Fluid handling – Processes – With control of flow by a condition or characteristic of a...
Patent
1994-12-08
1997-05-27
Hepperle, Stephen M.
Fluid handling
Processes
With control of flow by a condition or characteristic of a...
48195, 137 9, 137 98, C10J 128
Patent
active
056322950
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a method of adding an odorant to a consumer gas which is distributed to a consumer site so as to draw to the attention of people in the vicinity of the risk of fire, explosion, poisoning, suffocation or some other danger should the consumer gas escape to the surrounding atmosphere. In the event of a gas escape, the odorant, which is in a concentrated form, preferably an organic sulphur compound, is dissolved in a condensed vehicle gas contained in a pressure vessel, for instance carbon dioxide, propane or butane, so as to form a solution, a master gas, which includes a liquid phase and a gas phase. The desired odorant concentration of the consumer gas is then achieved by diluting the odorant with an adapted quantity of the liquid phase of the master gas, which is vaporized prior to being mixed with the consumer gas. The amount of master gas added is determined by the flow rate of master gas and the odorant concentration of said master gas and the flow rate of the consumer gas. The invention also relates to an arrangement for use when carrying out the method.
BACKGROUND OF THE INVENTION
The concept of adding odorants to consumer gases in accordance with the aforegoing, so as to indicate the leakage of poisonous or explosive gases for instance, has long been known to the art. One example of gases which may be odorized in this way is oxygen, which if leaking to the surroundings can result in extremely serious accidents caused by fire or explosion. Other examples include combustible gases, such as natural gas, propane, butane, town gas, etc., which can also cause serious accidents in the form of fire and explosions. Since the majority of odorous additives, such as tetrahydro thiophene, butyl mercaptan, dimethyl sulphide, etc., are readily ignitable substances which require the application of special techniques when added to oxygen for instance.
Finish Patent Application 870146 discloses a method of adding an odorant to oxygen, in which a concentrated gas, so-called master gas, is produced in a separate chamber or space by adding to pure oxygen gas an odorant in a concentration of 1,000-10,000 ppm. This concentrated master gas is added to the consumer gas in a separate chamber, or space, in an amount such that the odorant will be present in the consumer gas in a concentration of 5-50 ppm.
When the master gas contains solely oxygen and odorant, for instance dimethyl sulphide, problems can occur, however, when filling the master gas containers. For instance, when filling the containers, it is impossible to avoid passing through a concentration range in which the mixture is combustible, at least in a part of the container. There is thus a risk of the mixture igniting and exploding.
One method of avoiding this risk is disclosed in the Finnish Patent Application No. 872278. This application describes a method of producing a concentrated master gas comprising oxygen and an odorant, such as dimethyl sulphide. According to this method, the master gas container is first filled with a mixture of dimethyl sulphide and nitrogen or helium gas. The concentration of dimethyl sulphide lies within a range of 0.5-2.5%. Pure oxygen gas is then added until the desired working pressure in the container is reached, for instance a pressure of 200 bars.
One drawback with the master gas produced in accordance with the aforedescribed methods, however, is that the master gas must not be subjected to temperatures which are so low as to cause the odorant to condense, for instance during transportation and storage. Once being condensed, it takes a very long time for the dimethyl sulphide to return to its gaseous state.
Prior publications DE-B-1185330 and WO 91/17817 describes methods which reduce this problem in that the odorant is dissolved in a gas which exists in liquid phase at room temperature and under pressure. Propane, butane, carbon dioxide, sulphur hexafluoride and nitrous oxide have been given as examples of suitable gases in this respect. These gases also fulfil the require
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Synonym fur Sicherheit, Gas Erdgas, Feb. 1970, pp. 159-166.
AGA Aktiebolag
Hepperle Stephen M.
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