Abstract
SO3 is one of pollutants in flue gas of coal power plants. It mainly derived from coal combustion in boiler and selective catalytic reduction denitrification system. The content of SO3 in flue gas were influenced by the combustion mode, sulfur content in fuel, composition of denitrification catalyst and fly ash. SO3 and water vapour generated H2SO4 droplets. Sulfate secondary particles in atmosphere could cause haze, acid rain and other disastrous weather. High concentration of SO3 could cause blockage and corrosion and affect the safe operation of the units. The generation mechanism of SO3 was discussed. The latest research progress on control and removal technology of SO3 was summarized. The study in this paper provides a reference for pollutant treatment in coal-fired power plants.
Highlights
SO3 is one of pollutants in flue gas of coal power plants
The generation and emission of SO3 in coal-fired power plants cause problems such as ash, blockage and corrosion of the equipment, which affects the safe operation of the unit and causes environmental pollution
The control and removal technology SO3 in flue gas are received extensive attention
Summary
Combustible sulfur in coal organic sulfur, including organic sulfur, elemental sulfur and ferrous sulfide, conversed to SO2 during combustion progress. Deactivation of the catalyst reduced the denitrification efficiency, but the oxidation rate of SO2 increased instead. Sulfuric acid vapor or droplets adhered to metal surfaces of the flue and air preheaters, causing low temperature corrosion and ash blocking. If the flue gas acid dew point increased, the boiler exhaust temperature needed to be increased . The temperature of the flue gas at the outlet of the air preheater is about 10 °C-15°C higher than the acid dew point of the flue gas. The ammonium bisulfate and the fly ash in the flue gas adhered to the wall of the air preheater, which caused corrosion and blockage of the air preheater. In the SCR denitrification reactor, permanent deactivation of the catalyst could occur if the catalyst was covered by ammonium bisulfate for a long time[6]
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