very small (except for the case of two gases from the same homologous series). The wavelength of the reference LED is selected so that its wavelength is not absorbed by the gaseous medium of a given composition.

The operation of the gas analyzer is illustrated by the example of the detection of exhaust gases (H 2 O, CO 2 , CO and CH 4 ) (Fig. 4). As a radiation source, a 6-LED matrix is selected. Five LEDs operate in the measuring mode, one as a reference (not absorbed in the test gas mixture). A beam at a wavelength of 1.3 μm was chosen as the reference, since it practically does not overlap with any of the absorption bands. A wavelength of 1.4 μm is chosen in this wavelength range to characterize water vapor (H 2 O), a wavelength of 2.0 μm is carbon dioxide (CO 2 ), 1.6 μm is methane (CH 4 ), and 2.3 μm is carbon monoxide (CO). In principle, these four wavelengths for the selected absorption spectra are sufficient, but the 1.8 μm line is also used to increase the accuracy of concentration recovery due to partially overlapping spectra of water (H 2 O) and carbon dioxide (CO).

Monitoring the composition of the gas composition of the medium is carried out on the basis of successive measurements of the transmittance of radiation from all LEDs of the LED matrix at wavelengths of 1.4, 1.5, 1.6, 1.8, 2.0 and 2.3 μm. For this purpose, the LEDs are sequentially switched on and emit infrared optical radiation. The radiation propagates in the analyzed atmosphere and is recorded by the photodetector in the form of photodiode 6. In this case, the different sensitivity of the photodiode at different wavelengths is taken into account. A decrease in transmittance at the measured wavelength indicates the presence of an absorbing corresponding gas.

The transmission coefficients of light from five measuring LEDs are normalized to the transmission coefficient from the reference LED to exclude the influence of uncontrolled atmospheric factors (temperature, pressure, wind, fog, etc.), the effects of light scattering and absorption in the measuring path.

After such normalization, the data on transmission coefficients are cleaned from noise and processed on the basis of the Bera-Lambert law of light absorption. As a rule, it is not possible to ensure that the spectrum of one LED line covers only one absorption band, cross sensitivity occurs, but due to the use of several LEDs, it is nevertheless possible to determine the concentrations of all gases of the mixture under study.

The results obtained are presented in Table 1.

Figure 00000001

Emission LEDs have a wide divergence of radiation. This limits the distance between the source and the receiver of optical radiation due to a decrease in the radiation intensity of the radiation incident on the receiver. The use of parabolic reflectors 8 (Fig. 1) can reduce the divergence of radiation by several times, thereby increasing the directivity of the optical beam.

In addition, the LED matrix as the radiation sources in block 1 can be used separate light-emitting LEDs in parabolic cases (Fig. 5).

The emission spectrum of LEDs depends on their temperature, which can increase due to heat generation during radiation. To eliminate this effect, the LEDs are placed on a cooled base 3, which allows you to stabilize the temperature of the LED.

Claims (8)

1. The gas analyzer of multicomponent gas mixtures containing an optical radiation source unit based on light emitting diodes and an optical radiation receiver unit based on a photodiode located on the same optical axis at a distance from each other, characterized in that the optical radiation source is made with the possibility of radiation at three or more wavelengths in the range 1.3-2.3 μm, and the receiver unit of the optical radiation is made with a semiconductor photodiode with the ability to receive radiation waves Nia in the range 1.3-2.3 microns.
2. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the source of optical radiation is an LED array located in the housing of the transmitter unit.
3. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the LED matrix is placed in the transmitter housing with a parabolic reflector.
4. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the light-emitting diodes are made in the form of discrete elements placed in the transmitter housing.
5. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the light emitting diodes are made in separate cases with parabolic reflectors and placed in the transmitter case.
6. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the LED matrix is placed on a cooled base.
7. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the photodiode is located on a cooled base.
8. The gas analyzer of multicomponent gas mixtures according to claim 1, characterized in that the photodiode is located in a parabolic housing collecting optical radiation.
RU2016144462U 2016-11-14 2016-11-14 Multi-way track gas analyzer RU174760U1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6995360B2 (en) * 2003-05-23 2006-02-07 Schlumberger Technology Corporation Method and sensor for monitoring gas in a downhole environment
RU96971U1 (en) * 2010-02-02 2010-08-20 Государственное образовательное учреждение высшего профессионального образования "Тверской государственный технический университет" Analysis aerosol
RU2451285C1 (en) * 2010-11-12 2012-05-20 Общество С Ограниченной Ответственностью "Оптосенс" Gas analyser and optical unit used therein
RU157463U1 (en) * 2015-06-26 2015-12-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Московский авиационный институт (национальный исследовательский университет)" (МАИ) Track gas analyzer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6995360B2 (en) * 2003-05-23 2006-02-07 Schlumberger Technology Corporation Method and sensor for monitoring gas in a downhole environment
RU96971U1 (en) * 2010-02-02 2010-08-20 Государственное образовательное учреждение высшего профессионального образования "Тверской государственный технический университет" Analysis aerosol
RU2451285C1 (en) * 2010-11-12 2012-05-20 Общество С Ограниченной Ответственностью "Оптосенс" Gas analyser and optical unit used therein
RU157463U1 (en) * 2015-06-26 2015-12-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Московский авиационный институт (национальный исследовательский университет)" (МАИ) Track gas analyzer

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