Detection of first melting temperature in superheater ash deposits using In situ electrochemical diagnostics

Partial melting of ash deposits on superheater surfaces plays a critical role in fouling, slagging, and corrosion in high-temperature combustion systems. Accurate identification of the first melting temperature (T 0 ) is therefore essential for safe and efficient operation of these systems. However, in situ, real-time detection using conventional thermoanalytical approaches remains challenging in boiler environments. In this work, an in situ electrochemical method is applied to detect the first melting temperature of superheater ash deposits by monitoring ionic conductivity. While electrochemical methods are widely used, the approach applied here enables precise determination of T 0 , with results matching those of independent thermal and thermodynamic analyses. Arrhenius analysis reveals a mechanistic shift from vacancy-mediated diffusion below T 0 to liquid-like ion transport above T 0 , which shows the influence of composition and melt fraction on ionic conductivity in different phases. This methodology can enable real-time detection of T 0 in superheater ash deposits under boiler-relevant conditions and contributes to improved understanding of phase-transition behavior in complex, multicomponent salt systems relevant to high temperature energy systems. • Optimized high-temperature electrochemical cell for partially molten superheater ash deposits. • Rapid activation of ionic conductivity enables accurate detection of the first melting temperature ( T 0 ). • Consistency with thermal and thermodynamic analyses confirms the reliability of the approach.