Corrosion of HR3C heat exchanger alloy in a biomass fired PF utility boiler

Detailed microscopic examinations have been conducted on two, temperature-r egulated probes (commercial HR3C heat exchanger alloy) after being exposed to biomass flue gas inside a PF boiler for 3770 h at 600 degreesC and 650 d egreesC respectively. Corrosion of the tube proceeds via scale formation an d internal element depletion. Three characteristic types of internal corros ion have been identified depending on their position relative to the flue g as passage and deposit/flue gas chemistry. Severe, mainly internal corrosio n occurs at down-stream locations where higher potassium chloride content e xists within the deposit. Corrosion mechanisms corresponding to each type o f internal corrosion have been proposed based on further laboratory tests a nd thermodynamic analysis. The increased temperature (650 degreesC) causes slightly higher material wastage for the alloy.