Sulfuric Acid Mist Formation
Fossil fuels such as coal and oil contain a significant amount of sulfur. When fossil fuels are burned, about 95 percent or more of the sulfur is generally converted to sulfur dioxide (SO2). Such conversion happens under normal conditions of temperature and of oxygen present in the flue gas. However, there are circumstances, under which such reaction may not occur.
When flue gas has too much oxygen, the SO2 further oxidizes into sulfur trioxide (SO3). Too much oxygen is only one of the ways that SO3 is formed. Gas temperature is also an important factor. At about 800 °C, formation of SO3 is favored. Another way that SO3 can be formed is through catalysis by metals in the fuel. Such reaction is particularly true for heavy fuel oil, where a significant amount of vanadium is present. In whatever way SO3 is formed, it does not behave like SO2 in that it forms a liquid aerosol known as sulfuric acid (H2SO4) mist that is very difficult to remove. Generally, about 1% of the sulfur dioxide will be converted to SO3. Sulfuric acid mist is often the cause of the blue haze that often appears as the flue gas plume dissipates. Increasingly, this problem is being addressed by the use of wet electrostatic precipitators.
Read more about this topic: Flue-gas Desulfurization
Famous quotes containing the words mist and/or formation:
“Gold conjures up a mist about a man, more destructive of all his old senses and lulling to his feelings than the fumes of charcoal.”
—Charles Dickens (1812–1870)
“Those who were skillful in Anatomy among the Ancients, concluded from the outward and inward Make of an Human Body, that it was the Work of a Being transcendently Wise and Powerful. As the World grew more enlightened in this Art, their Discoveries gave them fresh Opportunities of admiring the Conduct of Providence in the Formation of an Human Body.”
—Joseph Addison (1672–1719)