51312-01638-Fireside Corrosion and Carburization of Superheater Materials in Oxyfuel Combustion

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Product Number: 51312-01638-SG

ISBN: 01638 2012 CP

Author: Pekka Pohjanne

Publication Date: 2012

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Oxyfuel combustion is considered as one of the most promising technologies to facilitate CO2 capture from flue gases. In oxy-fuel combustion the fuel is burned in a mixture of oxygen and recirculated flue gas. Flue gas recirculation can increase the levels of fireside CO2 SO2 Cl and moisture and thus promote fouling and corrosion. It has been suggested that oxide scales developing in O2/CO2/H2O atmospheres are not well protective and internal carburisation may occur. In this study three boiler tube steels X20CrMoV11-1 TP347HFG and 310HCbN were subjected to oxidation/corrosion testing at 600 and 650°C under simulated oxyfuel fired atmospheres (60% CO2-30% H2O-4% O2-Ar) with and without CaCO3-CaSO4 deposit up to 1000 h. Reference tests were performed at the same temperatures in an atmosphere simulating conventional air-fired coal combustion. The results showed that the corrosion resistance increased when the chromium content increased but that without added impurities like sulphur and chlorides the simulated oxyfuel conditions didn’t result in more severe corrosion than under air firing environment. No carburization of the metal substrate was observed after exposure to simulated oxyfuel gas atmospheres without deposit although some carbon enrichment was detected near the oxide-surface interface. With extended exposure time the oxide scale properties may change to enable metal carburisation. The exposure with CaCO3-CaSO4 deposit at 650°C resulted in corrosion of all tested alloys and clear carburization of steels X20CrMoV11-1 and TP347HFG.