RU2208783C1 - Facility to prepare testing gas mixtures - Google Patents

Abstract

FIELD: analytical instrumentation, preparation of testing gas mixtures used to calibrate and test gas analyzers. SUBSTANCE: facility to prepare testing gas mixtures has source of testing gas or mixture of gases in the form of high-pressure bottle, gas mixer and system diluting gas mixture installed downwards from mixer with additional stream of diluting gas. Gas mixer of facility comes in the form of vessel possessing two conduits to feed mixed gases, one conduit is linked through shut-off valve to source of testing gas or gas mixture and another conduit communicates with atmospheric air. Third conduit of gas mixer is intended for discharge of gas mixture, is connected to system diluting gas mixture and houses sensor controlling content of testing gas and agitator. Facility is supplemented with additional sensor to control content of testing gas in mixer. EFFECT: development of facility preparing testing gas mixture using only one cylinder as source of starting substance without employment of high-pressure bottle with gas-diluent. 4 cl, 1 dwg

Description

 The invention relates to the field of analytical instrumentation, in particular to devices for the preparation of calibration gas mixtures. It can find application in the calibration and calibration of gas analyzers, chromatographs, and other instruments for gas analysis.

 Known sources of calibration gas mixtures are high-pressure cylinders up to 40 l filled with gas mixtures of a certain composition at pressures of up to 100 atmospheres and above (see Control of chemical and biological environmental parameters. Encyclopedia "Econometrics". Series of reference books under the leadership of Prof. Isaev, St. Petersburg, 1998, p. 587-602). These cylinders are subject to the “Rules and Design of Pressure Vessels,” requiring specific operating, transportation, and storage conditions. Often, the "Rules" do not allow the use of cylinders in workshops and other categorized rooms, which creates additional difficulties. In addition, large cylinders are heavy and difficult to transport.

 For calibration of instruments in the working measuring range, several mixtures with different concentrations are used. This requires either the use of several cylinders or expensive dilution systems.

 And finally, the composition of the calibration mixture in a metal cylinder may change over time in an uncontrolled way. Mixtures with a low span gas content and mixtures containing corrosive gases are particularly susceptible to this phenomenon.

 A device for preparing calibration gas mixtures is known, containing a source of pure calibration gas in the form of a high-pressure cylinder and one or more sources of diluent gas, for example, purified air, a gas mixer and a gas mixture dilution system after the mixer with an additional stream of diluent gas (see, for example, Auth. USSR USSR 1546945, G 01 D 11/035, 1990).

 In the known device, high pressure cylinders are also used as diluent gas sources. This, as described above, requires certain security measures and makes the verification procedure more expensive.

 The objective of the invention was to create a device for the preparation of calibration gas mixtures, allowing to obtain calibration mixtures in a wide range of concentrations, using only one cylinder as a source of source gas, without the use of high-pressure cylinders with a diluent gas.

 This problem is solved by the fact that the proposed device for the preparation of calibration gas mixtures containing a source of calibration gas or gas mixture in the form of a high-pressure cylinder, a source of diluent gas, a gas mixer and a dilution system of the gas mixture after the mixer with an additional stream of diluent gas, in which According to the invention, the gas mixer is made in the form of a container having two channels for supplying mixed gases, one of which is connected through a controlled shut-off valve to a source of span gas and a mixture of gases, and the second channel is connected to atmospheric air, and a channel for outputting the gas mixture, which is connected to a dilution system of the gas mixture and in which a detector is installed in series for monitoring the span gas content in the output mixture and a flow inducer.

 Another difference of the proposed device is that it introduced a detector to monitor the content of span gas in the gas mixer. To this end, in a preferred embodiment of the device, the gas mixer is provided with a channel for extracting part of the gas mixture from the mixer and a channel for returning this part of the gas mixture to the mixer, forming a closed gas circuit in which an additional flow inducer and a detector for monitoring the span gas content are installed.

 Another difference of the proposed device is that the dilution system of the gas mixture after the mixer contains a microcompressor, the inlet of which is connected to atmospheric air, and the outlet is connected to a channel for outputting the gas mixture from the mixer.

 Among the differences of the device, it should be noted that a microprocessor control unit is introduced into it, the inputs of which are connected to the outputs of the detectors to control the span gas content in the gas mixer and in the output mixture, and the control outputs are connected to the drive of the controlled shut-off valve and the drive of the microcompressor.

 Due to the above-mentioned performance features, the proposed device not only eliminates the need for high pressure cylinders with diluent gas, but also provides control of the concentration of the calibration mixture during its preparation in a wide range of dilution of the calibration gas.

 The invention is illustrated in the drawing, which shows a schematic diagram of the proposed device.

 The proposed device contains a source 1 of span gas or a mixture of gases of a certain composition in the form of a high pressure cylinder equipped with a pressure regulator 2 and a gas mixer 3, made in the form of a container of a material inert with respect to the mixed gases, for example glass. The mixer 3 is connected to a span gas source 1 through a channel 4 and a controllable shut-off valve 5 provided with a drive 6, for example an electromagnetic drive. The mixer 3 through the channel 7 for supplying a diluent gas and a filter 8 is connected to atmospheric air, which serves as the diluent gas in the present invention.

 Filter 8 is designed to purify air from mechanical impurities (particles, dust), moisture and chemical impurities present in the air. The mixer 3 is connected to the channel 9 for outputting the gas mixture, in which a detector 10 is installed in series for monitoring the content of span gas in the air and a flow driver 11. The channel 9 for outputting the gas mixture is equipped with a dilution system, which contains a microcompressor 12, the inlet of which through the filter 13 is connected by atmospheric air, and the outlet is connected to the channel 9 for outputting the gas mixture from the mixer 3. The mixer 3 is equipped with a channel 14 for taking part of the mixture from the mixer 3 and a channel 15 for returning this part of the mixture to the mixer 3, forming a closed gas circuit 16, in which an additional detector 17 is installed to control the content of span gas in the mixer 3 and an additional flow driver 18.

 The device is equipped with a microprocessor control unit 19, the inputs 20 and 21 of which are connected to the outputs of the detectors 10 and 17 to control the concentration of span gas in the output mixture and mixer 3, and the outputs 22 and 23 are connected to the drive of the microcompressor 12 and the actuator 6 of the controlled shut-off valve 5.

 The choice of the type of detectors 10 and 17 for monitoring the concentration of span gas is determined by the composition of the span mixture. For example, if the calibration mixture is a mixture of methane with air, then detectors operating on the principle of absorption of radiation in the infrared region can be used as detectors 10 and 17.

 The device operates as follows. Before the device starts, the flow drivers 11 and 18, as well as the detectors 10 and 17 connected in series with them, are activated. After the detectors 10 and 17 are in stationary mode, the microprocessor control unit 19 gives a control signal to open the shutoff valve 5. gas or a mixture of gases from the cylinder 1 through an open shut-off valve 5 enters the tank 3, where it is mixed with the atmospheric air contained in it. A part of this mixture through the channels 14 and 15 under the influence of the flow inducer 18 circulates in a closed gas circuit through the detector 17. After the concentration of the span gas in the tank 3 reaches a predetermined value and the detector 17 gives a corresponding signal to the control input 21 of the microprocessor control unit 19, the shut-off the valve 5 is closed and the tank 3 begins to work as a source of calibration gas mixture. The calibration gas mixture, taken from the tank 3 through the channel 9, is diluted with atmospheric air, cleaned with a filter 13 and pumped with a microcompressor 12. The atmospheric pressure in the tank 3 is maintained by atmospheric air entering the tank 3 through the channel 7 through the filter 8. The concentration of the test substance in the mixture is measured by the detector 10, after which the mixture is fed to the device to be verified through the flow inducer 11. The signal received from the detector 10 is supplied to the microprocessor control unit 19, which compares it with a predetermined value and maintains a predetermined signal value corresponding to the desired concentration value by adjusting the voltage at the microcompressor 12. The concentration of span gas in the mixture at the detector output can vary widely starting from the initial concentration of the span gas in the tank 3 to any lower concentration measured by the detector with the necessary accuracy. When the microprocessor control unit 19 is not able to maintain a given concentration, which occurs depending on the rate of loss of span gas from the tank sooner or later, the shut-off valve 5 opens again and the process is repeated again.

Claims (5)

 1. A device for preparing calibration gas mixtures, containing a source of calibration gas or gas mixture in the form of a high pressure cylinder, a gas diluent source, a gas mixer and a gas mixture dilution system after the mixer with an additional gas diluent stream, characterized in that the gas mixer is made in the form of a container having two channels for supplying mixed gases, one of which is connected via a controlled shut-off valve to a source of span gas or a mixture of gases, and the second channel is connected to atmospheric water air, and a channel for outputting a mixture of gases, which is connected to a dilution system of the gas mixture and in which a detector is installed in series for monitoring the content of span gas in the air and a flow inducer.  2. The device according to claim 1, characterized in that a detector is introduced into it for monitoring span gas in the gas mixer.  3. The device according to claim 2, characterized in that the gas mixer is equipped with a channel for sampling a portion of the gas mixture from the mixer and a channel for returning this part to the mixer, forming a closed loop in which a detector for monitoring the span gas in the mixer and an additional inducer are installed expense.  4. The device according to claim 1, or 2, or 3, characterized in that the dilution system of the gas mixture after the mixer contains a microcompressor, the inlet of which is connected to atmospheric air, and the output is connected to a channel for outputting the gas mixture from the mixer.  5. The device according to claim 4, characterized in that a microprocessor control unit is inserted into it, the inputs of which are connected to the outputs of the detectors to control the span gas content in the mixer and in the channel for outputting the gas mixture after the dilution system, and the outputs are connected to a controlled shut-off actuator valve and actuator microcompressor dilution system.