Diminishing the Role of Sulfur Oxides in Air Pollution

Each year, in the US, more than 20 million tons of sulfur are discharged into the atmosphere, most of it in the form of SO/sub 2/. This gas is slowly converted into sulfuric acid, which is corrosive to many materials, including metals, building stones, and clothing. The toxicity of SO/sub 2/ and H/sub 2/SO/sub 4/ to plants and animals is controversial, as is the effect of these compounds when they are inhaled along with other components of smog. Principal targets for such restrictions are electric power generating plants. These are a major source of air pollutants when they use coal or residual oil as fuel. Five means of meeting the sulfur pollution problem seem feasible. One is to use fuel containing only small amounts of sulfur. A second is to discharge the fumes from tall smokestacks (more than 200 meters high). A third method is to add a material such as powdered limestone to the flue-gas stream, following combustion, to convert the gaseous sulfur oxides into a solid form. A fourth is to convert the coal to gas and to remove the sulfur from the gas prior to combustion. A fifth method is to pass the flue gases through amore » chemical processing plant, the sulfur being recovered in elemental form or as H/sub 2/SO/sub 4/. Both the sulfur and the H/sub 2/SO/sub 4/ are consumed on a large scale. The price of sulfur has advanced sharply during the last year and is currently quoted at close to $50 a ton. With present technology the value of the sulfur recovered from coal-fired power plants would about offset the cost of investment and operation of the processing plants. A combination of better technology with a higher price for sulfur may eventually convert a nuisance into a valued asset.« less