Sulfur dioxide, from industrial processes

Hydromag A process for removing sulfur dioxide from industrial gas streams by absorption in magnesia. Developed in Japan by Nissan Chemical Industries. 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

Sulfidine A process for removing sulfur dioxide from smelter gases by reaction with a suspension of xylidene in water. Developed by the Gesellschaft fiir Chemische Industrie, Basel and Metallgesellschaft, Frankfurt, and used in Germany in the 1930s now probably obsolete. 

The detrimental effects of acid rain are a major reason why legislation such as the Clean Air Act places strict limitations on sulfur and nitrogen emissions. It is also a reason why low sulfur coal is preferred over high sulfur coal. To reduce sulfur dioxide emissions, industry also uses a technique call scrubbing. Industrial scrubbers employ a variety of physical and chemical processes to remove sulfur dioxide from emissions. Another technique used to combat acidification of lakes is to treat these systems with lime. The lime acts to neutralize the acid, but such techniques are usually costly and are only a temporary remedy for combating the problem. 

There is currently great concern about the enviromnental effects of airborne sulfur dioxide. Although SO2 is released into the atmosphere from natural sources such as volcanoes, the majority (ca. 200 million tonnes per year) is man-made either from industrial processes or domestic use such as coal and oil burning. The long-term consequences of large-scale release of SO2 into the atmosphere are undoubtedly severe, and have been the subject of much public debate. The most objectionable aspect of the problem is that often the acid rain , which results from SO2, occurs hundreds of miles from the source. 

Calcium hydroxide, Ca(OH)2, often called slaked lime, is widely used in industry because it is inexpensive and plentiful. For example, slaked lime is used in scrubbing stack gases to remove sulfur dioxide from the exhaust of power plants and factories. In the scrubbing process a suspension of slaked lime is sprayed into the stack gases to react with sulfur dioxide gas according to the following equations ... 

Beginning in 1966, both industry and government started working seriously to develop processes capable of removing sulfur dioxides from... 

The oil and chemical industries use the adsorption process in the cleanup and purification of wastewater streams and for the dehydration of gases. The process is also used in gas purification involving the removal of sulfur dioxide from a stack gas. In addition, adsorption is employed to fractionate fluids that are difficult to separate by other separating methods. The amount of adsorbate that is collected on a unit of surface area is negligible. Therefore, porous desiccants (adsorbent) having a large internal surface area are used for industrial applications. 

After Mr. Semrau s introductory chapter follow four papers which present alternative techniques for recovering sulfur dioxide from the more concentrated smelter gas streams in the non-ferrous smelting industry. Presently, the only commercially available recovery techniques produce sulfuric acid or liquid sulfur dioxide. However, two of the discussions present developments in new processes for recovery of the sulfur values as elemental sulfur. 

The paper pulping industry is reportedly not, in total, a very large emitter of sulfur oxides, although individual plants may present local problems. Kraft mills emit more malodorous reduced sulfur compounds, whereas sulfite mills are more important as emitters of sulfur dioxide. The pulping processes (particularly sulfite) are most interesting because the chemical recovery cycles use basic chemistry that could well be applied to recovery of sulfur dioxide and sulfur from the flue and process waste gases of other types of sources. 

Contrary to popular belief, acid rain is not a new phenomenon nor does it result solely from industrial pollution. Natural processes—volcanic eruptions and forest fires, for example—produce and release acid particles into the air, and the burning of foresf areas to clear land in Brazil, Africa, and other countries also contributes to acid rain however, the rise in manufacturing that began with the Industrial Revolution literally dwarfs all other contributions to the problem. The main culprits are emissions of sulfur dioxide from the burning of fossil fuels, such as oil and coal, and nitrogen oxide, formed mostly from internal combustion engine emissions, which is readily transformed into nitrogen dioxide. These mix in the atmosphere to form sulfuric acid and nitric acid. 

An industrial atmosphere is characterized by pollution composed mainly of sulfur compoimds such as sulfur dioxide (SO ), a precursor to acid rain, and nitrogen oxides (NO ), the backbone of smog in modern dties. Sulfur dioxide from burning coal or other fossil fuels is picked up by moisture on dust particles as sulfurous add. This is oxidized by some catalytic process on the dust particles to sulfuric acid, which settles in microscopic droplets and fall as acid rain on exposed surfaces. The result is that contaminants in an industrial atmosphere, plus dew or fog, produce a highly corrosive, wet, acid film on exposed surfaces. 

About 70 percent of total sulfur dioxide emissions in 1985 in Canada came from industrial processes—69 percent of this was from copper, nickel, lead, zinc, gold, and aluminum production, and a further 21 percent was from oil and natural gas recovery and processing. Fuel combustion, mainly by power plants and industries, accounted for 28 percent of total Canadian emissions of sulfur dioxide. Between 1970 and 1985, sulfru dioxide emissions declined by almost 45 percent (Fig. P-3), mainly because of modifications to industrial processes and technology, the capture and use of sulfur dioxide to make commercially usefrd sulfuric acid, and the increased use of low-sulfur fuels. 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

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