Sulfur dioxide is the chemical compound with the formula SO₂. It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel. Further oxidation of SO₂, usually in the presence of a catalyst such as NO₂, forms H₂SO₄, and thus acid rain. Sulfur dioxide emissions are also a precursor to particulates in the atmosphere. Both of these impacts are cause for concern over the environmental impact of these fuels¹.
Method Of Production
Sulfur dioxide can be produced using the following methods²:
1. Sulfur dioxide has been produced by burning molten sulfur in a special burner with a controlled amount of air. The burner gas, free of dust and cooled, is dissolved in water in a series of two towers. In a third tower, the solution is sprayed at the top and flows down while steam is injected at the base. The gas issuing from the third tower is then cooled to remove most moisture and passed up a fourth tower against a countercurrent of sulfuric acid. The dried gas is liquefied by compression.
2. Sulfur dioxide has been produced commercially from the following raw materials: elemental sulfur; pyrites; sulfide ores of non-ferrous metals; waste sulfuric acid and sulfates; gypsum and anhydrite; hydrogen sulfide containing waste gases; and flue gases from the combustion of sulfurous fossil fuels. It is most commonly produced by burning sulfur but can also be produced by burning pyrites in a special furnace or by purifying and compressing sulfur dioxide gas from smelting operations.
3. Sulfur dioxide can also be produced commercially by liquefying gas obtained during smelting of non-ferrous metals such as lead, copper, and nickel. Much of this smelter by-product is recovered and oxidized to sulfur trioxide for producing sulfuric acid. Sulfur dioxide recovery, however, usually occurs only for environmental reasons.
Sulfur dioxide has numerous commercial uses which are based on its function as an acid, as a reducing or oxidizing agent, or as a catalyst. Sulfur dioxide is used in large quantities as a captive intermediate in the production of sulfuric acid and in the pulp and paper industry. Other common uses of sulfur dioxide include the following: fumigant, preservative, bleach, and steeping agent for grain in food processing; catalyst or extraction solvent in the petroleum industry; flotation depressant for sulfide ores in the mining industry; intermediate for bleach production; and reducing agent in several industrial processes³.
High concentrations of sulfur dioxide (SO₂) can result in breathing problems with asthmatic children and adults who are active outdoors. Short-term exposure has been linked to wheezing, chest tightness and shortness of breath. Other effects associated with longer-term exposure to sulfur dioxide, in conjunction with high levels of particulate soot, include respiratory illness, alterations in the lungs’ defenses and aggravation of existing cardiovascular disease.
Sulfur dioxide and nitrogen oxides are the major precursors of acid rain, which has acidified soils, lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility. Sulfur dioxide also is a major precursor of fine particulate soot, which poses a significant health threat.
In conclusion, to be free from the hazards produced by carbon monoxide the world must look for alternative energy solutions.
The following are resources for sulfur dioxide information:
1. Sulfur Dioxide – Wikipedia
2. New School Chemistry by Osei Yaw Ababio
3. New School Chemistry by Osei Yaw Ababio
Image Credit: Wikipedia