SK17089A3 - Process for preparing mixture of gasses with exact composition and device for executing this process - Google Patents

Abstract

process preparation mixtures gases exactly desired evil zenith feeding each gases from stock metal through regulatory valves (1) so, that the indi Vé gases supplied through regulatory valves at the same time about stable pressure single gas in pipeline (2), which through closing valves (4) to nozzles with critical regime flow gas (5), from those is based gas to collection pipeline (6), in which the measures pressure inspection pressure gauge (7) and through closing valve (9) the leads to collection tla kovej container (10), while pressure gas before nozzle with critical regime flow and for it must a flat the KY to secured critical stream gas and for management on the his making

Description

The present invention relates to an apparatus and method for mixing gases to form a gas mixture having a prescribed proportion of the individual gas components.

One of the known methods is mixing according to the partial pressures of the individual components. The principle of the method is shown in Fig. 1. the total pressure of the mixture is given by the Lalton law the sum of the partial pressures of the individual components? = E p _± / vl = t where P is the total pressure of the mixture

P ^ partial pressure of one component where ^p i “ ^Σ χ · ^ρ

n.

r * ¹ i- n. <= 1 i / 2 / / 3 / molar fraction of i-th component of gas Uj. the quantity of the i-th component of the gas.

Accordingly, the mixing of the individual gas components can be effected by successively flowing the individual gas components sequentially into a collecting vessel which is initially evacuated and in which the pressure is measured with a pressure gauge 6. The first gas component is filled after opening the valve of the vessel 2. The gas flows from the cylinder 6 and when the pressure is reached, the vessel valve is closed. The second component is analogous. After connecting the cylinder with the second gas, the vessel valve 2 is opened and the gas is allowed to flow until the pressure is reached. in the collection vessel, the pressure P? The same procedure is followed for the third or further gas component.

The disadvantage of this method is the necessity of accurate pressure measurement, which is particularly difficult when mixing orders of varying amounts of gas. Other errors are caused by the opening and closing of the valves when the desired pressure value in the collecting vessel is reached.

in another method of gas mixing, nozzles operating in the critical flow mode are used. For the critical flow mode venturi nozzle mass flow, the relationship is

Q _b - S .- *. V2.P .Q _{0 0/4} / where the mass flow of gas

S nozzle throat area P _Q nozzle inlet pressure φ _ο gas density in nozzle inlet ΊΤ outlet coefficient

As long as the critical flow condition is met, ie the ratio of the outlet 8 of the inlet gas pressure at the outlet and the inlet of the nozzle is less than the critical ratio, the mass flow is independent of the outlet pressure of the nozzle. Fig.2. The gas from the pressure gas line of the first gas 6 after opening the valve j flows into the collecting vessel during the time interval t ₁ , which is determined by

m.

/ 5 /

m.

where m is the mass of the first component of the gas mixture

Q is the mass flow rate of the first gas component according to m.

equation / 4 /.

The desired concentration of the first gas component is expressed as m.

(6) wherein c is the mass concentration of the first gas component m is the mass of the i component of the gas.

Analogously, weights of other gas components are calculated according to relation (6) and time intervals of flow of the respective component

The disadvantage of said sequential gas mixing is the fact that with large differences between the amounts of mixed gases there is also a large difference between the flow intervals of the individual gas components, which can cause significant errors in the composition of the resulting gas mixture. is that good reproducibility in the composition of the resulting gas mixture cannot be achieved by sequential dosing of the individual components of the DC gas.

Disadvantages of the known gas mixing methods Eliminates the gas mixing method of the present invention. The gas mixing device consists essentially of parallel-thinned, constant-flow nozzles, at the outlet of which the air of the desired composition flows, as shown in Fig. 3. of individual gases it is necessary to use nozzles with the required flow rate, which depends on the nozzle throat area.

The throat area of the i-th nozzle is calculated from the relationship

m.

S, = / 7 / flow parameters of individual nozzles can be verified by means of an etalon flowmeter. Manometers 10, 11, 12 ^and 20 allow the reading of the inlet and outlet pressures of the nozzles and thus verify that the critical pressure ratio on the nozzles is maintained.

The advantage of the gas mixing method is that the composition of the gas mixture does not depend on the gas flow time interval and since the accuracy of the mixing depends only on the nozzle dimensions, in this way a high re-reducibility of the gas mixture composition is ensured.

An example of a specific embodiment of a three-gas mixing apparatus is shown in FIG. 3. From the cylinders 1, 2, J, the individual gases are fed in parallel through the pressure reducing valves 4 and the shut-off valves 7, 14 to the nozzles 13, 14. «1g, at the inlet of which there are sufficiently high gas pressures to achieve a critical flow condition

At the outlet of the parallel-arranged nozzles there is a manifold 16 from which at the beginning of the filling the gas exits through a valve 17 with the valve of the collecting vessel 18 closed to expel air or other air from the system. then the valve 12a is closed and the valve - · = 18 of the evacuated vessel 1¾ is closed into which the gas mixture of the exact composition flows. The nozzles are replaceable and therefore the desired gas mixture composition can be adjusted.

Said gas mixing method can be used for the preparation of a gas mixture, for example to ensure the metrology of the quantities of ionizing radiation, whereby it is necessary to produce a mixture of gases CH 2, CO ₂ · Ng ^with P ^{re <i}

Another advantage is that the gas mixture preparation apparatus does not have mechanically movable parts, therefore the individual components have a long lifetime and a high reproducibility when mixed. the simple design of the device is economically advantageous, does not require complicated operation, is sufficiently fast and safe to operate.Individual workplaces can use this device and thus save the cost of transporting gas cylinders that were previously supplied to other organizations by supply, the composition of the gas mixture had to be additionally verified.

Ä -í.- · ..

I. '

ä -0 1 - Γ > O O <C · cd < <_ 2 m> m <f— -c m N - <

s?

Claims (2)

Patent claims 1. A method of preparing a gas mixture of exactly the desired composition by supplying gaseous gas units to containers through control valves and shut-off valves into a pressure receptacle characterized in that the individual gases are supplied through control valves; »At the same time about the stable pressure of the individual gas in the pipeline and further through the shut-off valves“ to the nozzles with critical gas flow regime. . from which the gas flows into the manifold and through the shut-off valve is fed to the manifold, wherein the gas pressure before the nozzle with the critical gas flow mode? and behind it must be such as to provide a critical flow of gas, the first part of the mixture being discharged outside the collecting vessel by the discharge valve. Apparatus for the preparation of a gas mixture precisely of the desired composition according to claim 1, comprising individual gas reservoirs and control valves _Z characterized in that ^{and the} control valve (1), the individual gas outlet pipes (2) are provided with pressure gauges (3) and shut-off valves. valves (4) in any order, downstream of which discharge nozzles (2) are provided with nozzles with critical gas flow mode (5), which are connected to the manifold (6), equipped with a check pressure gauge (7), an outlet valve (8) and a shut-off valve (9) located upstream of the pressure collection vessel (10).