RU2302629C2 - Mode of production of a gas flow with constant concentrations and an arrangement for its execution - Google Patents

Abstract

FIELD: the invention refers to the field of gas industry.

SUBSTANCE: the mode is executed by way of successive bubble contact of a gas flow with two portions of solution of volatile matters in low-volatile solvent. The received gas flow is additionally mixed with a flow of an inert gas-reducer. The consumption of the inert gas-reducer passing through two portions of the solution is changed depending from concentration of volatile matters in the gas flow at the withdrawal out of the second portion of the solution measured with a quality analyzer. The arrangement for execution of the mode has in-series connected a capacity and a thermostatically controlled mixer filled with initial solution of volatile matters in low-volatile solvent. Two throttles of fine regulation are connected with a line for feeding an inert gas-reducer with a regulator of consumption. The outlet of one of the throttles is connected with the line for withdrawal of the gas flow saturated with volatile matters out of the mixer before the quality analyzer located in it. The outlet of the second throttle is connected to the capacity with initial solution. The quality analyzer is switched in a feedback circuit having a block of regulation of consumption of the inert gas-reducer coming into the capacity and the mixer.

EFFECT: increases time of supporting constant concentrations of volatile matters in a gas flow.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of gas analysis and can be used for calibrating gas analysis equipment, in particular for calibrating gas chromatographic devices and creating calibration gas-vapor mixtures when developing analysis methods for environmental objects and toxicological studies, as well as for various production technologies, where constant time concentration of volatiles in an inert diluent gas.

A known method and device for producing vapor-gas mixtures, in which a stream of diluent gas is passed through a solution of volatile substances with a fixed concentration. The solution container is connected to a mixer, into which a diluent gas is simultaneously supplied. As a result of contact with the liquid solution, the gas stream is saturated to equilibrium concentrations with vapors of volatile substances in accordance with the distribution constant at a constant temperature. After making contact of the gas stream with a solution of volatile substances, a part of the liquid solution depleted in the volatile substance is continuously separated from the vapor-gas stream and the initial solution (see Berezkin V.G., Budantseva M.N. Method for the preparation of gas-vapor mixtures. Auth. Certificate. USSR No. 697922 from 05/17/78. // Bull. No. 42 of 11/15/79).

The disadvantages of the known method and device are the need to use a significant amount of a solution of volatile substances in a low-volatile solvent, as well as the insufficient accuracy of the preparation of gas-vapor mixtures by the dynamic method, since the amount of volatile substances recovered is affected by the accuracy of maintaining at a given level both the parameters of the flow of the solution of volatile substances and the flow diluent gas.

The closest to the claimed invention in terms of essential features is a method of obtaining constant microconcentrations of volatile compounds in a gas stream, in which the gas stream is saturated to a predetermined equilibrium concentration by successively bubbling contact of the gas stream with at least three fixed portions of a solution of volatile compounds in a low-volatile solvent, concentration which successively decreases from the first portion of the solution to the next or remains constant with the exception of the first portion of the solution, in which the concentration of volatiles is higher, and the resulting gas stream, saturated with vapor of volatiles to equilibrium concentrations, is additionally mixed with a stream of inert diluent gas (Berezkin V.G., Platonov I.A. Method for obtaining constant microconcentrations of volatile compounds in a gas stream. Patent of the Russian Federation No. 2213958 from 11.23.01. // Bull. No. 28 from 10.10.2003).

Closest to the invention in terms of essential features is a device for the preparation of vapor-gas mixtures, containing a container with a mixture of the initial pre-prepared solution of a volatile substance in a low-volatile solvent, a thermostatic mixer, a line for supplying diluent gas to the mixer, a line for discharging the resulting vapor-gas mixture, a line for discharge of a solution depleted in volatile matter, two alternately working containers for waste solution regeneration, equipped with an analyzer quality and level, flow regulators on the line connecting the tank with the mixer, on the line for supplying diluent gas to the mixer and on the line for feeding the tank with the initial solution (see Berezkin V.G., Budantseva M.N., Voronova G. N., A device for the preparation of gas-vapor mixtures, Auth. Certificate of the USSR No. 759953 // Bull. No. 32 from 08.30.80.).

The disadvantages of the known method and device are the significant consumption of initial solutions of volatile substances in a low-volatile solvent, as well as the inability to increase the time to maintain constant concentrations of volatile substances in the gas stream at specified amounts of volatile substances in a low-volatile solvent.

The objective of the invention is to increase the degree of extraction of volatile substances from solution in a low volatile solvent and to extend the time interval for maintaining constant concentrations of volatile substances in the gas stream.

This problem is solved due to the fact that in the method of producing a gas stream with constant concentrations of substances, in which the inert diluent gas is saturated to a predetermined equilibrium concentration by successive bubbling contact of the gas stream with two portions of a solution of volatile substances in a low-volatile solvent, and the resulting gas stream is additionally mixed with the flow of inert diluent gas, while changing the flow rate of inert diluent gas passing through the first and second portions of the solution, depending on ontsentratsii these substances in the gas stream at the outlet of the second portion of the solution, measured quality analyzer.

This problem is also solved due to the fact that in a device for producing a gas stream with constant concentrations of volatile substances, containing a series-connected container filled with an initial solution of volatile substances in a low-volatile solvent, and a thermostatic mixer, an inert diluent gas supply line with a flow regulator and a line for exhausting a gas stream saturated with volatile substances, a quality analyzer, it additionally contains two fine-adjustment chokes connected to a supply line an inert diluent gas with a flow regulator, the output of one of which is connected to the exhaust line of the mixer saturated with volatile substances from the mixer in front of the quality analyzer located in it, which measures the concentration of volatile substances, the output of the other is to the container with the initial solution, with which the mixer is filled, and the quality analyzer is included in the feedback circuit containing an inert diluent gas flow control unit entering the tank and mixer.

When solving this problem, a technical result is created consisting in a more complete extraction of volatile substances from the initial solution in a low-volatile solvent by changing the flow of an inert diluent gas in the tank and mixer. At the same time, the time interval for maintaining constant concentrations of volatiles in the gas stream is significantly increased due to the feeding of the liquid solution in the mixer, which is the second stage of extraction, the required amount of volatiles from the portion of the solution (capacity) by the signal of the quality analyzer installed in the gas flow line at the mixer outlet and controlling the inert diluent gas flow using the inert diluent gas flow control unit.

This allows us to conclude that the claimed invention is interconnected by a single inventive concept.

An example of a specific implementation of the method and device for its implementation

The drawing schematically shows a device for producing a gas stream with constant concentrations of volatile substances. The device comprises: a container 1 filled with a stock solution of volatile substances in a low-volatile solvent; a thermostatic mixer 2, which is connected to the output of the tank 1; line 3 for supplying an inert diluent gas with an inert diluent gas flow regulator 4; line 5 for venting a gas stream saturated with volatiles; fine adjustment chokes 6 and 7 on line 3 for an inert diluent gas; a quality analyzer 8, which measures the concentration of volatile substances in the gas stream of line 5. A quality analyzer is included in the feedback circuit containing an inert diluent gas flow control unit 9 entering the tank 1 and a mixer 2. An inert diluent gas flow control unit 9 is connected to fine adjustment throttle 7. With an increase in the diluent gas flow rate, more volatiles are transferred to the mixer and the second portion of the solution is fed with volatiles, which ensures an increase time maintaining a constant concentration of volatiles in line 5.

The proposed device operates as follows.

A solution of a given concentration consisting of a mixture of volatile substances in a low-volatile solvent is preliminarily prepared by the gravimetric or volumetric method. The prepared solution is used to fill the tank 1. After that, the inert diluent gas stream set by the inert diluent gas flow regulator 4 is fed to the inlet of the tank 1. At the same time, the fine adjustment valves 6 and 7 are set to the middle position.

The mixer 2 plays the role of the second extraction stage, and the liquid phase is constantly fed with volatile substances due to the gas stream leaving the first extraction stage - tank 1. As the volatile substances are consumed, their concentration in the gas stream of line 5, measured by quality analyzer 8, is kept constant for by changing the flow rate of the inert diluent gas in the first extraction stage according to the signal of the quality analyzer 8, which controls thinly the throttle with the throttle control unit 9 th adjustment 7. In this case, the ratio between the flows of inert diluent gas in the tank 1 and mixer 2 (throttle 7) and the supply of inert diluent gas to line 5 (throttle 6) changes, and the total gas flow rate at the outlet remains unchanged, since the inert diluent gas is supplied to line 3 using an independent inert diluent gas flow rate regulator 4. Changing the flow through tank 1 causes a decrease or increase in the amount of volatile substances transferred by the gas phase from the first extraction stage (tank 1) to the second stage (s mixer 2), which is necessary to maintain a constant concentration of volatile substances in line 5 at the outlet of thermostatic mixer 2.

The material balance equation for a system containing a container filled with a solution of volatile substances in a low-volatile solvent and a mixer through which an inert diluent gas stream is passed has the form (see Forma M. // Annali di Chimica, 1975. V. 95. P. 49)

- количество летучего вещества, поступившего из емкости в смеситель с объемом инертного газа-разбавителя ·dV_G;

- количество летучего, извлекаемого из смесителя объемом инертного газа-разбавителя dV_G; dn_L(см)-dn_G(см) - изменение количества летучего вещества в жидкой и газовой фазах в смесителе, при этом

- константа распределения летучего вещества между жидкой и газовой фазами при T=const; dV_G=F·dτ - объем инертного газа-разбавителя; F - объемная скорость инертного газа-разбавителя; dτ - время пропускания объема инертного газа-разбавителя dV_G.Where

- the amount of volatile matter coming from the tank into the mixer with a volume of inert diluent gas · dV _G ;

- the amount of volatile recovered from the mixer with an inert diluent gas volume dV _G ; dn _{L (cm)} -dn _{G (cm)} - change in the amount of volatile matter in the liquid and gas phases in the mixer, while

is the distribution constant of the volatile substance between the liquid and gas phases at T = const; dV _G = F · dτ - volume of inert diluent gas; F is the space velocity of the inert diluent gas; dτ is the transmission time of the inert diluent gas volume dV _G.

The equation of material balance can also be represented as:

- константа смесителя.Where

- mixer constant.

мкг/см³, н-гептана с

мкг/см³ и толуола

мкг/см³. При этом расход азота был равен 12 см³/мин, а температура в последней ступени экстракции (в смесителе) Т=20°С.An experimental evaluation of the implementation of the proposed and known methods for obtaining constant concentrations of volatile substances in a stream of an inert diluent gas (nitrogen) was carried out on the example of obtaining gas streams with constant concentrations in time for benzene with a concentration at T = 20 ° C,

μg / cm ³ n-heptane s

μg / cm ³ and toluene

μg / cm ³ . At the same time, the nitrogen flow rate was 12 cm ³ / min, and the temperature in the last stage of extraction (in the mixer) T = 20 ° C.

The initial concentration of each of the volatile substances in the solution of the non-volatile solvent tetradecane was taken for the two compared methods, the same 20 mg / cm ³ , and the total volume of the initial solution of substances in tetradecane equal to 80 cm ^{3 was} chosen the same in the experiments.

In the known method, the nitrogen stream was saturated to predetermined equilibrium concentrations at T = 20 ° C by successively bubbling contact of nitrogen with two portions of a solution of volatile substances in tetradecane, the volumes of these solutions being taken to be the same and equal to 40 cm ³ each. Moreover, in the first bubbler, the concentration of each volatile substance was 21.4 mg / cm ³ , and in the second 18.6 mg / cm ³ and the gas stream from the first bubbler fed the solution of the second bubbler with new portions of volatile substances to obtain their equilibrium concentrations in a stream of nitrogen at the outlet of the second bubbler in the range

In the proposed method, the role of the first bubbler is played by a container 1, the temperature of which is equal to the ambient temperature. The role of the second bubbler or the second stage of extraction is played by a thermostatic mixer 2. The operating mode of the mixer is isothermal at T = 20 ° C.

The total volume of the solution in tank 1 is 80 cm ³ , and the concentrations of each volatile substance in the solution are assumed to be the same at 20 mg / cm ³ .

При этом происходит более полное извлечение летучих веществ и значительно увеличивается время поддержания постоянной концентрации в газовом потоке, так как при уменьшении этой концентрации по сигналу анализатора качества 8 повышается расход инертного газа-разбавителя в емкости 1 и смесителе 2, т.е. происходит более полное и дополнительное по сравнению с постоянным первоначальным расходом F=12 см³/мин извлечение летучих веществ из раствора.The gas stream from the tank 1 constantly feeds the liquid phase in the mixer 2 with the required amount of volatile substances to ensure the constancy of their concentrations in the flow of an inert nitrogen diluent gas from the mixer in the range

In this case, a more complete extraction of volatile substances occurs and the time to maintain a constant concentration in the gas stream increases significantly, since with a decrease in this concentration, the consumption of an inert diluent gas in tank 1 and mixer 2 increases with the signal of quality analyzer 8, i.e. there is a more complete and additional in comparison with the constant initial flow rate F = 12 cm ³ / min the extraction of volatile substances from the solution.

Example 1. The inert diluent gas flow rate was varied from 12 cm ³ / min to 20 cm ³ / min. We measured the time of maintaining the equilibrium concentration of volatile components in the gas stream at the mixer outlet τ, (min) upon reaching a flow rate of 20 cm ³ / min and the concentration of volatile substances remaining in the tetradecane C _L solution, mg / cm ³ .

Example 2. The inert diluent gas flow rate was varied from 12 cm ³ / min to 60 cm ³ / min. Τ and C _{L were} measured.

Example 3. The inert gas diluent flow rate was varied from 12 cm ³ / min to 100 cm ³ / min. Τ and C _{L were} measured.

The experimental results are summarized in the table "Comparative data of the experimental verification of the known and proposed methods."

Comparative data of experimental verification of the known and proposed methods Volatile substances in the mixture

The known method F = 12 cm ³ / min The proposed method F = 20 cm ³ / min F = 60 cm ³ / min F = 100 cm ³ / min C _L , mg / cm ³ τ min C _L , mg / cm ³ τ min Q, mg / cm ³ τ min C _L , mg / cm ³ τ min Benzene 24.5 ± 5% 17.7 13.5 10.6 22.5 3,54 67.5 2.12 112.5 n-heptane 9.91 ± 5% 17.6 33.0 10.7 55.0 3.52 165.0 2.11 275.0 toluene 7.75 ± 5% 18.1 43.0 10.9 71.7 3.62 215.0 2.17 358.3

Например, при изменении расхода в системе от 12 см³/мин до 100 см³/мин время поддержания постоянной концентрации на выходе

для исследуемых веществ в 8,3 раза больше по сравнению с известным способом. Так, для н-гептана С_L=2,11 мг/см³, а в известном способе при F=12 см³/мин С_L=17,6 мг/см³.As can be seen from the data in the table, the proposed method provides a significant increase in the time to maintain constant concentrations of volatile substances in the gas stream. In this case, the volatiles under investigation are more fully extracted from the tetradecane solution, i.e. the flow rate of the initial solution of volatiles in tetradecane sharply decreases to obtain their constant concentrations in the gas stream

For example, when the flow rate in the system changes from 12 cm ³ / min to 100 cm ³ / min, the time to maintain a constant concentration at the outlet

for the investigated substances 8.3 times more compared to the known method. So, for n-heptane C _L = 2.11 mg / cm ³ , and in the known method at F = 12 cm ³ / min C _L = 17.6 mg / cm ³ .

Using the proposed method for producing a gas stream with constant concentrations of volatile substances and a device for its implementation allows you to:

1. Significantly increase the time to maintain constant concentrations of volatile substances in the inert diluent gas stream by changing the inert diluent gas flow rate during extraction, depending on the concentration of these substances in the gas stream at the outlet of the second extraction stage.

2. To reduce the flow rate of the initial solution of volatile substances in a low-volatile solvent to obtain the same number of gas streams with a constant concentration of volatile substances in the inert diluent gas stream.

3. Organize metrological support for gas analytical and chromatographic measurements during critical analytical and physico-chemical studies.

Claims (2)

1. A method of obtaining a gas stream with constant concentrations of volatile substances, in which an inert diluent gas is saturated to a predetermined equilibrium concentration by successively bubbling contact of the gas stream with two portions of a solution of volatile substances in a low-volatile solvent, and the resulting gas stream is additionally mixed with an inert gas stream diluent, characterized in that the flow rate of the inert diluent gas passing through the first and second portions of the solution, depending on the concentration of these substances in the gas stream at the outlet of the second portion of the solution, measured quality analyzer. 2. A device for producing a gas stream with constant concentrations of volatile substances, containing a series-connected container filled with a stock solution of volatile substances in a low-volatile solvent, and a thermostatic mixer, a line for supplying an inert diluent gas with a flow regulator, and a line for venting a gas stream saturated with volatile substances , a quality analyzer, characterized in that it further comprises two fine adjustment chokes connected to the inert gas supply line an amplifier with a flow regulator, the output of one of which is connected to a line for discharging a gas stream saturated with volatile substances from the mixer in front of the quality analyzer located in it, which measures the concentration of volatile substances, the output of the second is to the container with the initial solution, with which the mixer is filled, and the quality analyzer included in the feedback circuit containing a unit for controlling the flow of inert diluent gas entering the tank, and a mixer.