RU114528U1 - DEVICE FOR PREPARING TEST GAS MIXTURES IN DYNAMIC MODE - Google Patents

Abstract

The invention relates to the field of analytical instrumentation and can be used in gas analytical complexes for testing sensitive elements and sensors for measuring gas parameters in order to calibrate and verify gas analytical devices and sensors in serial production.

A device for preparing calibration gas mixtures (CGS) in dynamic mode contains a gas mixer, at least one channel for supplying the target gas to the gas mixer, at least two channels for supplying diluent gas to the gas mixer and a channel for discharging the gas mixture from the gas mixer. In each channel for supplying gas to the gas mixer, a gas mass flow regulator and an electromagnetic valve are sequentially installed. At the same time, at least one channel for supplying diluent gas to the gas mixer has a gas humidifier and an additional electromagnetic valve, the output of the gas flow regulator of this channel being connected through an electromagnetic valve to the gas humidifier inlet, the output of which is connected to an additional electromagnetic valve.

The technical result is the production of wet calibration gas mixtures in a wide range of concentrations and relative humidity, as well as reducing the cost of ASG supplied to the device under test, if necessary, preparation of wet calibration gas mixtures.

1 s.p. f-ly, 2 ill.

Description

The invention relates to the field of analytical instrumentation and can be used in gas analytical complexes for testing sensitive elements and sensors for measuring gas parameters in order to calibrate and verify gas analytical devices and sensors in serial production.

Calibration and metrological verification of gas composition analyzers is performed using appropriate standards, which can be used as calibration gas mixtures (ASG). ASGs can either be produced in the form of certified mixtures stored in pressurized containers, or prepared according to the specified procedure directly at the place of use with the help of generators of mixtures having certified metrological characteristics.

The experience of studying the technical and metrological characteristics of gas detectors, gas analyzers, gas and ion chromatographs convincingly showed the advantages of continuous (dynamic) methods for preparing gas mixtures with a known content of the analyzed substances. In gas analytics, two main dynamic methods for preparing calibration gas mixtures are used: mixing gas flows and diffusion dosing of analytes.

The method of thermal diffusion dosing of microflows of analytes into a diluent gas stream has received the greatest application in environmental and analytical control. The principle of operation of a thermal diffusion generator of gas mixtures is based on a mixture of flows of the target component and diluent gas. The flow of the target component is set by the source of microflow (MI), located in a thermostat with a controlled temperature. The diluent gas flow is regulated and measured by the heat regulator of the gas mass flow rate. By replacing sources of microflows with various substances in the installation, it is possible to create highly stable gas flows of a given concentration of different compositions (patent RU 2219516, published December 20, 2003; patent RU 2275661, published April 27, 2006; patent RU 2284498, published September 27, 2006).

Thermodiffusion generators of gas mixtures do not have special advantages in comparison with finished gas mixtures. The duration of the microflow sources directly depends on the intensity of operation. The peculiarity of MI is that MI can be used for unstable and aggressive substances that cannot be stored in a cylinder for a long time.

The principle of operation of dynamic plants with gas mass flow controllers is based on a mixture of the target component and diluent gas flows, each of which is measured and regulated by a separate gas mass flow controller. The preparation of binary gas mixtures is carried out by the method of dynamic dilution of certified source span gases (target gas) with certified diluent gas (air or nitrogen). As source gases, technically pure gases or gas mixtures can be used.

The main advantages of this type of plant are its simple and convenient control and smooth setting of the dilution coefficient in a wide range, which can significantly reduce the number of required cylinders with the target gas.

A device for preparing calibration gas mixtures is known (patent RU 2208783, published July 20, 2003), containing a source of calibration gas or gas mixture in the form of a high-pressure cylinder, a gas mixer and a system for diluting the gas mixture after the mixer with an additional stream of diluent gas. In the device, 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 air, a channel for discharging a gas mixture, which is connected to a gas mixture dilution system and in which a detector is installed to control the span gas content and a flow inducer, and an additional detector is introduced into the device to monitor the span gas content in the mixer e.

In the known device it is required to control the content of the gas mixture at the outlet, which is possible if there is a detector for a specific gas, the error of which determines the accuracy of preparation of the gas mixture. Temporary instability of the detector characteristics affects the accuracy of the prepared gas mixture. This device requires the filtration of atmospheric air used as a diluent gas. The device does not allow to prepare a gas mixture of a given relative humidity.

However, often for calibration and calibration of gas analytical instruments and sensors (for example, semiconductor, electrochemical), it is necessary to moisten the calibration gas mixture, for which additional types of gas humidifiers are used to moisten the gas mixture supplied from the mixer to the device under test, which leads to an increase material costs and increase the cost of ASG.

According to the technical nature of the known devices, the closest to the claimed device is a device for the preparation of ASG, presented in the materials of the IMEKO World Congress on Fundamental and Applied Metrology, namely: Nuno J.F. Rodrigues, Paulo Gomes. GAS ANALYZERS CALIBRATION BY DYNAMIC DILUTION FOR MONITORING AIR POLLUTION AND AIR EMISSIONS // XIX IMEKO World Congress Fundamental and Applied Metrology, September 6-11, 2009, Lisbon, Portugal, p. 217-2220 (http://www.imeko2009.it .pt / Papers / FP_222.pdf). The gas mixing device is a dynamic gas mixer, the principle of which is to mix the streams of the target gas and diluent gas, the flow rate of which is regulated and measured using gas mass flow regulators. The device contains one or more channels for supplying the target gas to the mixer, several channels for supplying diluent gas to the mixer, and a channel for discharging the gas mixture from the mixer. In each channel for supplying gases to the mixer, a gas mass flow regulator and an electromagnetic valve are installed in series.

The use of mass flow rate controllers as part of a known device allows gas mixtures to be obtained in a wide range of concentrations, which increases the possibilities of using the device. The disadvantage of this device is the impossibility of preparing gas mixtures with specified humidity parameters, as well as the increased cost of ASG supplied to the device under test, due to material costs for the additional installation of a humidifier for gas mixtures.

The specified device for the preparation of calibration gas mixtures is taken as a prototype.

An undeniable convenience for users is the ability to simultaneously obtain gas mixtures of a given concentration and humidity. However, the existing systems still have not solved the problem of ensuring the possibility of obtaining and humidifying calibration gas mixtures in one device.

The purpose of the invention is the production of wet calibration gas mixtures in a wide range of concentrations and relative humidity, as well as reducing the cost of ASG supplied to the device under test, if necessary, preparation of wet calibration gas mixtures.

This goal is achieved in that in a device for the preparation of calibration gas mixtures in a dynamic mode containing a gas mixer, at least one channel for supplying the target gas to the gas mixer, at least two channels for supplying diluent gas to the gas mixer and a channel for withdrawing the gas mixture from the gas mixer, where in each channel for supplying gas to the gas mixer, a mass flow rate controller and an electromagnetic valve are sequentially installed in at least one channel for supplying gas In the gas mixer, a gas humidifier and an additional electromagnetic valve are installed, and the output of the gas flow regulator of this channel is connected through an electromagnetic valve to the inlet of the gas humidifier, the output of which is connected to the additional electromagnetic valve.

Installing a gas humidifier in at least one of the channels for supplying diluent gas to the gas mixer allows creating at the outlet of this channel 100% relative humidity of the diluent gas. The required relative humidity of the calibration gas mixture obtained in the gas mixer is created by mixing dry diluent gas, wet diluent gas and dry target gas. Using automatically switched solenoid valves, including an additional solenoid valve in the feed channel of the wet diluent gas, and the choice of the operating modes of the gas mass flow controllers, it is possible to prepare a calibration gas mixture not only with a wide range in concentration, but also with a wide range in relative humidity.

Installing a gas humidifier in at least one of the channels for supplying diluent gas to the gas mixer eliminates the need for additional acquisition and installation of various devices for humidifying the resulting calibration gas mixtures, if necessary, preparing wet ASGs, reduces material costs and reduces the cost of ASGs, served on the device under test.

The identified distinctive feature in the proposed combination was not found in previously known technical solutions, ensures the achievement of the goal, and can be qualified as a significant difference.

The invention is illustrated by drawings:

Figure 1 - structural diagram of a device for the preparation of calibration gas mixtures in a dynamic mode, containing three channels for supplying mixed gases;

Figure 2 - structural diagram of a device for the preparation of calibration gas mixtures in a dynamic mode, containing seven channels for supplying mixed gases.

The proposed device for the preparation of calibration gas mixtures in dynamic mode (figure 1) contains a gas mixer 1, channel 2 for supplying the target gas to the gas mixer 1 from the source of the target gas, two channels 3 for supplying diluent gas to the gas mixer 1 from the gas source -the diluent and channel 4 for withdrawing the prepared gas mixture from the gas mixer 1. In each channel for supplying gases to the gas mixer 1, a mass gas flow regulator 5 is sequentially installed for controlling and measuring the flow rate gas and automatically switched solenoid valve 6. In one of the channels 3 for supplying diluent gas between the gas flow regulator 5 and gas mixer 1, a gas humidifier 7 and an additional automatically switched electromagnetic valve 6 are installed, and the output of the gas flow regulator 5 of this channel 3 for supplying humidified diluent gas to the gas mixer 1 is connected through an automatic solenoid valve 6 to the inlet of the gas humidifier 7, the output of which is connected to an additional automatic electro agnitnym valve 6. The gas humidifier 7 is a humidifying cartridge (wet sand filter) during the passage through which the necessary part of the diluent gas stream is generated at the output verification gas mixture the desired relative humidity. Switching of gas channels 2 and 3 to the gas mixer 1 is done by automatic electromagnetic valves 6. Manual valves 8 located at the inlets of gas channels 2 and 3 are designed to direct the target gas from the target gas source and diluent gas from the diluent gas source , as well as for cleaning gas channels when changing the target gas.

To obtain a wider variety of gas mixtures with different concentrations and relative humidity for verifying a wide range of gas analyzers, gas detectors and sensors, as one of the versions, a variant of the device for preparing ASG with seven channels for supplying mixed gases is possible (Fig. 2). In this embodiment, the device comprises a gas mixer 1, three channels 2 for supplying the target gas, four channels 3 for supplying diluent gas to the gas mixer 1 and channel 4 for outputting the prepared gas mixture from the gas mixer 1. In each of the channels 2 and 3 for the mixed gas supply is also sequentially equipped with a gas mass flow regulator 5 and an automatically switched solenoid valve 6. In two channels 3 for supplying a diluent gas between the gas flow regulator 5 and the gas mixer 1, a humidifier is installed in series rer gas 7 and the additional solenoid valve 6. At the input of gas channels 2 and 3 are arranged manual valves 8 for guiding to the respective target gas feeds and a diluent gas, as well as for the purification of gas channels by changing the target gas. The use of a larger number of channels 2 and 3 for gas supply, with gas flow controllers 5 installed in them, makes it possible to prepare ASGs with wider concentration and flow rate parameters at the device output, as well as increase the range of ASGs relative humidity at high flows of mixed gases due to use of two gas humidifiers 7.

The proposed device is structurally made in the form of a separate desktop unit, in which all the components of the device are placed and switched.

A device for the preparation of calibration gas mixtures in a dynamic (continuous) mode works as follows.

The preparation of calibration gas mixtures is carried out by dosing the target gas with a specified volume fraction of the target component in a pure diluent gas. When the device is operating (Fig. 1), the target gas from the source of the target gas and the diluent gas from the source of the diluent gas are sent through manual valves 8 to the corresponding channel 2 for supplying the target gas to the gas mixer 1 and channels 3 for supplying the diluent gas to the mixer gases 1. The target gas and diluent gas enter the gas mixer 1 through gas mass flow controllers 5 and automatically switched solenoid valves 6 under the action of a pressure differential between the input and output in the channels for supplying the mixed gases. In the gas mixer 1, the resulting mixture of the target gas and diluent gas is brought to a homogeneous composition and is fed to the consumption channel 4 for outputting the prepared gas mixture.

To obtain a wet gas mixture, part of the diluent gas gas stream is sent through channel 3 with a gas humidifier 7 installed in it, which creates at the outlet 100% relative humidity of the diluent gas. Gas humidification is based on the effect of natural “cold” evaporation of water (without heating), in which the diluent gas, passing through the gas humidifier, is saturated with moisture. By changing the flow rates of dry and wet diluent gas, the relative humidity of the prepared gas mixture is set at the outlet of the device. The required relative humidity of the gas mixture is created by mixing dry diluent gas, wet diluent gas and dry target gas.

The required flow rates of the target gas, dry diluent gas and wet diluent gas in each channel, set by the user and controlled by gas mass flow regulators, are formed using automatically switched solenoid valves and the choice of operating modes of gas mass flow controllers. The required values of the gas flow through the channels and the values of the molar (volume) fraction of the components in the prepared mixture are set using a PC. The basis for calculating the composition of the mixture is the material balance for the determined component in the dosed gas, dry and wet diluent gas, and the resulting mixture.

The proposed device has a linear mode of operation, which involves the connection of all channels of dry and wet gas diluent and the target gas at the outlet of the device. This mode of operation provides at the device output the preparation of a test gas mixture with a wide range of regulation in concentration, flow rate and humidity at the same time, and also maintains the required characteristics for the necessary time for testing the sensitive elements of gas analytical instruments and sensors.

The device provides:

- automated preparation of gas mixtures based on N ₂ , CO, CO ₂ , NO, NO ₂ , CH ₄ , SO ₂ and other gases of the required concentration;

- the range of relative humidity of the gas mixture is 0.10-90%.

Filling the humidifier with water does not require installation work. The humidifier is replaced by closing the solenoid valves (primary and secondary) of the corresponding wet diluent gas feed channel. The gas channels are cleaned when changing the target gas using a diluent gas when switching the corresponding manual valves.

The device operates in automatic mode, control is carried out using a personal computer. Information exchange with a personal computer via a serial radial interface RS 232. Software for remote control of the operating modes of a device for preparing ASG allows accelerating verification of gas analyzers by automating the calculation of parameters and the gas mixing process.

Similarly, a device for the preparation of calibration gas mixtures, containing seven channels for supplying mixed gases (figure 2). The use of the device in this design expands the range of gas mixtures with various concentrations and relative humidity

Thus, the proposed design of a device for the preparation of calibration gas mixtures in a dynamic mode ensures the achievement of the goal, namely:

- obtaining wet calibration gas mixtures in a wide range of concentrations and relative humidity;

- reducing the cost of ASG supplied to the device under test, if necessary, the preparation of wet calibration gas mixtures.

Claims (1)

A device for preparing calibration gas mixtures in dynamic mode, comprising a gas mixer, at least one channel for supplying the target gas to the gas mixer, at least two channels for supplying diluent gas to the gas mixer and a channel for discharging the gas mixture from the mixer gases, while in each channel for supplying gas to the gas mixer, a gas mass flow regulator and an electromagnetic valve are sequentially installed, characterized in that at least in one channel for supplying a diluent gas in rer gas humidifier installed gas and an additional solenoid valve, wherein the channel gas flow regulator output is connected through a solenoid valve to an input gas humidifier, whose output is connected to an additional solenoid valve.