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An odorizer is a device that adds an
odorant An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently vol ...
to a gas. The most common type is one that adds a mercaptan liquid into
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon di ...
distribution systems so that leaks can be readily detected. Other types have been used for carbon dioxide
fire extinguishers A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which ha ...
.


Natural gas odorizers

Natural gas odorizers run the gamut from a simple wick in a container to computerized equipment, which controls the amount of odorant based on flow rate, tracks the amount of odorant in inventory, and alarms when odorant is not being injected into the gas stream. Odorants used for natural gas vary from country to country, depending on gas distribution regulations. Some odorants contain sulfur, which is oxidized to sulfur dioxide when the gas is burned. Sulfur containing odorants include: * tert-Butylthiol (TBM) the main ingredient in many gas odorant blends * Tetrahydrothiophene (THT), used as an odorant for natural gas, usually in mixtures containing tert-butylthiol * 2-Propanethiol, commonly known as isopropyl mercaptan (IPM) is used as an odorant for natural gas usually in mixtures containing tert-butylthiol *
Ethanethiol Ethanethiol, commonly known as ethyl mercaptan, is an organosulfur compound with the formula CH3CH2SH. is a colorless liquid with a distinct odor. Abbreviated EtSH, it consists of an ethyl group (Et), CH3CH2, attached to a thiol group, SH. Its st ...
(EM), commonly known as ethyl mercaptan is used in
Liquefied petroleum gas Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane. LPG is used as a fuel gas in heating appliances, cooking eq ...
(LPG), and resembles odor of leeks, onions, durian, or cooked cabbage *
Methanethiol Methanethiol (also known as methyl mercaptan) is an organosulfur compound with the chemical formula . It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals (including humans ...
, commonly known as methyl mercaptan, is added to natural gas as an odorant, usually in mixtures containing methane. Its smell is reminiscent of rotten eggs or cabbage. * Dimethyl sulfide (DMS), a component of the smell produced from cooking of certain vegetables, notably maize, cabbage, beetroot, and seafoods Non-sulfur containing odorants include: *
Methyl acrylate Methyl acrylate is an organic compound, more accurately the methyl ester of acrylic acid. It is a colourless liquid with a characteristic acrid odor. It is mainly produced to make acrylate fiber, which is used to weave synthetic carpets. It is al ...
(MA) *
Ethyl acrylate Ethyl acrylate is an organic compound with the formula CH2CHCO2CH2CH3. It is the ethyl ester of acrylic acid. It is a colourless liquid with a characteristic acrid odor. It is mainly produced for paints, textiles, and non-woven fibers. It is ...
(EA) * Methylethyl pyrazine, odor of various foods including coffee and wines


Wick type odorizers

Wick type odorizers can be very small, odorizing the gas for as few as one gas customer to much larger ones that can odorize the gas for a small town (10,000 MCF). They use a
wick Wick most often refers to: * Capillary action ("wicking") ** Candle wick, the cord used in a candle or oil lamp ** Solder wick, a copper-braided wire used to desolder electronic contacts Wick or WICK may also refer to: Places and placename ...
which is very similar to those used in a
kerosene lantern A kerosene lamp (also known as a paraffin lamp in some countries) is a type of lighting device that uses kerosene as a fuel. Kerosene lamps have a wick or mantle as light source, protected by a glass chimney or globe; lamps may be used on a ta ...
. The odorant is drawn up the wick from the container and into the gas stream.


Absorption bypass odorizers

Absorption bypass odorizers take a portion of the gas stream, the amount being dependent on the flow of gas in the line, and run it through a tank containing liquid odorant. The gas is passed over the top of the liquid. Variations exist where wicks are utilized to increase odorant vaporization.


Liquid injection type odorizers

For very high volume systems (and for some smaller volume systems), liquid injection odorizers are being manufactured. These odorizers work by the addition of small amounts of liquid odorant to the moving gas. A pump that can be controlled to give the range of addition rates necessary is a very important aspect of this type of odorizer. Computer control to monitor flow rates and vary injection rate is a significant part of the more modern versions of this. Previous versions worked off a variety of schemes to control the odorization level. The Peerless odorizer was the first example of this type of odorizer. The Peerless natural-gas odorizer was recognized as a Mechanical Engineering Landmark by the
American Society of Mechanical Engineers The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via " continuin ...
in 1992. This odorizer was said to have been developed in response to the New London School explosion that occurred in March 1937. It was first shipped in July 1937, the Peerless odorizer overcame two of the major problems of previous devices: they avoided problems with leaky shaft seals by encapsulating the entire unit within a pressure vessel and added odorant in proportion to the gas flow by using a gas meter to drive the odorant pump.


Other odorizers


Carbon dioxide fire extinguishers

Odorizers are used in carbon dioxide fire extinguisher systems, the odorizer assembly injects
wintergreen oil Methyl salicylate (oil of wintergreen or wintergreen oil) is an organic compound with the formula C8H8O3. It is the methyl ester of salicylic acid. It is a colorless, viscous liquid with a sweet, fruity odor reminiscent of root beer, but often a ...
into the carbon dioxide stream when the agent is discharged. Approximately 50 cc of wintergreen oil contained within a frangible glass cartridge is mounted within a protective housing attached to the discharge piping in such a manner as to rupture the glass container when the carbon dioxide manifold is pressurized during discharge, atomizing the oil and dispersing it. The strong wintergreen scent effectively notifies the occupants of the presence of carbon dioxide gas after carbon dioxide has been discharged into the hazard.


Mine gas warning systems

Similar systems are used in mines, where, in the case of an emergency such as a gas leak in the mine, ampoules of
ethanethiol Ethanethiol, commonly known as ethyl mercaptan, is an organosulfur compound with the formula CH3CH2SH. is a colorless liquid with a distinct odor. Abbreviated EtSH, it consists of an ethyl group (Et), CH3CH2, attached to a thiol group, SH. Its st ...
are broken in front of ventilation fans to warn the miners of the emergency.


References


External links


Engines of our ingenuity episode 735, by John H. Lienhard
{{Fuel gas Gas technologies cs:Odorizace de:Odorierung it:Odorizzazione ru:Душистые вещества