Sulfur dioxide requirements

Certain of the above reactions are of practical importance. The oxidation of hydrogen sulfide in a flame is one means for producing the sulfur dioxide required for a sulfuric acid plant. Oxidation of hydrogen sulfide by sulfur dioxide is the basis of the Claus process for sulfur recovery. The Claus reaction can also take place under mil der conditions in the presence of water, which catalyzes the reaction. However, the oxidation of hydrogen sulfide by sulfur dioxide in water is a complex process leading to the formation of sulfur and polythionic acids, the mixture known as Wackenroeder s Hquid (105). 

Note The generation of sulfur dioxide requires that the following reaction be carried out in a hood. 

Do piping specifications meet chlorine/sulfur dioxide requirements for the service ... 

Sulfur dioxide, in the presence of sulfuric acid, reduces the precipitated manganese dioxide to the soluble sulfate the removal of this large quantity of flocculent material greatly facilitates separation of the heptoic acid. The addition of sulfur dioxide requires about two hours, and an excess is to be avoided. Sodium bisulfite may be used if gaseous siilfur dioxide is not available. 

Prior to the energy crisis, it could be demonstrated that the cost differential between high and low sulfur fuels would balance the increased expenses for operating pollution control equipment. With the current erratic fuel pricing situation it is difficult to make such a comparison. However, Research-Cottrell offers processes capable of meeting federal particulate and sulfur dioxide requirements and thereby allows the user more freedom in his fuel selection. 

Ion-selective electrodes using a sulfur dioxide gassensing membrane probe have been developed into commercial models for the determination of sul-fur(IV) oxo-species. A typical procedure for the determination of free sulfur dioxide requires the probe to be immersed in a stirred solution at pH 1, whereas total sulfur dioxide requires the sample to be treated with strong alkali prior to acidification and analysis at pH 1. Molecular sulfur dioxide passes through the membrane into a solution of hydrogen sulfite ion and the pH of the SO2 H20/HS03 buffer can be determined with a glass electrode. 

Suzzi, G., P. Romano, and C. Zambonelli. 1985. Saccharomyces strain selection in minimizing sulfur dioxide requirements during vinification. Am. J. Enol. Vitic. 36 199-202. 

A geoengineering approach based on production of light-reflecting atmospheric sulfate aerosols would entail discharging large quantities of sulfur dioxide from the anthrosphere into the atmosphere. The enormous quantities of sulfur dioxide required and the collateral consequences, particularly increased acid rain, make it unlikely that this solution will ever be employed. 

The dosage liqueur can be acidified with citric acid, if necessary. It also contains the quantity of sulfur dioxide required to eliminate any dissolved oxygen, and may be supplemented with ascorbic acid (50 mg/1). This offsets the sudden oxidative effect of disgorging the redox potential may increase by 150 mV, or even more, depending on the redox buffer capacity of the wine. 

A slurry of elemental sulfur in glycol flows from the bottom of the reactor to a settling tank where the mixture is heated to 250°-275°F. Excess sulfur dioxide is stripped from the solution and returned to the reactor. Liquid sulfur is withdrawn from the bottom of the settling tank. A portion of the liquid sulfur flows to a sulfur burner where it is burned to supply the sulfur dioxide required in the process. 

Plant investment and maintenance costs are relatively high for a new iodine plant in the United States or in Japan because of the deep weUs required for brine production and disposal as weU as the corrosive nature of the plant streams. The principal materials cost is for chlorine and for sulfur dioxide, although in the United States the additives used for the brines, such as scale inhibitors and bactericides, also have a considerable influence on costs. 

Air Pollution. Particulates and sulfur dioxide emissions from commercial oil shale operations would require proper control technology. Compliance monitoring carried out at the Unocal Parachute Creek Project for respirable particulates, oxides of nitrogen, and sulfur dioxide from 1986 to 1990 indicate a +99% reduction in sulfur emissions at the retort and shale oil upgrading faciUties. No violations for unauthorized air emissions were issued by the U.S. Environmental Protection Agency during this time (62). 

Emissions control systems play an important role at most coal-fired power plants. For example, PC-fired plants sited in the United States require some type of sulfur dioxide control system to meet the regulations set forth in the Clean Air Act Amendments of 1990, unless the boiler bums low sulfur coal or benefits from offsets from other highly controlled boilers within a given utiUty system. Flue-gas desulfurization (FGD) is most commonly accomphshed by the appHcation of either dry- or wet-limestone systems. Wet FGD systems, also referred to as wet scmbbers, are the most effective solution for large faciUties. Modem scmbbers can typically produce a saleable waUboard-quaUty gypsum as a by-product of the SO2 control process (see SULFURREMOVAL AND RECOVERY). 

In the United States, amendments to the Clean Air Act in November 1990 limited the amount of sulfur dioxide emissions that coal-based power uthities could produce. The cost of compliance incurred by the uthities was expected to be passed along to the power consumers. The U.S. Bureau of Mines estimated that the requirements to limit sulfur dioxide emissions would increase the operational cost of certain shicon producers by up to 0.02/kg (31). 

The 1990 Amendments to the U.S. Clean Air Act require a 50% reduction of sulfur dioxide emissions by the year 2000. Electric power stations are beheved to be the source of 70% of all sulfur dioxide emissions (see Power generation). As of the mid-1990s, no utiUties were recovering commercial quantities of elemental sulfur ia the United States. Two projects had been aimounced Tampa Electric Company s plan to recover 75,000—90,000 metric tons of sulfuric acid (25,000—30,000 metric tons sulfur equivalent) aimuaHy at its power plant ia Polk County, Elorida, and a full-scale sulfur recovery system to be iastaHed at PSl Energy s Wabash River generating station ia Terre Haute, Indiana. Completed ia 1995, the Terre Haute plant should recover about 14,000 t/yr of elemental sulfur. 

In addition to domestic production of Frasch and recovered elemental sulfur, U.S. requirements for sulfur are met with by-product sulfuric acid from copper, lead, molybdenum, and zinc smelting operations as well as imports from Canada and Mexico. By-product sulfur is also recovered as sulfur dioxide and hydrogen sulfide (see Sulfurremoval and recovery). 

Reduction of sulfur dioxide to sulfur includes an industrially important group of reactions (227). Hydrogen sulfide reduces sulfur dioxide even at ambient temperature in the presence of water, but in the dry state and in the absence of a catalyst, a temperature of ca 300°C is required. 

Combustion of Sulfur. For most chemical process appHcations requiring sulfur dioxide gas or sulfurous acid, sulfur dioxide is prepared by the burning of sulfur or pyrite [1309-36-0], FeS2. A variety of sulfur and pyrite burners have been developed for sulfuric acid and for the pulp (qv) and paper (qv) iadustries, which produce and immediately consume about 90% of the captive sulfur dioxide produced ia the United States. Information on the European sulfur-to-sulfuric acid technology (with emphasis on Lurgi) is available (255). 

Shipment and Storage. Liquid sulfur dioxide is commonly shipped in North America using 55- and 90-t tank cars, 20-ton tank tmcks, 1-ton cylinders, and 150-lb cylinders. Cylinders made of specified steel are affixed with the green label for nonflammable gases. The DOT classification is Poison Gas, Inhalation Ha2ard. Purchasers of tank-car quantities are required to have adequate storage faciUties for prompt transfer. 

The Reich test is used to estimate sulfur dioxide content of a gas by measuring the volume of gas required to decolorize a standard iodine solution (274). Equipment has been developed commercially for continuous monitoring of stack gas by measuring the near-ultraviolet absorption bands of sulfur dioxide (275—277). The deterrnination of sulfur dioxide in food is conducted by distilling the sulfur dioxide from the acidulated sample into a solution of hydrogen peroxide, foUowed by acidimetric titration of the sulfuric acid thus produced (278). Analytical methods for sulfur dioxide have been reviewed (279). 

Ma.nufa.cture. In a typical process, a solution of sodium carbonate is allowed to percolate downward through a series of absorption towers through which sulfur dioxide is passed countercurrently. The solution leaving the towers is chiefly sodium bisulfite of typically 27 wt % combined sulfur dioxide content. The solution is then mn into a stirred vessel where aqueous sodium carbonate or sodium hydroxide is added to the point where the bisulfite is fully converted to sulfite. The solution may be filtered if necessary to attain the required product grade. A pure grade of anhydrous sodium sulfite can then be crystallized above 40°C because the solubiUty decreases with increasing temperature. 

A variation of the n on regen erabi e absorption is the spray dry process. Time slurry is sprayed through an atomizing nozzle into a tower where it countercurtendy contacts the flue gas. The sulfur dioxide is absorbed and water in the slurry evaporated as calcium sulfite-sulfate collects as a powder at the bottom of the tower. The process requires less capital investment, but is less efficient than regular scmbbing operations. 

Sulfur Dioxide Reductant. The Mathieson process uses sulfur dioxide, sodium chlorate, and sulfuric acid to produce chlorine dioxide gas with a much lower chlorine content. The sulfur dioxide gas reductant is oxidized to make sulfuric acid, reducing the overall acid requirement of the process. Air is used to dilute the chlorine dioxide produced by this process. The exit gases flow through a scmbber to which chlorate is added in order to remove any unreacted sulfur dioxide. Spent Hquor, containing some unreacted chlorate, sulfuric acid, and sodium sulfate, continuously overflows from this process. 

The sihca dux combines with iron(II) sulfide and iron(II) oxide to form slag. The duidity of the slag, in which unwanted impurities dissolve, is controlled by the addition of limestone. Reverberatory furnaces have been largely replaced by more advanced smelting furnaces, which require lower energy input, have higher capacity, and produce higher sulfur dioxide content off-gas. 

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