Odorization
The addition of odor-intensive substances (odorants) is referred to as odorization , in particular adding them to gases without a significant inherent odor. As a safety measure, the added can perfumes herein serve as a warning or alarm signal and will therefore as Odor one hand, the risk characterizing by the largely odorless gas odor have.
Odorisation of natural gas and other fuel gases
The odorization of natural gas , liquefied petroleum gas / LPG and other fuel gases is an important security measure, not only for the gas consumer. In contrast to the previously used city or coke oven gases with a strong odor, the purified natural gas commonly used today is almost odorless. So that leaks in the public gas supply or leaky systems in the internal gas installation are immediately noticeable, specific warning odors are added to this natural gas for safety reasons, because if a leak is not noticed in time, explosive gas / air mixtures with a high hazard potential can build up within a short time. In the event of gas escaping from pipes in the ground, however, odorization is not a reliable safety measure, as the ground can sorb odorants.
The odorization is carried out in gas distribution networks that serve the general supply (household customers and comparable consumers). In pipeline networks, on the other hand, the gas is transported without odorization. As a rule, the odorization device is installed in gas pressure control and measuring systems through which the gas from the pipeline networks reaches the distribution networks. Industrial companies that use natural gas exclusively on the factory premises can do without odorization if safety is achieved through other measures.
The odorants used must also be perceptible in great dilution and trigger an alarming association. To do this, the odorant must not only have an unpleasant and unmistakable smell, but also clearly represent a warning odor. The smell of the odorized gas must therefore not come from everyday life, e.g. B. from the kitchen and household.
For this purpose, highly volatile, typically smelling organic sulfur compounds are widely used in Germany , primarily tetrahydrothiophene (THT) (minimum concentration 10 mg / m 3 ), the smell of which is reminiscent of rotten eggs, as well as mixtures of mercaptans (minimum concentration 3 mg / m 3 ), including tert -butyl mercaptan (TBM). Since additional sulfur oxides are produced as combustion products during the specific combustion of such odorized gases, sulfur-free odorants have also been used for some time, for example a mixture of ethyl acrylate (over 50%), methyl acrylate and 2-ethyl-3-methylpyrazine . Such a mixture has a solvent-like odor, which, according to studies by the DVGW, is still associated with natural gas by test subjects, but the effectiveness of this agent is controversial. The odorization specifications are described in DVGW worksheet G 280, part 1–3.
Impact odorization is a temporarily increased admixture of the odorization additive over a certain period of time, for example after new installations or repeated at regular intervals in order to find small leaks at an early stage.
Odorisation of extinguishing gases
In inert gas extinguishing systems , an odorant that smells of lemon is usually used, which makes the odorless extinguishing gas perceptible. If there is a risk that in lower-lying unventilated rooms, e.g. B. pits of hydraulic systems or cellars, people are endangered by escaping extinguishing gas, it is prescribed in Germany according to trade association rules to odorize the extinguishing agent to smell perception by additives. In high-pressure inert gas extinguishing systems, the odorant is added to the extinguishing agent when it is filled into the high-pressure gas bottles; in low-pressure inert gas extinguishing systems, it is only added to the extinguishing gas during the extinguishing process by a so-called odorization device.
Odorization of oxygen for welding and cutting
In the case of oxygen used, for example, for welding or cutting steel, odorization is carried out when there is a risk of oxygenating narrow spaces. An increase in the proportion of oxygen in the room air compared to the 21 percent by volume in air increases the flammability of otherwise flame-retardant substances (such as protective clothing) considerably and increases the speed and temperature of combustion.
One application is working in ship hulls, for example in shipyards. N , N - dimethylsulfamide (DMS) is used to odorize oxygen .
Odorisation of formaldehyde, 1,2-dichloroethane or benzenes with trichloronitromethane
Due to strict regulations of the EU ( Directive 2000/29 / EG ) for protection against the introduction of harmful organisms, containers, goods or packaging material made of wood from overseas are often fumigated in the export country. The most common gases introduced are methyl bromide (90%), sulfuryl fluoride , hydrogen phosphide and formaldehyde . In addition, in the manufacture or further treatment of certain goods, substances are used that release gases in concentrations that are hazardous to health during transport.
Previously detected gases in concentrations dangerous to health are benzene , formaldehyde and 1,2-dichloroethane . Here is Trichloronitromethane (in all probability) for the odorization of fumigants and as an indication of ausgedünstete gases of goods. Containers with shoes (benzene) and textiles (formaldehyde) are particularly often affected by exceeding the limit values. According to the ArbSchG , these containers should be adequately ventilated.
Analytics
Gas chromatography , ion mobility spectrometers or olfactometry are used to determine the concentration of odorants .
Web links
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- ↑ Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 158-160, ISBN 978-3-8348-1245-2 .
- ↑ Susanne Donner: The scent of danger. In: Image of Science. June 30, 2009, accessed November 30, 2013 .
- ↑ LEWA pumps and metering systems for the odorization of gas lewa.at, Lewa Nikkiso Austria GmbH, called January 1, 2018.