Sulfur dioxide is one of the two main precursors to acid rain (the other one is NOx). It is produced mainly by oxidation of sulfur-containing ores and fuels. (In Australia it has not been a major problem, and probably won't be a major problem in the future, because of the relatively low sulfur content of Australian coals (typically <1 wt.%). Elsewhere in the world (especially in Europe and the USA) it has been a major problem because of the high sulfur content (up to 5%) of many coals used in electric power plants.
The concentration of SOx in the atmosphere can be reduced by (a) source reduction, e.g., removing the sulfur from the fuel before combustion or switching to a lower-sulfur fuel; (b) removing SO2 from the products of combustion during the combustion process (in fluidized-bed combustion); and (c) removing SOx from the products of combustion after the combustion process has been completed.
For a more detailed qualitative discussion, see Task 1 Report. For quantitative analyses, be sure to know the following:
•how to convert µg/m3 to ppm and vice versa (e.g., Problem 1.2 in Benítez)
•how to use simple stoichiometric arguments to calculate actual (uncontrolled) SO2 emissions (see columns 4 and 5 in Table 4.2 in de Nevers)
•how to compare actual and allowed SO2 emissions (e.g., Problems 1.11 in Benítez and 11.29 in de Nevers).
See also class handout "Clean Air Legislation" and compare USA and Australian SOx standards.
lrr3@psu.edu (revised 11/3/98)