Sulfur dioxide oxidation advantages

The increasing number of atomic reactors used for power generation has been questioned from several environmental points of view. A modern atomic plant, as shown in Fig. 28-3, appears to be relatively pollution free compared to the more familiar fossil fuel-fired plant, which emits carbon monoxide and carbon dioxide, oxides of nitrogen and sulfur, hydrocarbons, and fly ash. However, waste and spent-fuel disposal problems may offset the apparent advantages. These problems (along with steam generator leaks) caused the plant shown in Fig. 28-3 to close permanently in 199T. 

Another reducing agent relevant to chlorination reactions is sulfur dioxide. When the material to be chlorinated contains calcium oxide, it is advantageous to convert it to calcium sulfate rather than to calcium chloride. The advantages are less chlorine consumption and easy disposal of calcium sulfate (which is water-insoluble). The chlorination of scheelite is an important example of the use of the sulfur dioxide chlorine reagent ... 

The advantage of this technique is the rapidity of monitoring for many compounds simultaneously, including some of the liquid and solid inorganic materials—such as sulfuric acid, ammonium sulfate, and ammonium nitrate—that may be the final products of the primary pollutants nitric oxide and sulfur dioxide. Also, monitoring the many par-... 

The Pictet-Spengler cyclization of )VA -dimethyltryptamine (V-oxide (66) to the tetrahydrocarboline (78) using sulfur dioxide in anhydrous formic acid and the selective (V-dealkylation of the morphinan iV-oxide (79) using catalytic quantities of iron(II) chloride (equations 19 and 20) illustrate the advantages of using these activating reagents in the Polonovski reaction. 

Temperatures of about 1100°C are necessary in the presence of added air in order to promote complete oxidation of any organic impurities and thermolysis of the acid. Oxygen-enriched air may be used with advantage [71]. Subsequently, the sulfur dioxide is recovered and passed through a conventional contact plant for regeneration to sulfur trioxide and thence via rehydration to concentrated sulfuric acid (Fqs. 9.25 and 9.26). 

MISCELLANEOUS. Sodium hydride, particularly as the dispersion, is effective for removing the last traces of water, alcohols, oxygen, and some sulfur compounds from solvents and certain gases. It reacts with ammonia to form sodium amide, with carbon oxides to form products including formate and oxalate, and with sulfur dioxide to form sodium hydrosulflte. Smalley (52) has tried it for the desulfurization of iron and steel. Its advantage over sodium metal for these reactions is that it holds its fine particle size and reactive surface up to 400 °C., while sodium melts and coalesces at 100°C. unless continually redispersed. 

A high-temperature combustion method for the determination of sulfur in solid fuels has also been adopted in many laboratories and is advantageous insofar as chlorine can be determined simultaneously. The method requires that the coal sample be heated to 1250°C-1350°C (2280 F-2460°F) in the presence of excess kaolin, ferric phosphate, or aluminum oxide to enhance the ranoval of the sulfur (as sulfate) from the ash. Oxygen is also included to produce oxides of sulfur which are absorbed in hydrogen peroxide (whereby sulfur dioxide is converted to sulfur trioxide). The solution is then titrated with standard alkali solution which gives the total acidity (due to the hydrochloric and sulfuric acids that are formed). 

The temperature in the fluidized-bed combustor is on the order of 800°C-900°C (1470°F-1650°F) compared with 1300°C-1500°C (2370°F-2730°F) in pulverized coal combustion systems (PCC). Low temperature helps minimize the production of nitrogen oxides and, with the addition of a sorbent (typically limestone) into the fluidized bed, much of the sulfur dioxide formed can be captured. The other advantages of fluidized-bed combustors are compactness, ability to bum low calorific values (as low as 1800 kcal/kg), and production of ash which is less erosive. 

Any addition of sulfur dioxide to a wine results in the combination of a part of this sulfur dioxide. Conversely, the depletion of free sulfur dioxide by oxidation results in a decrease of the bound fraction to such a degree that the loss of free sulfur dioxide is less than the amount oxidized. This hberation mechanism is advantageous, since it... 

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