Abstract
The unusual properties of supercritical water including density, ion dissociation product, dielectric constant and hydrogen bond were introduced. Furthermore, the basic law of corrosion and deposition on supercritical and ultra-supercritical units was revealed. With regard to supercritical and ultra-supercritical units, the deposition inside boiler tubes especially consists of magnetite which accumulated principally on inner surface in the front of economizer. Furthermore, with respect to vertical type water wall, magnetite deposition can also foul control orifices. It is predicted that adequate control of corrosion product transport to supercritical boilers is not achievable with AVT. Both AVT (R) and AVT (O) inevitably result in a significant increase in pressure drop through the furnace walls due to internal deposition, and hence increase in metal temperature and necessity for frequent chemical cleaning. To restrain flow-accelerated corrosion and magnetite deposition in supercritical and/or ultra-supercritical units, OT is doubtless the excellent feedwater treatment regime, and it should be adopted as soon as possible if the feedwater conditions once become acceptable.
