Abstract
Thermodynamic calculations and experiments were performed to determine the SO3 partial pressures and temperatures at which K2SO4-CoSO4 binary mixed liquid phases form on CoO and Co3O4 in the presence of K2SO4. The calculations and experiments are in excellent agreement. Similar calculations were also made of the compositions at the liquidus surface and the associated SO3 partial pressures for the K2SO4-Na2SO4-CoSO4 ternary system. These calculations show that the presence of K2SO4 substantially reduces the SO3 partial pressures required to stabilize a liquid salt phase on the surface of oxidized cobalt alloys at 600–800°C. Consequently, at these temperatures the hot corrosion in coal-fired systems, where K levels are high, is expected to be worse than in oil-fired systems, where K levels are low. This prediction was confirmed by experiments in a pressurized fluidized bed coal combustor and in an atmospheric pressure burner rig.
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LeBlanc, O.H., Luthra, K.L. & Haskell, R.W. Thermodynamics of the Na2SO4-K2SO4-CoSO4 system and their relevance to low-temperature hot corrosion. Oxid Met 31, 393–414 (1989). https://doi.org/10.1007/BF00666464
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DOI: https://doi.org/10.1007/BF00666464