SO2/air

The Hargreaves process (late 19th C) is a variant of the salt-cake process in which NaCl is reacted with a gaseous mixture of SO2, air and H2O (i,e, H2SO4 ) in a self-sustaining exothermic reaction ... 

Wet chemical (solutions and filters) Widely used for H2S and SO2 air pollution studies Tedious... 

The Hargreaves process produces K2SO4 directly from KCl by passing SO2, air, and water vapor through beds of KCl briquettes. 

Fig. 8. Mass change versus time plot of Fe-A110-Cr2 in comparison to alloy 800H after cyclic ex posure in sulphidising 10%SO2/air gas atmosphere at 650°C...

Fig. 9. Typical corrosion attack of an iron-aluminium-chromium alloy and 80011 after 2016 hours of cyclic exposure in sulphidising 10%SO2/air gas atmosphere at 650°C a) Fe-A110-Cr2, b) Alloy 800H...

In a separate study, the effects of NaCl and SO2 air pollutants on the corrosion of zinc were investigated by Qu et at. [68]. Influence of NaCl deposition and SO2 on atmospheric corrosion of zinc at 90% RH and 25 °C is shown in Fig. 10.20 [68]. The corrosion rate decreases with time due to the large amounts of deposit buildup onto the zinc surface. NaCl increases the initial corrosion of zinc in air in the presence and absence of SO2. Presence of only SO2 slowly increases the initial corrosion rate. The synergistic corrosion effect was observed in the presence of both contaminants. 

Sulfur in coal that is burned to generate electricity is a major source of acid rain and SO2 air pollution. In Eschka s method to measure S, coal is fused with 5 times its mass of a 2 1 (by mass) mixture of MgO and anhydrous Na2C03 at 800°C for 4 h in air. Sulfur ends up as sulfate (SO ) and sulfite (SOf") salts. The fused mass is dissolved in 6 M HCl and boiled with aqueous Br2 to oxidize S03 to SO . Excess Br2 is evaporated. The solution is adjusted to pH 3 and aqueous BaCl2 is added to precipitate BaS04, which is filtered, washed, dried by ignition, and weighed. 

Gas-liquid equilibrium data. To illustrate the obtaining of experimental gas-liquid equilibrium data, the system SO -air-water will be considered. An amount of gaseous SO2, air, and water are put in a closed container and shaken repeatedly at a given temperature until equilibrium is reached. Samples of the gas and liquid are analyzed to give the partial pressure in atm of SO, (A) in the gas and mole fraction in the liquid. Figure 10.2-1 shows a plot of data from Appendix A.3 of the partial pressure p of SO2 in the vapor in equilibrium with the mole fractionx,< ofS02 in the liquid at 293 K (20°C). 

The Dowa Dual Alkali Process uses a solution of basic aluminum sulfate to absorb SO2, air injection to oxidize sulfite to sulfate, and limestone to precipitate the resulting excess sulfate in the form of gypsum. 

Sulphur dioxide, SO2, m.p. — 72-7°C, b.p. — I0"C. Colourless gas with characteristic smell. Formed by burning S, metal sulphides, H2S in air or acid on a sulphite or hydrogen sulphite. Powerful reducing agent, particularly in water. Dissolves in water to give a gas hydrate the solution behaves as an acid - see sulphurous acid. Used in the production of SO3 for sulphuric acid. 

STM has been used to study adsorption on surfaces as it relates to corrosion phenomena [6, 7]. Sulfiir is a well known corrosion agent and is often found in air (SO2, FI2S) and in aqueous solution as dissolved anions ( HSO7) or dissolved gas (FI2S). By studying the interaction of sulfur with surfaces, insights can be gained into... 

At high temperatures oxygen reacts with the nitrogen in the air forming small amounts of nitrogen oxide (p. 210). Sulphur burns with a blue flame when heated in air to form sulphur dioxide SO2, and a little sulphur trioxide SO3. Selenium and tellurium also burn with a blue flame when heated in air, but form only their dioxides, Se02 and Te02. 

This experiment describes the construction of an air sampler using an aquarium pump, a flow meter, a filter holder, and bottles that serve as traps for analytes. Applications include the determinations of SO2, NO2, HCHO, and suspended particulate matter. 

The concentration of SO2 in atmospheric samples can be determined by bubbling a sample of air through a trap containing H2O2. Oxidation of SO2 by H2O2 results in the... 

After adding p-rosaniline and formaldehyde, the colored solution was diluted to 25 ml in a volumetric flask. The absorbance was measured at 569 nm in a 1-cm cell, yielding a value of 0.485. A standard sample was prepared by substituting a 1.00-mL sample of a standard solution containing the equivalent of 15.00 ppm SO2 for the air sample. The absorbance of the standard was found to be 0.181. Report the concentration of SO2 in the air in parts per million. The density of air maybe taken as 1.18 g/L. 

Large sources of SO2 and NO may also require additional emission reductions because of the 1990 Clean Air Act Amendments. To reduce acid... 

Since SO2 and NO2 are criteria pollutants, their emissions are regulated. In addition, for the purposes of abating acid deposition in the United States, the 1990 Clean Air Act Amendments require that nationwide SO2 and NO emissions be reduced by approximately 10 million and 2 million t/yr, respectively, by the year 2000. Reasons for these reductions are based on concerns which include acidification of lakes and streams, acidification of poorly buffered soils, and acid damage to materials. An additional major concern is that acid deposition is contributing to the die-back of forests at high elevations in the eastern United States and in Europe. 

Selection of pollution control methods is generally based on the need to control ambient air quaUty in order to achieve compliance with standards for critetia pollutants, or, in the case of nonregulated contaminants, to protect human health and vegetation. There are three elements to a pollution problem a source, a receptor affected by the pollutants, and the transport of pollutants from source to receptor. Modification or elimination of any one of these elements can change the nature of a pollution problem. For instance, tall stacks which disperse effluent modify the transport of pollutants and can thus reduce nearby SO2 deposition from sulfur-containing fossil fuel combustion. Although better dispersion aloft can solve a local problem, if done from numerous sources it can unfortunately cause a regional one, such as the acid rain now evident in the northeastern United States and Canada (see Atmospheric models). References 3—15 discuss atmospheric dilution as a control measure. The better approach, however, is to control emissions at the source. 

There has been considerable improvement, especially in industrial areas, in U.S. air quaUty since the adoption of the Clean Air Act of 1972. Appreciable reductions in particulate emissions and in SO2 levels ate especially evident. In 1990, however, almost every metropoUtan area was in nonattainment status on o2one air quaUty standards 50 metropoUtan areas exceeded the CO standard and between 50 and 100 exceeded the PM q standard for particulate level (29). 

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