抄録
Some ash particles from solid fuels adhere to heat exchanger tube surfaces, which causes some trouble, such as heat transfer inhibition, operational problems and hot corrosion in coal/biomass-fired boilers. Thus, monitoring techniques for deposition and corrosion are important in order to maintain plant conditions and keep boiler thermal efficiency high. In this study, the corrosion and the ash adhesive properties in corrosive conditions were evaluated through an Electrochemical Impedance Spectroscopy in order to develop monitoring techniques. Moreover, corrosion and deposition characteristics of coal ash were evaluated on site using a new monitoring probe. The major conclusions were drawn as follows: A positive correlation between the polarization conductance and the corrosion current density was obtained in the hot corrosion tests for sulfate ash with simulated gas. Although the standard deviation of the impedance data was influenced by temperature, gas and ash composition, the ash adhesive properties was confirmed to estimate using the standard deviation of the impedance Z_<SD>. The corrosive property of solid fuel on-site could be evaluated qualitatively with the polarization conductance. It is possible to monitor ash adhesive properties on-site using the measurement values of the Z_<SD>, temperature conditions and gas compositions.
