Prevention of stack corrosion under wet flue gas desulfurization conditions in a coal-fired power plant: performance analysis and comparative study

Abstract

Background: This study investigated the prevention of stack corrosion under wet flue gas desulfurization conditions in a coal-fired power plant. The performance analysis and comparative studies of six materials for the prevention of stack corrosion were investigated. Results:The ion chromatography analysis showed the acid condensation contained fluoride, chloride, nitrate, sulphate, and sulphite. The weight loss method showed titanium alloy and foam glass blocks were heat and acid resistant. The scanning electron microscopy indicated the morphologies were pits, cracks, and flakes for sulfuric acid dew corrosion resistant steel, and X-ray diffraction showed the corrosion products mainly consisted of Fe 2 O 3 , FeSO 4 , FeOOH, with some Fe 3 O 4 or FeF 3 . The comparative study indicated that cyclic wet-dry conditions resulted in more aggressive corrosion to the stack than acid condensation. Conclusions:Titanium alloy and foam glass blocks had the best performance and could be applied in the stack to prevent corrosion. The effects of cyclic wet-dry conditions should be taken into account to mitigate stack corrosion in coal-fired power plants.

Overview of Wet Flue Gas Desulphurisation System & Condensate Flow Study in view of new stringent environment regulations for fossil fuel based power plants in India

“…Wet limestone based FGD have advantages like high desulfurization efficiency, wide adaptation, long-run stability and low operating cost. However, it creates serious corrosion problems inside surface of stack wall [7]. Due to the high moisture content in the flue gas after the absorber, condensation occurs in these stacks during steady-state and start-up conditions [9].…”

“…Acid condensation occurs due to lower flue gas temperature in the both conditions ( 2) & (3) where FGD is used without GGH. This leads to corrosion which would generates a need for good corrosion resistant material [7]. Thus it was concluded that low alloy steel, Borosilicate and ND steel can be applied in higher temperature flue gas stacks in thermal power station [7].…”

“…This leads to corrosion which would generates a need for good corrosion resistant material [7]. Thus it was concluded that low alloy steel, Borosilicate and ND steel can be applied in higher temperature flue gas stacks in thermal power station [7].…”

“…The three material viz. titanium alloy, Borosilicate and ND steel are able to withstand for variable temperature condition following wet stack operation in power station [7].…”

“…Unlike other materials, no significant change in colour or corrosion signs were observed which shows its good corrosion resistant property in acidic and cyclic conditions. The formation of TiO2 layer on the metal surface of Titanium alloy makes it an excellent corrosion resistant material, thus can be used as material for stacks despite being expensive [7].…”