RU34749U1 - Equivalent gas and vapor detector - Google Patents

Description

EQUIVALENT GAS AND VAPOR DETECTOR The utility model relates to the field of analytical technology, namely, to detectors for gas chromatographic and evapororographic analysis.

Known is an equally sensitive gas and vapor detector (Farzane P.G. et al. Automatic detectors of gases and liquids. M: Energoatomizdat, 1983, p. 59-60), the operation of which is based on the phenomenon of drawing in paramagnetic gases, for example, oxygen or air, in a magnetic field and measuring (when the detected components arrive from the chromatographic column into the detector chamber) changes in the flow rate of the comparative gas from the pole piece equipped with a permanent magnet using a thermistor included in an unbalanced bridge and perform its function hot-wire anemometer.

The downside of such a detector is low sensitivity (0.25mZ /% vol.) And the ability to work only when using air or oxygen as a gas carrier.

The closest in technical essence is a diffusion isosensitive detector (Farzane N.G., Ilyasov L.V. An isosensitive diffusion detector for gas chromatography. Journal of Physical Chemistry, 1974, No. 8, p. 2024-2028), containing flow chambers of the carrier gas and auxiliary gas with inlet channels, separated from each other by a semipermeable membrane, in which the output channel of the auxiliary gas chamber is connected to the input channel of the gas detector, which is related to the concentration of carrier gas in the auxiliary AZE. The concentration measurement using such an equally sensitive detector is carried out by changing the detector signal, which is sensitive to the concentration of the carrier gas in the auxiliary

MGOS G01N30 / 76

gas, which occurs when components enter the gas carrier chamber by reducing the concentration of the carrier gas (hydrogen or helium), which diffuses through the semipermeable membrane into the auxiliary gas stream.

The disadvantage of this detector is the need to use, in addition to the carrier gas, auxiliary gas, which differs in physical and chemical properties from the carrier gas, to create a flow rate of which it is necessary to use a source of compressed auxiliary gas, which complicates the operation of the detector.

The objective of the proposed utility model is to simplify the operation of an equally sensitive gas and vapor detector.

EFFECT: creation of a simple, equally sensitive gas and vapor detector capable of working with a single source of compressed gas.

The technical result is achieved in that an isosensitive gas and vapor detector containing carrier gas and auxiliary gas chambers with inlet and outlet channels, separated from each other by a semi-permeable membrane, in which the output channel of the auxiliary gas chamber is connected to the input channel of a concentration sensitive gas detector carrier gas in the auxiliary gas, according to a utility model, further comprises a gas flow inducer, two variable chokes connected to the input channels of the gas chambers anositelya and auxiliary gas, a tee connected to the outlet of the detector, the output channel chamber

carrier gas and the inlet of the gas flow inducer, wherein the input of the variable choke connected to the input channel of the auxiliary gas chamber is connected to the atmosphere.

This design of an equally sensitive detector allows to simplify its operation, as it provides the possibility of detecting a component using only one source

compressed gas (helium or hydrogen) due to the fact that the auxiliary gas in the proposed detector is atmospheric air entering the auxiliary gas chamber under the influence of a small vacuum created by the flow inducer.

Compared with the prototype, the claimed design has a distinctive feature in the combination of elements and their relative position.

The circuit of an equally sensitive gas and vapor detector is shown in the drawing.

An equally sensitive gas and vapor detector comprises a gas carrier chamber 1 and an auxiliary gas chamber 2 with input 3 and 4 and output 5 and 6 channels, which are separated from each other by a semipermeable membrane 7. The output channel 6 of the auxiliary gas chamber 2 is connected to the input channel 8 of the gas detector 9 sensitive to the concentration of the carrier gas in the auxiliary gas.

The equally sensitive detector further comprises a gas flow inducer 10, two variable chokes 11 and 12 connected to the input channels 3 and 4 of the carrier gas and auxiliary gas chambers, a tee 13 connected to the output channel 14 of the detector 9, the output channel 5 of the carrier gas chamber 1 and the inlet 15 of the gas flow inducer 10. The inlet of the variable choke 11 connected to the auxiliary gas chamber is connected to the atmosphere. To supply the chromatographic column 16, a source of carrier gas 17 (a cylinder with compressed gas) is used, and an input device 18 is used to enter a sample of the analyzed medium.

The operation of an equally sensitive detector is as follows.

From the source 17, a carrier gas (helium or hydrogen) is supplied to the chromatographic column with a constant volume flow, which, passing through the chromatographic column 16, through the inductor 12, the resistance of which is preselected, enters the chamber 1, and then to the input 15

gas flow inducer 10. The semi-permeable membrane 7 has selective permeability to hydrogen (fluoroplastic or palladium-silver alloy membranes) or helium (graviton or fluoroplastic membranes). Therefore, part of the carrier gas penetrates through the membrane into the chamber 2. Through this chamber, under the influence of a small vacuum created by the flow inducer 10, the auxiliary gas stream flows as air, which enters through the variable orifice 11 from the atmosphere. The value of the auxiliary gas flow rate is selected by changing the resistance of the inductor 11. The carrier gas penetrating through the membrane 7 is mixed with the auxiliary gas stream. As a result, a constant volume concentration of the carrier gas in the auxiliary gas is created in the gas flow that enters the detector 9, and since the detector 9 is sensitive to the concentration of the carrier gas in the auxiliary gas, this causes a constant value signal of this detector.

In the process of chromatographic analysis using device 18, a sample of the analyzed medium is introduced into the column. After separation of this medium in a chromatographic column into separate components, the latter are transported by a gas carrier to chamber 1. Moreover, when a carrier gas stream containing any detectable component flows through the chamber 1, a carrier gas stream penetrating from the chamber 1 through the membrane 7 into the chamber 2, decreases, since the concentration of the gas carrier in the chamber 1 decreases due to the appearance of the detected component in the stream. Moreover, the decrease in the volume concentration of the carrier gas in the chamber 1 is equal to the volume concentration of the detected component in the gas stream flowing from the chromatographic column. As a result, the signal of the detector 9 changes in proportion to the volume concentration of the detected component in the stream of gases flowing through the chamber 1. In this case, the decrease in the concentration of the carrier gas in the auxiliary gas stream in the chamber 2 does not depend on the nature of the detected

component i.e. the proposed detector has the same sensitivity to any detectable substances.

During the experimental verification, the operation of an equally sensitive detector, in which a standard thermoconductometric detector, a fluoroplastic membrane with a thickness of 5-10 μm and an area of 4 cm was used as a detector 9, and helium as a carrier gas, it was found that the sensitivity of the detector is 0.3 - 0.5 mV /% vol.

Advantages of the proposed detector:

- simplicity of design;

- ease of use, determined by using only one source of compressed gas (source of carrier gas).

The proposed device can be implemented on the basis of a serial thermoconductometric detector, a gas flow inducer and measuring equipment commonly used in analytical technology.

The detector can be used in gas chromatography to obtain information on volumetric concentrations in the gas phase of the detected components of complex gaseous and liquid media, as well as in combination with a gas density detector, in systems for measuring the molecular mass of trace amounts of substances and their identification. It can also find application in the evaporographic analysis of fractional composition, volatility and other characteristics of oil products (Ilyasov L.V. Evaporographic and diffusion methods of analysis of substances. M.: TsNIITENneftekhim, 1979) fractional composition, volatility and other characteristics of oil products.

Claims (1)

An equally sensitive gas and vapor detector containing carrier gas and auxiliary gas chambers with inlet and outlet channels, separated from each other by a semipermeable membrane, in which the auxiliary gas chamber has an output channel connected to the gas detector inlet channel, which is sensitive to the concentration of the carrier gas in the auxiliary gas characterized in that the isosensitive detector further comprises a gas flow inducer, two variable throttles connected to the input channels of the carrier gas and mogatelnogo gas tee connected to the outlet of the detector, the output channel carrier gas entry chamber and the stimulus flow wherein a variable throttle input connected to an input channel of the auxiliary gas chamber is connected to atmosphere.