It has generally been known that erosion of inbed heat exchanger tubes is one of the most serious problems in fluidized bed coal combustion. The present study aimed to make clear the mechnism of fouling phenomenon in coal combustion.
Combustion experiments for several kinds of coal were made using 0.15m id combustor, which immersed model tubes in the bed, at the conditions of 850°C and singlestage combustion scheme. Fouling appeared with increasing in Na2O content in the coal ash, and the thickness of scale became a maximum value when the suface temprature of the model tubes was between 550 to 700°C.
It was comfirmed from the chemical analyses with a Xray diffraction meter that major contents of the scale were CaSO4, Na2SO4 and Na2Si2O5. Fouling phenomenon could appeare for Na2O content in coal ash of around 2% or higher.
