WO1994019614A1

WO1994019614A1 - Gas mixtures

Info

Publication number: WO1994019614A1
Application number: PCT/AU1994/000085
Authority: WO
Inventors: Rudolf Hartmann
Original assignee: Air Liquide Australia Limited
Priority date: 1993-02-26
Filing date: 1994-02-25
Publication date: 1994-09-01
Also published as: FR2703262B1; ES2122837A1; ES2122837B1; FR2703262A1; BR9406318A

Abstract

A process for preparing a substantially stable and homogeneous gas mixture including greater than approximately 50 % by volume of a liquefiable gas, which process includes: providing a source of liquefiable gas; a source of a permanent gas; and a gas container; delivering the permanent gas to the gas container; and delivering the liquefiable gas to the container wherein the liquefiable gas is introduced at elevated temperature and/or elevated velocity such that the final volume thereof is greater than approximately 50 %.

Description

GAS MIXTURES The present invention relates to certain gas mixtures, and to the use of such gas mixtures in food, beverage, welding and like applications.

It is known in the prior art to utilise gas mixtures containing a liquefiable gas component such as C0₂ or N₂0 in combination with other gaseous components (so called permanent gases). However if the concentration of liquefiable gas in such gas mixtures is high (approximately 50% or more by volume) the liquefiable gas fails to mix within a reasonable time with the other components if classical mixing methods are applied, Accordingly, the liquefiable gas can be filled into a standard cylinder only to a limited pressure to avoid this problem.

For example, carbon dioxide is extensively used as a dispensing gas for beverages such as beer and post-mix soft drinks.

In the art of dispensing beer, it is very important that the appearance of the beer in the glass be attractive to the user. While flavour is the aspect most talked about in beer, appearance is the first thing noticed by the customer. The shade and depth of colour, the clarity, beading, type of head foam, the foam retention, and the foam cling, all contribute to making the initial impression. It is desirable that the foam atop a glass of beer dispensed from a tap be smooth, creamy, be relatively stable and have an attractive taste.

Whilst pure CO2 is often used as a dispensing gas, this tends to lead to an over-carbonation of the beer, which is less attractive to the consumer, and may lead to an excessive generation of foam when the beer is dispensed, thus leading to excess wastage. Whilst it is known to utilise a gas mixture of carbon dioxide and nitrogen to overcome this problem, a high nitrogen content tends to generate a flat beer, which is again unacceptable to the consumer. Whilst a gas mixture of, for example, carbon dioxide in a major amount together with nitrogen, would theoretically deal with both problems, attempts to produce such a gaseous mixture which can be filled to a significant pressure have not been successful in the prior art, due to the problems of mixing of liquefied CO2 as discussed above.

It would accordingly be a significant advance in the art if a gaseous mixture could be produced with a concentration of liquefiable gas of greater than 50%, but which provides very stable gas mixing characteristics in use at normal working temperatures, pressures and flow rates. Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties and deficiencies relating to the prior art.

Accordingly, in a first aspect of the present invention, there is provided a process for preparing a substantially stable and homogeneous gas mixture including greater than approximately 50% by volume of a liquefiable gas, which process includes providing a source of a liquefiable gas; a source of a permanent gas; and a gas container; delivering the permanent gas to the gas container; and delivering the liquefiable gas to the container wherein the liquefiable gas is introduced at elevated temperature and/or elevated velocity such that the final volume thereof is greater than approximately 50%.

The invention also provides a gas mixture including greater than approximately 50% by volume of a liquefiable gas in a suitable gas container, the mixture being substantially stable and homogeneous under filled pressures from approximately 10,000 kPa to approximately 30,000 kPa. It has surprisingly been found that by delivering the permanent gas first to the gas container and delivering the liquefiable gas under elevated temperature and/or at an elevated velocity a gas mixture is produced which is both substantially stable and homogeneous, and includes more than approximately 50% of the liquefiable gas. Such stability is retained over an extended range of both pressure and temperature. For example the gas mixture is substantially stable and homogenous in a suitable container under filled pressures from approximately 10,000 kPa to approximately 30,000 kPa. The gas mixture is substantially stable and homogeneous in use at normal working temperatures and flow rates, e.g. from approximately 5°C to 25°C. The liquefiable gas may be present in the gas mixture in any suitable amounts above approximately 50%. The liquefiable gas may be present in amounts of from approximately 50% by volume to 97.5% by volume, preferably approximately 55% to 85% by volume, more preferably approximately 60% to 75% by volume. The liquefiable gas may be carbon dioxide (C0₂), nitrous oxide (N₂0) or other liquefiable gases or mixtures thereof depending on the usage of the gas mixture. Carbon dioxide is preferred. The permanent gas may be selected from nitrogen, helium, argon, oxygen or other permanent gases, depending on the usage of the gas mixtures. Nitrogen is preferred. The permanent gas may be present in the gas mixture in amounts from approximately 2.5% by volume to less than 50% by volume.

The permanent gas may be delivered into the gas container, for example a gas cylinder, utilising any standard techniques. The liquefiable gas is pumped into the cylinder by preheating it to a temperature of approximately 40°C to 250°C, preferably 80°C to 1 10°C and at elevated velocity. A cryogenic pump may be used. The pump may for example generate gas velocities of approximately 10 to 50 metres per second during filling.

As stated above, the resultant gas mixture has surprisingly been found to be both substantially stable and homogeneous over a wide range of temperature and pressure. Whilst we do not wish to be limited by theory, it is postulated that the high velocity and high temperature delivery of the liquefiable gas introduces the gas in a supercritical state, which is apparently why the mixture is more stable and homogeneous than may otherwise be achieved. Accordingly, in a further aspect of the present invention there is provided a gas mixture including greater than approximately 50% by volume of a liquefiable gas in a suitable gas container which is substantially stable and homogeneous under filled pressures from approximately 10,000 kPa to approximately 30,000 kPa. The liquefiable gas and permanent gas components of the gas mixture may be as described above.

Preferably, the gas mixture includes from approximately 55% to 85% by volume CO2; and approximately 15% to 45% by volume of nitrogen (N ). In a preferred aspect, the gas mixture may further include a supplementary gas component selected from helium (He), hydrogen (H₂), argon (Ar) and oxygen (0₂). The supplementary gas component may be added to further modify the characteristics of the gas mixture depending on the application therefor. The supplementary gas component may comprise approximately 0.5% to 25% by volume, preferably approximately 1 % to 20% by volume. As stated above, the gas mixtures may be used in applications including food, beverage and the like. Gas mixtures are particularly applicable to the dispensing of beverages such as beers and post-mix soft drinks, as well as packaging food products. Accordingly, in a further aspect of the present invention, there is provided a process for dispensing a beverage which includes providing a gas mixture including greater than approximately 50% by volume of a liquefiable gas in a suitable gas container, the mixture being substantially stable and homogeneous under filled pressures from approximately 10,000 KPa to approximately 30,000 KPa; a dispensing apparatus including a beverage; pressurising the beverage with the gas mixture; and dispensing the beverage.

Desirably dispensing is conducted at temperatures above approximately 5°C, preferably above approximately 7°C, more preferably above approximately 10°C.

The beverage source may be a malt beverage such as a beer. The dispensing apparatus may be any standard beer dispenser. The dispensed beverage may exhibit a creamy, stable foam and an improved taste.

The present invention will now be more fully described with reference to the accompanying examples. It should be understood, however, that the description following is illustrative only and should not be taken as a restriction on the generality of the invention described above.

Examples Cylinders were filled with gas to produce various gas mixtures, designated "Aligal" gases. The filling process is set out graphically in Figure 1 and proceeds as follows: 1. Cylinders are connected to filling ramp, valves open, ready for filling.

2. A control cylinder is placed on an electronic scale to monitor the weight of gas introduced into cylinders. This scale is connected to a programmable controller, which is programmed to open and close the pneumatic valves according to the mixture selected to introduce the correct amount of each gas component into the cylinders.

3. The programmable controller introduces first the permanent gas according to programme into the cylinder, then as a last component, the CO2 in gaseous form.

4. After the control cylinder reaches its programmed weight, the main valve shuts off, the cylinder valves are shut off, and the cylinders are ready for despatch (after analysing samples). PRODUCT RANGE FOR STANDARD ALIGAL CASES

Aligal 13 - 30% C0₂ - 70% N₂

Aligal 15 - 50% C0₂ - 50% N₂

Aligal 15+ - 55% C0₂ - 45% N₂ Aligal 17 - 70% C0₂ - 30% N₂

Aligal 18 - 80% C0₂ - 20% N₂ Aligal 19 - 90% C0₂ - 10% N₂ Aligal gases are at present preferably filled into high pressure gas cylinders (aluminium or steel) containing from 6 m³ (35 litre water capacity, Alu.) to 10 m³ (35 litre water capacity, Steel), possibly up to 20 m³ (50 litre water capacity, Steel) of gas. The volumes are measured in cubic metres (m²) according to Australian Standard AS2992/1987 in which 1 m³ is defined as 1 m³ of gas measured under 101.325 kPa and 15°C.

Several tests were then conducted to prove the viability of producing these mixtures.

Tests conducted by filling Aligal 17 with the classical method (first

CO2 at low pressures and temperatures, then N2) proved it was impossible to achieve a homogeneous mixture; within a reasonable time after filling.

The C0₂ content of the gaseous phase never reached 40% shortly after filling was completed (instead of 70% as required).

EXAMPLE I Tests were conducted to study the emptying of a 10 m³ cylinder. The gas mixture was 72% Cθ2, 28% N2. It was found that the composition of the gas did not change between the tested pressures of 12700 kPa to 2100 kPa over the test period. It is noted that fluctuations of less than + 3% CO2 content are not considered critical, being within the measuring tolerance of the analysis instruments used. The test results are as follows:

EXAMPLE II Additional tests were conducted to investigate the safety of the cylinders at high temperatures. It is noted that across the range of temperatures, the pressure changed but the gas mixture remained stable.

A further test investigated the effect of fast emptying a cylinder, using the same gas mixture as Example I. The cylinder was emptied in approximately 35 minutes. Normally, a cylinder of this size would be emptied over several days. A minor variation of composition appeared to occur during fast emptying, but this was within the +3% CO2 tolerance of the measuring instruments and is not considered significant.

Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.

Claims

1. A process for preparing a substantially stable and homogeneous gas mixture including greater than approximately 50% by volume of a liquefiable gas, which process includes: providing a source of liquefiable gas; a source of a permanent gas; and a gas container; delivering the permanent gas to the gas container; and delivering the liquefiable gas to the container wherein the liquefiable gas is introduced at elevated temperature and/or elevated velocity such that the final volume thereof is greater than approximately 50%.

2. A process according to claim 1 wherein the liquefiable gas in the gas mixture is present in an amount of approximately 50% to 97.5% by volume.

3. A process according to claim 2 wherein the liquefiable gas is present in the gas mixture in an amount of approximately 55% to 85% by volume.

4. A process according to claim 2 wherein the liquefiable gas is present in the gas mixture in an amount of approximately 60% to 75% by volume.

5. A process according to any one of the preceding claims wherein the liquefiable gas is heated to a temperature of approximately 40°C to 250°C.

6. A process according to claim 5 wherein the liquefiable gas is heated to a temperature in the range of 80°C to 110°C.

7. A process according to any one of the preceding claims wherein the heated gas is delivered to the container at a velocity of approximately 10 to 50 metres per second.

8. A process according to any one of the preceding claims wherein the liquefiable gas is selected from carbon dioxide, nitrous oxide, other liquefiable gases or mixtures thereof.

9. A process according to claim 8 wherein the liquefiable gas is carbon dioxide.

10. A process according to any one of the preceding claims wherein the permanent gas is present in the mixture in an amount from approximately 2.5% to 50% by volume.

11. A process according to any one of the preceding claims wherein the permanent gas is selected from nitrogen, helium, argon, oxygen or mixtures thereof.

12. A gas mixture including greater than approximately 50% by volume of a liquefiable gas in a suitable gas container, the mixture being substantially stable and homogeneous under filled pressures from approximately 10,000 kPa to approximately 30,000 kPa.

13. A gas mixture according to claim 12 wherein said liquefiable gas is present in an amount of approximately 50% to 97.5% by volume.

14. A gas mixture according to claim 13 wherein said liquefiable gas is present in an amount of approximately 55% to 85% by volume.

15. A gas mixture according to claim 13 wherein said liquefiable gas is present in an amount of approximately 60% to 75% by volume.

16. A gas mixture according to any one of claims 12 to 15 wherein the liquefiable gas is selected from carbon dioxide, nitrous oxide, other liquefiable gases, or mixtures thereof.

17. A gas mixture according to any one of claims 12 to 16 wherein the gas mixture includes a permanent gas.

18. A gas mixture according to claim 17 wherein the permanent gas is present in an amount from approximately 2.5% to 50% by volume.

19. A gas mixture according to claim 17 or claim 18 wherein the permanent gas is selected from nitrogen, helium, argon, oxygen or mixtures thereof.

20. A gas mixture according to any one of claims 12 to 19 wherein the liquefiable gas is carbon dioxide and the permanent gas is nitrogen.

21. A gas mixture according to any one of claims 12 to 18 wherein the gas mixture includes a supplementary gas.

22. A gas mixture according to claim 21 wherein the supplementary gas is selected from helium, hydrogen, oxygen and argon or mixtures thereof.

23. A gas mixture according to claim 21 or claim 22 wherein the supplementary gas is present in an amount of approximately 0.5% to 25% by volume.

24. A gas mixture according to claim 23 wherein the supplementary gas is present in an amount of approximately 1 % to 20% by volume.

25. A process for dispensing a beverage which process includes: providing a gas mixture according to any one of claims 12 to 24; and a dispensing apparatus including a beverage; pressurising the beverage with the gas mixture; and dispensing the beverage.

26. A process according to claim 1 1 wherein the beverage is a malt beverage such as beer.

27. A method of preparing a substantially stable and homogeneous gas mixture including greater than approximately 50% by volume of a liquefiable gas substantially as hereinbefore described with reference to any one of the examples.

28. A gas mixture substantially as hereinbefore described with reference to any one of the examples.