FR2713105A1 - Prodn. of mixt. of gases of controlled composition - Google Patents

Abstract

A gas mixture of controlled composition is made from two or more gases supplied under pressure. Each component gas (A, B and C) is fed to the mixing vessel (14) via an electric valve (7, 8 and 9) which opens and closes on a timed cycle, depending on the required concentration of that gas.

Description

 The "GAS MIXER" are devices or devices capable of supplying1 from n gases, a mixture of predefined constitution.

 Known mixers obtain the desired mixture, either from predefined and continuous flow rates of each component, or by slaving the flow rate of each component to a direct measurement of its rate in the mixture obtained.

 In the first case, each flow must be calibrated according to the pressure, the cross-section and the nature of the gas. In the second case, at least n-l specific analyzers will be required for a mixture of n gases.

 The present invention relates to a new gas mixer called "switching" where, from n gases under pressure, the mixing is carried out in a reservoir fed cyclically by the n gases, via n remote-controlled solenoid valves.

 Initially closed, the electro-valves will then all be temporarily and cyclically open then closed again according to opening times for each electro-valve, in proportion to the desired rate for each gas in the mixture obtained.

 The pressure in the mixing tank, which increases in proportion to the ratio between the cyclically entering quantity and the possible sampling of the mixture, can be regulated simply by stopping the cyclic process as long as the pressure exceeds a predetermined set value.

 The remote control of the solenoid valves is advantageously obtained by a programmed computer which, in view of the desired rates and their possible changes, calculates and defines the respective cyclic sequences of each solenoid valve while conditioning the order of a new sequence at tank pressure conditions.

 The frequency of the cycles has theoretically no influence on the composition of the mixture obtained. However, a frequency of 1 to 0.2 Hz seems to be generally the most suitable.

 The following description, with reference to the single diagram, is a non-limiting example of a mixer for three gases A, B, C where: 1,2 and 3 are the three compressed gas reserves A, B, C.

4,5 and 6 are three pressure reducers.

7,8 and 9 are three solenoid valves.

10, 11 and 12 are three adjustable nozzles.

13 is a programmed computer.

14 is the reservoir where the mixing takes place.

15 is an electronic mixture pressure sensor.

16 is a mixture outlet valve.

 The three regulators 4,5 and 6 are adjusted to provide a pressure higher than twice that of regulating the tank.

 The flows through the nozzles 10, 11 and 12 are then under critical conditions: they only depend on the absolute upstream pressure (regulators).

 The three nozzles 10, 11 and 12 are adjusted so that, with the solenoid valves open, the gas flows A> B and C are equal.

 Suppose then that the computer 13 is instructed to supply a mixture composed of: 50X of gas A, 30X of gas B, 20% of gas C and maintain the tank under the pressure of 3 bars.

 Under these conditions, every second for example, the computer can open the solenoid valve 7 for 0.5 seconds> 6 for 0.3 seconds and 9 for 0.2 seconds.

 For instantaneous flow rates of 1 1 / sec each cycle then supplies the reservoir 14: 0.5 1 of gas A 0.3 1 of gas B 0.2 1 of gas C or 1 1 of mixture having the desired composition.

 If the reservoir 14 has a volume of 5 liters, its pressure rises at each cycle by to 0.5 bar. The computer will stop its cycles beyond the 10th, waiting for a pressure drop dQ i a sample at 16, fall which will trigger the resumption of at least one cycle etc ...

Claims (5)

CLAIMS:  1) Produced intended to generate, from at least two sources of pressurized gas, a gaseous mixture whose rate of each constituent is pre-defined and programmable, characterized in that each source supplies, via an electro-valve, the same tank where the mixing takes place, each electro-valve being simultaneously and cyclically opened then closed, so that at the end of a cycle, the rate of each constituent thus supplied to the tank, depends only on the respective times d 'opening of each solenoid valve during the said cycle.  2) Method according to claim 1, characterized in that the command to open the solenoid valves is programmed from a computer which, in view of the desired rates and their possible changes, calculates and orders accordingly the cutting of cycles.  3) Method according to claims 1 or 2, characterized in that the pressure of the mixture obtained in the tank is regulated by interrupting the cycles as long as the pressure in the tank is greater than a predefined setpoint.  4) Method according to claims 1 or 2, characterized in that the duration of each cycle is of the order of a few seconds.  5) Device for mixing n gases together, comprising a mixing tank supplied by the n gases from n solenoid valves, characterized in that the solenoid valves are cyclically opened and then closed on the order of a programmer such as a programmed computer.