2016 Volume 65 Issue 11 Pages 454-457
Boiler steam conditions of MSW incinerators have recently been shifting to higher temperature and pressure to attain more efficient energy recovery from the waste. Consequently, boiler tubes are now exposed to more harmful environment than before. Flyash comprising particulate matters in the hot gas stream, part of which finally accumulates on the surface of boiler tubes, plays a crucial role in erosion and corrosion mechanism of boiler materials. However, the thermophysical properties of these substances at actual gas temperatures are not well reported. Test samples were collected from several MSW incinerators in order to clarify high temperature thermal conductivities of flyash adhered to boiler tubes, outer surface scale formed on riser tubes, and incinerated ash. Results from the measurement showed flyash adhered to riser tubes and that to superheater have respective high- temperature thermal conductivities and the thermal conductivity of outer surface scale on riser tubes has a decreasing tendency with increasing temperature. Besides, two thermal conductivity values obtained from laser flash and hot wire measurements of the identical powdered test sample presented a fairly good agreement if the difference in bulk density was taken into consideration.