Corrosion Analysis of Superheat Tube in Bagasse-Fuel Biomass Power Plant

This
work is aimed at corrosion analysis of STBA12 superheat tube from bagasse-fuel
biomass power plant. The results indicated that the fouling on tube surface composed
of K₂SO₄, KCl and low-melting point eutectics compound
such as KCl-K₂SO₄. In service the tube
surface temperature was in a range of 510-780^oC at which
eutectics
compound melted. This
high corrosive molten salt was a reactant for deterioration of steel superheat tube.
Cross-sectional investigation found the uniform iron oxide layer which was a
product from high temperature oxidation reaction. Additionally localized
corrosion attacks, sulfur attack (S-attack) and chlorine attack (Cl-attack),
were observed. The S-attack was a superficial and sharp attack about 5-10 mm depth along
grain boundaries; whereas, the Cl-attack was a deep attack about 20-50 mm depth along
grain boundaries. Source of chlorine was from molten salt and products of
sulfation reaction such as chlorine gas (Cl₂) and hydrochloride
(HCl)