Natural gas odorant: features of odorants, norms and rules for their introduction

Explosions, destruction and lost lives are all tragic consequences of improper operation of gas equipment.Their likelihood decreases significantly the more quickly the leak is identified and repaired. But is it that simple? detect leak?

You have repeatedly heard that gas smells on its own and when there is a leak, the smell comes from it, right? But this opinion is erroneous - a component known as natural gas odorant is added to the final odor composition.

The presented article examines in detail the properties and composition of odorants, the main methods of their introduction to ensure safety both at industrial facilities and in everyday life. The standards for odorization of natural gas, as well as the latest changes in legislation, are scrupulously reviewed. For easy comprehension, the text is supplemented with videos and illustrations.

Basic properties of odorants

The gas is widely used in everyday life and can cause severe poisoning, and its high concentration creates an explosive environment. Initially domestic gas (methane with other impurities, including propane, ethane, butane) is odorless, and any leak from a closed system could be detected exclusively with the help of special sensors.

This problem is solved by adding a component with a pronounced odor to the gas - an odorant. And the direct process of entering the stream is called odorization. Mixing is carried out at a gas distribution station or at centralized points.

Ideally, odorants should have the following qualities:

1. Have a pronounced, specific smell for clear and quick recognition.
2. Ensure stable dosage. When mixed with methane and moved through a gas pipe, odorants must exhibit chemical and physical resistance.
3. Have sufficient concentration to reduce overall consumption.
4. Do not form toxic products during operation.
5. Additives should not exhibit a corrosive effect on containers and fittings, which will ensure a long service life of gas equipment and pipelines.

There is no odorant that fully meets all these criteria. Therefore, technical specifications TU 51-31323949-94-2002 and Operating Regulations were developed for Gazprom VRD 39-1.10-069-2002. But these are internal documents of Gazprom, binding only on organizations included in the Gazprom Group.

The document VRD 39-1.10-06-2002 provides the basic requirements for the production, storage, transportation and use of additives.

To neutralize the strong odor of the odorant in places of its leakage, use a solution of potassium permanganate or bleach. In this case, you will definitely need a gas mask and other protective equipment.

The correct use of odorants is regulated in the Rules for the Operation of Trunk Gas Pipelines STO Gazprom 2-3.5-454-2010, where it is stated that the explosive limit of a flammable liquid is 2.8-18%, and the maximum permissible concentration is 1 mg/m³.

To determine the intensity of the odor of an odorant in points, as well as measure its mass concentration, the gas analyzer ANKAT-7631 Micro-RSH can be used

Inhalation of vapors can provoke vomiting, loss of creation; in large quantities the substance causes convulsions, paralysis and death. According to the degree of impact on the body, these are harmful substances of the 2nd hazard class. Their concentration in a room can be determined using a gas analyzer such as RSH.

Standards and composition of odorants

Natural gas must be detectable by odor in the air when its concentration is no more than 20% of the lower explosive limit, which is equal to 1% by volume of the organic compound. We described in detail what to do if your apartment smells of gas. next article.

The amount of odorant in the gas supplied to the consumer depends on the chemical composition of the mixture.

The Regulations on the technical operation of GDS of main gas pipelines VRD 39-1.10-069-2002 indicate that the commissioning rate ethyl mercaptan equals 16 g per 1,000 m³ of gas.

This odorant was one of the first industrial additives to be used in the former USSR, but EtSH has several significant disadvantages:

• exhibits easy oxidation;
• interacts with iron oxides;
• has high toxicity;
• dissolves in water.

The formation of diethyl sulfide, to which ethyl mercaptan is prone, reduces the intensity of the odor, especially when transported over long distances. Since 1984, almost throughout Russia, a mixture of natural mercaptans has been used, which includes isopropyl mercaptan, ethyl mercaptan, tert-butyl mercaptan, butyl mercaptan, tetrohydrothiophene, n-propyl mercaptan and n-butyl mercaptan.

The odorant complies with TU 51-31323949-94-2002 “Natural odorant LLC Orenburggazprom”.The rate for this multicomponent additive does not differ from the recommended amount of ethyl mercaptan.

Loading barrels for filling with odorant, transporting dangerous cargo, and rearranging it on the site must be carried out exclusively by mechanization. This is done to avoid damage to the containers, each of which must also be marked

So called mercaptans produced on the basis of hydrogen sulfide, sulfur and sulfides. But modern production is based on the use of sulfur-free compounds; for example, in Germany they produce an environmentally friendly product called Gasodor™ S-Free™.

GASODOR™ S-Free™ odorant base uses ethyl acrylate and methyl acrylate, which upon combustion produce water and carbon dioxide. Despite good performance characteristics, some polymer materials can cause a sharp decrease in the concentration of acrylates, and as a result, a decrease in the intensity of gas odor

This odorant has a sharp, specific odor, remains stable even during long-term storage, and does not change its qualities when the temperature changes.

The additive is also highly valued for the fact that it does not dissolve in water. When conducting tests that confirmed the suitability of the substance at one of Gazprom’s domestic facilities, an odorant concentration of 10-12 mg/m³ was used.

Ethanethiol is transported in road and rail tanks, cylinders, and containers. The maximum permissible storage volume is 1.6 tons in above-ground cylindrical tanks, the filling factor should be 0.9-0.95

Crotonaldehyde is considered as a potential odorant.A highly flammable liquid with a pungent odor, it belongs to the second hazard class in terms of the degree of impact on the body.

Has several significant advantages over ethanethiol:

• contains no sulfur;
• has less toxic effects;
• It is slightly volatile under normal conditions.

The maximum level of emissions from crotonaldehyde does not exceed the maximum permissible standard and is 0.02007 mg/m3. The possibility of practical use of the substance as an odorant has not yet been studied in detail.

Determination of odorization quality

Complaints about strictly regulated standards for the odorization of household gas are being received more and more often.

In return, it is proposed to focus on several factors affecting the quality of odorization of natural gas:

1. Condition of the gas pipeline and its length. The intensity of the odor may decrease as a result of chemical reactions between the walls of the gas pipeline and the odorant, in which case it will be necessary to increase the rate of introduction of the substance into the gas flow.
2. The need to change the norm may also be associated with the specific gravity of mercaptan sulfur in the composition. Knowing its percentage, you can reduce the amount of odorant. If the quality of the fuel is poor or condensate accumulates in the gas pipeline, on the contrary, an increase in the concentration of the substance will be required.
3. Transportation and storage conditions also affect the intensity of the odor.. The use of unsuitable containers, including those made of black steel, sudden changes in temperature and exposure to precipitation, negatively affect the quality of the odorant.

As for the factor of changing the component composition, significant costs will be required to carry out the analysis.Unjustified consumption of additives can be reduced by using an automated process for adding them; this will also resolve the issue of ecology and safety.

The concentration of the odorant can also be determined in a closed container under pressure. The sensor, whose operating principle is based on the hydrostatic method, uses a microprocessor control unit to calculate the volume, level and mass of the liquid

The effectiveness of odorization also depends on the equipment base, the degree of automation and the mixing method; let’s consider the last parameter in more detail.

Methods for odorizing natural gas

The type of odorant is chosen based on several requirements:

• required level of accuracy;
• sufficient performance;
• material opportunities.

The additive is used in both liquid and vapor form. The first method involves drip administration or the use of a dosing pump. To saturate with vapor, an odorant is introduced into a portion of the gas flow by branching or blowing onto a wetted wick.

Method #1 - drip injection of the substance

This input method is characterized by relatively low costs and a simple usage scheme. The operating principle is based on counting the number of drops per unit of time, which allows you to obtain the required flow rate.

To transport gas in large volumes, drops are transformed into a stream of liquid; in such cases, a level gauge scale or a special container with divisions is used.

The dropper is used for visual monitoring of the consumption of aggressive substances, including when dosing odorant. All parts, including the body, are made of sustainable materials

This method requires constant manual adjustment and checking of flow, in particular when the number of consumers changes.

The process cannot be automated, so its accuracy is low - only 10-25%.In modern installations, the dripper is used only as a reserve in the event of a malfunction of the main equipment.

Method #2 - using a wick odorizer

Using a wick odorizer is another method that is suitable for small volumes of gas. All operations are carried out manually. The odorant is used for vapor and liquid state; its content is determined by the amount of consumption per unit of time.

Evaporation in wick odorizers, unlike other devices, occurs directly from the surface over which the gas passes. The coating often consists of flannel wicks

The supply is regulated by changing the amount of gas that is passed through the wick.

Method #3 - bubbling introduction of odor into gas

Installations that use bubbling, unlike the previous two, can be automated.

The odorant is supplied using a diaphragm and a dispenser; its quantity is calculated in proportion to the gas consumption. The substance flows by gravity from the supply container. The ejector is responsible for the filling process.

Scheme of a bubble odorizer. The main elements include the diaphragm, gas pipeline, valve, chamber and filter. They produce different sizes of devices depending on the performance of the gas distribution station

Recent developments to improve the odorization process include the use of dosing pumps. They consist of a cleaning filter, an electronic control unit and a control device - a magnet or valve.

Conclusions and useful video on the topic

An employee of the Museum of Trunk Gas Transport will tell you in detail about the transportation of fuel, how and with what natural gas is odorized:

An interesting story about the modernization of an odorization plant:

The installation of the odorization device can be seen in the video:

The appearance of a characteristic odor during a gas leak in a room is one of the key conditions safe use gas in everyday life. Odorants are used to promptly detect unplanned gas release.

The intensity of the gas odor must be sufficient to detect and not exceed the permissible explosion threshold. As the temperature drops, the smell weakens, so in winter the amount of odorant administered should be several times lower than in summer.

If you have questions about the topic under consideration or want to add useful information on the odorization of natural gas, please leave your comments. The block is located below the text.