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An odorizer is a device that adds an odorant to a gas. The most common type is one that adds a mercaptan liquid into natural gas distribution systems so that leaks can be readily detected. Other types have been used for carbon dioxide fire extinguishers.
Natural gas odorizers [1] can vary 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 the following:
Non-sulfur-containing odorants include the following:
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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 which is very similar to those used in a kerosene lantern. The odorant is drawn up the wick from the container and into the gas stream.
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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.
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 in 1992. [2] 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.
Odorizers are used in carbon dioxide fire extinguisher systems, the odorizer assembly injects wintergreen oil 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. [3] [4] [5]
Similar systems are used in mines, where, in the case of an emergency such as a gas leak in the mine, ampoules of ethanethiol are broken in front of ventilation fans to warn the miners of the emergency. [6] [7]
Natural 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 dioxide, nitrogen, hydrogen sulfide, and helium are also usually present. Methane is colorless and odorless, and the second largest greenhouse gas contributor to global climate change after carbon dioxide. Because natural gas is odorless, odorizers such as mercaptan are commonly added to it for safety so that leaks can be readily detected.
In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".
Methanethiol is an organosulfur compound with the chemical formula CH
3SH. It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals, as well as in plant tissues. It also occurs naturally in certain foods, such as some nuts and cheese. It is one of the chemical compounds responsible for bad breath and the smell of flatus. Methanethiol is the simplest thiol and is sometimes abbreviated as MeSH. It is very flammable.
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 structure parallels that of ethanol, but with sulfur in place of oxygen. The odor of EtSH is infamous. Ethanethiol is more volatile than ethanol due to a diminished ability to engage in hydrogen bonding. Ethanethiol is toxic in high concentrations. It occurs naturally as a minor component of petroleum, and may be added to otherwise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks. At these concentrations, ethanethiol is not harmful.
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 volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds.
Acid gas is a particular typology of natural gas or any other gas mixture containing significant quantities of hydrogen sulfide (H2S), carbon dioxide (CO2), or similar acidic gases. A gas is determined to be acidic or not after it is mixed with water. The pH scale ranges from 0 to 14, anything above 7 is basic while anything below 7 is acidic. Water has a neutral pH of 7 so once a gas is mixed with water, if the resulting mixture has a pH of less than 7 that means it is an acidic gas.
A stink bomb, sometimes called a stinkpot, is a device designed to create an unpleasant smell. They range in effectiveness from being used as simple pranks to military grade malodorants or riot control chemical agents.
Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S).
Amine gas treating, also known as amine scrubbing, gas sweetening and acid gas removal, refers to a group of processes that use aqueous solutions of various alkylamines (commonly referred to simply as amines) to remove hydrogen sulfide (H2S) and carbon dioxide (CO2) from gases. It is a common unit process used in refineries, and is also used in petrochemical plants, natural gas processing plants and other industries.
Sulfur compounds are chemical compounds formed the element sulfur (S). Common oxidation states of sulfur range from −2 to +6. Sulfur forms stable compounds with all elements except the noble gases.
Hydrodesulfurization (HDS), also called hydrotreatment or hydrotreating, is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur, and creating products such as ultra-low-sulfur diesel, is to reduce the sulfur dioxide emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.
Tetrahydrothiophene is an organosulfur compound with the formula (CH2)4S. The molecule consists of a five-membered saturated ring with four methylene groups and a sulfur atom. It is the saturated analog of thiophene. It is a volatile, colorless liquid with an intensely unpleasant odor. It is also known as thiophane, thiolane, or THT.
Merox is an acronym for mercaptan oxidation. It is a proprietary catalytic chemical process developed by UOP used in oil refineries and natural gas processing plants to remove mercaptans from LPG, propane, butanes, light naphthas, kerosene and jet fuel by converting them to liquid hydrocarbon disulfides.
An asphyxiant gas, also known as a simple asphyxiant, is a nontoxic or minimally toxic gas which reduces or displaces the normal oxygen concentration in breathing air. Breathing of oxygen-depleted air can lead to death by asphyxiation (suffocation). Because asphyxiant gases are relatively inert and odorless, their presence in high concentration may not be noticed, except in the case of carbon dioxide (hypercapnia).
Natural-gas processing is a range of industrial processes designed to purify raw natural gas by removing contaminants such as solids, water, carbon dioxide (CO2), hydrogen sulfide (H2S), mercury and higher molecular mass hydrocarbons (condensate) to produce pipeline quality dry natural gas for pipeline distribution and final use. Some of the substances which contaminate natural gas have economic value and are further processed or sold. Hydrocarbons that are liquid at ambient conditions: temperature and pressure (i.e., pentane and heavier) are called natural-gas condensate (sometimes also called natural gasoline or simply condensate).
1-Butanethiol, also known as butyl mercaptan, is a volatile, clear to yellowish liquid with a fetid odor, commonly described as "skunk" odor. In fact, 1-butanethiol is structurally similar to several major constituents of a skunk's defensive spray but is not actually present in the spray. The scent of 1-butanethiol is so strong that the human nose can easily detect it in the air at concentrations as low as 10 parts per billion. The threshold level for 1-butanethiol is reported as 1.4 ppb
A hydrogen odorant in any form, is a minute amount of odorant such as ethyl isobutyrate, with a rotting-cabbage-like smell, that is added to the otherwise colorless and almost odorless hydrogen gas, so that leaks can be detected before a fire or explosion occurs. Odorants are considered non-toxic in the extremely low concentrations occurring in hydrogen gas delivered to the end user.
The molecular formula C4H10S may refer to:
tert-Butylthiol, also known as 2-methylpropane-2-thiol, 2-methyl-2-propanethiol, tert-butyl mercaptan (TBM), and t-BuSH, is an organosulfur compound with the formula (CH3)3CSH. This thiol is used as an odorant for natural gas, which is otherwise odorless. It may also have been used as a flavoring agent.
A Diving rebreather is an underwater breathing apparatus that absorbs the carbon dioxide of a diver's exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the diver. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose is to extend the breathing endurance of a limited gas supply, and, for covert military use by frogmen or observation of underwater life, to eliminate the bubbles produced by an open circuit system. A diving rebreather is generally understood to be a portable unit carried by the user, and is therefore a type of self-contained underwater breathing apparatus (scuba). A semi-closed rebreather carried by the diver may also be known as a gas extender. The same technology on a submersible or surface installation is more likely to be referred to as a life-support system.
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