Sulfur continued ambient concentrations

Some automatic analyzers use conductance to indicate the concentration of some specific component. For example, ambient concentrations of SO2 in air as low as O.OI ppm can be recorded continuously. Sulfur dioxide is oxidized to sulfuric acid, after which the increase in conductance due to the hydrogen and sulfate ions is directly proportional to the SO2 concentration. The moisture content of wood and soil has been measured with special electrodes. 

A third emission reduction choice is to remain with the existing front end process, which continues to produce a sulfur dioxide-containing waste gas stream, and move to some system which can effectively remove the sulfur dioxide from this waste gas before it is discharged. Many methods are available, each with features which may make one more attractive than the others for the specific sulfur dioxide removal requirements (Table 3.8). Some of the selection factors to be considered are the waste gas volumes and sulfur dioxide concentrations which have to be treated and the degree of sulfur dioxide removal required. It should be remembered that the trend is toward a continued decrease in allowable discharges. The type of sulfur dioxide capture product which is produced by the process and the overall cost are also factors. Any by-product credit which may be available to offset process costs could also influence the decision. Finally, the type of treated gas discharge required for the operation (i.e., warm or ambient temperature, moist or dry, etc.), also has to be taken into account. Chemical details of the processes of Table 3.8 are outlined below. 

The Erlenmeyer flask is charged with 100 mL of the 1.0 M stock solution of K[C2B9H12] (see this volume, Chapter 5, Section 53) and 31.2 g (0.4 mole) of dimethyl sulfoxide. While the solution is being stirred, 100 mL of concentrated sulfuric acid is added dropwise over a 1-hr period. Stirring is continued for an additional 5 hr. The resultant two-layer mixture is then set aside overnight. After dilution with 500 mL of cold water, the mixture is vacuum filtered, to isolate the solid residue, and this is washed with two 100-mL portions of water and recrystallized from 80% methanol. White needles separate which are isolated by vaccum filtration and dried in air at ambient temperature for 8 hr. The yield is 10.8 g (55.6%). 

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