A review on sulfur trioxide (SO3) removal from coal combustion process: Research progress challenges and suggestions

Abstract

With the increasingly strict requirements for pollutant emissions from coal-burning power stations, the excessive emission issues of SO₃ has attracted increasing attention. SO₃ can be generated by containing-sulfur substance combustion in furnace and catalytic action of selective catalytic reduction (SCR) denitration catalyzer. When the contents of SO₃ in flue gas are too high, it can cause several problems such as ash accumulation, blockage, and corrosion of various equipments, which seriously affects the safe and stable operation of coal-burning power stations. Besides, excessive emissions of SO₃ can form colored smoke, causing serious impacts on the ecological environment and human health. Some countries and regions have introduced relevant regulations to control SO₃ emission and promote the development of SO₃ control technology and strategy. This article focuses on reviewing various removal technology of SO₃ from coal-fired flue gas, mainly including SO₃ removal inside furnace, SO₃ control by SCR catalyst, SO₃ removal using dust collectors, SO₃ removal using desulfurization devices, SO₃ removal using flue gas injection adsorbent, and combined use of various removal technologies. The principles and performance of various SO₃ removal technologies are introduced. The applicability and limitations of these SO₃ removal technologies are also analyzed and compared. The alkaline adsorbent injection technology has strong adaptability and good desulfurization effect, receiving widespread attention. By adjusting the molar ratio of the adsorbent to SO₃, it is possible to achieve SO₃ removal efficiency of over 90%. Regulating the structure and active components of catalysts can reduce the amount of SO₃ generated in SCR system. Wet electrostatic precipitators can achieve a SO₃ removal efficiency of up to 90%, and reducing inlet flue gas temperature of wet electrostatic precipitators can effectively enhance the SO₃ removal. This review can provide necessary reference and guidance for design and development of new technologies for SO₃ control.