Odorous hydrogen sulfides

Industrial effluents contain sulfur compounds, with their burnt, pungent quality, and fishy or ruinous-smelling nitrogen compounds. Humans are veiy sensitive to these odors hydrogen sulfide has an extremely low recognition threshold of0.00047ppm (vol.) (Cain, 1978). 

Silane, SiH, is a colorless gas. Phosphine, PHj, is also a gas it catches fire spontaneously when exposed to air, is very toxic, and has a bad odor. Hydrogen sulfide, H2S, is a toxic gas with a foul, rotten-egg odor. Natural gas contaminated with hydrogen sulfide is said to be sour, and the hydrogen sulfide must be removed before the natural gas can be used as a fuel. Fortunately, HjS is readily converted to elemental sulfur or to sulfuric acid, for which there are ready markets. Hydrogen chloride, HCl, gas has a sharp odor and is very soluble in water. Solutions of hydrogen chloride in water are called hydrochloric add. About 2.5 million tons of hydrochloric acid are produced for industrial applications in the U.S. each year. 

Various processes are used to remove agents that cause taste, odor, and color. Simple aeration can remove volatile materials such as odorous hydrogen sulfide. Oxidation that destroys organics usually removes taste, odor, and color as does adsorption of organics onto activated carbon. 

A colorless gas with a foul, rotten-egg odor, hydrogen sulfide is very toxic. In some cases, inhalation of H2S kills faster than even hydrogen cyanide rapid death ensues from exposure to air containing more than about 1000 ppm H2S due to asphyxiation from respiratory system paralysis. Lower doses cause sjunptoms that include headache, dizziness, and excitement due to damage to the central nervous system. General debility is one of the numerous effects of chronic H2S poisoning. 

Crude oils appear as liquids of varying viscosities. Their color can range from green (crude from Moonie, Australia) to dark brown (crude from Ghawar, Saudi Arabia). They can have an odor of hydrogen sulfide, turpentine or simply hydrocarbon. 

Sour and sweet are terms referring to a cmde oil s approximate sulfur content, which relates to odor. A cmde oil that has a high sulfur content usually contains hydrogen sulfide, H2S, and/or mercaptans, RSH it is called sour. Without this disagreeable odor, the cmde oil is judged sweet. 

Physical Properties. Hydrogen sulfide, H2S, is a colorless gas having a characteristic rotten-egg odor. The physical properties of hydrogen sulfide are given in Table 2. 

Another area in which sulfur compounds have long found use is in the area of agricultural chemicals. Many of these materials had been produced by the manufacturer of the agricultural chemicals, but difficulties in containing odor and the use of hydrogen sulfide in heavily populated areas again pushed toward specialization by several companies. A Hst of agricultural chemicals, and the thiol that is used or has been used in production, follows ... 

Methods of Purification. Although carbon dioxide produced and recovered by the methods outlined above has a high purity, it may contain traces of hydrogen sulfide and sulfur dioxide, which cause a slight odor or taste. The fermentation gas recovery processes include a purification stage, but carbon dioxide recovered by other methods must be further purified before it is acceptable for beverage, dry ice, or other uses. The most commonly used purification methods are treatments with potassium permanganate, potassium dichromate, or active carbon. 

The odor threshold of carbon disulfide is about 1 ppm in air but varies widely depending on individual sensitivity and purity of the carbon disulfide. However, using the sense of smell to detect excessive concentrations of carbon disulfide is unreHable because of the frequent co-presence of hydrogen sulfide that dulls the olfactory sense. 

Sodium chlorite has also been used for treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans. Chlorine dioxide from chlorite is also useful for microbial and slime control in paper mills and alkaline paper machine systems (164,165). The use of sodium chlorite in textile bleaching and stripping is well known. Cotton is not degraded by sodium chlorite because the oxidation reactions are specific for the hemiceUulose and lignin components of the fibers. 

Hydrogen sulfide Refinery gases, crude oil, sulfur recovery, various chemical industries using sulfur compounds Petroleum and chemicals Kraft pulping process Foul odor of rotten eggs irritating to eyes and respiratory tract darkening exterior paint... 

Paint and varnish manufacturing Resin manufacturing closed reaction vessel Varnish cooldng-open or closed vessels Solvent thinning Acrolein, other aldehydes and fatty acids (odors), phthalic anhydride (sublimed) Ketones, fatty acids, formic acids, acetic acid, glycerine, acrolein, other aldehydes, phenols and terpenes from tall oils, hydrogen sulfide, alkyl sulfide, butyl mercaptan, and thiofen (odors) Olefins, branched-chain aromatics and ketones (odors), solvents Exhaust systems with scrubbers and fume burners Exhaust system with scrubbers and fume burners close-fitting hoods required for open kettles Exhaust system with fume burners... 

Corrosion products and deposits. All sulfate reducers produce metal sulfides as corrosion products. Sulfide usually lines pits or is entrapped in material just above the pit surface. When freshly corroded surfaces are exposed to hydrochloric acid, the rotten-egg odor of hydrogen sulfide is easily detected. Rapid, spontaneous decomposition of metal sulfides occurs after sample removal, as water vapor in the air adsorbs onto metal surfaces and reacts with the metal sulfide. The metal sulfides are slowly converted to hydrogen sulfide gas, eventually removing all traces of sulfide (Fig. 6.11). Therefore, only freshly corroded surfaces contain appreciable sulfide. More sensitive spot tests using sodium azide are often successful at detecting metal sulfides at very low concentrations on surfaces. 

Hydrogen Sulfide HjS Cause of rotten egg odor corrosion Aeration, chlorination, highly basic anion exchange... 

Hydrogen sulfide gas Hydrogen sulfide is a gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly dangerous because it dulls your sense of smell so that you don t notice it after you have been around it for a while and because the odor is not noticeable in high concentrations. The gas is very poisonous to your respiratory system, explosive, flammable, and colorless. 

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