Analysis and quantification of high-temperature corrosion in lignite fired boilers using an online monitoring system

Corrosion monitoring in industrial boilers is typically performed using offline techniques, such as coupons or ultrasonic testing, to assess component lifetime. These techniques lack temporal resolution, hindering their ability to detect dynamic influences on corrosion attack, such as fuel inhomogeneity, load changes, or unfavourable operational parameters. Electrochemical online monitoring has been successfully implemented in the chemical industry, yet studies in power plants remain limited to short tests or laboratory-scale parameter investigations. This work aims to highlight the added value of online monitoring and evaluate the ability to record reliable data in industrial environments. Additionally, the study presents an approach to quantify sensor data and enable operators to derive actionable recommendations. Twelve sensors were strategically positioned around burners in the membrane wall and monitored for three years to investigate spatial distribution and temperature influence on corrosion attack. Sampling of near-wall gas atmosphere during partial and full-load conditions facilitated research into gas phase influence. Multiple analytical approaches validated sensor data: Temperature measurements demonstrated correlation between deposit accumulation and corrosion signals. Event-based analysis revealed intense corrosion during plant shutdowns across all sensor positions. Statistical evaluation established correlation between mill utilization and corrosion intensity. Gravimetric quantification methods, expressing results in mm/1000 h, enhanced interpretability and chemical analysis of deposits provided insight into dominant corrosion mechanisms. This study offers significant insight to operators as well as researchers, enabling them to evaluate the benefits of online monitoring systems and to compare laboratory experiments with industrial results.